DEPARTMENT OP THE INTERIOR

Hubert Work, Secretary

U. S. GEOLOGICAL SURVEY 

George Otis Smith, Director

Bulletin 788

TOPOGEAPHIC INSTRUCTIONS

OF THE

UNITED STATES GEOLOGICAL SURVEY

C. H. BIRDSEYE

Chief Topographic Engineer

UNITED STATES

GOVERNMENT PRINTING OFFICE

WASHINGTON

1928
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t « .«_ 

 !? 
CONTENTS

[The letters in parentheses preceding the-titles are those used to designate the papers for advance

publication]

Page

(A) Administration, by H. M. Frye (published November 15, 1926)____ 1

(B) Triangulation, by E. M. Douglas (published December 22, 1926)___ 47

(C) Transit traverse, by E. M. Douglas (published December 18, 1926) _ 89

(D) Leveling, by E. M. Douglas (published December 13, 1926)...__ 117 

(E) Topographic mapping, by W. M. Beaman (published April 2, 1928). 161 

(F) Map compilation from aerial photographs, by T. P. Pendleton (published February 27, 1928).________________________ 379 

Index____._._....._._.__._-__ . 421

ILLUSTRATIONS

PLATE 1. Observing tower and signals_--_____-__________ ________ 52

2. Vernier transit-theodolite_-----__--___-___-_-__-__-_____ 52

3. Micrometer theodolite_ ____-__-_-____________ 52

4. Geological Survey marks for triangulation, transit traverse, and

leveling ______________________________________________ 52

5. Apparatus used in transit traverse____________ ________ 90

6. Vernier transit, stadia rod, and range rod._ ______________ 91

7. Instruments used in leveling. _______________ 128

8. Bumstead projection plate_---__ ______ ______________ 178

9. Plotting scales____.______________________ 178

10. Plane table and tripods---------------------------------- 194

11. Telescopic alidades-------------- _________ ____ 194

12. Stadia rod and rope_____----------_---_- _____________ 194

13. Aneroid barometer___________.___________________________ 194

14. Baldwin solar chart_-____-_________-_ ______________ 218

15. Marginal lettering for topographic maps.___- ____ ____ 282

16. Marginal lettering for river survey sheets______________ 282

17. Reproduction of part of a topographic map.________________ 282

18-23. Standard map symbols.-._...__________________ 282

24. A single-lens camera______ _______________ ________ 382

25. T-2 camera: A, Rear view; B, front view______________ 382

26. T-2 camera: A, Focal planes and dark chambers; B, arrangement of lenses____-_____-___-----_-_____-____________- 382

27. The fixed T-2 transforming printer __ ___________ 382

28. Displacement chart_______________--_______-_____________ 390

29. Map compiled from aerial photographs_____________________ 402

in
IV CONTENTS

	Page 

FIGURE 1. Quadrilateral for adjustment by least-square method-____ 70

2. Condition to be introduced in connecting new triangles to those

previously adjusted_____-_______-__-___-_---__________ 78

3. Method of adjusting a level net__________________________ 158

4. Diagram illustrating 1° polyconic projection_______________ 168

5. Diagram illustrating 15' polyconic projection._____________ 171

6. Graphic solution of three-point problem___________________ 203

7. Diagram illustrating correction of base line____________ 210

8. Graphic adjustment of traverse-_________________--___--_ 214

9. Pattern and symbols for designation of forest land________ 260

10. Patterns and symbols for designation of arable land ________ 260

11. Pattern and symbols for designation of grazing land________ 261

12. Diagram showing registration marks for rectangular grid____ 300

13. Lateral field of view of T-l camera____^___-----_--______- 382

14. Nodal points of a double convex lens_____________________ 387

15. Conjugate focal planes________.._____________________ 388

16. Relation of angles on photographic plate to corresponding

angles on the ground._________________________________ 391

17. Displacement of photographic image due to relief ________ 392

18. Displacement of photographic image due to tilt____________ 393
PKEFACE

This manual is intended to replace all former instructions relating 

to the topographic work of the United States Geological Survey and 

to provide a manual of instruction for the personnel of other organizations engaged in topographic surveying. An attempt has been 

made to have these instructions complete so far as the technical work 

of topographic mapping is concerned. General regulations and instructions for the Geological Survey have for the most part been 

omitted, but those relating to fiscal affairs and to a few other important phases of administration have been digested and repeated 

herein.

The manual is issued in several parts, each covering a general 

subject, thus saving public funds by providing a distribution of separate parts to those interested only in one or more of the subjects. 

These several parts have been prepared by the members of the 

topographic branch best qualified for each task, and each part has 

been reviewed and revised by the section chief responsible for the 

administration of that particular part of topographic work.

Each part, except "Administration," has been approved by the 

Board of Surveys and Maps. In fact, all the technical parts have 

been reviewed by a committee of the board and made a part of a 

report of that committee.

Criticism of these instructions, suggestions for their improvement, 

and notice of errors or omissions are invited.

C. H. BlRDSEYE,

Chief Topographic Engineer. 

Approved:

GEO. OTIS SMITH, Director.

WASHINGTON, D. C., June 7, 1926.

v

TOPOGRAPHIC INSTRUCTIONS OF THE

UNITED STATES GEOLOGICAL

SURVEY

A. ADMINISTRATION

Compiled by H. M. FRYE

AUTHORIZATION FOR TOPOGRAPHIC WORK

The United States Geological Survey was created by act of Congress approved March 3, 1879, and the formation of the topographic 

branch was the natural result of the .growth of the organization. It 

was apparent from the beginning that no adequate classification of 

lands or conclusive geologic determinations could be made without 

base maps. Hence in the earlier years the topographic maps were 

made as a part of the general work of the Geological Survey, and 

allotments for the cost of such maps were made from the general 

appropriation.

. APPROPRIATION ACTS

The sundry civil act for the fiscal year 1889 appropriated funds 

for one chief geographer, three geographers, and three topographers. 

These positions were provided for until the end of the fiscal year 

1892. For the fiscal years 1893 to 1924 one chief geographer, one 

geographer, and two topographers were specifically provided for 

under the heading " Scientific assistants," except that for the fiscal 

years 1897 to 1924 the title " chief " was omitted. Beginning with the 

fiscal year 1923 appropriations for the topographic work have been 

made in the Interior Department appropriation act. For the fiscal 

years 1925-1927 the compensations of " scientific assistants" were 

not itemized but were included in a lump sum.

A specific appropriation for topographic surveys was first made in 

the sundry civil act of October 2,1888, for the fiscal year 1889.

Below are quotations from the sundry civil and Interior Department appropriation acts for several years, showing the principal

1
2 TOPOGEAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

changes in the wording of the acts; the intervening acts contain 

changes only in amounts appropriated or slight changes in the wording of the authorizations.

Fiscal year 1889. For topographic surveys in various portions of the United 

States, including the pay of temporary employees in field and in office, the cost 

of all instruments, apparatus, and materials, and all other necessary expenses 

connected therewith, $199,000.

Fiscal yew 1891. For topographic surveys in various portions of the United 

States, $325,000, one-half of which sum shall be expended west of the one 

hundredth meridian.

Fiscal year 1898. For topographic surveys in various portions of the United 

States, $240,000; $60,000 of which shall be expended west of the ninetyseventh meridian in the States of North Dakota, South Dakota, Nebraska, 

Kansas,1 and the Territory of Oklahoma, and at least one-half of the remainder 

shall be expended west of the one hundred and third meridian.

Fiscal year 1891. For topographic surveys in various portions of the United 

States, $175,000, to be immediately available, $35,000 of which shall be expended west of the ninety-seventh meridian in the States of North Dakota, 

South Dakota, Nebraska, Kansas, Texas, and the Territory of Oklahoma, and 

at least one-third of the remainder shall be expended west of the one hundred 

and third meridian: Provided, That hereafter in such surveys west of the 

ninety-fifth meridian elevations above a base level located in each area under 

survey shall be determined and marked on the ground by iron or stone posts 

or permanent bench marks, at least two such posts or bench marks to be 

established in each township or equivalent area, except in the forest-clad and 

mountain areas, where at least one shall be established, and these shall be 

placed, whenever practicable, near the township corners of the public-land surveys ; and in the areas east of the ninety-fifth meridian at least one such post 

or bench mark shall be similarly established in each area equivalent to the 

area of a township of the public-land surveys.

Fiscal year 1898. For the survey of the public lands that have been or may 

hereafter be designated as forest reserves by Executive proclamation, * * * 

and including public lands adjacent thereto, which may be designated for survey 

by the Secretary of the Interior, $150,000, to be immediately available; * * * 

The surveys herein provided for shall be made under the supervision of the 

Director of the Geological Survey, * * * and if subdivision surveys shall 

be found to be necessary, they shall be executed under the rectangular system, 

as now provided by law. The plats and field notes prepared shall be approved 

and certified to by the Director of the Geological Survey, and two copies of 

the field notes shall be returned; * * * and twenty photolithographic 

copies of the plat shall be returned, * * * the original plat and other 

copies * * * shall have the facsimile signature of the Director of the 

Survey attached. * * * Provided, however, That a copy of every topographic map and other maps showing the distribution of the forests, together 

with such field notes as may be taken relating thereto, shall be certified thereto 

by the Director of the Survey and filed in the General Land Office.

Fiscal year 1900. For topographic surveys in various portions of the United 

States, $240,000, to be immediately available; 2

1 In subsequent years Texas was included.

2 For 1913 and 1916 the words " to be immediately available" were eliminated, and 

for 1914 and 1915 the words " one-half to be immediately available " were included.
ADMINISTRATION 6

For continuation of the survey 8 of the public lands that have been or may 

hereafter be designated as forest reserves,4 $130,000, to be immediately 

available.2

And provided further, That hereafter all standard, meander, township, and 

section lines of the public-land surveys shall, as heretofore, be established 

under the direction and supervision of the Commissioner of the General Land 

Office, whether the lands to be surveyed are within or without reservations, 

except that where the exterior boundaries of public forest reservations are 

required to be coincident with standard, township, or section lines such boundaries may,-if not previously established in the ordinary course of the publicland surveys, be established and marked under the supervision of the Director 

of the United States Geological»Survey whenever necessary to complete the 

survey of such exterior boundaries.

Fiscal year 1911. For topographic surveys in various portions of the United 

States, $350,000: Provided, That in expending this sum preference shall be 

given special topographic surveys of areas selected by the War Department 

and in securing such extra topographic data as are requested by the War 

Department in these or other areas;

For continuation of topographic surveys of the public lands that have been 

or may hereafter be designated as national forests, $75,000.

Fiscal year 1920. For topographic surveys in various portions of the United 

States, including lands in national forests, $325,000.

Fiscal year 192^. For topographic surveys in various portions of the United 

States, including lands in national forests, $500,000: Prowled, That no part of 

this appropriation shall be expended in cooperation with States or municipalities except upon the basis of the State or municipality bearing all of the expense incident thereto in excess of such an amount as is necessary for the 

Geological Survey to perform its share of standard topographic surveys.

Fiscal year 1926. For topographic surveys in various portions of the United 

States, including lands in national forests, $485,000, of which amount not to exceed $305,900 may be expended for personal services in the District of Columbia : Provided, That no part of this appropriation shall be expended in cooperation with States or municipalities except upon the basis of the State 

or municipality bearing all of the expense incident thereto in excess of such an 

amount as is necessary for the Geological Survey to perform its share of 

standard topographic surveys.

Fiscal year 1927. For topographic surveys in various portions of the United 

States, including lands in national forests, $451,700, of which amount not to 

exceed $267,000 may be expended for personal services in the District of Columbia : Provided, That no part of this appropriation shall be expended in cooperation with States or municipalities1 except upon the basis of the State or 

municipality bearing all of the expense incident thereto in excess of such an 

amount as is necessary for the Geological Survey to perform its share of standard topographic surveys, such share of the Geological Survey in no case exceeding 50 per cent: Provided further, That $372,200 of this amount shall be 

available only for such cooperation with States or municipalities.

2 See footnote 2, p. 2.

8 For 1909 arid subsequent years this wording was changed to " topographic survey."

* For 1910 and subsequent years this wording was changed to " national forests."
4 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

DEFICIENCY ACTS

The Geological Survey has had only two deficiency appropriations 

for topographic surveys. The deficiency act of July 28,1892, carried 

the following appropriation:

Geological Survey: For topography east of one hundredth meridian, 

fiscal year 1891, $3,818.87; for topography west of one hundredth 

meridian, fiscal year 1891, $754.51____________________ $4, 573.38

The first deficiency act for the fiscal year 1926, approved March 3, 

1926, contained the following provision:

United States Geological Survey. For topographic surveys in various portions of the United States, including the general objects of expenditure enumerated in the second paragraph under the caption " United States Geological 

Survey," in the Interior Department appropriation act for the fiscal year 

1926, and including not to exceed $33,000 for personal services in the District 

of Columbia, fiscal year 1926, $73,300, to be expended in cooperation with 

States or municipalities on standard topographic surveys and on a basis on 

which the share of the Geological Survey shall in no case exceed 50 per cent.

TEMPLE ACT

Since the war engineers and others have demanded more rapid 

progress in the completion of the standard topographic map. This 

interest resulted in the passage by the Sixty-eighth Congress of 

what is known as the Temple Act, approved February 27, 1925, 

which is as follows:

AN ACT To provide for the completion of the topographical survey of the United States.

Be it enacted, "by the Senate and House of Representatives of the United 

States of America in Congress assembled, That the President be, and hereby 

is, authorized to complete, within a period of twenty years from the date of 

the passage of this act, a general utility topographical survey of the territory of the United States, including adequate horizontal and vertical control, 

and the securing of such topographic and hydrographic data as may be required for this purpose, and the preparation and publication of the resulting 

maps and data: Provided, That in carrying out the provisions of this act the 

President is authorized to utilize the services and facilities or such agencies 

of the Government as now exist or may hereafter be created, and to allot to 

them (in addition to and not in substitution for other funds available to 

such agencies under other appropriations or from other sources) funds from 

the appropriation herein authorized, or from such appropriation or appropriations as may hereafter be made for the purpose of this act.

SEC. 2. That the agencies which may be engaged in carrying out the provisions of this act are authorized to enter into cooperative agreements with 

and to receive funds made available by any State or civic subdivision for the 

purpose of expediting the completion of the mapping within its borders.

SEC. 3. The sum of $950,000 is hereby authorized to be appropriated out of 

any moneys in the Treasury not otherwise appropriated, to be available until 

the 30th day of June, 1926, for the purpose of carrying out the provisions of 

this act, both in the District of Columbia and elsewhere as the President may 

deem essential and proper.
ADMINISTRATION 5

COOPERATION WITH WAR DEPARTMENT ON SPECIAL. 

MILITARY INFORMATION

First agreement. On January 12, 1905, an agreement was approved by the Secretary of the Interior and the Secretary of War 

designed to make the topographic maps of the Geological Survey 

more useful to the War Department. This agreement provided that 

the Geological Survey should show on its topographic maps resulting 

from new surveys or resurveys the location and extent of timbered 

areas, of important railroad cuts and embankments, and of important 

arroyos, and should furnish to the War Department one photolithographic copy of each new topographic map on which the following special military information should be lettered by appropriate 

and authorized abbreviations: Whether streams are fordable or unfordable; the width, depth of water, character of bottom, and 

height and steepness of banks of all unfordable streams at points of 

crossing; the length, kind, character of material, and height above 

water of wagon and railroad bridges over the unfordable streams; 

the location of the highest points of hills and ridges; the nature of 

ferries; and the location of mills, waterworks, and roundhouses.

Second agreement. The photolithographic maps furnished under 

the first agreement did not prove satisfactory to the War Department, and on October 14, 1911, a second agreement was approved 

by the Secretary of the Interior and the Secretary of War, which 

provided that the Geological Survey should issue a special War 

Department edition of 100 copies of each topographic map published 

on a scale of 1:62,500 or larger, on which should be printed the 

special military information previously requested, together with the 

location of blacksmith shops, permanent post-office buildings, 

churches, and schoolhouses.

The agreement also provided that the Geological Survey should 

concentrate its topographic mapping efforts on those unmapped areas 

of the United States along the. coasts and borders, and should comply, so far as practicable, with requests made by the War Department to give priority to work in areas of which maps were needed 

for military purposes. The War Department agreed to obtain 

annual appropriations of about $60,000 to reimburse the Geological 

Survey for this additional work, but the first of these appropriations was not approved until July 1, 1916, and was carried in the 

sundry civil act for 1917, as follows:

Topographic maps, War Department. For reimbursing the United States 

Geological Survey for expenses incurred in making special topographic surveys of areas selected by the War Department, and for additional expenses 

incurred in securing such extra topographic data as are requested by the War 

Department in these or other areas, and engraving and printing the same on 

atlas sheets of the United States Geological Survey, $35,000: Provided, That
the Secretary of War is authorized to advance from this appropriation to the 

United States Geological Survey such sums as the Secretary of the Interior 

may request.

This agreement remained in effect until after the end of the World 

War, and the Geological Survey delivered to the War Department 

special military editions of its topographic maps, each accompanied 

by a confidential report containing military information.

During the World War the topographic branch of the Geological 

Survey gave its entire attention to special military surveys, and the 

importance of topographic mapping was emphasized as a matter of 

vital military necessity.

Since 1917 appropriations have been made in War Department 

acts under the heading " Military surveys and maps," and funds have 

been allotted from such appropriations to repay the Geological Survey for topographic surveys requested by the War Department.

Third agreement. In 1920 the War Department adopted the 

standard topographic maps of the Geological Survey as the tactical 

maps for the use of the Army, and a third agreement between the 

Secretary of the Interior and the Secretary of War canceled the 

former agreements and authorized the abandonment of the collection by the Geological Survey of confidential military information.

This agreement provided that the Geological Survey should show 

on its standard topographic maps a classification of highways and 

highway bridges and the rectangular grid adopted by the Army 

and should furnish to the War Department 200 copies of each 

standard topographic map published thereafter.

The agreement also provided that the War Department would, 

except in emergency, cease publication of progressive military or

tactical maps of areas mapped by the Geological Survey, and would 

concentrate its topographic mapping in the continental United States 

to special military surveys, to quadrangle mapping of areas not 

mapped by the Geological Survey, and to the revision of old maps.

The agreement further provided that the War Department would 

allot to the Geological Survey not less than 50 per cent annually of 

its appropriation for military surveys and maps, to be expended 

on topographic surveys of such areas as were mutually agreed upon.

Fourth agreement. In 1926 a fourth agreement was approved by 

the Secretary of the Interior and the Secretary of War replacing all 

former agreements. This agreement embodied the principal features 

of the third agreement with the following exceptions: Provision was 

made that the Geological Survey would furnish the War Department 

with 300 instead of 200 copies of each standard topographic map 

published by the Geological Survey, credit to be applied to the War 

Department's quota for the number of copies not delivered and all 

requests for maps to be made through the Chief of Engineers.
ADMINISTRATION 7

The agreement provided that the Corps of Engineers would allot 

to the Geological Survey not less than $12,500 annually from its 

appropriation for military surveys and maps.

Provision was also made to add the Harriman index number of 

the quadrangle to each topographic map if the use of that system is 

approved by the Board of Surveys and Maps.

The following is an extract from the War Department appropriation act of 192T:

Military surveys and, maps. For the execution of topographic and other 

surveys, the securing of such extra topographic data as may be required, and 

the preparation and printing of maps required for military purposes and for 

research and development of surveying by means of aerial photography and in 

field reproduction methods, to be immediately available and remain available 

until December 31, 1927, $80,000: 5 Provided, That the Secretary of War is

authorized to secure the assistance, wherever practicable, of the United States 

Geological Survey, the Coast and Geodetic Survey, or other mapping agencies 

of the Government in this work and to allot funds therefor to them from this 

appropriation.

STATE COOPERATION

In addition to funds appropriated direct to the Geological Survey 

and allotments made by the War Department, the Geological Survey 

has, since the fiscal year 1885, engaged in cooperation with many 

States and their subdivisions,- the States paying part (usually half) 

of the expense of topographic mapping. For the fiscal year 1927 

the several States have allotted $378,791.88.

On page 36 is a table showing by fiscal years the funds made available for topographic mapping from all sources, and on pages 29-35 

detailed information in regard to such cooperation.

ORGANIZATION OF THE TOPOGRAPHIC BRANCH

The topographic branch is organized under the direction of a 

chief topographic engineer into three field divisions (Atlantic, Central, and Pacific), each of which is in charge of a division engineer.

The Atlantic division is subdivided into the New England, Middle Atlantic, South Atlantic, and Ohio Valley sections; the Central 

division into the Great Lakes, Missouri Valley, Bed Kiver, and 

Rocky Mountain sections; and the Pacific division into the North 

Pacific, South Pacific, Salt Lake Basin, and Hawaiian sections. 

Each section is in charge of a topographic engineer.

The office work is both administrative and technical in character.

The administrative work is handled by a chief clerk allocated to 

clerical, administrative, and fiscal service, grade 7, assisted by clerical employees ranging from grades 5 to 2.

B Of this amount $12,500 was allotted to the Geological Survey.
8 TOPOGRAPHIC INSTRUCTION'S OF GEOLOGICAL SURVEY

Technical office work is divided into five sections computing, 

inspection and editing, cartography, photographic surveying, and 

relief mapping and each section is in charge of a topographic 

engineer in professional and scientific service, grade 4, or an associate 

engineer in professional and scientific service, grade 3. The personnel of each of these sections is made up of professional, subprofessional, and clerical employees of various grades.

The members of the technical force, with headquarters at Washington, D. C., and those with headquarters in the field, are classified 

in professional, subprofessional, and field grades as follows:

Associate engineers. -.._. _ .... ___ : __ ... __ ..

Junior engineers ____________________

Senior engineering aids _________________

Assistant engineering aids _______________

District of Columbia 

classification

P. andS.-5 _ ........

P. and S.-4-. ......I..

P. and S.-3 ____ ...

}p.andS.-2orS.P.-8._

|P. and S.-l or S. P.-3._

S. P.-4................

S. P.-2..... ...........

Field 

classification

F.-16..-

F.-15....

F.-13. 

F.-ll....

F.-9.....

F.-7.....

F.-5.....

Range of 

salaries

$5, 200-$6, 000

5, 200- 6, 000

3, 800- 5, 000

3, 000- 3, 600

2, 400- 3, 000

1, 860- 2, 400

1, 500- 1, 860

1, 140- 1, 500

Promotions within the grades are made by the Department of 

the Interior on the basis of efficiency ratings, but reallocations to fill 

vacancies in a different grade require the approval of the Personnel 

Classification Board.

Entrance into the engineering aid group has been made through 

certification by the Civil Service Commission after the applicant 

passed an examination for topographic aid, No examination for this

position has been held since 1924, and no new appointments in the 

engineering aid groups are contemplated. ^Those who entered the 

service through the examination for topographic aid in 1924 are not 

eligible for promotion above $1,800 without qualifying for the professional service.

Entrance into the professional grade is made through certification by the Civil Service Commission after the applicant has passed 

the technical examination for junior topographic engineer. This examination is usually held yearly, during the college spring-vacation 

period, and one of the necessary requirements is a degree in civil engineering from an institution of recognized standing. Engineers with 

the proper qualifications and civil-service status may be transferred 

to the professional grade from other departments, providing there 

are vacancies.

PUBLICATIONS

The published results of the work of the topographic branch are 

maps and geodetic reports. The office work consists principally of
ADMINISTRATION 9

computing and adjusting field observations, inking and drafting field 

sheets, and inspecting and editing maps for final publication. The 

engraving and printing of these maps is done by the division of 

engraving and printing, another unit of the Geological Survey.

GENERAL. OFFICE INSTRUCTIONS

Travel authorization. Every permanent man must have a travel 

authorization before leaving for the field, the number and date of 

which must be shown on all vouchers claiming expenses for travel or 

per diem.

Letters of instruction. At the beginning of the field season and at 

the completion of an assignment, letters of instruction are issued to 

permanent men in regard to their field work. Authority for purchases or repairs exceeding $100, for the employment or promotion 

of temporary assistants, and for the delivery of camp outfits, animals, or automobiles is also given when necessary.

Miscellaneous instructions. Before leaving the Washington office 

for an assignment, field men should turn in all office instruments and 

map material, clear their desks and map file cases, submit a report 

of their office work, send address cards to the new post offices, and 

report to their division engineers that they have carried out these 

instructions.

ORGANIZATION OF FIELD PARTIES 

CLASSIFICATION

The chief topographic engineer is responsible for the administrative and technical control of all the work of the topographic branch, 

acting under the general supervision of the Director.

The division engineers are responsible for all the technical and 

administrative work of their respective divisions, acting under the 

general supervision of the chief topographic engineer.

Topographic engineers in charge of sections exercise such specific 

technical and adminstrative control over the employees of the section as may be delegated to them by the division engineer. The 

technical supervision is usually close and specific; the administrative supervision is more general.

The party chiefs are usually in the grade of associate engineer, 

and they exercise immediate supervision over the members of their 

parties under the general or specific instructions of the section and 

division chiefs. Under some conditions engineers of lower grades 

act as party chiefs, but usually the sequence of work and authority 

is graded down to the lowest engineering aid, and the entire field 

party, in charge of an associate engineer, is made up of one or more 

employees of each lower grade. Kecorders, rodmen, chainmen, packers, teamsters, chauffeurs, and cooks are in the unclassified service 

and are employed as temporary assistants.
10 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY 

EMPLOYMENT OF TEMPORARY ASSISTANTS

Applications. Persons desiring temporary employment as rodmen, recorders, chainmen, etc. (grade 1), must file applications, on 

the form provided for that purpose, with the chief topographic 

engineer in Washington. Appointments will be made by the section 

or party chiefs from the list of applicants on file as vacancies occur 

in field parties, preference being given to former employees of the 

Survey whose services have been satisfactory and who are endeavoring to prepare themselves for civil-service examination for the grade 

of junior topographic engineer; to applicants who are available for 

the entire field season (usually April 15 to November 15); to residents of States in which service is to be performed; to other applicants in order of priority of application and fitness for the work.

Applicants for grade 1 must be free from all contagious diseases 

and qualified for rigorous outdoor work and must be between the 

ages of 20 and 40 years. The rate of pay for initial employment is 

$110 to $120 a month, the employee paying his own subsistence expenses and his traveling expenses to and from the place of employment.

Laborers, chauffeurs, teamsters, packers, and cooks (grade 2) are 

employed by the party chiefs as the necessity may arise.

Letters of employment. Before entering upon his field duties every 

temporary employee must sign an agreement specifying the terms of 

his employment, and the party chief must forward this letter of employment immediately to the section chief or division engineer for 

approval and transmittal to the chief topographic engineer. Salaries for more than one week's services can not be paid until letters 

of employment are on file. Temporary employees hired in connec- 

^ion with their automobiles should sign letters of employment. Application cards should be made out by temporary employees hired in 

the field and should be submitted with their letters of employment.

FIELD ADMINISTRATION

Field insurance. As no leave of absence is given to temporary employees in the field, whether employed by the month or by the day, 

their pay stops immediately if they become incapacitated by reason 

of accident or sickness. In order that other members of a party may 

not be called on to bear the expenses entailed by sickness or accident 

of one member, chiefs of parties are instructed to urge all employees 

to take out insurance. To provide this insurance at the lowest possible rate a mutual-benefit association has been formed by members of 

the Geological Survey and other Government bureaus. This association exists solely for the purpose of giving health and accident insurance to field men at cost and of preventing unnecessary burdens
ADMINISTRATION ll

from falling on the immediate associates of those disabled. Information concerning membership may be obtained from chiefs of parties.

Right to compensation for personal injuries. Under the Federal 

compensation act of September 7, 1916, all civil employees of the 

United States are entitled to compensation for injuries sustained in 

the performance of duty which cause disability to perform work for 

a period of more than three days. The act also provides for the payment of certain expenses incurred for medical and hospital attention resulting from such injuries.

The act provides no benefits for sickness not due to injuries, but an 

amendment, approved June 6, 1924, provides that compensation shall 

be paid for occupational diseases or " any disease proximately caused 

by the employment."

The mere fact that disease develops after the employee enters 

Government service can not be accepted as sufficient basis for an 

award of compensation; direct causal relationship of the employment must be shown, and common diseases, such as colds, pneumonia, 

tuberculosis, typhoid fever, or rheumatism, which may be and usually 

are due to causes entirely outside the employment, can rarely and 

only under the most unusual conditions be the basis of an award 

under this act.

Section 20 of the compensation act provides that original claims' 

for compensation for disability shall be made within 60 days after 

the injury, but for any reasonable cause the commission may allow 

such claims to be made at any time within one year. All original 

claims for compensation for death shall be made within one year 

after death.

Chiefs of parties should provide themselves with a copy of " Regulations concerning duties of employees, official supervisors, medical 

officers, and others," a printed list showing the location of all designated medical officers, hospitals, and dispensaries, and blank forms 

for reporting injuries and filing claims for compensation in compliance with the regulations.

In case an employee is injured in a section of the country where no 

United States medical officer or hospital is located, and there is no 

physician designated for that vicinity in the printed list issued by 

the commission, a local physician may be employed. (See the regulations above cited, p. 36, pars. 93-98.)

The chief topographic engineer should be notified immediately in 

regard to every injury resulting in death, or in any loss of time, or 

in any expenditure for medical, surgical, or hospital services or 

supplies. These reports should not be omitted in cases in which 

the time lost was covered by annual or sick leave or in which no 

claim for compensation is contemplated.

58515° 28 2
12 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

The blanks covering the employee's injury and claim for expenses 

should be properly filled out in the field and forwarded to the 

chief topographic engineer for transmittal to the Employees' Compensation Commission.

Typhoid-fever prevention. Field men are more liable to contract 

typhoid fever than any other disease. It is therefore urged that 

everyone who has not already had that disease protect himself 

against it by inoculation with any antityphoid serum or " vaccine " 

as prepared and administered by the United States Army surgeons. 

This prophylactic will be administered without charge to .anyone 

applying in person to the designated officers of the Public Health 

Service in each State. (See Treasury Department Circular, Public 

Health Service, November 24, 1922.)

Farmers' Bulletin 4T8, United States Department of Agriculture, 

gives valuable suggestions on means of avoiding typhoid fever and 

the use of the prophylactic for its prevention.

Care of public property. Chiefs of parties will be held responsible 

for the public property intrusted to their care and are expected to 

see that it receives no rougher usage than conditions necessitate.

Pv/rchase of property in -field. Every article of property which 

appears on a voucher as having been purchased and which is not 

' expendable must be accounted for on the returns to the custodian. 

In cooperating States separate Federal vouchers for such articles 

must be submitted for payment. Those in direct charge of property 

should be prepared to make a statement to the custodian as to its 

condition and the amount on hand. Animals, tents, wagons, and 

property of considerable value must not be purchased without 

authority from the division engineer. Animals purchased must be 

reported on Form 9-061.

Storage. In arranging for the care of field property at the end 

of a season efforts should be made to store it near a main line of 

railway; if possible, in a fireproof building.

Contracts for storage, etc. If the total storage charge estimated 

for the winter season will not exceed $100, it is only necessary to 

have a record of the transaction that will place some obligation 

on the .caretaker. Three copies of " Receipt, proposal, and acceptance," for storage or pasturage (Form 9-007 or 9-008) must therefore be prepared, one copy to'be delivered to the caretaker and two 

to be sent to the chief topographic engineer through the division 

engineer.

The following requirements must be observed if the total charge 

for storage, or the other services indicated, will exceed $100:

1. A contract must be entered into for continuing services such 

as pasturage and storage, hire of team or automobile not employed 

in connection with services of individual, hire of horses, hire of
AD'MINISTEATION 13

room for office or storage, and all other continuing services other 

than personal when the total payments for the fiscal year will exceed 

$100. Field men must determine whether or not the payments will 

run above this figure and act accordingly.

2. If it is found that a contract will be necessary, bids for the 

service must be obtained from three or more dealers if possible; 

the lowest bid is to be accepted if satisfactory, and a contract entered 

into. The contract must be sent to the Washington office for approval. If the lowest bid is not accepted, a detailed statement of the 

reasons for accepting a higher bid must accompany the contract.

3. The short-form contract should be submitted in quadruplicate, 

two copies to be signed by the contractor and a third to bear the 

"Oath of disinterestedness." After approval, one of the signed 

copies will be returned to the contractor by the Washington office.

4. If no competition is available and a contract is necessary, it 

may be entered into with the only available dealer, but a statement to that effect should accompany it, and each voucher covering 

payment for the service should indicate by the symbols "4(c)" that 

there was only one contractor from whom the service could be obtained, and by "A" under " Form of agreement" that a contract has 

been entered into.

5. Day-to-day purchases of oil and gasoline and repairs to automobiles are not continuing services, and therefore the only limitation 

to such transactions is that no daily purchase or repair bill may exceed $100 without a formal contract. Vouchers must not be split in 

order to avoid the necessity of entering into a formal contract.

All contracts for continuing service, except personal employment, 

should be renewed at the beginning of the fiscal year.

Prior authority should be procured from the chief topographic 

engineer for all expenditures in excess of $100 and from the Director 

for all in excess of $500.

Inventories. When nonexpendable property is stored a detailed 

inventory (Form 9-054) stating the condition of each article must 

be made and forwarded to the chief topographic engineer. Keports 

on condition and transfer of automobiles and of livestock should be 

made at the same time. When property, automobiles, or animals -are 

removed from storage or pasturage, inventories and proper reports 

should be made in triplicate, one copy to be retained by the field man, 

one copy to be delivered to the caretaker, and one copy to be mailed 

to the branch chief clerk for transmission to the division of field 

equipment. At the end of a field season an inventory on Form 

9-445-b must be made of all property charged against the party 

chief by the division of field equipment since the beginning of the 

year that has not been previously reported.on this form. All prop-
14 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

erty that is being returned, held, transferred, or stored or that has 

been lost should be included.

Transfer of property. When equipment is transferred from one 

field man to another an inventory of property (Form 9-054) should 

be made out; for automobiles Form 9-057 should be used, and for 

livestock Form 9-061. Instruments and other property should be 

recorded on Forms 9-139 and 9-455-b. All these reports should be 

transmitted to the branch chief clerk.

Sale of property. Survey property can be sold only at public 

auction (see instructions in par. 74, fiscal regulations) ; an inspection report on Form 9-047 and authorization from the Director are 

required before the sale is held. When so authorized, unserviceable 

passenger-carrying vehicles may be exchanged as part payment for 

new passenger-carrying or freight-carrying vehicles, but unserviceable freight-carrying vehicles may be exchanged only for new 

freight-carrying vehicles.

Abandonment of property. If property is so unserviceable that 

the expense of holding an auction sale of it is unwarranted, it may 

be abandoned after submitting an inspection report (Form 9-047) 

and obtaining the approval of the Director. (See p. 18 for instructions concerning abandonment of automobiles.)

Lost or stolen property. If any Government property is lost or 

stolen, a report must be made promptly on Form 9-445-b and explained fully on Form 9-048; Form 9-061 should be used for livestock, and reasonable charges for recovering animals are allowed.

Returned property. All property that is being returned to the 

division of field equipment must be reported in triplicate on Form

9-445-b ; no property will be accepted or credited until this signed 

form has been received. This report should be sent along with the 

bill of lading to the branch chief clerk ; it must not be inclosed in the 

boxes shipped.

CAMP ADMINISTRATION

If camp outfits are used, their character should be determined by 

the size of the party, the means of transportation, and the nature of 

the work. The party chief should insist on punctuality, order, and 

neatness. Proper discipline is absolutely essential to efficiency.

A United States flag and a Geological Survey pennant must be displayed over each camp.

Camp sites should be carefully selected and the tents arranged in 

definite order and not at random. Wagons and other vehicles should 

be parked on one side. Harness, saddles, etc., should be kept off the 

ground and either hung on racks or placed in the wagons. Anirv.ls 

should be corralled at a sufficient distance from the tents to

them from interfering with comfort and sanitation. The camp
ADMINISTRATION 15

should be kept neat at all times; no loose articles, papers, or refuse 

should be allowed to litter the grounds.

Chiefs of parties should formulate sanitary regulations for camp 

administration adapted to the locality and should see that they are 

rigidly enforced. Promiscuous drinking from streams, failure to use 

boiled drinking water, .carelessness in selecting camp sites, inadequate 

provision for the disposal of refuse, failure to observe sanitation in 

the arrangement of toilet facilities, insufficient screening from flies, 

and failure to use mosquito netting in malarial districts are responsible for most of the sickness in camp. (See " Typhoid-fever prevention," p. 12.)

Subsistence. The Geological Survey allows a per diem in lieu of 

subsistence for camp parties. The following ration list is recommended as a general guide. Experience has shown it to be ample in 

amount for all essential articles.

Ration list for topographic Held parties 1

[100 rations]

Fresh meat, including fish and poultry________pounds 100

Cured meat, canned meat, or cheese___________do__ 50

Lard ____________do__ 15

Flour, bread, or crackers ________________do__ 80

Cornmeal, cereals, macaroni, sago, or cornstarch___do__ 15

Baking powder or yeast cakes_______________do__ 5

Sugar _ _ _do__ 40

Molasses __ _____ _gallon 1

Coffee __pounds__ 12

Tea, chocolate, or cocoa__ _______________do__ 2

Milk, condensed ______________cans_ 10

Butter _ __pounds__ 10

Dried fruit____ ___ ________________do__ 20

Eice or beans ____ __do____ 20

Potatoes or other fresh vegetables____________do__ 100

Canned vegetables or fruit ____ _ __cans__ 30

Spices ___ ounces 4

Flavoring extracts_ _ _ _ do 4

Pepper or mustard do 8

Pickles_____ _ __ quarts 3

Vinegar _____ _ __ quart 1

Salt __________ -__ pounds 4 

Miscellaneous items:

Soap______ __ bars 12

Sapolio__ cans 4

Matches_____-_ _ - boxes 24

Candles ___________-______ dozen 4

Paper lunch bags _ 100

Kerosene gallons 15

1 The following substitutions may be made: 8 eggs for 1 pound of meat; 5 pounds of 

fresh meat for 2 pounds of cured meat; 5 quarts of fresh milk for 1 can of condensed 

milk; 5 pounds of fresh fruit for 1 pound of dried fruit; 3 pounds of fresh vegetables 

for 1 pound of dried vegetables.
16 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

Rations for stock. For stock the following ration may be used 

as a basis for estimate:

Daily ration, in pounds, for stock

Heavy horses.. ________________________________

Oats 0

12

10

Corn"

15

12

Hay

24

20

"The rations of oats and corn are substitutes for each other.

Camp equipage. In order to facilitate field work in regions where 

camping is necessary or desirable, parties will be furnished with complete camp equipage, including tents, stoves, camp furniture, mess 

and cooking outfits, as well as means of transportation, such as 

wagons, automobiles, and other vehicles, harness, riding saddles, 

packsaddles, and necessary accessories.

Camp beds. When necessary, a camp bed, consisting of one folding cot, two lamb's wool comforts, one woolen double blanket, one 

pillow, and one canvas bed cover, will be supplied for each permanent employee, on properly approved requisition through the Washington office. Temporary employees must furnish their own beds 

except on special field trips in which standardization of equipment 

is required.

Care of camp property. As wear of camp property results mostly 

from carelessness in packing, loading, and transporting when camp is 

moved, party chiefs should take pains to instruct their assistants as 

to proper methods of handling it. Wagons should be painted and 

harness should be oiled as often as is necessary to keep in good condition. The teamster should be required to give proper attention to 

these details.

Storing and pasturing. Storing should be done with order and 

system. The materials should be placed in boxes, the boxes numbered, and lists made of the articles in each box. The boxes should 

be securely packed and nailed, so that, if necessary, they may be safely 

shipped by rail. When wagon outfits are used the boxes may be left 

on the wagons ready to haul away. Precautions must be taken to 

protect property against dampness and rodents. Tents, harness, 

blankets, etc., must be thoroughly dried before packing; otherwise 

they will be ruined by mildew. Axles of vehicles must be cleaned 

with coal oil and well covered with axle grease. Cooking utensils 

and tableware must not be packed unwashed but must be thoroughly 

cleaned and dried. No food, matches, or grain should be stored.

Chiefs of parties must exercise great care in selecting proper localities and responsible caretakers for public animals to be placed in 

pasturage. Shelter, water, and character of forage, as well as the 

reliability of the caretaker, should govern selection. All shoes should
ADMINISTRATION 17

be removed, and an inventory and a complete description of all 

animals should be made before they are delivered to the caretaker. 

(See "Inventories," pp. 13-14; "Contracts for storage," pp. 12-13.

Entertaining persons in camp. Chiefs of parties and all other 

employees of the Survey are cautioned against entertaining in camp, 

when on field duty, any persons in a manner calculated to interfere 

with public business or to entail public expense.

Personal baggage. Personal baggage should consist of essentials 

only and should be carried in canvas bags, suit cases, or locker trunks. 

Large trunks should not be taken to camp, except where they can be 

readily transported by wagon or rail,

GENERAL INFORMATION

AUTOMOBILES

Pwchase of automobiles. Automobiles must not be purchased 

without authority from the chief topographic engineer. A report 

on Form 9-057 of the engine and body numbers, make and type of 

car, Survey identification tag number, and date and place purchased must be made for new automobiles.

Purchase of automobile tires and tubes. Chiefs of parties should 

anticipate their needs for tires and tubes for each quarter and be 

prepared to order them through the division engineer when a call 

for a definite quantity order is made. Vouchers in payment of 

emergency purchases in the field must be accompanied by a brief 

note addressed to the division engineer, explaining the emergency 

purchase and giving the reason why these supplies were not procured 

from the Washington office.

Identification tags for Survey automobiles. When automobiles 

are purchased a set of tags bearing a Survey number are sent from 

the Washington office and should be attached to the machine. Paper 

Survey emblems, one to be attached on each side of the car, are also 

furnished. All Geological Survey automobiles must carry Survey 

emblems as well as tags, and request should be made for them if 

they are not already on the car. In placing emblems on the car 

a light coat of shellac or varnish for outside protection is desirable. 

Unnumbered tags to replace lost or defaced tags will be sent upon 

request, the same number to be painted on them.

State licenses. The United States Government does not recognize 

the right of State officers to enforce State laws so as to require 

Federal employees (including temporary employees) to submit to an 

examination or to obtain State permits to perform their official 

duties. (See Supreme Court decision 289, October term, 1920.) 

This policy applies to drivers' licenses and State registration tags. 

Some States furnish without charge special Federal registration tags,
18 TOPOGBAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

and tags so furnished should be carried on Survey cars, but one of 

the Survey identification tags should also be fastened inside the car. 

If a Survey employee is arrested for failure to have a State driver's 

license or a State registration tag, the fact should be reported to 

the nearest United States district attorney and to the chief topographic engineer. The Survey will not condone violations of traffic 

regulations and will take proper disciplinary measures if such violations are reported. Every driver of a Survey car is expected to be 

capable of handling it and to observe all local traffic regulations.

Care of automobiles. Survey automobiles are intended for official 

use only. Repairs should be made promptly and with as little time 

lost to field work as practicable. All parts requiring oil or grease 

must be examined frequently, and all bolts and nuts must be kept 

tight. Radiators should be kept full of water, and attention must 

be given to storage batteries every 10 days.

Maintenance-cost record for automobiles. A cost record is being 

kept on all cars purchased since January 1, 1926. Field engineers 

will keep a supply of automobile maintenance account blanks (Form 

7876) and from them must compile a monthly automobile cost 

sheet in duplicate, one copy being forwarded to the Washington 

office and one copy being retained for future use. The cost sheet 

should show the total quantity and total cost of each item of expense. 

From these records the upkeep cost per mile will be computed in the 

Washington office. To obtain accurate mileage records it is necessary that speedometers on all cars purchased since January 1, 1926, 

be kept in good adjustment.

Storage of automobiles. Automobiles should be stored in a fireproof building. Air should be let out of tires, if necessary, and the 

cars jacked up. Storage batteries should be taken out and provision 

made for recharging them monthly. A single contract should be 

made for all Survey cars in the vicinity at a rate of so much per car 

per month, so that cars can be added or withdrawn without necessitating a change in contract. (See " Contracts for storage," pp. 12-13.)

Abandonment of automobiles. If an automobile is so unserviceable that the expense of holding an auction sale of it is unwarranted, 

it may be abandoned after submitting an inspection report (Form 

9-047) and obtaining the approval of the Director. Serviceable 

parts should be taken out for use on other machines. When engines 

are interchanged, a report must be made, giving correct numbers. 

All tags from automobiles that are sold, exchanged, or abandoned 

must be forwarded to the division of field equipment. (See p. 14 

for instructions concerning transfer or sale of automobiles.)

Automobile accidents. Drivers of Geological Survey cars must 

drive carefully. All accidents must be immediately reported to the 

chief topographic engineer. Should, there be a possibility of arrest
ADMINISTBATION 19

or of a suit for damages, complete details should be wired to him, 

and he will request the Department of the Interior to ask the Department of Justice to assign the nearest United States district attorney 

to defend the case. Survey employees should not pay charges for 

damages unless the damages are due to their personal negligence. 

If the claim is considered just, a voucher should be submitted to the 

chief topographic engineer, supported by evidence to show the obligation of the United States, and he will submit it as a claim.

Travel in 'privately owned automobiles. Prior authority must be 

obtained for travel in privately owned automobiles to and from field 

assignments. Requests for such authority should be made to the 

chief topographic engineer. A copy of this authorization or a reference to it must accompany voucher claims for reimbursement for 

expenses thus incurred.

OFFICE BEPORTS

Every day's service of permanent employees, except administrative officers and clerks, must be reported on either an office or a 

field report blank. Each office report must show whether the service 

was performed in the District of Columbia or at a field office. 

Leave of absence preceded and followed by service in the District 

of Columbia should be so charged and entered on the Washington 

office report blank. Leave preceded by service in the District of 

Columbia and followed by service in the field or leave preceded by 

service in the field and followed by service in the District of Columbia should be counted as service in the District of Columbia if taken 

within the District of Columbia or as field service if taken outside. 

Office reports must not cover any service in the field or any travel 

to and from the field. Office reports are used both for work records 

and for pay-roll charges, and they must be so complete that there 

will be no uncertainty as to the amount of work done or the number 

of days spent on each particular job. Each day covered by the 

report should be accounted for, and, if practicable, Sundays, holidays, and leave of absence should be prorated against some particular job for which there is an allotment. However, periods of 

leave of one day or more should be indicated under " Remarks " for 

a check on office leave records.

REPORTS OF FIELD PARTIES

A monthly report is required from each chief of party on the 

topographic, transit-control, or level work done under his direction. 

Reports should be made out in triplicate unless otherwise instructed. 

One copy is sent directly to the chief topographic engineer, one copy 

to the division engineer, and one copy to the topographic engineer
20 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

in charge of the section. Reports should be complete in every detail and should include the names and work of all employees rendering technical service as well as the names and time of all temporary men employed during the month. Absence from duty 

through leave or other causes should be fully reported. Reports 

should be mailed not later than the first day of each month, as a 

summary must be submitted to the Director early in the month. 

At the conclusion of field work reports should be submitted 

promptly and should not be delayed by leave of absence or extended 

travel. The regular monthly form is to be used for topographic, 

triangulation, traverse, and level work, and a separate report must 

be made for each quadrangle and State. Diagrams should be carefully drawn, as they are used to keep the office progress maps up 

to date.

Expenditures for services in the District of Columbia are limited 

by statute, and it is necessary to keep a close check on such services. 

Therefore, reports of field parties must not include service in the 

Washington office or any field office. Travel to and from these offices 

and leave taken on the way should be included on the field report, 

and an office report should be submitted covering the time beginning 

with the day of arrival at the location of the office even though leave 

of absence may be taken at the location of the office before duty is 

begun.

Reports of "transfer of permanent and temporary employees" 

should be submitted to the chief topographic engineer when the 

transfers are made.

A report (Form 9-946) giving the names of the field assistants 

of grades 1 and 2 and the dates of their employment is required of 

all party chiefs. This report is to be made out at the end of each 

field season or on December £1 should field work be continuous. 

Recommendations concerning these temporary employees should be 

transmitted to the chief topographic engineer at the same time.

At the end of the field season a " certificate of users of Survey field 

property " (Form 9-036) should be filled out and transmitted to 

the branch chief clerk.

FIELD NOTEBOOKS AND RECORDS

Party chiefs will be held responsible for plane-table sheets, traverse sheets, field notebooks, and other valuable manuscript data 

until they are delivered to the agent of an express company or the 

registry clerk of a post office and a receipt is obtained. Field sheets 

should be protected from injury or loss and when completed should 

be sent to the proper office by registered mail or express. Should 

any maps or map material be carried to the Washington, office in
ADMINISTRATION 21

personal baggage they must be delivered immediately on arrival to 

the section of inspection and editing for recording. Adjustments or 

corrections should not be allowed to accumulate but should be transferred promptly to the final field sheet. Information sheets, name 

sheets, road-classification sheets, and woodland sheets should be 

examined before leaving the field in order to insure complete data. 

Should maps and records be turned over to a successor in the field 

a receipt covering each item must be obtained. All party records 

and memoranda should be kept up to date and preferably in a separate file or book. Notebooks should usually be forwarded to the 

Washington office by registered mail, addressed to the chief topographic engineer. If duplicate data are entered in separate notebooks the books should be forwarded on different days, so that if 

either set is lost the other may be used. Every effort should be made 

to prevent the possibility of entire loss of results. Under no circumstance should valuable records be forwarded by ordinary mail.

CHANGES OF ADDRESS

All changes of address while in the field or on leave should 

be reported promptly to the chief topographic engineer, division 

engineers, and section chiefs. Arrangements should be made for the 

prompt delivery of mail, express, telegrams, and telephone messages. 

Addresses given on final party pay rolls and other vouchers should 

be correct, so that checks will be sent to the proper points. Individual addresses for members of the party should be given when 

necessary.

LEAVE OF ABSENCE

Permanent employees in the field desiring to take leave at the 

end of the field season should forward the request on Form 1-034 

through their section chief long enough in advance to obtain approval of the request before the beginning of leave status. If the 

exact date is dependent upon the completion of the field work, and 

this date can not be determined in advance, the request should state 

the number of days desired, and when the exact date is known it 

should be communicated to the division engineer, who will insert 

proper dates on the leave request. Telegraphic requests for leave 

can not be charged to the Government.

UNPAID BILLS

Engineers should pay all outstanding bills before leaving the field 

and should make every effort to see that temporary assistants leave 

no unpaid bills.
22 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

VOUCHERS

Engineers assigned to sections should submit all vouchers, reports, 

or other official papers to their section chief, who will forward them 

to the division engineer, unless specific instructions have been given 

to send the originals directly to the division engineer or to the 

Washington office, and copies of the reports and a summary of the 

vouchers to the section chief. Vouchers should be submitted 

promptly at the end of each month, and complete data as to appropriation, allotment, and cost should be entered on the memorandum 

copy. During the last quarter of the fiscal year the voucher should 

be submitted semimonthly. On June 1 an itemized estimate of expenditures for June should be submitted, and on June 16 a revised 

estimate for the last half of the month. All changes to be made on 

the Washington office pay roll should be reported by wire to the 

chief topographic engineer.

Cost records. The entries at the top of a voucher under "Appropriation symbol" and "Allotment" are for the bookkeepers' records 

and not for cost of work records. The field man should enter the 

appropriation and allotment in pencil on the memorandum copy 

of the voucher, and the section topographic engineer will verify 

these entries and stamp the correct entries on both original and 

memorandum copies. Cost records are kept by quadrangles or 

projects with the following entries: Field salaries, miscellaneous 

field expenses, office salaries, and miscellaneous office expenses. All 

salaries and miscellaneous expenditures should be classified as follows : Horizontal control, levels, aerial surveys, and sketching. The 

field engineers must enter this classification on memorandum copies 

of all vouchers, both Federal and State, and on memorandum copies

of transportation requests and bills of lading. Under the heading 

" Salaries " will be entered all temporary salaries and full permanent 

salaries, including the retirement deduction. Under " Miscellaneous 

field expenses " will be entered all other field charges.

Cost records should therefore be entered on accounts by typewriter or in ink, in the following form:

Quadrangle

Flint, Mich.-...... ...................

Field 

salaries

$200. 00

150. 00

350.00

Miscellaneous 

field 

expenses

$50.00

75.00

125.00

Horizontal control

$50.00

50.00

. 100. 00

Levels

$75. 00

50.00

125.00

Sketching

$125. 00

125.00

250.00

Total

$250.00

225.00

475.00

If the voucher covers expenditures on only one quadrangle, omit 

the last line giving totals. If the voucher covers only one class of
ADMINISTRATION 23

work, such as sketching, omit the columns for other classes of work 

and the total column, and mark the sketching column " Total 

sketching."

On Federal vouchers the cost entry will be made in the space for 

" Remarks," or in a party pay roll at the left of the title-page, the 

space marked " Classification summary " being left for a different 

classification which is to be reported to Congress. On State vouchers 

the classification will be made in the body of the voucher, below and 

to the left unless there is a suitable blank space elsewhere on the 

voucher. On memorandum copies of transportation requests and 

bills of lading the cost entry will be made directly below the statement of appropriation and allotment. (See fiscal regulations for 

specimen memorandum copies of vouchers.)

Expenditures for services in the District of Columbia are limited 

by statute, and every voucher, both Federal and 'State, covering payment for services in the District of Columbia, must carry on the 

memorandum copy the added entry " Service in D. C. days, 

$ ." All other pay vouchers should carry the entry " No service in D. C." Leave of absence immediately preceded and followed 

by service in the District of Columbia will be counted as service in 

the District of Columbia. (See " Office reports " and " Reports of 

field parties," pp. 19-20.)

Supplemental instructions as to cost records and memoranda in 

regard to the submission of State and Federal vouchers will be given 

by the division engineer at the beginning of the field season and at 

such other times as may be necessary.

Memorandum copies of transportation requests and bills of lading 

must be transmitted through the division engineer to the chief topographic engineer immediately after the use of the original, and the 

cost of the service (estimated if necessary) should be indicated as 

well as the quadrangle or project charge. A record should be kept 

of transportation requests for use in preparation of travel-expense 

vouchers and of both transportation requests and bills of lading for 

use in preparation of monthly reports.

Suggestion^ for rendition of vouchers. Most of the following suggestions are repetitions of the requirements of the Geological Survey's fiscal regulations, to which references by pages or paragraphs 

are made herein.

Follow specimen copies of vouchers given in fiscal regulations.

Items must be stated in chronologic order. (Par. 164 (c).)

The time of departure from and arrival at official headquarters 

must be stated. (Par. 164 (f) and par. (a) on p. 86.)

If meals are taken en route that should or might have been taken 

at official headquarters the necessity of so taking them must be 

explained.
24 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

Keference to the method of all travel must be made in the body 

of the voucher.

Transportation requests covering more than one person must 

plainly indicate the name of each person. This information must 

also be given in the voucher. An employee who renders a voucher 

involving transportation issued by another employee must mention 

that fact. (Par. 114 (b).)

Telegrams from Washington must be sent paid; telegrams to 

Washington must be sent collect and marked " Official business." 

Charges for telegrams between points in the field must be supported 

by copies of the telegrams, which must be receipted by the company's representative.

Each employee, either permanent or temporary, should submit his 

own travel-expense voucher, which must be certified to by the chief 

of party.

Form 1012 must be used as a voucher for per diem if travel is performed during the period it covers. Transportation requests or scrip 

must be mentioned in the body of the voucher (p. 94) and listed in 

the space provided for them.

The number of pieces of baggage transferred and the charges for 

the transfer must be stated. A charge for transfer of baggage in 

excess of 75 cents must be explained. (The notation " Usual charge " 

will suffice.) (Par. 126 and par. (c) on p. 86, as amended.)

A charge for excess baggage must contain, in addition to a statement of the points between which the baggage was shipped, the rate, 

the weight, and a statement that the excess consisted of Government 

property or of personal property carried for officialese. (Par. 124 

and par. (w) on p. 89.)

Charges for transportation (street car, bus, taxi, auto, etc.) between places of temporary residence and places of temporary employment are items of subsistence and are included in the maximum 

amount allowed by the travel order. (1 Comp. Gen. 403 and 773.) 

Charges for transportation between working points are items of 

travel. The charges of these two kinds should be clearly distinguished on the voucher.

A voucher covering a period in which leave is 0 taken while the 

employee is in a " travel status " must state the hours at which official duty was stopped and resumed. (Pars. 150 and 154.) It must 

show plainly any detour made for personal convenience and must 

state the direct route of official travel. (Par. 122.) Meals taken just 

prior to or immediately after annual leave are usually not proper 

items for charges, and claims therefor must be explained.

If the account includes a period in which no expenses are charged, 

a reason for the break must be given. In other words, a voucher for

f
ADMINISTRATION 25

reimbursement of expenses for subsistence must show a complete 

history of the period it covers.

Charges for bus or taxi fares for personal transfer between station and hotel or hotel and station must state why street cars were 

not used. (Par. 126 and par. (o) on p. 88.)

The place where expenses were incurred must be indicated. This 

requirement includes expenses of all kinds meals, lodging, or miscellaneous items. (Par. 164 (g).) For meals taken on train the 

phrase " en route " will suffice. The fiscal regulations do not permit 

a charge for cleaning clothes; they permit a charge for pressing 

only, and this charge is included in the allowance for subsistence 

or per diem. (Par. 137 as amended.)

The name of any person involved in an expenditure for which reimbursement is claimed must be stated. If charges are made for subsistence furnished for a driver or helper used in connection with the 

hire of an automobile, the name of the person from whom the car is 

hired must be given. (Par. 165 (j).)

A claim for reimbursement for a package shipped by parcel post 

must state the weight of the package and the points between which 

it was shipped. Government parcel-post packages may be insured 

the same as private shipments. (Par. 85 as amended.)

All vouchers for reimbursement of traveling expenses or subsistence other than those covering travel from and to headquarters 

should contain the statement " Continuing voucher; in field."

Every voucher and subvoucher must contain the name (not initials) and title of the person signing. (Par. 165* (m).) If any 

change is made in a subvoucher, it must be accompanied by the 

statement " Change made before signature by payee," and the statement must be initialed by the payee. (Par. 165 (g) and p. 89.)

Any unusual expenditure should be briefly explained.

All charges for automobile or livery hire, whether on direct 

vouchers or reimbursement vouchers, must contain the statement, if 

appropriate, "No other practicable means of transportation available." (Par. 125 (a) and par. (o) on p. 88.)

If an automobile or other conveyance, with a driver, is hired by 

oral agreement with the understanding that the Geological Survey 

is to pay for the subsistence of the driver, the items covering such 

subsistence must contain the driver's name and a reference to the 

person from whom the conveyance was hired, in order that the 

auditors can readily connect the two. (Par. (q) on p. 88.)

In submitting direct vouchers or reimbursement vouchers covering supplies, storage, etc., for a hired car, reference must be made 

to the person from whom the car was hired. (Par. 125 (e).) In 

order to prevent complications it is suggested that automobiles be 

hired with the understanding that the owner is to pay all charges
26 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

for repairs or replacements. If a rodman is hired with his car, the 

letter of employment should specify that the Geological Survey 

will pay for gasoline, oil, ferriage, tolls, and storage away from the 

owner's garage.

All charges for automobile supplies, hire, storage, etc., must contain one of the following notations: " Government-owned passenger 

car," "Government-owned truck," "Passenger car hired from 

 ," or "Truck hired from ." (Par. 125 (e).) If a 

Government car, the number must be given.

[Reimbursement from public funds for the hire of an automobile 

by one employee from another employee, or from any members of 

an employee's family, is not authorized. (See 4 Comp. Gen. 370.)

The dates of all expenditures must be shown. (Par. 65 (b).)

The unit price of articles must be given.

On principal vouchers the method of advertising or the absence 

of advertising must always be stated. If a purchase is made under 

the provision covering purchases amounting to not more than $100 

that fact must be indicated. The form of agreement must also be 

stated. (Pp. 39, 44.)

Certain States impose a consumer's tax on gasoline. This tax will 

not be paid by the Federal Government, and vouchers covering purchases of gasoline in these States must show whether or not they include the tax.

When a temporary employee is being returned to the initial point 

of employment or to his home, salary should also be paid for the period included in° the travel, the only exception being that half-day 

salaries will not be paid and if the man reaches the point to which he 

is allowed traveling expenses before noon his salary will not be paid

for that day. Transportation requests for such travel must be used 

whenever possible, and the trip for which salary and expenses are 

claimed must be one that is actually made. If a man elects to go to 

some other point than that to which he is entitled to travel, his account must state the travel that was actually made, and if the expense 

is greater than that authorized, the difference will be disallowed by 

the section of accounts.

FIGHTING FOREST FIRES

Chiefs of parties are directed to render such assistance as may be 

necessary for the suppression of fires in or threatening national 

forests and to respond promptly to emergency fire calls which the 

district forest officers may make. Fires discovered by members of 

Geological Survey parties which can not be put out should be reported to the nearest known forest officer immediately.
AD'MINISTBATION 27 

PBIVATE INTEREST IN LANDS OB MINES

A provision of the organic law prohibits employees of the Geological Survey from having any personal or private interest in the 

land or mineral wealth of a region under survey and also prohibits 

them from making an examination or survey of property for private 

persons or for corporations.

RELATIONS TO THE GOVERNMENT

Loyalty on the part of every member of the Geological Survey to 

the Survey as an organization and as a part of the Interior Department is essential to its continued efficiency and high standing.

The topographic branch cooperates with other branches of the 

Survey, and to render such cooperation effective the interests of the 

Survey as a whole must be kept in mind rather than the special 

interests of any particular branch or division.

Members of the topographic branch should keep themselves informed regarding Survey work in general and topographic work in 

particular. (See "Uses of topographic maps," pp. 28-29.)

The topographic branch is frequently called upon to cooperate 

with the General Land Office, the Bureau of Keclamation, the Forest 

Service, the Bureau of Soils, the Coast and Geodetic Survey, the 

Corps of Engineers, the Army Air Service, and other Government 

bureaus. Topographers assigned to such work should so far as practicable familiarize themselves with the regulations and methods of 

procedure of the cooperating bureau and should conform to %them.

RELATIONS TO STATE SURVEYS

It is essential to efficiency and economy that cordial relations exist 

between the United States Geological Survey and the State organizations with which it cooperates. When formal cooperation with 

a State is in force, engineers submitting expense vouchers should 

first familiarize themselves with the State methods of accounting 

so as to avoid confusion and delay in settlement of vouchers. State 

cooperating officials should be given every facility for examination of field sheets or control data whenever they desire to do so 

during the field season.

RELATIONS TO THE PUBLIC

Courtesy to the public is enjoined on every member and employee 

of the topographic branch. Should persons make serious inquiry 

concerning work that the Survey is carrying on, .time, should be 

taken to give them the information, and when Federal and State

58515° 28 3
28 TOPOGEAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

governments are cooperating Survey employees will be expected 

on all proper occasions to make known to citizens the relations of 

the State to the work which is being done.

Should chiefs of parties be requested to give out tracings of 

topographic field sheets, they should wire to the chief topographic 

engineer for instructions. Elevations of bench marks may be furnished to engineers or local officials, upon request, provided they are 

marked " Preliminary figures, subject to adjustment." Other incomplete data should not be furnished, but names and addresses of 

interested persons should be taken, so that the final results may be 

sent to them when available.

Objection is sometimes made to entry on private property by 

members of the Geological Survey engaged in official work, but it is 

believed that such objections may generally be overcome by an 

explanation of the public character of the work. Should the objections persist, the chief topographic engineer must be notified, and he 

will endeavor to obtain authority through the proper State officials. 

No forcible entry should be made. Laws enacted by certain State 

legislatures grant authority for entry on private property to officials of the United States Geological Survey.

INFORMATION TO THE PRESS

Employees in the field are permitted and even encouraged to make 

known the nature and character of their work and its relation to 

the other work of the Geological Survey and the Government. This 

may be done by carefully prepared statements to the press and by 

papers or talks before civic organizations.

However, no statements relative to the policy of the Geological

Survey other than quotations from previously authorized statements 

may be given to the press without authorization from the Director. 

Whenever a member of the Survey is asked for a statement regarding 

official matters which involve Survey policies that have not been 

made public, he must, before giving it, obtain authorization from 

the Director. These restrictions apply to employees in the field as 

well as in Washington.

USES OF TOPOGRAPHIC MAPS

The need for topographic surveys may be measured in terms of 

the uses to which the resulting topographic maps are put. In general 

a topographic map is essential to any problem dealing with the use 

of the land. Specific examples of these uses are given below.

1. Natural-resources base map for Geologic Atlas of the United 

States; special geologic problems (economic, physiographic, etc.);
ADMINISTRATION 29

determination of the mineral and water resources; classification of 

the public lands; soil surveys; forest investigations.

2. Federal administration of national parks; national forests; 

national monuments; Indian, military, and game reservations; 

postal and rural delivery service; census service; transportation 

services; aerial navigation; education.

3. State administration by State engineers, State geologists, State 

foresters, State highway commissioners; in the location of State and 

county boundary lines; in the conservation of State resources; in 

legislation involving charters, rights, etc., of State agricultural 

colleges.

4. Military; as a base for military maps in the national defense; 

for maneuvers by the Army and National Guard; in the selection of 

routes of travel and transportation.

5. Engineering, in railroad and highway location; projects for 

power; irrigation, drainage, reservoir, and power sites and canal 

lines; affording bench marks and triangulation points for further 

large-scale surveys; river and harbor improvements.

6. Municipal administration of water supply; flood control; sewage disposal; establishment of local bench marks and triangulation; 

extension of city limits; changes in property lines; subdivision of 

land.

7. Aviation, in study of aerial routes, landing fields, etc.; data for 

preparation of special flight maps.

8. Educational, in teaching geography and physiography; as a 

base for miscellaneous educational studies.

9. Travel, as guide maps.

COOPERATION IN TOPOGRAPHIC SURVEYS 

GENERAL CHARACTER

Cooperation in scientific work may consist in an exchange of information between two or more parties or in the expenditure by 

them of money for investigation or work in which they are mutually 

interested.

The United States Geological Survey has for many years cooperated with other bureaus of the Federal Government, particularly 

the Coast and Geodetic Survey, the Army Air Service, the General Land Office, the Bureau of Reclamation, the Corps of Engineers of the Army, the Bureau of Soils, the Forest Service, and 

the Weather Bureau, thus avoiding much expensive duplication 

of work. It has also received each year assistance in various forms 

from many individuals and corporations and has thus acquired 

much valuable information which otherwise could not have been
30 TOPOGRAPHIC INSTRUCTORS OF GEOLOGICAL SURVEY

readily obtained. In return for this aid it has furnished maps and 

other publications to those assisting.

Cooperation to promote the common purpose of advancing knowledge and aiding development has existed between State organizations and the Federal Survey, and definite agreements were entered 

into early in the history of the Federal Survey. In the fiscal year 

1885 it was agreed between the Director of the Survey and the 

Board of Commissioners of the State of Massachusetts that the 

topographic work in the State should be divided; that the State 

should pay one-half of the expense of field work and the Federal 

Survey one-half; and that the Survey should engrave the maps 

and give transfers from plates to the State commissioners.

Under terms varied to suit the conditions of each special case, 

agreements involving cooperation of some sort have been made between the Director of the United States Geological Survey and State 

officials of Alabama, Arizona, California, Colorado, Connecticut, 

Delaware, Georgia, Hawaii, Idaho, Illinois, Indiana, Iowa, Kentucky, 

Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, 

Mississippi, Missouri, Nebraska, New Hampshire, New Jersey, New 

York, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, 

Pennsylvania, Rhode Island, South Dakota, Tennessee, Texas, Utah, 

Vermont, Virginia, Washington, West Virginia, and Wisconsin.

The object of each State in these agreements was to direct and 

promote topographic mapping, to procure scientific information 

which it was not equipped to obtain, to insure completion of work at 

an earlier date than would be possible with the Federal or State 

appropriations alone, or to avail itself in some other way of the 

special facilities of the Federal Survey; the object of the Director 

was to expedite the work and carry it on with more detail in areas 

where the public interest was greatest, to encourage the development 

of scientific work of value to the people of the country, and to maintain cordial relations among organizations having an essentially 

common purpose.

On the completion of the field surveys by the Federal Survey, the 

resulting maps are published by the Government and thus become 

available to the State. If, for example, the cooperation covers even 

no more than the preparation of a topographic map, the State benefits by the fact that this will surely be followed more promptly than 

otherwise would be the case by geologic investigations and mapping, and by the study of mineral, water, and timber resources, for 

which the topographic maps are primarily prepared as bases.

The Federal Survey benefits by the extension of its legitimate operations made possible through cooperation with the States. The Survey is charged with the duty of making a topographic and geologic 

map of the entire area of the United States, as well as of studying its
ADMINISTRATION 31

water resources and reporting on its other economic products. The 

area that can be covered within a given time is increased by means of 

the greater funds available through cooperation, and the completion 

of the work is thereby hastened. This advantage is of especial 

importance in the work on the topographic maps, which form the 

bases for the studies of economic resources, geology, and hydrography 

and the classification of lands.

GENERAL POLICY IN COOPERATIVE WORK

From the experience gained, certain conditions essential to the 

success of cooperation have been established. All work which is in 

part paid for by the Federal Survey and whose results may be published by it or on its authority must be controlled by the Director. 

He selects assistants to perform such work or approves their selection. In its execution the work is subject to the supervision and 

approval of the appropriate chief of branch of the Federal Survey. 

Payments for continuous service on account of State cooperation can, 

under civil-service rules, be made to a State official only in case he 

also receives a Federal appointment. Each year plans and estimates 

for the season are mutually prepared, and a report of operations and 

results is submitted to the State officials as well as to the United 

States Geological Survey. All agreements for cooperation are drawn 

in such manner as not to conflict with the organic law of the Survey 

in regard to making or disposing of collections, furnishing information, or giving expert testimony.

One important point to be considered in all such work is that the 

general plans and methods of the Federal Survey can not be set 

aside on account of State cooperation. The only warrant for the 

Geological Survey to engage in cooperative mapping is to expedite 

the topographic mapping of the United States. In this work certain standards must be maintained, and the relative importance of 

different areas must be considered with relation to the general public benefit. Congress has recognized State cooperation but has so 

limited it as to require the States to bear all of the expense in excess 

of such an amount as is necessary for the Geological Survey to perform its share of standard topographic surveys, such share in no 

case to exceed 50 per cent.

The Federal allotments to meet State cooperation will bear their 

proportionate share of the expenses necessary in connection with the 

proper administration of the field and office work namely, charges 

for internal administration of the topographic branch, for repair 

(but not for purchase) of instruments, for map editing, and for 

stationery, including field notebooks.
32

METHODS OF COOPERATION

In the establishment and conduct of cooperative surveys certain 

methods which have been developed through an experience of over 

40 years are followed.

The Director is requested by citizens of a State that may be interested in procuring topographic surveys to inform them as to his 

ability to accept such offers of cooperation as the State may be prepared to make, it being understood that efforts to secure cooperation 

must originate with the residents of the State. This Survey furnishes such information concerning the details of previous cooperative arrangements as may be sought. The object desired is usually 

attained by the introduction in the State legislature of a special bill 

or an item in the general appropriation bill providing for a cooperative survey to be conducted under the supervision of a State official 

or commission, who shall have control of the expenditure of the 

money appropriated, make agreements with the United States Geological Survey as to the methods of conducting the work, and recommend the order in which different portions of the State shall be 

surveyed. It is usually stipulated that the field operations shall be 

conducted under the supervision of the Director of the Geological 

Survey. This Survey furnishes expert assistants, who make the 

field surveys and office computations and draft the manuscript maps. 

The Federal Survey accepts the recommendations of the State officials for the employment of such temporary assistants as may prove 

qualified for the work, thus insuring the employment of residents of 

the State so far as practicable. The State law usually specifies that a 

sum equal to that appropriated by the State shall be expended in the 

same time by the United States Geological Survey.

The following sample act, passed by the Legislature of New Hampshire at its session of 1925, provides appropriations for the complete 

topographic map of a State:

To provide for the cooperation with the United States Geological Survey for the completion of the topographic mapping of the State of New Hampshire

Resolved by the senate and house of representatives in general court convened:

Topographic maps. That in order to complete the topographic mapping of 

the State of New Hampshire and to revise existing United States geological 

maps of certain areas so that a complete and accurate map of the State of 

New Hampshire may be obtained to meet the urgent needs of the several State 

departments, the Federal Government, and all individuals who desire reliable 

information relative to the natural resources of the State, there is hereby 

appropriated the sum of $25,000 annually for a period of five years for the 

cooperation with those branches of the United States Geological Survey engaged 

in such work, making a total of $125,000 available, only on condition that the 

United States Government by its duly authorized agents apportions an equal 

amount to be expended for the same purpose within the State. That so much
ADMINISTRATION 33

of the annual appropriation as remains unexpended at the end of any fiscal 

year may be available for expenditure until the object of the survey is accomplished.

Agreement for survey. That the governor and council are hereby authorized 

and directed to enter into such agreements with the Director of the United 

States Geological Survey as will assure that the surveys shall be carried out in 

the most economical manner and that the maps and data be made available 

for public use as early as practicable.

Authority to cross land. That in order to carry out the purpose of this resolution all persons employed hereunder are authorized to enter and cross all 

lands within the State: Provided, That in so doing no damage shall be done 

to private property.

Appropriation. That the sum of $25,000 shall become immediately available 

upon the passage of this resolution and like sums for the fiscal years ending 

June 30, 1926, 1927, 1928, and 1929.

In some States an item in the general appropriation bill similar to 

the following was considered sufficient:

For cooperation with the United States Geological Survey in the preparation 

and completion of a contour topographic survey and map of this State, to be 

paid upon vouchers approved by the governor, the governor is hereby authorized 

to arrange with the Director or representative of the United States Geological 

Survey concerning this survey and map, its scale, method of execution, form, 

and all details of the work in behalf of this State, and may accept or reject 

the work executed by the United States Geological Survey, the sum of $25,000.

It is hereby provided that said map shall accurately show the outlines of all 

townships, counties, and extensive wooded areas in this State as existing on 

the ground at the time of the execution of these surveys; the location of all 

roads, railroads, streams, canals, lakes, and rivers, and shall show by contour 

lines the elevation and depression of the surface of the country: Provided 

further, That the State shall pay not to exceed one-half of the cost of survey as 

completed.

In other States cooperation is arranged through some bureau 

having specific authority from the legislature, as shown in the 

Illinois law:

AN ACT To establish and create, at the University of Illinois, the bureau to be known 

as a State Geological Survey, defining its duties and providing for the preparation 

and publication of its reports and maps to illustrate the natural resources of the 

State, and making appropriation therefor.

SECTION 1. Be it enacted ~by the people of the State of Illinois, represented in 

the general assembly, That there be, and is hereby, created and established at 

the University of Illinois a bureau, to be known as a State Geological Survey, 

which shall be under the direction of a commission, to be known as a State 

Geological Commission, composed of the governor, who shall be ex officio chairman of said commission, the president of the University of Illinois, and one 

other competent person to be appointed by the governor, who shall hold office

for the term of four years and until his successor is appointed and qualified. 

* * * * <t * *

10. The said commissioners are hereby authorized to arrange with the Director or the representative of the United States Geological Survey in regard 

to cooperation between the said United States Geological Survey and the said 

Geological Commission in the preparation and completion of a contour topo-
34 TOPOGEAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

graphic survey and map or maps of this State, and said commission may accept 

or reject 

»«««$«*

the work of the United States Geological Survey.

12. The commission may expend in the prosecution of such work a sum equal 

to that which shall be expended thereon by the United States Geological Survey, provided that not more than .$10,000 be expended in this work in any one 

year. [The appropriation for 1927 is $50,000.]

In some States a department has funds appropriated for its general use which are available for miscellaneous work, and allotments 

from such funds are often made for cooperation with the Geological 

Survey without specific legislative authority.

BENEFITS OF COOPERATION

The appropriations made by the States for cooperative surveys are 

accepted chiefly for actual field work, in which are included the services of temporary employees, who are usually residents of the State, 

and for the living and traveling expenses of the field force. They 

may be used in paying office salaries only in so far as is necessary to 

equalize the expenses of both parties to the cooperation. Thus the 

larger part of the amount appropriated by the State is returned to 

its people. The appropriation of the Federal Government is devoted 

chiefly to paying the salaries of the permanent employees, a small 

portion of it being expended on general administration and a considerable portion on field and office work. The field work of the cooperative topographic surveys is invariably in charge of engineers of the 

Federal Survey, who are appointed under the rules of the United 

States Civil Service Commission by the Secretary of the Interior. 

Kodmen, recorders, chainmen, packers, teamsters, chauffeurs, cooks, 

laborers, and other minor assistants are employed in the locality in 

which the work is being done.

The topographic map is the base upon which the field investigations 

of geologists, hydrographers, and others are recorded and which 

makes possible a broader and more general study of the results of 

their work than is otherwise practicable. It was at once realized by 

State officials to whom such investigations had been assigned that an 

accurate and comprehensive performance of their duties was impossible without an adequate topographic base map. The expense of 

making such maps, however, was found to exceed in most localities 

the resources procurable through State aid, and the lack of the skilled 

men required in making such surveys was a barrier not easily surmounted. Competent topographic engineers are rare, and there is 

little inducement for young engineers of ability to make this their 

profession outside of the work of the Federal Government, as there 

is so little opportunity for steady employment in work of this kind 

elsewhere. It was apparent that in States availing themselves of 

the personnel and administrative knowledge of the Federal Survey 

the opportunities for systematic mapping would be greatly increased.
ADMINISTRATION" 

STATUS OF COOPERATIVE WORK

35

State

Idaho.......... ......

Illinois..-- ...-.-.--

Now Hampshire.. ......

Utah-.---.... ... .

Washington... ____ .

West Virginia. ..........

Date of cooperation (fiscal years)

1900-1907, 1911-12, 1924-1927....

1919, 1920-21, 1926-27..... .-.

1904-1927........ ........... ....

1921, 1924-1927 

1890-91, 1923-25... 

1926-27.... ......................

.....do.. ........................

1910-1915, 1921-1927 .

1913,1920-1922,1926. ..

1906-1927............. -----------

1020

1QftS-lQ17 1Q1Q-1Q97

1903-1917, 1919-1925, 1927........

1903-04, 1907, 1910, 1923..... ..

1900-1927.......... ----

1897-1901, 1903-1912.. 

1885-1888 

1902, 1904-1921, 1926-27. .........

1910-1917 

1902-03, 1908-09, 1920-1923

1908-1916, 1920-1927 

1912, 1914, 1916.. 

1906, 1925-1927. 

1885-1887 

1893-1917, 1920-1927 _ -_ 

1897, 1902-03, 1906-07, 1909-10..,.

1920-21, 1923, 1926-27...-. ...

1902-1916- -- 

1906-1908,1912-1915.. 

1906-1917,1922-1927. 

1900-1915, 1919-1927 

1888-1889 

1922-23... 

1911, 1922-23, 1925-1927.. 

1902,1905, 1910, 1915-16, 1920-1927.

1923-1927 . 

1914-1917, 1919-1927 

1909-1911, 1913-1927. 

1910-1925. _ .

1899, 1902-1916, 1919-1927 

1915, 1917, 1919-1927..... 

Cooperating agencies

State geologist.

State bureau of mines, governor through Bureau of Reclamation, State water commissioner. 

State board of examiners, department of engineering, University of California, board 

of public service commissioners of the 

City of Los Angeles, Klamath-Shasta 

Valley irrigation district, East Bay municipal utility district, Los Angeles County 

surveyor, department of public works. 

State geologist, State engineer, State School

of Mines. 

State board of commissioners, State highway

commission. (State completely surveyed.) 

State highway department.

State geologist.

Superintendent of public works, governor,

commissioner of public lands.

State engineer, State bureau of mines and

geology. 

State geological survey commission, department of registration and education. 

State geologist.

State geological survey. 

Director of Sfrte experiment station, State

geologist, board of commissioners, Fifth 

Louisiana levee district, department of 

conservation. 

State survey commission, public utilities

commission, State water-power commission. 

State geologist. (State completely surveyed.)

State topographic survey commissioners.

(State completely surveyed.)

State drainage commission.

Director of State experiment station, Tallahatchie drainage commission, State geological survey. 

State bureau of geology and mines, State

geologist. 

Board of regents of the University of Nebraska. 

Governor, State highway department.

State geologist. (State completely surveyed.)

pletely surveyed; revision in progress.) 

Governor, State geologist, commissioner of

the department of agriculture.

Governor. (State completely surveyed.)

Territorial survey commission, State geological survey.

engineer.

topographic and geological survey.

completely surveyed.)

ways and public works.

drainage and levee board, State bureau of 

economic geology and technology, State 

board of water engineers, State reclamation engineer. Harris and Orange Counties, 

Beaumont Chamber of Commerce. 

Box Elder, Davis, Salt Lake, Toole, Utah,

and Weber Counties.

partment of conservation and development.

(State completely surveyed; revision in 

progress.)
36 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

FUNDS EXPENDED FOR TOPOGRAPHIC MAPPING

Funds allotted for topographic mapping, fiscal years 1880-1927

Fiscal year

1880.... ...............

1881 

1882. . 

1883..---..-- .-.

1884...... .... ...... ...

1885.. 

1886 

1887. 

1888... . ......... .

1889. 

1890 

1891 

1892 . 

1893 

1894 

1895 ... ..........

1896 

1897 

1898 

1899 

1900 

1901 

1902 . 

1903... 

1904. _ ......

1905... ........

1906 

1907.. . 

1908 

1909 

1910 

1911 

1912. 

1913 

1914 

1915 

1916 

1917 

1918 

1919 

1920 ....... .......

1921 

1923 

1924 

1925 

1926 __

1927 

Federal funds

Scientific assistants

$16, 200 

16,200 

16,200 

16,200 

16, 200 

16,200 

16,200 

16, 200 

16, 200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

9,200 

10,600 

11, 000.

461,800

Topographic 

surveys

« $19, 624. 00 

o 44, 541. 00 

« 40, 575. 00 

o 70, 700. 00 

< 83, 950. 00 

 144, 665. 00 

< 168, 310. 00 

° 188, 456. 00 

« 186,111.00 

199, 000. 00 

200, 000. 00 

d 329, 573. 38 

250, 000. 00 

240, 000. 00 

200, 000. 00 

150, 000. 00 

150, 000. 00 

175, 000. 00 

175, 000. 00 

180, 000. 00 

240, 000. 00 

240, 000. 00 

250, 000. 00 

300, 000. 00 

300, 000. 00 

300, 000. 00 

350, 000. 00 

350, 000. 00 

300, 000. 00 

300, 000. 00 

350, 000. 00 

350, 000. 00 

350, 000. 00 

350, 000. 00 

350, 000. 00 

350, 000. 00 

350, 000. 00 

350, 000. 00 

350, 000. 00 

142, 196. 00 

325, 000. 00 

330, 000. 00 

330, 000. 00 

325, 000. 00 

500, 000. 00 

500, 000. 00 

 558, 300. 00 

451, 700. 00

12, 737, 701. 38

Surveying 

national 

forests

$150, 000. 00 

150, 000. 00 

130, 000. 00 

130, 000. 00 

130, 000. 00 

130, 000. 00 

130, 000. 00 

130, 000. 00 

130, 000. 00 

100, 000. 00 

100, 000. 00 

75, 000. 00 

75, 000. 00 

75, 000. 00 

75, 000. 00 

75, 000. 00 

75, 000. 00 

75, 000. 00 

75, 000. 00 

75, 000. 00 

75, 000. 00 

74, 219. 60

2,234,219.60

Military 

surveys 

and maps

$34,808.30 

553, 328. 49 

374, 889. 89 

259,040.13 

50, 646. 72 

14, 321. 72 

34,629.11 

36,048.41 

14, 975. 99 

11, 227. 96 

12, 500. 00

1,396,416.72

State funds

" $59, 670. 60

4, 866. 65 

c 24, 599. 21

3, 000. 00 

24, 000. 00 

4, 000. 00 

5, 000. 00 

20, 312. 00 

16, 000. 00 

30, 500. 00 

45, 000. 00 

46, 000. 00 

96, 500. 00 

89, Oil. 00 

105, 750. 00 

96, 100. 00 

103, 300. 00 

121, 800. 00 

103, 850. 00 

124, 410. 23 

180, 689. 36 

154, 383. 04 

177, 853. 00 

161, 267. 09 

179, 047. 96 

186, 800. 07 

166, 789. 39 

109, 440. 69 

56, 000. 00 

102, 475. 00 

190,904.46 

282, 557. 71 

230, 848. 81 

286, 412. 18 

353,198.22 

412, 935. 99 

344, 950. 14 

378, 791. 88

5,079,014.03

Total

$19, 624. 00 

44, 541. 00 

40, 575. 00 

70, 700. 00 

100, 150. 00 

220, 535. 60 

184, 510. 00 

204, 656. 00 

202, 311. 00 

220, 066. 00 

240, 799. 21 

345, 773. 38 

266, 200. 00 

252, 200. 00 

233, 200. 00 

163, 200. 00 

164, 200. 00 

204, 512. 00 

350, 200. 00 

369, 700. 00 

424, 200. 00 

425, 200. 00 

485, 700. 00 

528, 211. 00 

544, 950. 00 

535, 300. 00 

592, 500. 00 

581, 000. 00 

513, 050. 00 

508, 610. 23 

614, 889. 36 

588, 583. 04 

612, 053. 00 

595, 467. 09 

613, 247. 96 

621, 000. 07 

600, 989. 39 

578, 448. 99 

1, 043, 528. 49 

702, 980. 49 

784, 144. 59 

672,404.43 

584, 370. 53 

655, 241. 29 

898, 446. 63 

938, 511. 98 

925, 478. 10 

842, 991. 88

21,909,151.73

» Allotted from general Survey appropriation.

" Cooperative appropriation of $40,000 in Massachusetts available for three fiscal years, 1885-87.

« Continuous appropriation in Connecticut available for two fiscal years, 1890-91.

d Includes deficiency appropriation of $4,573.38.

 Includes deficiency appropriation of $73,300.

REQUISITIONS

STATIONERY

In ordering stationery it is advisable to request not more than 

three months' supply at one time. Requisitions should be made 

on Form 14618 or on a separate sheet of paper and should designate 

articles by numbers if any are known. Below are summarized the 

amount and kinds of stationery suitable for the field parties of
ADMINISTRATION 37

several classes. Schedules of general articles, any of which may 

be supplied to a party of any class, are given on page 42.

TBIAKGULATION PABTY

1 account book. 

10 address, notifications of, 1-567.

2 automobile maintenance account books, 9-086. 

12 automobile monthly cost sheets, 7876.

6 automobile, reports on condition of, 9-058.

6 automobile transfer records, 9-057.

6 bills of lading.

3 certificates of users of Survey field property, 9-036.

1 computation book, large, 9-889.

8 contracts, short form, 1-003 h.

4 employment, field, applications for, 9-067. 

15 employment, letters of, 9-026.

2 employees, temporary, reports of, to Civil Service Commission, 9-946. 

25 envelopes, standard letter size, 3% by 8% inches.

6 envelopes, white, extra letter size, 4% by 10% inches.

6 envelopes, manila, 5 by 10 inches.

6 envelopes, manila, 10 by 15 inches. 

12 envelopes, addressed to topographic branch.

6 envelopes, return-penalty, 3% by 8% inches.

1 ephemeris of the sun and Polaris.

6 freight or express shipment, labels for, 9-050b.

2 geodetic coordinates, computations of, 9-902.

1 geodetic distances, computation of, 9-901.

4 injuries, forms for reporting.

1 ink, fountain-pen, wood case.

2 instruments returned to custodian, 9-445-b.

2 instruments, transfer of, 9-139.

2 leave of absence, applications for, 1-034.

1 logarithms, 7-place or 5-place. 

10 mail forwarding cards, postmaster, 1-044. 

10 mail, second class, labels for, 9-160.

1 natural sines and cosines.

1 paste, tube.

6 pencils, No. 4.

3 pencil tips, metal and rubber. 

20 postal cards, plain, 9-482.

2 property, inventories of, 9-054.

6 receipts, proposal and acceptance, 9-007. 

12 recommendations of temporary employees. 

12 reports of field party, 9-908.

2 requisitions, instruments, 9-445-a.

1 rubber bands, box.

4 tags, instrument repair, 9-1021.

5 tags, linen, penalty or plain.

5 tags, linen, express shipment.

6 temporary receipts, freight and express, 9-994.

4 triangulation field notebooks, 9-912.

6 vouchers, pay, 9-013a.

6 vouchers, party pay and subsistence, 9-015.
38 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

15 vouchers, purchase, 9-012.

2 vouchers, subvoucher book, 9-017 (2 additional for camping party). 

6 vouchers, traveling expense, with detached memorandum, 1012.

PRIMARY-TRAVEBSE PABTY

1 account book. 

20 address, notifications of, 1-567.

2 automobile maintenance account books, 9-086. 

12 automobile monthly cost sheets, 7876.

6 automobile, reports on condition of, 9-058.

6 automobile transfer records, 9-057. 

12 bills of lading.

3 certificates of users of Survey field property, 9-036.

8 contracts, short form, 1-003 h.

8 employment, field, applications for, 9-067. 

25 employment, letters of, 9-026.

2 employees, temporary, reports of, to Civil Service Commission, 9-946. 

25 envelopes, standard letter size, 3% by 8% inches.

6 envelopes, white, extra letter size, 4y2 by 10% inches.

6 envelopes, manila, 5 by 10 inches.

6 envelopes, manila, 10 by 15 inches. 

12 envelopes, addressed to topographic branch.

6 envelopes, return-penalty, 3% by 8% inches.

1 ephemeris of the sun and Polaris. 

10 freight or express shipment, labels for, 9-050b.

4 injuries, forms for reporting.

1 ink, fountain pen, wood case.

2 instruments returned to custodian, 9^445-b.

2 instruments, transfer of, 9-139.

2 leave of absence, applications for, 1-034.

1 logarithms, 7-place or 5-place. 

24 mail forwarding cards, postmaster, 1-044. 

15 mail, second class, labels for, 9-160. 

1,000 paper, manila, sheets 3 by 5 inches.

1 natural sines and cosines.

1 paste, tube. 

10 pencils, No. 4.

4 pencil tips, metal and rubber. 

20 postal cards, plain, 9-482.

1 primary-traverse computation notebook, 9-931. 

10 primary-traverse distance record notebooks, 9-929. 

12 primary-traverse field notebooks, 9-928.

2 property, inventories of, 9-054.

6 receipts, proposal and acceptance, 9-007. 

12 recommendations of temporary employees. 

12 reports of field party, 9-908.

2 requisitions, instruments, 9-445-a.

1 rubber bands, box, No. 32.

3 tags, instrument repair, 9-1021.

5 tags, linen, penalty or plain. 

10 tags, linen, express shipment.

6 temporary receipts, freight and express, 9-994.

6 vouchers, pay, 9-013a. '

6 vouchers, party pay and subsistence, 9-015.
ADMINISTRATION 39

15 vouchers, purchase, 9-012.

3 vouchers, sub voucher book, 9-017 (2 additional for camping party). 

6 vouchers, traveling expense, with detached memorandum, 1012.

PBISM-LEVEL PABTY

1 account book. 

12 address, notifications of, 1-567.

2 automobile maintenance account books, 9-086. 

12 automobile monthly cost sheets, 7876.

6 automobile, reports on condition of, 9-058.

6 automobile transfer records, 9-057.

6 bills of lading.

3 certificates of users of Survey field property, 9-036.

8 contracts, short form, 1-003 h.

G employment, field, applications for, 9-067. 

25 employment, letters of, 9-026.

2 employees, temporary, reports of, to Civil Service Commission, 9-946.

25 envelopes, standard letter size, 3% by 8% inches.

6 envelopes, white, extra letter size, 4% by 10% inches.

6 envelopes, manila, 5 by 10 inches.

6 envelopes, manila, 10 by 15 inches. 

12 envelopes, addressed to topographic branch.

6 envelopes, return-penalty, 3% by 8% inches. 

10 freight or express shipment, labels for, 9-050b.

4 injuries, forms for reporting.

2 ink, fountain pen, wood case.

2 instruments returned to custodian, 9-445-b.

2 instruments, transfer of, 9-139.

2 leave of absence, applications for, 1-034.

1 level book, bench-mark descriptions, 9-916.

4 level notebooks, yard rod, 9-940 and 9-940-a. 

24 mail forwarding cards, postmaster, 1-044. 

15 mail, second class, labels for, 9-160.

1 paste, tube.

6 pencils, No. 4. 

20 postal cards, plain, 9-182. 

20 precise levels, computation forms, 9-932a.

2 property, inventories of, 9-054.

6 receipts, proposal and acceptance, 9-007. 

12 recommendations of temporary employees. 

15 reports of field party, 9-908.

2 requisitions, instruments, 9-445-a.

1 rubber bands, box.

3 tags, instrument repair, 9-1021.

5 tags, linen, penalty or plain. 

10 tags, linen, express shipment.

6 temporary receipts, freight and express, 9-994.

6 vouchers, pay, 9-013a.

6 vouchers, party pay and subsistence, 9-015. 

15 vouchers, purchase, 9-012.

2 vouchers, subvoucher book, 9-017 (2 additional for camping party).

6 vouchers, traveling expense, with detached memorandum, 1012.
40 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

WYE-LEVEL PARTY

1 account book. 

12 address, notifications of, 1-567.

2 automobile maintenance account books, 9-086. 

12 automobile monthly cost sheets, 7876.

6 automobile, reports on condition of, 9-058.

6 automobile transfer records, 9-057.

6 bills of lading.

3 certificates of users of Survey field property, 9-036.

8 contracts, short form, 1-003 h.

6 employment, field, applications for, 9-067. 

15 employment, letters of, 9-026.

2 employees, temporary, reports of, to Civil Service Commission, 9-946. 

25 envelopes, standard letter size, 3% by 8% inches.

6 envelopes, white, extra letter size, 4% by 10% inches.

6 envelopes, manila, 5 by 10 inches.

4 envelopes, manila, 10 by 15 inches. 

12 envelopes, addressed to topographic branch.

6 envelopes, return-penalty, 3% by 8% inches. 

10 freight or express shipment, labels for, 9-050b.

4 injuries, forms for reporting.

1 ink, fountain pen, wood case.

2 instruments returned to custodian, 9^145-b.

2 instruments, transfer of, 9-139.

2 leave of absence, applications for, 1-034.

1 level book, bench-mark description, 9-916.

3 level notebooks, primary, black cover, 9-903.

3 level notebooks, primary, yellow cover, 9-903. 

24 mail forwarding cards, postmaster, 1-044. 

15 mail, second class, labels for, 9-160.

1 paste, tube. 

10 pencils, No. 4. 

20 postal cards, plain, 9-482.

2 property, inventories of, 9-054.

6 receipts, proposal and acceptance, 9-007. 

12 recommendations of temporary employees. 

15 reports of field party, 9-908.

2 requisitions, instruments, 9-445-a.

1 rubber bands, box.

4 tags, instrument repair, 9-1021.

5 tags, linen, penalty or plain. 

10 tags, linen, express shipment.

6 temporary receipts, freight and express, 9-994.

6 vouchers, pay, 9-013a.

6 vouchers, party pay and subsistence, 9-015. 

15 vouchers, purchase, 9-012.

1 voucher, subvoucher book, 9-017 (2 additional for camping party).

6 vouchers, traveling expense, with' detached memorandum, 1012.

TOPOGRAPHIC PARTY (1 TOPOGRAPHER)

1 account book. 

10 address, notifications of, 1-567.

2 automobile maintenance account books, 9-086. 

12 automobile monthly cost sheets, 7876.
ADMINISTRATION 41

6 automobile, reports on condition of, 9-058. 

6 automobile transfer records, 9-057.

2 Beaman alidade notebooks, 9-913a. 

12 bills of lading.

3 certificates of users of Survey field property, 9-036.

8 contracts, short form, 1-003 h.

6 employment, field, applications for, 9-067. 

15 employment, letters of, 9-026.

2 employees, temporary, reports of, to Civil Service Commission, 9-946. 

25 envelopes, standard letter size, 3% by 8% inches.

6 envelopes, white, extra letter size, 4% by 10% inches.

6 envelopes, manila, 5 by 10 inches.

6 envelopes, manila, 10 by 15 inches. 

25 envelopes, addressed to topograpic branch.

6 envelopes, return-penalty, 3% by 8% inches. 

10 freight or express shipment, labels for, 9-050b.

1 geographic tables and formulas, Bulletin 650.

4 injuries, forms for reporting.

1 ink, fountain pen, wood case. 

Ink, waterproof, black, red, green.

2 instruments returned to custodian, 9-445-b.

2 instruments, transfer of, 9-139.

2 leave of absence, applications for, 1-034. 

10 mail forwarding cards, postmaster, 1-044. 

10 mail, second class, labels for, 9-160. 

Paper, double mounted, 18 by 24 or 24 by 31 inches. 

Paper, manila, 3 by 5 inches. 

Paper, single mounted, 15 by 15 or 9 by 9 inches.

1 paste, tube.

3 pencil tips, metal and rubber. 

10 pencils, No. 4.

2 penholders, drawing, writing. 

Pens, drawing, K. & E., Gillott's, 290, 291, 303. 

Pens, writing, stub, falcon, etc.

1 pins, pyramid. 

10 postal cards, plain, 9-482.

4 property, inventories of, 9-054.

6 receipts, proposal and acceptance, 9-007. 

12 recommendations of temporary employees. 

12 reports of field party, 9-908.

2 requisitions, instruments, 9-445-a.

1 rubber bands, box No. 32.

2 Ruby erasers.

1 sandpaper pencil pointer.

1 stadia table, Johnson's.

1 stadia table, Andersen's. 

12 tags, linen, express shipment.

6 tags, instrument repair. 9-1021.

6 temporary receipts, freight and express, 9-994. 

Tracing linen. 

Tracing paper, thin. 

Tracing vellum.

1 vertical-angle record, 9-914.

2 vertical-angle traverse records, 9-913.
42 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

1 vertical-angle tables, Davis's.

3 vouchers, pay, 9-013a.

3 vouchers, party pay and subsistence, 9-015. 

12 vouchers, purchase, 9-012.

1 voucher, subvoucher book, 9-017 (2 additional for camping party).

4 vouchers, traveling expense, with detached memorandum, 1012. 

Water colors, saucers, and brushes.

The following articles are usually required in camping parties 

only:

Auction sale, advertisement, 9-051.

Auction sale, report of, 9-040.

Flags.

Livestock, description of, 9-061.

Pasturage of public animals, proposal, acceptance, and receipt, 9-008.

Property affidavit, 9-048.

Property, inspection report of, 9-047.

Storage of public property, proposal, acceptance, and receipt, 9-007.

The following articles may also be had upon request if not already 

supplied:

Baldwin solar charts.

Blotting paper, sheets.

Canteens, 2-quart (on instrument requisition).

Celluloid sheets, 18 by 24 inches, clear, frosted, or opaque.

Clips, Gem, Mogul, etc.

Fasteners, paper.

Letter file, Favorite.

Paper, carbon copy books, official.

Paper, carbon sheets.

Paper, manila covers, 18 by 24 or 15 by 15 inches.

Paper, official letter.

Paper, ruled, 8 by lO1/^ inches.

Paper, scratch, note size.

Pencils, Kohinoor, 6-H, 7-H, 8-H, 9-H.

Pencils, blue, green, red.

Regulations of Geological Survey.

Scales, plotting, flat boxwood, 1: 240,000,1:125,000,1: 96,000,1: 62,500,1: 48,000,

1: 31,680, 1: 24,000, 1: 21,120, 1: 20,000, 1:10,000; inches, tenths, and fiftieths;

inches, tenths, and eightieths; also 1: 48,000 for chains. (Either of these may

be made into Burkland sight alidades on request.) 

Sealing wax. 

Tacks, thumb. 

Telegram blanks, official. 

Topographic instructions. 

Water colors, burnt sienna, Prussian blue.

INSTRUMENTS

Requisitions for instruments for individual field parties of the 

classes named below should be made on Form 9-445 a (white) and 

should be signed by or marked to be charged to the man who will 

be responsible for their use and custody:
ADMINISTRATION 43 

TRIANGULATION PABTY

1 aneroid.

Bags, book, large or small.

Batteries for flash lamps, round or flat.

2 compasses, prismatic.

2 glasses, field.

1 lamp, electric, hand.

1 plumb bob.

1 protractor, celluloid.

1 tape, steel, 6-foot.

1 tape, steel, 25-foot, meters on back.

I theodolite.

PRIMARY-TRAVERSE PABTY

Bags, book, large or small. 

Batteries, flash lamp, large or small. 

3 counters, hand. 

Dies, figures, 1 set. 

Dies, letters.

1 glass, field.

2 lamps, electric, hand.

II pins, tally. 

2 plumb bobs. 

2 rods, range. 

1 rod, stadia.

1 tape, 100-foot, steel.

2 tapes, 300-foot, steel. 

1 tape-repair outfit. 

1 transit, 30-second.

PRISM-LEVEL PARTY (FIRST OR SECOND ORDER WORK)

Bags, book, large or small.

Bench marks, copper nails with washers.

Bench-mark tablets (cooperative or standard).

Cement, cans.

Dies, figures, 1 set.

Dies, letters.

Drills, iy8 -inch bit.

Hammers.

Hatchets.

Keel, red or blue.

1 level, Locke.

1 level, prism.

Paint, cans, with brushes.

2 pins, turning. 

2 rods, yard. 

1 tape, steel, 25-foot. 

1 umbrella.

WYE-LEVEL PARTY (SECOND OR THIRD ORDSB WORK)

Bags, book, large or small.

Bench marks, copper nails with washers.

Bench-mark tablets (cooperative or standard).

5S515 0 28 i
44 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

Cement, cans. 

Dies, figures, 1 set. 

Dies, letters. 

Drills, 1%-inch bit. 

Hammers. 

Hatchets. 

Keel, red or blue. 

1 level, plumbing.

1 level, wye, 18-inch. 

Paint, cans, with brushes.

2 pins, turning. 

1 rod, New York. 

1 tape, 25-foot, steel.

WYE-LEVEL PARTY (FOURTH ORDER WORK)

Bags, book, large or small.

3 glass, field.

1 level, 15-inch.

1 rod, Philadelphia.

1 tape, metallic, 50-foot

6 keels, red or blue.

PLANE-TABLE TRIANGT7LATION PARTY

1 alidade, 25-inch telescopic.

Bags, book, large or small.

1 compass, 4-inch.

1 glass, field.

Level bubbles (specify size wanted).

1 level, circular.

1 plane-table board, 24 by 31 inches.

Scales, plotting.

1 straightedge.

1 tape, metallic, 50-foot.

1 tripod, Johnson.

TOPOGRAPHIC PARTY (1 TOPOGRAPHER)

1 alidade, 18-inch, telescopic.

1 alidade, sight, Burkland.

1 aneroid.

Bags, book, large or small.

1 compass, 4-inch.

1 counter, hand.

1 set dies, figures and letters VA.

1 glass, field.

Level bubbles (specify size wanted).

l level, circular.

1 level, Locke.

1 plane-table board, 15 by 15 inches.

1 plane-table board, 18 by 24 inches.

1 protractor, celluloid.

1 rod, stadia.

1 rods, stadia, paper patterns.
ADMINISTRATION 45

Scales, plotting.

1 straightedge.

1 tape, 50-foot, metallic.

1 tripod, Johnson.

I tripod, Bumstead.

STADIA-TBAVEKSE PARTY

1 alidade, 18-inch, telescopic.

1 alidade, sight, Burkland.

Bags, book, large or small.

1 compass, 4-inch.

Level bubbles (specify size wanted).

1 level, circular.

1 plane-table board, 15 by 15 inches.

1 plane-table board, 18 by 24 inches.

1 rod, stadia.

Scales, plotting.

1 tape, 50-foot, metallic.

1 tripod, Johnson.

TAPE-TRAVERSE PARTY

1 alidade, sight, Burkland.

1 aneroid.

Bags, book, large or small.

1 compass, 4-inch.

1 compass, pocket. *

1 counter, hand.

1 level, circular.

1 level, Locke.

1 plane-table board, 9 by 9 inches, with compass.

1 plane-table board, 15 by 15 inches, with compass.

Scales, plotting.

1 tripod, Bumstead.

2 tapes, rope.

FOOT-TRAVERSE PARTY

1 alidade, sight, Burkland.

1 aneroid.

Bags, book, large or small.

1 plane-table board, 9 by 9 or 15 by 15 inches, with compass.

Scales, plotting.

1 tripod, Bumstead.

B. TRIANGULATION

Compiled by E. M. DOUGLAS

GENERAL CONDITIONS FOB MAP CONTROL

The boundary lines of all regular United States Geological Survey 

maps are parallels of latitude and meridians of longitude. In order 

that these shall be properly located and that intermediate points 

shall be placed in correct positions, some system of horizontal control is required. The method to be adopted for linear control should 

be fixed by the character of the country, one of the requirements 

being that all control work shall be so accurate that no errors will be 

apparent in maps several times as large in scale as those to be published. In mountainous regions or in hilly, partly timbered areas horizontal control is effected by a system of triangulation, the whole area 

being divided into triangles whose apexes are represented by stations 

established on prominent points several miles apart. The angles 

between each station and all others visible from it are carefully measured with a theodolite graduated to read angles by micrometer to 

two seconds of arc or by estimation to fifths of a second. One side 

of the triangles, called the base line, must be carefully measured 

with a steel tape, if its length has not been previously determined, 

account being taken of slope of the line, elevation above sea level, 

temperature of the tape, and other essential details; and for at 

least one station the exact latitude and longitude and also the azimuth of one of the lines leading from the station must be determined 

by astronomic observations or by a connection with stations previpusly 

located.

In heavily timbered areas, where it is difficult to see from any 

point more than a mile or two in any direction, horizontal control is 

best obtained from distances measured on the ground with a 300- 

foot steel tape, a record being made of angles measured with a transit 

at each bend in the line. Such control, called transit traverse, must 

begin and end at points whose positions have been previously determined, and regardless of the character of the country such control 

must be carried around the edge of each quadrangle and once across 

its center east and west.

Because of the great expense involved in base-line measurements 

and in the determination of positions from astronomic observations,

47
48

it is generally advisable to connect triangulation systems or traverse 

lines with positions previously determined, even though they may be 

a long distance away. There are now few localities in the United 

States that can not conveniently be connected with known positions, 

and therefore, before horizontal control work is begun, the records 

of the Coast and Geodetic Survey, the Lake Survey, the United 

States Army Engineers, and other Government organizations should 

be examined in order to ascertain what positions in or near the area 

to be surveyed have been determined and are available for use in 

the work in hand.

Wherever possible, geographic locations should be based on the 

North American datum (formerly known as the United States 

standard datum), for there is in many localities a considerable differerence between the standard and astronomic data.

The results of triangulation or transit traverse by the Geological 

Survey can always be obtained by anyone having occasion to use 

them by applying to the Director, United States Geological Survey, 

Washington, D. C.

The United States Board of Surveys and Maps has fixed requirements for triangulation control, from which geographic positions are 

to be computed, as follows:

First 

order

1

1:25,000

Second 

order

3

1:10,000

Third 

order

5

1:5,000

Triangulation by the Geological Survey as described on the following pages, which is intended for map control only, is classed by

the Board of Surveys and Maps as of the "third order," consequently 

the triangles should close with an average error of not more than 5 

seconds, and the check on the terminal line or base must not exceed 

1 part in 5,000 of the length of the line. Triangulation of the two 

higher orders serves both for geodetic investigations and for map 

control. At present such work is carried on by the United States 

Coast and Geodetic Survey in accordance with special instructions 

prepared by that bureau.

TRIANGULATION FIELD WORK

GENERAL REQUIREMENTS

Amount of control. At least three serviceable stations of the third 

or a higher order must be established for each quadrangle, regardless 

of the scale of the map, and as many more as may be necessary to 

afford adequate bases for plane-table control. In addition, a number 

of secondary points such as church spires, windmills, water tanks,
TEIANGULATION 49

trees, and in high mountain regions some of the more prominent 

summits must be located by intersection and checked by angles 

from one or more stations or by the "three-point method," which 

gives satisfactory results if a fourth point is sighted for a check. 

Where no such objects are available, at least two points should be 

flagged for intersection if practicable. These points are intended to 

afford supplemental control for the topographer and should be selected 

with special reference to their usefulness in that connection.

The triangulator is also expected to locate, when practicable, either 

by direct measurement from his stations or by the three-point method, 

conspicuous objects, marks on State and county boundary lines, and 

township and section corners. Especial attention should be given 

to township and section corners because of their recognized value in 

the control of the land-line net. The General Land Office will on

request addressed to the Washington office detail a cadastral engineer 

to assist in finding and identifying corners of the public-land surveys.

Selection of stations. Stations should be selected and signals built 

before any observing is done, and to this end the triangulator and 

his assistant should make a reconnaissance over the area to be controlled. This reconnaissance should be thorough enough to disclose 

every practical scheme of triangulation and the angles at each point 

should be measured with a prismatic compass and platted with the 

protractor so that the size and proportions of the figures may be 

ascertained. All preparatory work, such as setting tablets and posts, 

erecting signals and scaffolds, clearing lines of sight, and obtaining 

consent of the owner, if on private land, should be completed during 

this reconnaissance, so that the final observing may be performed 

with economy and dispatch. The reconnaissance affords the triangulator opportunity to acquaint himself with the shortest routes of 

travel, the best stopping places, the available camp sites, water holes, 

pastures, and trails, and the best routes for scaling each peak to be 

occupied; and it enables him to gain a familiarity with the special 

character of each station and its signal which will be invaluable to 

him in identifying the points when he sights them later on. Each 

station must be named, and as station names are to be published, 

efforts should be made to select those which have local significance. 

The name selected should be stamped into the metal station mark 

with steel dies.

Figures. The most desirable groups of triangles consist of either 

quadrilaterals with both diagonals sighted or central-point figures 

with four to seven sides. The triangles composing these figures 

should be well proportioned, angles measuring not less than 30° 

rior more than 120° each. The scheme should not be allowed to 

dwindle down to single, unsupported triangles, and especial care 

should be taken to connect the work done with other work by means
50 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

of well-proportioned triangles. Overlapping figures or an excess 

of observed lines beyond those necessary to insure a double determination of each length are undesirable, although a diagonal through 

some figure may occasionally be valuable as a check. As a rule 

additional lines of this kind only complicate the main scheme without materially adding to its strength, and the numerous observations made for them are discarded by the computers as superfluous. 

Judgment is to be used in this matter, however, for in many regions 

the atmospheric conditions are exceedingly uncertain, and the observer can not always count on being able to see in both directions 

over every line that may be essential to the main scheme. In such 

regions it is well to err on the safe side and obtain too many data 

rather than too few.

Angles should be read to all prominent points outside of the area 

for use in future expansion, even though the points lack signals or 

are not sharply defined.

Secondary points. In cutting in secondary points for topographic 

control it should be remembered that locations that depend on two 

sights only, even if the angles are of adequate size, are likely to be 

of doubtful value, because of the absence of any check on possible 

gross errors in observing or computing, or because of the possibility 

of mistakes in the identification of the points. An endeavor should 

therefore be made to obtain at least three sights to every secondary 

point, even if the triangles are not of the best shape. Observers are 

especially cautioned not to slight the location of secondary points 

merely because they happen to be of no importance in their scheme 

of figures. As the topographer may find it expedient to start his 

control from a secondary point, a blunder in the location of such a 

point may result in his starting with an erroneous base and having 

later to make corrections at a great cost.

Consent oj owner. Before a site for a station on private land is 

selected, the written consent of the owner should be obtained, if 

practicable, for establishing a permanent station mark and erecting 

the*required signal. If a summit must be cleared of timber, or if 

lines of sight must be cut, the value of the timber to be cut should 

be definitely fixed and agreed upon with the owner before cutting 

is begun.

When it is necessary to clear away timber and the owner or agent 

for the ground can not be reached without great delay, three residents of the locality should be asked to appraise the value of the 

timber cut and to sign a written statement regarding it. This statement should be forwarded to the office of the Survey for consideration 

if a claim for damage is filed.

Station marks. Triangulation stations must be permanently 

.marked by standard bench-mark tablets, each tablet to be set in
TBIANGULATION 51

rock in place or in the top of a concrete or stone pier. (See pi. 4 

and also p. 120 of leveling instructions, for instructions in regard to 

setting tablets.) When practicable, bottles or other imperishable 

material should be left as subsurface marks.

Two or more permanent reference marks should be established 

about each station mark. These may consist of holes drilled in rock 

in place in which a metal reference mark tablet is to be fixed, with 

the arrow pointing toward the station; spikes in roots of trees; or 

large stones set solidly in the ground. The azimuth and the distance 

to each reference mark must be duly entered in the field record.

When old stations are revisited and any of the marks are found to 

be defective or to have been destroyed, new marks must be established in their places, and a report regarding them must be sent at 

once to the Washington office.

Signals. Triangulation signals must be built with a view to their 

permanence as well as to their visibility. They may be of various 

forms, the form selected depending on the locality and the materials 

at hand. Thus, a signal on a bare mountain peak may be a rock 

cairn; one on a partly wooded summit may be a straight tree, the 

surrounding timber being cleared away; one on cleared land may be 

a tripod or quadripod. (See pi. 1.)

Rock cairns should be not less than 8 feet high and should be Avell 

put together, so that they will withstand strong winds and heavy 

snows. A pole or a small green tree placed in the top is of advantage 

in sighting.

Signal trees are most satisfactory if stripped of their branches, 

except a tuft at the top. They form the best of targets when sighted 

against the sky, but if they are to be sighted against a dark background, they should carry two triangular targets 3 to 6 feet on a side, 

placed at right angles to each other and covered with white cloth.

Tripods or quadripods should be built of sawed lumber if such material is available. For the legs and center pole 2 by 4 inch scantlings 

may be used; for the cross braces 1 by 6 inch boards. The base of 

the pyramid should be large enough to permit a theodolite to be 

set up under the center pole. In order to increase its visibility, 

boards may be nailed across the sides about a foot apart and covered with signal cloth, and cross targets may be attached to the center 

pole above the apex of the pyramid. The best colors for this cloth 

are white and black or white and red.

Most signals stand in exposed places and should be securely 

anchored to prevent their being blown over. The legs of tripods 

and quadripods should be placed in the ground at least 2 feet; each 

leg should be fastened to a "deadman" and the hole filled with 

thoroughly tamped earth or rocks, or else a stake 4 feet long should 

be driven into the ground at an angle with each leg and firmly spiked
52 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL, SURVEY

to it. If the ground is too rocky to permit the digging of holes, 

a 4-foot crosspiece should be nailed to each leg at right angles flat on 

the ground and weighted down with rocks. Signals built on solid 

rock should be fastened to ring bolts leaded or wedged in holes drilled 

in the rock.

Observing towers. High observing towers (pi. 1) should be avoided 

wherever possible, but where local conditions make them necessary 

provision should be made for determining the azimuth from the tower 

to some point visible from the ground. If no permanent object is 

visible, an azimuth mark should be set at least 500 feet distant and its 

direction determined, with at least one check observation. A description of the azimuth mark in sufficient detail to make its identification certain should be recorded. The distance to the mark from the 

station, either measured or estimated, should be stated. If it becomes 

necessary to elevate the instrument, a scaffold must be erected in the 

form of a tripod, capped with a thick board 12 inches square to support the instrument. Around this scaffold, but entirely independent 

of it, should be built another, in quadripod form supporting a platform 

on which the observer is to stand. If very high such a scaffold 

should be composed of successive bents, each 8 or 12 feet, with diagonal 

bracing. The outer scaffold is to serve also as a signal and for that 

purpose should extend at least 6 feet above the observing platform and 

be surmounted by a mast bearing cross targets. Before fixing signals 

in position the direction in which sights are, to be taken should be 

carefully ascertained, so that no woodwork will interfere with the 

observations.

The size of the timbers to be used necessarily depends on the 

height of the structure. The amount of lumber required may be 

determined by means of a rough drawing of the structure to scale.

Centering of signals. Signals should stand over station marks 

wherever possible, so as to avoid the necessity of computing swings 

for the angles. Great care must be taken to insure perfect centering 

of signal and scaffold over the station mark, a plumb bob being used 

for this purpose.

If centering the signal is impracticable, as it is with a tree signal, 

the distance and bearing of the signal to the station mark must 

be carefully measured and recorded.

The permanent mark, tablet, or concrete post must always be 

considered the station for which the geodetic position will later be 

computed, and when observations are made for angles the theodolite 

should be set up over its center if possible. If it is impracticable to 

center the instrument over the station mark, the distance between 

the point occupied and the station mark must be carefully measured 

and recorded. One or more sets of angles must also be read between 

the station mark and the other stations, in order of azimuth, preferably with the 0° 0' 00" for the pointing to the station mark.
TJ. S. GEOLOGICAL SURVEY BULLETIN 788 PLATE 1

k"

WHBfcjsm.'**!**

1

OBSERVING TOWER AND SIGNALS
U. S. GEOLOGICAL SURVEY BULLETIN 788 PLATE 2

VERNIER TRANSIT-THEODOLITE
U. S. GEOLOGICAL SURVEY BULLETIN 788 PLATE 3

MICROMETER THEODOLITE
U. S. GEOLOGICAL SURVEY BULLETIN 788 PLATE 4

> O E-LEVAT10N 

O ABOVE'A. S A

FEET

ELEVATION 

ABOVE A SEA

GEOLOGICAL SUKVEY MARKS FOR TRIANGULATION, TRANSIT TRAVERSE,

AND LEVELING
TRIANGULATION 53

Heliotroping. The heliotrope outfit commonly used by the Survey 

is either the Steinheil or a plane mirror with a screw hinged to the 

back to give it universal motion and improvised diaphragms of tin 

or wood with round apertures. The plane mirror is generally preferred to a heliotrope of the more elaborate form.

A heliotrope is usually set up by mounting the mirror on a stake 

or board immediately over the center of the station and the diaphragm 

on another stake, 10 or 20 feet away, carefully aligned with the distant 

station. The operator must constantly watch the reflection from the 

mirror and keep it symmetrically over the aperture. If the sun is 

back of the observer a second mirror, a foot or two from the first, may 

be used to reflect the light into the first.

To the observer the flash should appear as a clearly defined point 

of light; if of appreciable size it will be necessary to bisect it, and an 

error is thus likely to be introduced. The apparent size of the flash

depends more on the steadiness of the atmosphere than on the size 

of the aperture. An aperture greater than 1 inch will not be required 

in Geological Survey work.

PERSONNEL AND OUTFIT OP PARTY

In general each party consists of a chief of party, who acts as 

observer, and a recorder; also a cook and a teamster (or packer) 

when camping is necessary. Additional men are required for heliotroping, one for each heliotrope station, and local laborers may be 

employed to clear timbered summits or to erect large signals.

The following instruments and books are used in Geological Survey 

triangulation for map control:

One 8-inch theodolite, with leather carrying case and shoulder straps, or 

a transit.

Two pairs field glasses.

One prismatic compass.

One protractor (6-inch celluloid, full circle).

One boxwood scale, graduated to inches and tenths.

One 50-foot steel tape, meters on back.

Two electric hand lamps.

One 6-foot steel tape.

Heliotropes.

One plumb bob.

Triangulation tablets.

Cement, cans.

Signal notices, printed on cloth.

Climbing irons, for use in wooded regions.

Sun umbrella IFor use in regions where improvised sun and wind shelters

Wind screen j can not readily be built.

Triangulation field notes (9-912).

Computation of geodetic distances (9-901).

Computation of geodetic coordinates (9-902).

Computation book, blank (9-889).

Polaris positions for year.

Geographic tables and formulas (Bulletin 650).

Seven-place logarithmic tables.

A good watch must be provided by the chief of party.
54 TOPOGRAPHIC INSTRUCTION'S OF GEOLOGICAL, SURVEY

The following articles may be purchased in the field: Ax, hatchet, 

saw, nails, tacks, signal cloth, guy wire, stone drills (1^-inch bit), 

drill hammer, pesthole digger, wire cutter, and brace and bits.

For the standard triangulation of the Geological Survey an 8-inch 

theodolite reading by micrometer to 2 seconds of arc or by estimation to one-fifth of a second is used.

For the horizontal control of small areas inside of large triangles 

or inclosed by belts of triangles, a vernier theodolite or transit may 

with the approval of the division chief be substituted for the more 

accurate micrometer theodolite.

CARE OF INSTRUMENTS

Too much emphasis can not be laid upon the importance of care 

in the handling and transportation of instruments. Every employee 

intrusted with instruments in the field will be expected to keep 

them clean and in adjustment, to protect them from undue wear, and 

to return them to the custodian in fit order for use.

Minor repairs. Each topographer should provide himself with a 

few simple tools and supplies, such as a small pair of pliers with side 

wire cutter, screw drivers of two sizes, small flat and round files, a 

spool of soft copper or brass wire, a few assorted brass nails and 

screws, a bottle of oil, a bottle of liquid shellac, spider web, and plaster 

of Paris, all of which may be used for minor repairs to instruments.

Field work should never be delayed by sending an instrument 

away for repair if the topographer can possibly repair it himself. 

Even crude repairs may often be made to serve until a new instrument can be procured.

Setting oj bubbles. For setting level bubbles a small supply of 

plaster of Paris should be kept on hand. For use the plaster should 

be mixed with water to the consistency of a thick paste. If plaster 

is lacking, strips of paper may be used, but these should never be 

jammed in very tight, as the pressure may distort the glass and thus 

vitiate the bubble reading by an appreciable amount. A reflecting 

surface of colored paper should be placed under the bubble in order 

to make the graduations more readable; a subdued green or blue 

tint is recommended.

Mounting of cross wires. For mounting cross wires a small bottle 

containing shellac dissolved in alcohol, a pinch of beeswax, and a 

pair of dividers or a forked stick are needed. The best spider web 

is, of course, a freshly spun one from a small spider, for this will be 

both clean and elastic; but as spiders are not always available, it is 

well to keep on hand a spider cocoon. Such a cocoon will furnish 

webs enough to last for years, although with age the threads become 

stiff and brit^e and therefore more liable to break from a jar to the
TBlANGtTLATION 55

instrument. Most webs taken from grass or bushes are rough, 

coarse, and dirty.

To draw the reticule from the instrument, unscrew and remove 

the eyepiece slide; then take out two opposite capstan-headed screws 

and loosen the other two. Using the latter two as handles, revolve 

the cross-wire ring 90°, insert a pointed stick through the end of the 

telescope tube into a screw hole in the ring, and, using it as a handle, 

remove the other capstan screws and draw out the ring. To replace 

it in the telescope, reverse this procedure. When in place the cross 

wires should be on the side of the ring toward the eyepiece.

Having pressed a bit of beeswax to each prong of the dividers or' 

forked stick, let a small web fall from the end of one of the prongs, 

or pick with it from a cocoon a single thread, pressing the thread 

into the beeswax, stretch the thread moderately, and attach to the 

wax on the other prong. If an old web is used, it should first be 

dampened by dipping in water for a few seconds. In place of the 

dividers or forked stick, small sticks or lumps of wax may be attached to the web about 2 inches apart. Place the web across the 

reticule, using a magnifier to insure its coinciding exactly with the 

marked lines. Put a small drop of shellac on each end and leave 

until dry.

Cleaning instruments. Instruments having working parts exposed 

to air and dust require cleaning from time to time. Such exposed 

parts as the threads of tangent screws are particularly liable to collect 

dust and grit and should be wiped frequently with an oily rag, then 

rubbed dry. Only the best quality of clock or watch oil should be 

used for this purpose.

Steel tapes should be cleaned and oiled after use. All moisture 

or grit must be wiped from them each time they are reeled, or they 

will deteriorate rapidly.

Neither the object glass nor the eyepiece of a telescope should ever 

be rubbed with rough cloth or with the fingers, as the glass may 

thus be permanently scratched. The lenses should never be removed 

from the cell that holds them nor separated from one another.

Packing and shipping. In shipping instruments by freight or 

express transit and theodolite boxes must be filled in with paper or 

cloth, so that if any part of the instrument should jar loose during 

the journey it may not roll around in the box and damage other 

parts. Heavy articles, such as compasses, aneroids, or other small 

instruments, should never be placed in the instrument box. The 

micrometers of theodolites should be wrapped tightly with cloth, as 

they are easily jarred loose. The same precautions should be taken 

when these instrument are to be transported by pack train.

On no account should any instrument be shipped by express or 

freight in its own case only. A wooden box, large enough to permit a
56 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

generous amount of excelsior, hay, or other padding around the 

instrument case, should be provided.

In mountains where pack trains are the sole means of conveyance 

the triangulator's outfit is most conveniently carried in a pair of 

canvas pack bags (alforjas), which must be properly balanced. The 

tripod, umbrella, and wind screens should be placed lengthwise on 

top, lashed to the saddle, and further balanced by properly disposing 

them on each side of the center. A canvas pack cover should be 

thrown over the whole and tucked in on all sides.

ADJUSTMENT OF INSTRUMENTS 

PRECAUTIONS

The object glasses and eyepieces of all instruments must be properly focused. The cross wires projected against a distant object 

should appear immovable when the eye only is moved. Before the 

adjustments are commenced the instruments must be firmly set up 

and leveled. An instrument may appear to be out of adjustment 

simply because some part is loose. The object glass may be partly 

unscrewed or an adjusting screw may be only partly tightened; 

level bubbles or cross wires occasionally become loosened. Therefore, before commencing the adjustment of an instrument look out 

for such defects. When it is thought that an adjustment has been 

completed, always test it before using the instrument. All adjusting 

screws should be screwed tight enough to hold, yet not so tight as 

to injure the threads or put a severe strain on any other part. Especial care should be taken not to strain the cross-wire screws. Adjustments should be made in the order given under the following headings,

for some adjustments depend on the accuracy of others previously

made, and a change in any one may affect the others.

MICROMETER THEODOLITE

Striding level. Place the level (pi. 3) in the proper position on the 

telescope axis. Level carefully with the horizontal plates clamped, 

and rock the level slowly back and forth till the foot pieces strike. 

If the bubble leaves the center, bring it back by means of the side 

adjusting screws near one end of the tube.

Reverse the level and bring the bubble halfway back to the center 

by raising or lowering one end of the tube with the screw at that end 

and the other half with the leveling screws. Repeat these operations 

till the adjustment is perfect.

Standards. After the striding level is in adjustment with the 

lower horizontal circle clamped, level the instrument hi two positions at 90° from each other. Turn on the vertical axis 180° from one 

position; if the bubble runs away from the center, bring it halfway
TEIANGULATTON 57

back by loosening one of the large capstan-headed screws underneath the standards and tightening the other. Test the adjustment, 

and repeat it if necessary.

Plate levels. Level instrument with the striding level only, then 

bring the bubbles of the plate levels to the center of their tubes by 

means of the end adjusting screws; or use the method described for 

adjusting the transit plate levels (p. 92).

Micrometers. Each micrometer consists of three concentric tubes; 

the upper and lower ones slide in the central one. The lower tube, 

which holds the object lens when in proper position, is clamped to 

the middle one by means of the capstan-headed screw in the lower 

part of the J-shaped support. These two tubes may be moved 

together, or the lower one moved alone by loosening the proper 

screws. The upper tube contains the eyepiece lenses and is held in

place by friction only.

Focus the eyepiece on the two parallel movable threads, and do 

not change it afterwards. With the eye in position for setting the 

micrometer, tighten one and loosen the other of the two screws that 

hold the J-shaped microscope support to the main frame of the 

theodolite until the figures and graduations on the plate appear to 

be in the center of the field.

Clamp the plate and by turning the micrometer screw set the two 

movable threads over a long graduation. Examine carefully to see 

whether they appear exactly parallel to it. If they are not parallel, 

loosen the two capstan-headed screws which clamp the micrometer 

tube, and twist the tube until the threads and mark appear parallel. 

Clamp the side screws lightly.

Set the movable cross wires on a division to the apparent left of the 

field of view as for a regular angle reading, read the micrometer head, 

and record the reading. Turn the graduated head about five turns, 

stopping when the threads are set on the next 10' division to the 

right; read and record. Repeat this operation several times. If 

the mean of the left-hand readings is the same as the mean of the 

right-hand readings, or within one division of it, the adjustment 

may be accepted as satisfactory. An actual count of full revolutions should be made at least once; otherwise the adjustment might 

wrongly be thought perfect for 4^£ or 5^ revolutions.

When the space covered by the two parallel micrometer threads, 

moved by exactly five revolutions of the micrometer screw, appears 

to be longer than one 10' space on the graduated circle, to bring it 

into adjustment make the distance between the micrometer box and 

graduated plate longer by raising the middle part of the tube; but 

when the space is shorter than a 10' space make that distance shorter 

also that is, consider as connected or dependent the length of the 

thread space covered by an even five revolutions of the micrometer
58 TOPOGKAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

screw and the distance between the micrometer box and the graduated plate. When the former is longer than it should be, the latter 

should be made longer, if an adjustment is desired, and vice versa.

To make the adjustment, loosen the small capstan-headed screws 

which clamp the microscope tube; then, if the thread space is long, 

twist the middle part of the tube (including the micrometer box) 

back and forth and at the same time pull it upward, thus lengthening 

the distance to the graduated plate. When by estimation it has 

moved far enough, which can be roughly determined by the amount 

of blurring that results from the lower lens being thrown out of focus, 

clamp the upper capstan-headed screw. The lower part of the microscope tube holding the objective lens must now be twisted and gently 

pushed downward till the graduations again appear in focus. If the 

movable threads and graduations are not then parallel, the upper 

screw must be again loosened and the tube turned far enough to 

make them parallel, after which both screws' must be tightened. 

Test the adjustment by again measuring a 10' space with the micrometer. If it is still out of adjustment, repeat these operations till it is 

satisfactory. When the adjustment has been completed a scratch 

may be made on the tube below each support and used as a guide in 

future adjustments.

The opposite micrometers may be placed 180° apart by setting 

one at a reading of 0° 0' 0", with the comb scale exactly centered, and 

then centering the comb scale of the other micrometer over the 180° 

mark by means of the capstan-headed screw at the left-hand end of 

its box. Bring the micrometer threads over the 180° mark also; then, 

while holding the screw firmly in place, turn the graduated ring till 

it reads zero.

When setting the micrometer wires on a graduation, it is very 

important that they be moving toward the right when the turning of 

the screw is stopped. Should they be moved, the least bit^too far to 

the right, turn back not less than half a revolution of the screw and 

then bring them forward again. In general, when a setting is made 

by means of a screw working against a spring, the spring should 

always be undergoing compression when the motion stops.

Cross wires. The vertical wire should be truly vertical; otherwise 

an exact adjustment of the cross wires is not essential.

After the striding level has been adjusted and the horizontal axis 

of the telescope carefully leveled, sight a distant point, raise and 

lower the telescope through an angle of 5° or 10°, and note whether 

the cross wires follow the point. If not, loosen the cross-wire ring 

and twist slightly; repeat the adjustment if necessary.

Hold the striding level on the telescope parallel to the optical axis 

and, with the bubble in the center of the tube, set the intersection of 

the cross wires on a distant point and clamp both plates; lift the
TRIANGUIoATION 59

telescope out of its supports and turn 180° around its optical axis; 

set it again on the selected point. If the striding level when placed 

on top of the telescope is horizontal and the vertical wire still cuts the 

point, the adjustment is complete. If not, shift the cross-, wires in 

either direction by means of the capstan-headed screws for one-half 

the apparent error. Repeat the test till the error is nearly all eliminated. Finally readjust the vertical wire, if necessary; or both wires 

may be put in place by revolving them in temporary wooden. Y supports. /

TEANSIT THEODOLITE /

/ .. - ,

The adjustments for striding level, standards, and plate (level are 

the same for the transit theodolite (pi. 2) as for the micrometer 

theodolite.

Collimation. Level carefully, sight on a point about 500 feet distant, raise or lower the telescope slightly, and note whethervthe vertical wire remains on the point; if not, loosen the capstari-headed 

screw and turn the cross-wire ring till the vertical wire will ;remain 

on the point when the telescope is raised or lowered. Clamp the 

instrument, set the vertical wire so that it cuts the point selected* 

transit the telescope by revolving it 180° on its horizontal axis, and 

select a second point 500 feet distant in the opposite/ direction from 

the first. Unclamp the upper plate, turn the transit 180? on the 

vertical axis, set it on the point first selected, and again clamp the 

plate. Transit the telescope, and if the vertical cross wire exactly 

bisects the second point its adjustment is perfect; if it does not, 

bring it one-quarter of the way back to the second, point by turning 

the two capstan-headed screws on the sides of the telescope.

Eyepiece tube. The eyepiece may be put into/ position over the 

cross wires by turning the screws that hold the eyepiece ring until 

the cross wires appear in the center of the field; an exact centering 

is not required. /

Telescope level. If there is a level attached to/the telescope, it may 

be adjusted by the "peg method" after all the other adjustments are 

made, as follows. Level the transit and bring the bubble to the center 

of the tube under the telescope. Take a reacjing on a leveling rod or 

pole 300 or 400 feet distant, which is held on a stake set firmly in the 

ground. Revolve the transit 180° on the vertical axis and after 

again bringing the bubble to the center set a second stake at the 

same distance as the first and at such an elevation that the rod or 

pole reading is the same as on the first stake. The tops of the two 

stakes will then be at the same elevation. Move the transit 25 or 50 

feet back of one stake and on a line with the other. Make the telescope as nearly horizontal as possible by means of the attached level, 

clamp it, and then take a reading on the rod held on the near stake 

and another reading on the distant stake. If the two readings agree,

58515° 28 5
60 TOPOGRAPHIC INSTRUCTIONS OP GEOLOGICAL SURVEY

the telescope is horizontal; if they do not agree, turn the tangent 

screw so as to bring the cross wire while set on the distant rod nearly 

to an agreement; repeat the operation until an agreement is reached. 

The telescope is then level, and the adjusting nuts at the end of the 

level tube should be turned until the bubble is brought to the center. 

Vertical circle or arc. The screws holding the vernier for the vertical arc should now be loosened and the vernier moved until the reading 

is 0° wljjle the telescope is still level. If there is no level under the 

telescope, the level attached to the vertical-circle vernier arm may 

be adjusted atter the striding level and standard are adjusted, by 

revolving the instrument on its vertical axis and turning the slowmotion tangent screw (attached to the vernier arm) until the bubble 

remains in the center during an entire revolution. The index error 

of the vertical circle may then be found, and the vernier moved till 

the reading is 0°.

-''', OBSERVING AND RECORDING

Time- of observing. As a rule, the best time for observing is during 

the three hours before sunset; the atmosphere is then steadiest and 

shows no "boiling." The early morning hours are occasionally 

good but are likely to be less satisfactory. Cloudy or overcast days 

may be favorable. As a last resort, observations at night may 

sometimes be necessary, but these require special night signals and 

assistants to operate them and because of the additional cost involved 

are seldom warranted.

Preparation for observing. Wherever practicable the theodolite 

jiiust be set over the station mark for reading angles, to obviate 

reduction to center. In setting up the tripod the head-bolt thumbscrews must be left loose until the legs are firmly placed and then 

tightened.

The instrument must be sheltered from both wind and sun. If 

the region affords no material readily available for constructing 

wind screens and Vsun shelters, a folding wind screen and a sun 

umbrella must be carried as a part of the regular outfit.

Before observations are begun at a station all adjustments of 

the theodolite must be tested and such as are found in error must 

be corrected, special attention being paid to the micrometers to 

eliminate errors of run. The stations to be sighted must next be 

carefully identified by means of the directions shown on the plat 

or by means of angles previously taken with a prismatic compass. 

If any of the distant stations can not be seen with the unaided 

eye, some object in line with each which can be found quickly must 

be selected, or, if necessary.,,the direction to each may be marked 

by some object near by, so that no time need be lost in making the 

pointings when the angles are bemg^resAl.

Method of observing. With micrometer theodolites either single 

angles may be measured or circle reading^ (directions) may be made. 

In using the latter method select for the initial point some station
TRIANGULATION 61

that 19 especially distinct and easily sighted and use it as the initial 

point for all sets of readings. The telescope being set on the initial 

point, read both micrometers, then sight the other stations in succession in the order of their azimuths (clockwise rotations), closing 

on the initial point. Then reverse telescope, set on initial point, and 

sight the stations in reverse order. This completes one set of readings 

with telescope direct and reverse. Now shift the circle about 45° 

(examine the plate bubbles after this shift and relevel if necessary) 

and begin another set. When pressed for time, shift the circle when 

telescope is reversed. No angle should be considered well determined 

that has not been measured on at least four different parts of the circle 

or eight times in all, four with telescope direct and four with telescope 

reversed. When the telescope is reversed, each end of its axis will 

rest in the same Y as before. Reversals and releveling are of especial 

importance where there is an appreciable difference in the elevations 

of the points sighted.

If the observations are made in the afternoon, take all secondary 

pointings before commencing the observations to stations, and make 

at least two sets of such pointings; the remaining time for observing 

can then be devoted to the accurate measurement of the important 

angles while conditions are the most favorable.

The graduated circle should never be placed so that when pointing 

at any particular station the micrometers will be set to even degrees, 

except, as before noted, while data are being obtained for "reduction 

to center."

Field record. The field record is to be kept in book 9-912. It 

must be written in a plain neat hand with a No. 4 pencil or in ink, 

and no part of it must on any account ever be erased. A single 

line should be drawn through erroneous records, the corrected figures 

being written above. If deemed necessary, an explanation should 

be written in the column for remarks. The memory should not be 

trusted for data of any kind; the record must be faithfully kept in 

all particulars and must be made so complete that it can be understood by another person at any time.

On the flyleaf of each field notebook is a blank in which all information necessary to identify the book may be recorded. This blank 

should be filled so far as practicable on or before the first date of 

entry of field notes, and it must be completely filled before the book 

is forwarded to the Washington office. Any failure to fill in completely the blank on the flyleaf of a field notebook should be reported by the computer to the division engineer. One of the blank 

flyleaves must contain an index of the contents. The date, name of 

station, time of observing, and names of observer and recorder 

should be systematically entered at the head of each page.

The position of the instrument with respect to the center of the 

station must be clearly defined, and if it is set up off the center a 

full statement must be given of the distance and the angles measured.
62 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL, SURVEY

On the page immediately preceding the record of angles should be 

written a minute and complete description of the station occupied, 

the station's marks, character of signal, nearest camping or other 

stopping places, roads, and trails, also a statement regarding the 

ownership of the land and such other information as will be helpful 

to the topographer. The description must be written before the 

recorder leaves the station and should be accompanied by a rough 

diagram showing directions to other stations and plan indicating 

location of instrument or signal if it was not centered on the station.

The following is a suitable station description:

ELK, LEWIS COUNTY, KT.

About 4 miles north of Petersville and 2 miles south of Glen Springs, on a 

cleared round knob at the head of Elk Lick and Black Lick, branches of Kinniconick Creek. George Washburn lives at base of hill on north side, and his place 

can be reached by road up Elk Lick. An excellent view in every direction.

Signal: Chestnut oak aboxit 14 inches in diameter; distance 8.3 feet, true 

azimuth from station mark, 58° 11'.

Station mark: Stone post with tablet in top, set 30 inches in ground and resting on bedrock.

Underground mark: A + cut in rock.

A plat, drawn to scale, should always be prepared and forwarded to 

the office with the field notes.

Reading and recording of angles. When the micrometer wires are 

set for a reading with the Geological Survey theodolites it is very 

important that the last movement of the wires be toward the right. 

The readings on the graduated head are then decreasing, and the spring 

attached to the slide that holds the wires is being compressed. If the 

cross wires are moved the least bit too far to the right they must not be 

turned backward merely to the setting but must be turned backward 

at least a half turn of the screw and then brought forward slowly to 

correct setting. When the setting is properly made a division on 

the graduated plate will appear exactly midway between the two 

movable cross wires, and an equal amount of white space will show 

on each side of it. A part at least of the micrometer adjustment in 

errors can be eliminated by making the settings with less than five 

turns of the screw; this can always be done if the right-hand part of 

the comb scale is sometimes used for comb-scale and micrometerhead readings, the 10-minute space being taken from the left.

For all precision instruments in which a tangent screw and spring 

are used together, the setting should be made while the spring is 

being compressed; otherwise the "slack" of the screw may cause 

an error.

The recorder should not only take down the readings called off 

by the observer but should without delay compute the angles between 

successive stations and also the mean readings. The following form 

is to be used for recording angles by the method of directions:
[Left-hand page.] 

Station occupied, Elk. 

Date, January 6, 1925.

Stations sighted

Telescope direct

Taylor... _______ . ..........

Dick.............................

Telescope reversed 

Dick.. ...........................

Tweedy.. ........................

Browning. .. .....................

Taylor............................

Dick.............................

Microm. A

303 53 06

349 29 21 

30 03 03 

127 13 13 

280 46 00 

303 53 07

123 53 01 

100 45 27 

307 13 08 

210 03 02 

169 29 23 

123 53 03

Microm. B

123 53 04

169 29 23 

210 03 04 

307 13 10 

100 46 00 

125 53 04

303 53 02 

280 45 26 

127 13 08 

30 02 29 

349 29 22 

303 53 05

Mean

123 63 10

169 29 44 

210 03 07 

307 13 23 

100 46 00 

123 53 11

123 53 03 

100 45 53 

307 13 16 

30 03 01 

349 29 45 

123 53 08

Angle

45 36 34 

40 33 23 

97 10 16 

153 33 38 

23 07 10

23 07 10 

153 32 39 

97 10 15 

40 33 16 

45 36 37

(Station mark to left of Dick, 23° 07' 10".)

[Right-hand page.] 

[In these columns write sum

maries of the angles meas

ured.]

45 36 34 

37 

89 

32 

31

38 

36 

29 

37 

36

45 36 34.90

Taylor

Browning 

40 33 23 

16 

17 

15 

22

19 

16 

24 

23 

17

40 33 19.2
64 TOPOGRAPHIC INSTRUCTIONS OP GEOLOGICAL SURVEY

In this example five sets of circle readings direct and five reversed 

were taken. The angles between stations were found by subtracting the mean reading at one station from that for the next following 

They are grouped in these columns merely for convenience; they may 

fill several pages. The next group on this or a folio whig page would 

represent the angle Browning to Tweedy, and so on.

Only two readings on the station mark need be taken for reduction 

to center.

Opposite each angle record any necessary information as to visibility of signals or atmospheric conditions.

Field computations. Angles at each station should be reduced to 

center in the field in order to test the triangle closures, which for 

Geological Survey work should seldom exceed 10 seconds or average 

more than 5 seconds.

Arbitrary adjustments and preliminary computations of positions 

should also be made in the field. Book 9-889 should be used for 

summary of angles and for miscellaneous computations. Computations for distances should be entered in book 9-901 and for coordinates in book 9-902. For field computations of coordinates where 

the lines are short, five or six place logarithms will give sufficient 

accuracy, and the computations may be shortened by omitting some 

of the minor corrections, carrying results to tenths of seconds of 

latitude and longitude only.

As soon as the preliminary computations are made the record books 

should be sent to the Survey office by registered mail. The computation books should also be sent by registered mail but on another day.

Triangulation plot. A careful plot of the work should be kept on 

the scale of 8 miles to an inch, and each month a reduced copy, on 

which angles measured are indicated by the usual sign, should be 

sent in on the monthly report blank. If this plot is carefully made 

it can be transferred directly to the office State progress map.

In order to use the plot for finding the direction to distant stations 

place the protractor on it with 0° in line with a station that can be 

seen clearly; then read in turn the angle to each other station, thus 

obtaining an observing list.

Azimuths. Two true azimuths should generally be available for 

each square degree covered by the triangulation. These may be 

previously computed azimuths from independent sources or may be 

obtained by direct observations on Polaris.

Azimuth observations. An azimuth mark should be placed at least 

half a mile from the station. It should consist of a vertical slit onefourth to one-half inch wide and 6 inches long, cut in a small box 

containing a candle or lantern. To illuminate the cross wires of the 

instrument and to read the angles, an electric hand lamp is to be 

preferred.
TBIANGULATION 65

The observations should consist of not less than five direct and 

five reversed measurements between the star and mark. As the 

star is at a much higher angle of elevation than the mark, it is important that the horizontal axis of the theodolite be adjusted with 

care and leveled. The ends of the striding-level bubble must be 

read at each setting on the star and a level correction computed if 

there is an appreciable difference between them, as shown in the 

example below.

Observations on Polaris should be made immediately before and 

after elongation, as any error in the time of observation has then the 

least effect on the resulting azimuth. The time of setting the cross 

wires on the star must be recorded to the nearest second. The watch 

error must be known, and to this end the observer should compare 

his watch frequently with telegraphic time, which is sent over Western Union lines once a day, usually at noon, Washington standard 

time. The time meridian for which the watch is set must always 

be recorded; if "daylight saving" time is used, that fact must also 

be stated.

Example of record of azimuth observations

Station: Elk, Ky. 8-inch theodolite No. 434. One division of micrometer=2". One division of level 

2" of arc. January 6, 1925. Watch 0 23«° slow, 75th meridian standard time

Telescope direct

Object

Mark (1). ...............

Polaris (2)...............

Time a.m.

H. 771. S.

1 10 50

Level

West

Div.

11.0 

9.0

20.0

East

Div.

10.0 

12.0

22.0 

-.0

Micrometer

A

0 ' div. 

352 54 09 

288 35 24

B

0 ' div. 

172 53 21 

108 35 05

Mean

0 / //

172 54 00 

108 35 29

Angle

64 18 31

Telescope reversed

Mark (4). ...............

Polaris (3) ...............

Mark (5). ............ 

Polaris (6).... __ .. ....

1 16 48

1 20 26

11.0 

9.0

20.0-'<

10.0 

10.0

20.0

10.0 

12.0

22.0 

1.0

11.0 

11.0

220 

10

172 53 04 

108 34 10

202 41 13 

138 22 24

352 52 13 

288 33 27

22 40 22 

318 22 06

352 52 47 

288 34 07

22 41 05 

318 22 30

64 18 40 

64 18 35

Telescope direct

Mark ....................

1 26 52 10.0

11.0

21.0

0.

11.0

10.0

2LO

0

22 41 07

318 22 20

202 40 17

138 22 13

202 40 54

138 22 33

64 18 21

NOTE. Four other sets should be taken.
66 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

TRIANGTJLATION COMPUTATIONS

Preliminary computations of distances from unadjusted angles 

should be made in the field, as required by the rule on page 64.

The steps in the final adjustment and computation are set forth 

below.

Operations are completed in books 9-912, 9-889, 9-901, and 9-902. 

The results are tabulated on printed blanks 8 by 10% inches in size, 

one blank for each station.

CLOSING THE HORIZON

In careful work closing errors will always be small and may be 

distributed among the angles in proportion to their number. If 

any of the angles measured should equal the sums of smaller angles, 

proper adjustments must be made before the horizon is closed.

TABULATION OP ANGLES

For convenience of reference a rough plot should be made for each 

station on part of a page in book 9-889, showing the relative size 

and position of the angles with names of stations sighted, and on the 

same or the following page should be given a summary of all the 

angles at the station, in order of azimuth, with the angles and distances to signals for eccentric stations.

REDUCTION TO CENTER

For eccentric stations the data for reduction to center should be 

indicated on the plat, and figures should be given for them in the 

summary. An illustration of the method of producing these data 

is given below. (See also fig. 2, p. 78.) Two sets of angles were 

read at Elk station (where an eccentric point was occupied), with 

one of the micrometers set very nearly on 100° 45' when the telescope was pointing directly toward the center of the signal. The 

angle to each point in turn is given below. By measuring the angle 

with one micrometer reading 0° 00' the computer would have been 

saved considerable trouble and the possibility of error would have 

been lessened. The measured distance between the center of the 

instrument and the center of the station was 4.7 feet (1.43 meters).

The formula for computing the swing in seconds for any line is:

Distance to signal Sine of angle between signal and far station 

Sine 1" Distance to far station

The distance to signal will be a constant for each set up, hence 

its logarithm may be combined with the sine of 1" and this constant 

used throughout the computation. The distances to the distant 

stations hi logarithms of meters are derived from a preliminary

computation.

Log 1.43 =0. 15534 

Log sin 1" =4. 68557

Log constant =5. 46977
TRIANGTJLATION 67

ELK STATION

A. C. log distance .. -------------

23° 07' 10"

5. 46977

9. 59400

5. 70154

0. 76531

+5.83

BOO AV' AtVI

5. 46977

9. 96935

5. 59196

1. 03108

+10 74

109° 16' 54"

5. 46977

9. 97493

5. 74781

1. 19251

+15. 58

208° 27' 10"

5. 46977

9.64881

5.63275

0. 75133

-5.64

The sign for any correction is the same as that for the sine of the 

angle, therefore for an angle over 180° it will be negative.

The correction for any angle will be the difference between the 

corrections for the two lines bounding it, the lines always being 

taken in order of azimuth.

Thus, for Dick-Elk-Taylor it will be

+10. 74 5. 64

- 5- 83 For Browning-Elk-Tweedy it will be ~ 15- 58

+ 4. 91" 21. 22

The general rule is, change the sign of first correction (in order of

azimuth) and add algebraically to the second correction. The sum

will be the correction to the angle. The angles listed on page 72

have all been corrected.

The foregoing formula may be used also when it is desired to compute the swing for a line, which is to be applied at a distant 

station to change the pointing to the marked point that is, the 

station center from that taken to the signal. Whether the computed swing is to be added to or subtracted from a given angle may 

easily be found by an inspection of the diagram.

COMPUTATION OF AZIMUTH OBSERVATIONS

The daily change in Polaris is so slight that for the following 

computation no account need be taken of a fraction of a day in computing its position':

Elk sta., Ky. Lat. 37° 28' 47", long. 82° 00' 16". 

January 6, 1925, at lh 10 50s a. m. watch time. 1 

Watch 23 seconds slow, 75th meridian (standard) time. 

Long. 82° 00' 16" = 75° + 7° 00' 16", = 5h 28m 01- west of Greenwich, = 28m 01s west of 75°.

b. m. s. 

Watch time of observation Jan. 6, 1925, a. m_______- 1 10 50

Watch slow 23s ; correction_________________________ +23

Standard civil time-__-----________________________ 1 11 13

Correction to local meridian._______________________ 28 01

Local civil time.__________________________________ 0 43 12

Longitude in time.________________________________ 5 28 01

Time after O h Greenwich_________---______.________ 6 11 13

6 11. 22 

6. 187 hours

1 Commencing Jan. 1, 1925, the civil and astronomic days begin at midnight. Astronomic hours are 

counted from Oh at midnight to 24h the following night. Prior to 1925 the astronomic day commenced at 

noon 12 hours later than the civil day.
68 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL, SURVEY

h. m. s. 

Sidereal time Oh Greenwich, Jan. 6__________;_ 7 00 13

Correction for 6.187 h = 6.187 (9.8565")_________ +61

(Use Table III, Nautical Almanac, or p. 124 of Bulletin 660.) 

Local civil time_-_--_--_-__-----------------__-__ 0 43 12

Sidereal time of observation or hour angle of vernal

equinox._______________________________________ 7 44 26

Right ascension of Polaris, upper transit at Washington, Jan. 6, 1925--_-_------------------______ 1 34 41

Hour angle of Polaris at time of observation..._______ 6 9 45

Hour angle in arc = t (p. 125, Bull. 650) = 92° 26' 15".

The hour angle of Polaris can be computed with sufficient accuracy from the tables in the General Land Office ephemeris as follows:

Greenwich mean time of nearest upper culmination of

Polaris, Jan. 5, 1925, p. m. (General Land Office h. m. s. 

ephemeris)____-----__-__----------_---_-_----__ 6 35 24

Reduction to longitude 82° 00' 16" (BuU. 650, p. 126) _ -54

Local mean time of upper culmination.._____________ 6 34 30

Local mean time of observation, Jan. 6, 1925, a. m.

(lh llm 13" 28m 1 s)-______-__-_______--- 0 43 12

12

Mean time hour angle (or time interval from upper

culmination to observation)______________________ 6 8 42

Reduction to sidereal hour angle (Bull. 650, p. 126) _ _ _ +1 1

Sidereal hour angle.__________-_-___--__-_____-____ 6 9 43

The difference of 2 seconds between this and the figures obtained

above for .the hour angle is the result of the dropping of decimals in

the General Land Office tables.

The following are the formulas for azimuth and level correction:

tan A = i T -. a = sec <j> cot 5 6 = tan 4> cot 6 l o cos t

Level correction = j-l («;+_/) (e+e') Itan h.

in which, for the example above given,

0 = latitude of station (37° 28' 47"). 

A = azimuth of Polaris at time of observation. 

5 = declination of Polaris at time of observation (88° 54' 24"). 

t = hour angle of Polaris at time of observation (92° 26' 15") (the 

cosine is negative, sine plus in this example), value of one division of level (2.0").

w, w' = readings of west end of level bubble, direct and reversed. 

e, e' = readings of east end of level bubble, direct and reversed.

h = angular elevation of star (at elongation this is equal to the latitude, nearly).

The level correction is used as a correction to azimuth A only.
TBIANGULATION 69

Each azimuth computation should be made in a single column 

and for convenience the columns should be placed side by side in 

tabular form.

The following is the computation of this observation:

o

Level correction==-(2X0.77) =0.77"

Logtan<£(37° 28' ^1")................. 9.88466

Log cot 5 (88 54 24 )..._.________ 8.28068

Log cos t (92 26 15 )_________________ 8.62869 (negative)

Log b cos t.............-.------.-----.. 6.79403 (negative)

6 cos t...................___.____ 0. 000622

1

1-6 cos t................ _-___._______ 1. 000622

Logsec<£(37° 28' 47")--- ------------ 0.10042

Log cot 5 (88 54 24 )__.._......._._._ 8.28068

Log sin t (92 26 15 )______-__-___-___ 9.99961 (positive)

Log a sin f_____________________________ 8. 38071 (positive)

Log (1-6 cos «)------------------------- 0.00026 (positive)

Log tan A............................. 8. 38045

A (the minus sign indicates that the star was ° ' "

west of north).___________________ 1 22 32.1

Level correction_________________________ -f-0. 8

 1 22 32. 9

Add algebraically to 180° to refer to the 

south___________-_--_-__-_________ 180

Angle from star to mark.________________ 64 18 31

Azimuth of mark______________________ 242 55 58.1

TABULATION OF TRIANGLES

By an inspection of the field plat of the triangulation determine 

what groups of triangles are so interrelated that a change in one will 

affect the others and what groups of triangles should be adjusted as 

a unit. For the triangulation by the Geological Survey, which is 

not executed for geodetic purposes, it is not advisable to include 

more than fifteen or twenty triangles in such a group, because the 

labor of solving equations for the adjustment of any group increases 

rapidly with its size. Four overlapping triangles form one of the 

simplest groups that may be adjusted by the usual least-square 

methods.

Assume the group shown in Figure 1 for adjustment. Tabulate 

the angles for each triangle, as shown at (a), (b), (c), and (d) (p. 

72). Any angle in any of these triangles may be considered as the 

difference between the azimuths (directions) of its two sides. For
70 TOPOGKAPHIC IKSTETJCTIONS OF GEOLOGICAL, SURVEY

example, angle Dick-Elk-Taylor, or 4.3.1, as designated for convenience by the figures assigned to each angle vertex, would be the 

azimuth or direction of the line 4.3 subtracted from the azimuth or 

direction of the line 1-3. Azimuths are always measured in a clockwise direction. Therefore this angle may be indicated as 4.3 + 1.3

Tay/or

Dick

Browr

Elk

FIGURE 1. Quadrilateral for adjustment by least-square method

or 4/3 + 1/3. In the latter form the denominator is always the 

figure at the vertex of the angle, and with the vertex pointing toward 

the observer the left-hand direction is always given the minus sign. 

(Directions will hereafter be referred to as sides.)

COMPUTATION OF-SPHERICAL EXCESS

For any triangle on the earth's surface the sum of the three angles, 

if correctly measured, will exceed 180° by an amount varying with the 

area. For use in computing distances the observed angles must be 

reduced to their plane values by deducting one-third the spherical 

excess from each. The spherical excess for any triangle between 

latitude 25° and 45° is approximately 1 second for each 75.5 square 

miles of area, or exactly equals in seconds abm sin C, in which a, b, 

and C are, respectively, the lengths of the two sides in meters and 

the included angle of any triangle, and m is a constant depending 

on the latitude.2

In computing spherical excesses for any figure (as fig. 1, for example) arrange the work systematically, the logarithms of each of two

3 Logarithms of m are given in Geographic tables and formulas, U. S. Geol. Survey Bull. 650, p. 294,1918. 

Between latitudes 30° and 50° log m may be found with sufficient accuracy for preliminary computations 

from the formula 1.4040+(45°-0°, used as a unit in the fourth decimal place). For example: Lat. 37°, 

45-0=8, m=1.4048 (tabular value= 1.40482); lat. 49°, 45-£=-4, m=1.4036 (tabular value= 1.40359).
TBIANGTJLATION 71

sides in meters from a preliminary computation, the logarithm of 

the sine of their included angle, and the logarithm of m for the mean 

latitude for each triangle; place in a column. Give the figures for 

the triangle at the head of the column, as 4.3.1, using the angle 

4.3.1 and the sides 4-3 and 1-3 in the computation.

Computation for spherical excess

Triangle

Log m... ...... . .... ..... ... . ...................... . ... . ... .... . ........ .........

4.3.1

4.29846

4. 40804

9. 85406

1. 40475

9. 96531

0.92

1.3.2

4.40804

4. 25219

9. 81304

1. 40475

9. 87802

0.76

Mean latitude, 37° 35'.

In the same manner compute the spherical excess for each of the 

remaining triangles. Many such computations can be conveniently 

made in the book (9-901) used for preliminary distances, in the 

left-hand column adjacent to each triangle.

As the spherical excess for a given area is constant, the sum of the 

spherical excesses for the triangles 1.3.2 and 4.3.1 must equal the 

spherical excesses for the other two. This check should always be 

applied to the results.

LEAST-SQUARE ADJUSTMENT

By the least-square adjustment of a triangulation net, the most 

probable values are found from the more or less discordant measurements. These will not necessarily be the true values but they will 

be such as to produce consistent results. A line or position computed from them will be the same even if computed from different 

sets of triangles.

After deducting the spherical excesses from the sums of angles for 

each triangle (a), (6), (c), (<Z) (see below), the differences between the 

remainders and 180° will be the errors, plus for remainders over 180° 

and minus for those less than 180°.

The algebraic sum of the closing errors of two of the triangles (of 

any quadrilateral) should equal the algebraic sum of the closing 

errors of the other two which cover the same area:

-3. 45 +2. 74 

+ 4.70 1.49

+1. 25 +1. 25 

This check should always be applied.
72 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL, SURVEY

The rules for determining the number of angle equations and the 

number of sine or side equations required for the proper adjustment 

of any figure are these:

L S-\-l = angle equations.

L 2£+3 = side equations.

where L equals the number of lines in the figure observed in both 

directions and S the number of stations. A solution of these equations for a quadrilateral shows that three angle equations and one 

side equation are required. In selecting the equations for a large 

group of triangles, it is well to consider each part of the figure in 

detail, commencing with three stations, adding stations with the 

lines to them one at a time, and at each step computing the angle 

and side equations required.

The side equation in a quadrilateral fixes the condition that three 

lines shall meet in one point.

In the present example it is immaterial which three of the four 

triangles are used for the adjustment.

Angle equations

Stations

fElk---.. .............................

(.Browning.......... ...... .-.......-.-

fDick... ................. _ ...........

OwTaylor......... ....... __ __...... 

(.Browning. . . . . __ ... ..... __ ......

fElk...................................

(cKDick.......... ........... .............

iTaylor.... __ .. __ . __ .. .... ......

[Elk.-... .............................

(d)-pick-... -__-.._..........-..._.._._-..

iBrowning... ________ ______

Side

-1/3+2/3

-2/1+3/1

-3/2+1/2

-1/4+2/4

-2/1+4/1

-4/2+1/2

-4/3+1/3

-1/4+3/4

-3/1+4/1

-4/3+2/3

-2/4+3/4

-3/2+4/2

Observed angle

40 33 19.17

44 03 30.52

95 23 07.62

179 59 57.31 

Spherical excess. 0.76

40 09 14.16

94 38 08.09

45 12 37.04

179 59 59.29 

Spherical excess. 0.78

Error .. __ 1.49

45 36 34. 90

83 48 53.15

50 34 37.57

180 00 05.62 

Spherical excess. 0.92

Error......... +4.70

86 09 54.07

43 39 38.99

50 10 30.58

180 00 03.64 

Spherical excess . 0. 90

Error ........ +2.74

Correction

a 

+2.13

+0.61

+0.71

-0.90

+0.21

+2.18

-2.97

-1.33

-0.40

-0.84

_ 0 43

-1.47

Corrected 

spherical angle

0 / //

40 33 21.30

44 03 31.13

95 23 08.33

180 00 00.76 

-0.76

40 09 13.26

QA OQ no on

45 12 39.22

180 00 00. 78 

-0.78

83 48 51.82

50 34 37.17

180 00 00. 92 

-0.92

86 09 53.23

43 39 38.56

50 10 29.11

180 00 00.90 

-0.90

To select the sines for the side equation: Consider the figure as a 

pyramid with vertex (the pole) at 1; by redrawing the figure with the 

line 4-2 dotted and the triangle 1-3-4 shaded, it will appear to the eye 

as such a pyramid. Select for the first set of angles for the side equations those opening to the front in going around the base of the pyramid from 2 to 3 to 4 to 2; for future reference mark them with solid
TKIANGULATION 73

arcs of circles; the remaining angles around the base make up the 

other set and may be marked with dotted arcs. The pole should be 

selected so that the two smallest angles will be used in the equations. 

Find the sines for each set of angles, recording also the differences for 

1" for each; call the first set of sines plus and the second set minus, 

find the difference between them, and give it the sign of the greater.

Side equations

Sides

,,.

f- 1/4+3/4 r+^ -4/2+1/2

1-1/3+2/3

f- 1/4+2/4 

1-^-3/2+1/2 

-4/3+1/3

Observed angles

83 48 53.15 

45 12 37.04 

40 33 19.17

40 09 14.16 

95 23 07. 62 

45 36 34.90

Log. sines

9. 9974645 

9. 8510731 

9. 8130350

9. 6615726

9. 8094543 

9. 9980787 

9. 8540576

9. 6615906 

9. 6615726

-180

Difference 

for 1"

+2.2 

+20.9 

+24.6

+24.9 

-2.0 

+20.6

Correction in 

seconds

-1.33 

+2.18 

+2.12

-0.91 

+0.71 

-2.97

Correction to 

sines

-3 

+46 

+52

-23

-1 

-61

Corrected 

sines

9. 9974642 

9. 8510777 

9. 8130402

9. 6615821

9. 8094520 

9. 9980786 

9. 8540515

9. 6615821 

9. 6615821

0

Equations of condition are now made up as follows: For triangle 

(a), equation (f), error equals 3.45"; this is made up of the errors in 

the azimuth or direction of the sides -1/4 + 3/4 -4/2 +1/2 -1/3 + 2/3, 

six in all. In like manner form equations (g) and (h). The side 

equation (i) is made up as follows: The error of the sines, being the 

difference between the two sets, is 180. To correct the sines 

changes in seconds to be found for the angles must be multiplied by 

the differences for 1 second in column 4 of (e) for the given angle; 

hence for the first sine this will be +2.2 multiplied by the corrections 

to be given the directions 1/4 and +3/4, or if expressed in a simple 

form it will be 2.2 1/4 + 2.2 3/4. Treat each side and difference for 

1 second in like manner, noting, however, that for the second set of 

sines, which is considered negative, each sign given for the side will 

be reversed for example, the first pair is written +24.9 1/4 24.9 

2/4. It will be noticed that in the first form of (i) as written, 1/2 

appears twice with like signs, 1/4 appears twice with unlike signs; 

combine like terms algebraically, thus reducing the equations to the 

second form of (i). For the convenience of the computer and in 

order to avoid the handling of large numbers, equation (i) has been 

divided through by 100, which is equivalent to taking as the unit 

the fifth place of decimals of the logarithms.

(f) 0=-3.45-1/3+2/3-2/1 + 3/1-3/2+1/2.

(g) 0=-1.49-1/4+2/4-2/1 + 4/1-4/2+1/2. 

(h) 0=+4.70-4/3+1/3-1/4+3/4-3/1 + 4/1.

(i) 0=-1.80 -0.022 1/4+0.022 3/4-0.209 4/2+0.209 1/2-0.246 1/3+0.246 2/3 

 (-0.249 1/4+0.249 2/4+0.020 3/2-0.020 1/2-0.206 4/3+0.206 1/3).
74 TOPOGRAPHIC INSTRUCTIONS OP GEOLOGICAL, SURVEY

Combining like terms and changing all signs within the parentheses 

reduces equation (i) to the following form:

(i) 0=-1.80 + 0.227 1/4 + 0.022 3/4-0.209 4/2 + 0.229 1/2-0.452 1/3 + 0.246 2/3 

-0.249 2/4-0.020 3/2 + 0.206 4/3.

There are now four equations to be solved and 12 unknown 

quantities; the latter are combined and reduced to four by means of 

correlates. In the following table column (j) contains the designations of the sides or directions for which corrections are required. 

Column (k) contains on the proper lines the algebraic coefficients 

for the sides from equation (f); for example, 1/3, considered as a 

quantity, might be written 1(1/3), and +2/3 in like manner written 

+ 1(2/3); 1 and +1 are therefore the entries for column (k), lines

1/3 and 2/3.

Correlates

(j)

Sides

2/1 

3/1 

4/1 

1/2 

3/2 

4/2 

1/3 

2/3 

4/3 

1/4 

2/4 

3/4

W

1

-1 

1

1 

-1

 1 

1

(1)

2

-1

1 

1

-i

 i 

i

(m)

3

 1 

1

1

-1 

-1

1

(n)

4

 --

+0. 229 

-.020 

-.209

 .452 

+.246 

+.200 

+.227 

-.249

+.022

Correlates after substituting computed 

values

1 

 0. 314

+0. 314 

-.314

-.314 

+.314

+.314 

-.314

2 

+0. 590

-0. 590

""+."596" 

+.590

-.590

-.590 

+. 590

3

-0. 651

+0. 651 

 .651

-.651

+.651 

+.651

-. 651

4 

+3. 010

...........

+0. 689 

-.000 

-.629 

-1. 301 

+.740 

+.620 

+.683 

-.749 

+.066

Corrections

-0.276 

+. 337 

-.061 

+.965 

+.254 

-1. 219 

-1. 698 

+.426 

+1.271 

+.744 

-. 159 

-.585

Sides

2/1 

3/1 

4/1 

1/2 

3/2 

4/2 

1/3 

2/3 

4/3 

1/4 

2/4 

3/4

Normal equations are formed from the table of correlates as follows: Column 1, line 1, of (o) (p. 75) contains the sum of the squares 

of each quantity in column (k). Column 2, lines 1 and 2, contains, 

first, the sum of the products of each quantity in column (k) by 

corresponding quantities in column (1); second, the sum of the 

squares of each quantity in column (1). Column 3, lines 1, 2, and 3, 

contains the sum of the products of (k) by (m), (1) by (m), and (m) by 

(m) (the squares). Column 4 is made up in the same manner, using the 

quantities and signs as given. If columns 1, 2, and 3 are completely 

filled out by products found as indicated above, it will be found that 

the quantities from +6.000 down the column are the same as those 

from +6.000 along the lines to the right to column 4. But as the 

former are not needed in the solution they may be omitted; when 

retained, the equations in full will be as follows, the second member 

of each equation being zero:
TEIANGITLATION 

(o) Normal equations

75

1

+6.000

+2.000 

-2.000 

+0.947

2

+2.000 

+6.000

+2.000 

-0.038

3

-2.000 

+2.000 

+6.000

-0.863

4

+0.947 

-.038 

-.863 

+. 51779

Absolute 

term

-3. 450 

-1.490 

+4. 700 

-1.800

These are ordinary algebraic equations which may be solved by 

the usual rules of algebra, but, as the solution of 10, 15, or more 

equations is often required in Geological Survey work, the process 

should be conducted systematically as shown.

Solution of normal equations 

(P)

(Pi) (pj)

(PI)

(PO

(Pi)

(na)

(P7)

(Pa)

1

+6.000 

(-. 1667)

2

+2.000 

-.333

+5. 333

(-. 1875)

3

-2.000 

+.333

+2. 667

-.500

+4.000

(-. 250)

4

+0. 9470 

-. 1578

-.3537

+.0663

-. 3705

+.0926

+. 31060

(-3. 2196)

Absolute 

term

-3. 450 

+.575

-.340

+.064

+3. 720

-. 930

-.935

+3. 010

(q)

(qi) 

(Q«)

(qa)

(q<) (qs)

(q«) (qr)

(q»)

2

+6.000 

-.667

3

+2.000 

+.667

+6.000

-.607

-1.333

4

-0. 0380 

-. 3157

-.8630

+. 3157

+.1768

+. 51779

-. 149447

-. 023450

-. 034318

Absolute 

term

-1.490 

+1. 150

+4.700

-1. 150

+.170

-1.800

+.544

-.023

+.344

(ri) 

(rj)

(rs) 

(rO 

(r«)

1

+0. 575 

-.475

-i217 

-.197

-.314

2

+0.064 

+.200

+.326

+.590

3

-0. 930 

+.279

-.651

4

+3.010

58515° 28 6
!

76 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

The first normal equation is written in full on line (pO; parts of 

the other equations are written on lines (qO, (q3 ), and (q6 ). The 

reciprocal from Barlow's tables of the first quantity ( + 6.000, line 

(pi), column 1), is placed in parentheses, line (p2). The product of 

this reciprocal (0.1667) by the quantitites on line (pO, columns 2, 3, 

and 4, and absolute are written immediately under each in turn; 

the quantity +0.333 (line (p2 ), column 2) is now used as a multiplier 

for line (pO (omitting column 1), and the products are placed in 

columns 2, 3, 4, and absolute, line (q2 ); in like manner the quantities

 0.333 (line (p2 ), column 3) and 0.1578 (column 4) are used as 

multipliers and the products written on lines (q4) and (q7 ). The 

algebraic sums of lines (qO and (q2 ) are now written on line (p3 ), 

which is then used as if it were an original equation. The reciprocal 

of +5.333 is found and used as a multiplier as before, and the products are written on line (p4 ). The next products are wtitten on 

lines (qs) and (qs). The sums of each column of lines (q3 ), (q4), and 

(q5 ) is carried over to (p5 ). The process is repeated for each equation 

until finally the product +3.010 is found, which is the value for unknown quantity numbered 4. This value and also the quantitites 

in the column of absolute terms, lines (p6 ), (p4 ), and (p5), are copied 

in the table (r), line (ri). With +3.010 as a multiplier products of 

each quantity in column 4, lines (p6 ), (p4), and (p2 ), are found and 

written on line (r2 ), columns 3, 2, and 1. Column 3 or (r) is then 

summed and the result ( 0.651) is the value of unknown quantity 

numbered 3. This is used as a multiplier and products found with 

quantities from columns 3 and 2, lines (p4 ) and (p2 ), and in like manner 

values for unknown quantities numbered 2 and 1 are found.

The solution of the normal equations and the values found for the 

unknown quantities may be checked by substituting in the full 

equations (p. 75).

The next step in the adjustment is to substitute the values for the 

four unknown quantities in the table of correlates (p. 74) and to find 

the correction for each side. The method of doing this can be easily 

seen by following the process through the right-hand half of that 

table. For convenience, the value found for each unknown quantity is written at the head of columns 1, 2, 3, and 4. Each of these in 

turn is multiplied by quantities in columns 1, 2, 3, and 4 of the lefthand part of the table and the products are placed in the right-hand 

part on the same line with the multiplicand. The final correction 

for any side is then the algebraic sum of the quantities, which are on 

line with the side number in columns 1, 2, 3, and 4 (at the right side 

of the table). Thus the correction 2/1 is made up of +0.314

 0.590 = 0.276; this is the correction in seconds to the side. The 

correction for any angle, then, is the difference between the cor-
TEIANGTJLATION 77

rections for the two sides bounding it. For example: Angle at Elk, 

triangle (a), is:

 correction 1/3 = +1.698 

.+correction 2/3=+ .426

+ 2.124

The correction for any sine is the correction for the corresponding 

angle multiplied by the difference for I" in the sine.

It is desirable to have triangles close without errors greater than 

a tenth of a second and to have side equations close to the sixth 

place of the logarithm, but unless the normal equations are carried 

to three or four decimal places there will possibly be residual errors 

of two or three hundredths in some triangle closures. It is, however, 

considered allowable in Geological Survey work to make arbitrary 

changes of not over ±0.03" in angles in order to obtain consistent 

results.

The figures for adjustment will generally be larger than quadrilaterals, though they may be made up of quadrilaterals or triangles 

which do not overlap and are therefore independent each of the other. 

When they do overlap select for the first pyramid group (p. 70) the 

one which takes in the largest number of triangles and set down 

(according to the formula on p. 72) the number of triangle equations 

required to adjust it completely, remembering that the triangles 

used must always cover the whole area once but not twice. For the 

second group set down the number of triangle equations required by 

the rule as if they were from an independent pyramid group, but 

omit from those selected all which would be adjusted in or by the 

first group, the vertex of the pyramid being so situated that a base 

triangle will not be included in a former group. In other words, as 

group by group is added to the first find for each a single side equation 

and as many additional angle equations as are required, including in 

the number all triangles adjusted by a previous group excluding those 

which appear in each or which would appear in each if the vertex of 

the pyramid were taken in a different place.

In any figure in which each station is sighted from every other one 

no attention need be paid to the selection of triangles for use in the 

adjustment; they may be taken at random, provided the number 

required by the formula is used.

In order to adjust an extensive triangulation scheme, the strongest 

groups are adjusted first; then if lines or triangles in them form 

parts of other groups, their first adjusted values are given infinite 

weights and thus left unchanged.

In connecting new groups of triangles with those previously 

adjusted, if more than a single adjusted line is used a condition must 

be introduced fixing the relative length of .the adjusted lines. For
- I.

78 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL, SURVEY

example: Let the solid lines in Figure 2 represent an adjusted group 

and the dotted lines part of a new group of triangles to be adjusted. 

It is evident that the distance a c and the angle a b c are fixed by the 

completed adjustment; therefore in adjusting the new work a side 

equation must be used in order to maintain the relative length of the 

lines a 6 and & c. This may be taken from the quadrilateral a d c e 

with the central point &, infinite weight being given to the five 

adjusted lines.

The accuracy of figure adjustments will be increased if the sines 

of the smallest angles are used in forming the equations and if each

figure used covers the 

largest possible area; but 

on the other hand labor 

will be saved if as few 

angles as possible are in- 

, volved. These conditions 

appear when two figures 

overlap; in such cases a 

sum angle can be used in 

adjusting one figure, with 

a saving of labor, but

FIGURE 2.-Condition to be introduced in connecting new lin] pq_ fl l] fu p trianjrlpcs nrp triangles to those previously adjusted umess an me triangles are

of good shape it is better to

take the triangles which cover the largest area. Whether the slight 

increase in accuracy justifies the extra labor involved depends on the 

quality of the work.

The angles to be used depend on the position taken for the pole 

of the assumed pyramid.

WEIGHTED OBSERVATIONS

If the field notes show that certain angle measures are incomplete 

or uncertain it is generally advisable to introduce weights. These 

may be in the form of fractions or whole numbers, but in assigning 

them the field observations and records alone should be considered, 

not triangle closures. An infinite weight is given when it is desired 

to hold the value for a direction, as when it is taken from a previously 

adjusted figure. A weight of » for a side reduces all correlatetable products for it to 0 hi other words, eliminates its effect on 

the normal equations.

Weights are used only in the table of correlates on page 79. As 

an example of their use let weights be assumed for directions in the 

table of correlates as follows:

The rule for forming normal equations from weighted correlates 

is that each product for a given side is to be divided by the weight 

for that side before combining it to form a term in the equation.
TRIANGULATION 79

For example: The first term in equation 1 is made up as follows 

from column t of the correlates:

Side 2/1 (-1) (-1)

Side 3/1 (+1) (+1)

Side 1/2 (+1) (+1)

Side 3/2 (-1) (-1)

Side 1/3 (-1) (-1)

Side 2/3 (+1) (+1)

weight 2=+0.500 

weight 1= +1.000 

weight 2=+ 0.500 

weight 3=+ 0.333 

weight 1 = +1.000 

weight \= +2.000

+ 5.333

The sum of these quantities, +5.333, is the coefficient of the first 

term. The fourth term of equation 1 is

Side 1/2 (+1) (+0.229) -4- weight 2= +0.1145 

Side 3/2 (-1) (-0.020) -J- weight 3=+ 0.0067 

Side 1/3 ( 1) (-0.452) -=- weight 1 =+0.4520 

Side 2/3 (+1) (+0.246) -*- weight i=+0.4920

+ 1.0652

Combining these quantities gives +1.0652, which is the coefficient 

of the term desired Each other term of the normal equation is 

found in a similar manner.

These equations after solving by the usual methods give the 

values at the head of columns 1, 2, 3, and 4 in the right-hand part 

of the following table of correlates. These values after multiplying 

by the quantities in columns t, u, v, and w are placed in their appropriate spaces and the sum for each line found as described on 

page 76. Each sum thus found for a side is then divided by the 

weight for the side, the quotient being the correction for the side, 

and the corrections thus found, if applied to the triangles (p. 72) 

and the side equation (p. 75), will make a complete adjustment for 

the figure.

Correlates for weighted equations

Sides

9/1

3/1

4/1

1/2

3/2

4/2 i/<*

2/3

AM

1/4

2/4

3/4

2

1

1

2

3

1

1

A

1*

2

1

1

t

1

-1

1

1

-1

-1

1

U

2

-1

1

1

-1

-1

1

V

3

-1

1

1

-1

-1

1

w

4

+0.229

-.020

-.209

-.452

+.246

+.206

+.227

-.249

+.022

1

(-0.415)

+0. 415

-.415

-.415

+.415

+.415

-.415

2

(+0.703)

-0.703

+.703

+.703

-.703

-.703

+.703

3

(-0.756)

+0. 756

-.756

-.756

+.756

+.756

-.756

4

(+3.236)

+0. 741

-.065

-.676

-1.463

+.797

+.666

+.735

-.806

+.071

-0.288

+.341

-.053

+1. 029

+.350

-1.379

-L804

+.382

+1.422

+.788

-.103

-.685

Sums 

divided

by 

weights

-0.144

+.341

-.053

+.514

+.117

-1. 379

-1.804

+.764

+1.422

+.394

-.103

-.685
80 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY 

Normal equations

1

+5. 333 

+1.000 

-2.000 

+1. 0652

2

+1.000 

+4.500 

+1.500 

-.039

3

-2.000 

+1.500 

+5.500 

-.750

4

+1. 0652 

-.039 

-.750 

+. 526055

Absolute

-3.450 

-1.490 

+4.700 

-1.800

In the solutions of the normal equations on page 75 no method 

was shown for checking the work before the final values of the unknown had been found and substituted in the full equations. There 

is a simple method for checking a solution frequently, and as it involves but little extra labor it should be adopted when a large number 

of simultaneous equations are to be solved. The check requires an 

added term for each equation, the numerical value of which is the 

algebraic sum of all the coefficients and the absolute term of each 

full normal equation. The check numbers should be given a sign 

opposite to that of the sum, so that the equations will still have the 

form of (a) + (&)+etc. = 0.

In the following solution the check is used; the solution differs 

slightly in form of arrangement from that shown on page 75 and 

is in some respects simpler.

The check column is numbered 6; the first term, line (a), is the 

algebraic sum of each quantity on line (a) with the opposite sign; 

similarly lines (c), (g), and (1) contain check numbers found from 

the sum of the quantities in each of the full equations; but as all the 

terms of each equation are not written down they may be found, 

because of the symmetry of the equations, from quantities given in 

other equations. For example, for equation 3 add together the 

quantities in column 3 of the normal equations (p. 75) and those on 

the third line: -2.000 + 1.500 + 5.500-0.750+4.700 = 8.950; hence 

 8.950 is the check number. The check numbers are to be treated 

in the solution as if they were absolute quantities.

For the first equation the reciprocal of the first coefficient (5.333) 

with its sign changed is 0.1875; this multiplied by each term of 

line (a) gives the quantities in line (b).

The quantity 0.1875 (column 2, line b) is next taken as a multiplier for all the coefficients immediately above it and for others to 

the right on line (a), the products being written on line (d).
TBIANGULATION 

Solution of equations, with check

81

Reciprocals

-0. 1875

-.2319

-.2542

-3. 5132

1

+5.333 

-L

+.647

-.646

-.284

-.132

 .415

2

+1.000 

-. 1875

+4.500 

-.187

+4.313

-L

+.195

+.179

+.329

+.703

3

-2.000 

+.375

+1.500 

+.375

+1. 875

-.435

+5.500 

-.750 

-.816

+3. 934

-L

-.959

+.203

7>;fi

4

+L0652 

-. 1997

-.0390 

-.1997

-.2387

+.0554

-.7500 

+. 3995 

+.1038

 .2467

+.0627

+. 526055 

-. 212720 

-. 013224 

 . 015468

+.284643

-L 

+3.236

5 

(absolute)

-3. 450 

+.647

-1. 490 

+.647

-.843

' +. 195

+4.700 

-1.294 

+.367

+3. 773

-.959

-1.800 

+.689 

-.047 

+.236

-. 921

+3.236

6 

(check)

 1.948 

+.365

-5. 471 

+.365

-5.106

+1.184

-8.950 

-.730 

+2. 221

-7. 459

+1. 896

+.998 

+.389 

-.283 

-.468

+.636

-2.235

(a) 

(b)

(O 

(d)

(p\

(0

<<?>

(i)

(j) (b)

G) 

(m) 

(n) 

(o)

(P)

(q) 

(r)

(<i\

(t)

(u)

(v)

Products for equation 3, witten on line (h), are found with the 

multiplier +0.375 and the quantities in columns 3, 4, 5, and 6, 

Hne (a). All the other numbers on line (b) for any set of equations 

except those in the absolute column 5 and the check column 6, are 

used as multipliers, and the products are written under the equations 

to which they belong. Lines (c) and (d) are next added algebraically 

and the sums written on line (e).

Line (e) now consists of a complete equation containing but three 

unknown quantities, an absolute term, and a check term, and the 

algebraic sum of all the quantities on the Hne should be zero, reasonable allowance being made for sHght errors introduced from the 

dropping of decimal places beyond the fourth. This constitutes the 

first useful application of the check term.

The reciprocal of the first term in Hne (e) with sign changed is 

 0. 2319; this multiplied by each quantity in Hne (e) gives the products on Hne (f); these also if combined algebraically should equal 

zero, and thus the work is again checked.

Products from multipHers for each unknown quantity ( 0. 435 and 

+ 0. 0554) are next found in the same manner as for lines (a) and (b) 

and written under the equations to which they belong (on lines (i) 

and (m) in this example). The algebraic sum of each column under 

equation 3 is next to be found and written on line (j). This is now 

a complete equation with two unknown quantities, and the sum for 

the whole Hne should equal 0, this being the third use of the check
82

i

TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

term. This elimination process is repeated and the check applied 

until line (q) is reached, the absolute term then being the value of 

the fourth unknown. This value is written on line (r), column 4, 

and the absolute quantities from column 5, lines (k), (f), and (b), are 

written in columns 3, 2, and 1, line (r). The numerical value of 

number 4 is next to be multiplied by the coefficients of number 4 

in column 4, lines (k), (f), and (b), and the products written on line 

(s), columns 3, 2, and J, respectively. The sum of the quantities in 

lines (r) and (s), column 3, is 0. 7560, which is the value found 

for unknown number 3, and this value substituted in column 3 gives 

products for line (s).

ADJUSTING LINES TO UNOCCUPIED STATIONS

An adjustment can be made for the three lines to an unoccupied 

station as follows: Correct the observed angles to the unoccupied 

point to agree with previously adjusted angles at each occupied 

station; then form a side equation, making the unoccupied station 

the pole of the pyramid, if thereby the smaU angles are used in 

making up the equations.

The swings for the lines to the unoccupied station, which will be 

the corrections desired, will be the products of the sine differences 

for I" (coefficients of the sine equation) by the absolute term, divided 

by the sum of the squares of the former.

For each additional line more than three to the unoccupied station 

an additional side equation is required, all to be solved in the usual 

manner.

COMPUTATION OF DISTANCE

The computations of distance are to be made in book 9-901. 

The triangles are arranged in order from a given base or known side, 

one page or part of a page being taken for each new station. For 

each triangle the adjusted spherical angles and the spherical excess 

are given to hundredths of seconds.

Example of computation of distance

Station

Browning.. . _ .. _ ...... ___ ...... ____ ..

Elk....................... .....................

Dick........ .

Miles, 11.106

Spherical 

angle

50 10 29.11 

86 09 53.23 

43 39 38.56

180 00 00.90

Spherical 

excess

-0.30 

- .30 

- .30

"Brown

Miles, 16.050.. __ . ___ . ... ___ _____ _ . . ____ Brown

Plane angle 

(9.8853615)

50 10 28.81 

86 09 52. 93 

43 39 38.26

180 00 00. 00 

ting to Elk. 

ing to Dick.

Log sines 

and distances

4. 2984616 

0. 1146385 

9. 9990263 

9. 8390917

4. 2521918 

4. 4121264
TKIANGULrATION 83

After adjustment of several overlapping figures has-been completed, it is occasionally necessary to find the length of some line 

joining two points which has not been included in the adjustment. 

Such lines may usually be computed by the formula for "two sides 

and the included angle." 3

The rule for the solution of plane triangles for which the three 

angles and one side are given is that the sides are proportional to the 

sines of the opposite angles. By always arranging the angles in the 

form above suggested, with the new station first, the solution is made 

somewhat mechanical. The logarithms of the shies of plane angles 

are used; that for the angle at the new station from which distances 

are required to the other two stations is written immediately above 

the angle; its arithmetical complement (10 minus the sine) is written 

to the right and on line with the angle. Each of the other sines is 

placed on line with the angle to which it relates. Immediately 

above the sines is written the logarithm of the distance in meters 4 

between the second and third stations in the triangle; in the example 

this is 4.2984616 for the line Elk to Dick.

To get the logarithm of the distance from the new station (Browning in the example) to one of the other stations, omit the sine opposite 

the latter and add together the remaining logarithms in the righthand column. The distance to thousandths of a mile for each computed line must be found and placed to the left of the names of the 

terminal stations. The work should be verified by comparing distances for each line that has been computed from two or more 

triangles.

COMPUTATION OF GEODETIC COORDINATES

For the computation of geodetic coordinates use book 9-902 and 

check results by computing each position from two stations which 

form a triangle with the new station. For convenience, only one 

of the computations is here given:

3 U. S. Geol. Survey Bull. 650, p. 8, 1918.

4 Meters are used by tne Geological Survey in all triangulation computations for the reason that the 

best obtainable geodetic factors are those prepared by the United States Coast and Geodetic Survey, 

which are metric.
84 TOPOGRAPHIC INSTRUCTIONS OP GEOLOGICAL SURVEY

Azimuth a: .E7Zfc-Z>ic&--__----__----_---__-_- 96 56 01.12 

Spherical angle at Elk-..........--...-. 86 09 53.23+

Azimuth a': Elk-Browning................. 183 05 54.35

Aa+180°_.--______.___.__ ...-180 00 24.02

Azimuth (a): Browning-Elk................. 3 06 18.37

LATITUDE LONGITUDE

<f> ...... 37 28 47. 32

A<t>.... 9 38.

<(>... ... 37 38 26. 20

Computation for latitude : 

logs. ____ 4. 2521918 

log B... ... 8.511O415

log cos a'... 9. 99936 47 ( )

log (!)_____ 2. 7625980( 

log s2 ______ 8.60438

log C...... 1. 28943

log sin2 a'... 7. 46561

log (II)..__ 7.25942

log D-----. 2. 3771

log [I + II]2 - 5. 5252

log (III).___ 7. 9028

log #-__-__ 6. 0528 

log s2 sin2 a'. 5. 9700 

log (!)_____ 2. 7626(-)

-IV. 

(!)__

. .OOO(-)

578, 898(-) 

.002 + 

.008+

 A</>-__- 578. 883(-) 

i it

A4>_---_- 9 38. 88(+)

Elk.

Browning.

A arc and sine 

(logs').... 06 

(log V)_ +00

-06

<}>87 28 47. S 

<t>'S7 38 26. 2

67 IS. 5 

37 33 37. 0

AX.

00 16. 16 

0 39. 40(-)

X'_______ 81 69 36. 76

Computation for longitude:

logs.___---. 4.2521918

log sin a'.... 8. 7328074(-)

log A'....-.. 8.5091777

log sec </>.---_ 0. 1013532

Aaands____ ( 6)

1.5955295(-) 

39. 403-

AX--_____39. 40 

Computation for azimuth: 

log (V). ______ 1.595530(-)

log secf-^) 0. 000000 

\ « /

log (VI) ____ 1.380572(-)

-Aa______ 24". 02(-)

Ao__._______ 24".02(+)

Azimuth check.

[I+II] 678. 891 

log [I+ 11] 2. 762598

53 16 47. 48

3 06 18. 37

log [I+II? 5.525196 60 10 9. 11

Spherical angle

at Browning 50 10 29.11 

Computation of azimuth a, in book Al§05, page 26. 

Spherical angle and distance s, in book A1570, page 32.

Computed by D. M. E.

[NOTE. The signs (+) or ( ) placed after logarithms are the signs of the cosines or sines of the 

azimuth used in the computations.]
TRIANGTTLATION 85

In this example the azimuth, 96° 56' 01".12, is derived from a 

previous computation. The spherical angle is that at Elk from the 

adjusted figure. Whether to add or subtract this can be determined 

very easily by inspecting a plat of the stations, but when for one of 

the pair of computations the spherical angle is added, the other is 

always subtracted. The latitude and longitude at Elk are also 

derived from a previous computation. Logarithm s is the logarithm 

of the distance in meters between Elk and Browning. The constants 

B, C, D, and E are taken from "Geographic tables and formulas" 5 

for the known latitude at Elk. Cosine of and sine of are functions 

of the azimuth Elk to Browning. The algebraic sign of each of these 

functions as fixed by trigonometric rules determines the sign.of the 

resulting quantity. The signs of (II) and (III) are always positive; 

that for (IV) is always opposite to that of (I). The constant A' and 

secant $' in the longitudinal computation are for the new latitude, 

which requires that the latitude computation be made first. These 

two factors will be the same for each of the pair of computations for 

the new position. For short lines, corrections (III) and (IV) will 

generally be less than 0.01" and may be neglected.

When the logarithm of distance s in meters exceeds 4.0000000, a 

correction will usually be required for logarithm (V) for the difference between the arc and sine. The constants for computing this 

correction are given on page 292 of " Geographic tables and formulas," 6 

the arguments being log distance s and log (V). The difference 

between the values found is to be applied, according to the sign of the 

greater, to log (V) before finding the value of the latter in seconds.

Six places of decimals will usually give sufficient accuracy for

log (VI). The logarithm of secant ( ~o~ ) may be taken from page

291 of "Geographic tables and formulas." When log (V) is large, 

say over 3.5000000, a correction in seconds 6 will be needed for Aa 

expressed by the factor (AX)3 F. The logarithm of (V) is multiplied 

by 3 and added to the logarithm of F, which is given in the tables; 

the value in seconds for the resulting logarithm is always to be added 

to the previously found value in seconds for (VI).

The latitudes and longitudes for each point thus computed in 

pairs should agree within one or two one-hundredths of a second.

The difference between the two reverse azimuths should also agree 

with the corresponding adjusted spherical angle within one or two 

one-hundredths of a second.

The formulas for finding azimuth and distance between points 

whose latitude and longitude are known and the form for 3-point 

computations are given in "Geographic tables and formulas." 

Special blanks for 3-point work may be procured by application 

to the Washington office.

8 See also Coast and Geodetic Survey Special Pub. 8,1911. 

8 TJ. S. Geol. Survey Bull. 650,1924.
86 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY 

TABULATION OF RESULTS

The final step in the computation of triangulation is the tabulation 

of the results. A printed blank is used; on it is written the name of 

the station, the State and county in which the station is situated, 

the kind of signal and the center mark used, a full description of the 

station (see p. 62), the latitude and longitude, the azimuth, the back 

azimuth, and the logarithms of distances in meters and corresponding 

distances in miles to all other stations from which it is visible; also 

a statement regarding the datum on which positions are based. 

Whenever possible this should be the North American datum (formerly known as the United States standard datum).

SUGGESTIONS TO COMPUTERS

Do not crowd your work; paper is comparatively cheap.

Do your work in a systematic manner. If it permits tabular 

arrangement, always use the forms approved by other computers 

unless you can convince them that yours are better. The survey 

has printed forms for many purposes; these should be used whenever 

possible, for by their use the work is made more mechanical, and the 

more mechanically the work is done the less chance there is for error.

A computer who is inexperienced or out of practice should check 

his work in every way possible. He should check logarithms either 

of numbers or of circular functions by using first a tabular value for 

a quantity less than the given one and then a greater tabular value, 

so that the differences in one case may be added and in the other 

subtracted. This operation may be reversed when the logarithm 

is given and numbers or angles are required.

Many errors are made by taking out the first three figures of a 

logarithm from the wrong line of a seven-place table where a dash 

over the fourth figure indicates that the first three should come 

from a lower line.

As the algebraic signs of cosines and sines are so frequently required, the rides governing them should be firmly fixed in the mind; 

as an aid to this remember the general rule that distances measured 

upward or to the right on the conventional plat of the quadrants of 

the circle are considered positive, and others negative. The wrong 

use of signs is a very common source of error.

Where the function of an angle over 90° is desired, instead of 

subtracting 90° or 270° from the angle to find the argument, add 

the figures hi the tens and hundreds of degrees places together and 

prefix the sum to the unit degree figure, dropping the sum if it is 

9. Thus 121° gives 1+2 = 3, and 31° is the argument; 184° gives 

1+8 = 9, drop it, leaving 4° for the argument; 290° gives 9 + 2 = 11,
TBIANGULATION 8*7

drop 9 from the 11 or add the two figures a second time, giving an 

argument of 20°.

Each step in a long computation, if it is not at once automatically 

checked, should be checked by repeating the computation.

Check the copying of angles, distances, etc., taken from adjusted 

results for use in new computations; also check figures carried from 

page to page.

Gross errors are sometimes made by using the sine.when a cosine 

is required, or by writing a product in the wrong column, as east for 

west, in primary-traverse computations.

Placing the decimal point in the wrong place is a common mistake. 

This may in many cases be corrected by a mere inspection of the 

quantity to see whether it appears of proper value.

Good judgment should be exercised in the degree of accuracy 

sought for a given result. For the preliminary computation of 

geographic positions, for example, six-place logarithms will suffice; 

these can be taken from a seven-place table with only a rough interpolation. A four-place logarithm can often be used to advantage. 

The accuracy of the results obtained should equal the requirements; 

more than this involves a waste of tune.

The foot, yard, and mile are the units adopted for all Geological 

Survey field work, but for geodetic computations meters are used. 

The best conversion tables for metric and English measures are 

those published by the Bureau of Standards. In using these tables 

all changes from one system to another should be checked by reversing the operation. The logarithms for the interchange of these 

measures are given in "Geographic tables and formulas," page 364.

When computers are duplicating work and a difference is found, 

each should recompute the result before correcting either, as errors 

have frequently been made by changing the correct figures.

When two persons are comparing a copy with the original if the 

reader occasionally calls out a wrong figure or word intentionally 

and notes whether the error is caught up, it tends to keep the listener 

more intent on the work.

C. TRANSIT TRAVERSE

Compiled by E. M. DOUGLAS

GENERAL CONDITIONS FOR MAP CONTROL

The boundary lines of all regular United States Geological Survey 

maps are parallels of latitude and meridians of longitude. In order 

that these shall be properly located and that intermediate points shall 

be placed in correct positions, some system of horizontal control is 

required. The method to be adopted for linear control should be 

fixed by the character of the country, one of the requirements being 

that all control work shall be so accurate that no errors will be apparent in maps several times as large in scale as those to be published. 

In mountainous regions or in hilly, partly timbered areas horizontal 

control is effected by a system of triangulation, the whole area being 

divided up into triangles whose apexes are represented by stations 

established on prominent points several miles apart.

In heavily timbered areas, where it is difficult to see from any point 

more than a mile or two in any direction, horizontal control is best 

obtained from distances measured on the ground with a 300-foot 

steel tape, a record being made of angles measured with a transit at 

each bend in the line. Such control must begin and end at points 

whose positions have been previously determined, and regardless of 

the character of the country such control must be carried around the 

edge of each quadrangle and once across its center east and west.

The United States Board of Surveys and Maps has classified 

traverse control for geodetic or map use into four orders. The position check for the first order is 1 in 25,000; for the second order, 

1 in 10,000; for the third order, 1 in 5,000. Control of the fourth 

order is based on tape, wheel, or stadia distance measurements. For 

transit-traverse control as executed by the Geological Survey for map 

use an accuracy of the third order only is necessary, but the limit of 

error of 1 in 5,000 must be maintained. The main or trunk-line 

traverses that supplement the first-order (precise) work of the 

United States Coast and Geodetic Survey must be of such an accuracy that a control point near the corner of each degree quadrangle 

shall be located with an error of not more than 1 in 7,500.

89
90 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY 

TRANSIT-TRAVERSE FIELD WORK 

PERSONNEL AND OUTFIT OF PARTY

A transit-traverse party consists of an instrument man in charge, 

a recorder, two tapemen, and two rodmen; also a cook and a teamster when camping is necessary.

The following supplies (see pis. 5, 6) can be obtained on requisition :

One transit, graduated to 30 seconds and furnished with stadia wires.

Two 300-foot steel tapes, graduated to feet throughout.

One 100-foot steel tape.

Two red and white transit rods.

One stadia rod.

Two plumb bobs.

Eleven tally pins.

Three hand recorders.

Two electric hand lamps.

One tape repair outfit, punch, and rivets.

Three tape clips, temporary repairs.

Two tape holders.

One spring balance.

One thermometer.

One set steel dies, figures.

One set steel dies, letters.

Three large book bags.

Standard bench-mark tablets.

Canteens.

Cement (in cans).

Drills, hatchet, hammer, post-hole digger.

Transit-traverse field notebooks 9-928.

Tapemen's notebooks 9-929.

Blank notebooks 9-896, or 3 by 5 inch pieces of manila paper.

Book of instructions.

Polaris and sun tables.

The instrument man must carry a reliable watch.

ADJUSTMENT OF INSTRUMENTS 

PRECAUTIONS

The object glasses and eyepieces of all instruments must be properly focused. The cross wires projected against a distant object 

should appear immovable when the eye only is moved. Before the 

adjustments are commenced the instruments must be firmly set up 

and leveled. An instrument may appear to be out of adjustment 

simply because some part is loose. The object glass may be partly 

unscrewed, or an adjusting screw may be only partly tightened; 

level bubbles or cross wires occasionally become loosened. Therefore, before commencing the adjustment of an instrument look out
U. S. GEOLOGICAL SURVEY BULLETIN 788 PLATE 5

APPARATUS USED IN TRANSIT TRAVERSE

fl, 300-foot tape and reel; b, 100-foot tape; c, plumb bob; d, spring balance; c, hand counter; 

/, thermometer; g, Hash light; ft, steel dies
U. S. GEOLOGICAL SURVEY liULLETIX 7SS PLATE 6

VERNIER TRANSIT (&), STADIA ROD (a, right), AND RANGE ROD (a, left)
TRANSIT TRAVERSE 91

for such defects. When it is thought that an adjustment has been 

completed, always test it before using the instrument. All adjusting 

screws should be screwed tight enough to hold, yet not so tight as 

to injure the threads or put a severe strain on any other part. 

Especial care should be taken not to strain the cross-wire screws. 

Adjustments should be made in the order given under the following 

headings, for some adjustments depend on the accuracy of others 

previously made, and a change in any one may affect the others.

MINOR REPAIRS

Setting of buttles. For setting level bubbles a small supply of 

plaster of Paris should be kept on hand. For use the plaster should 

be mixed with water to the consistency of a thick paste. If plaster 

is lacking, strips of paper may be used, but these should never be 

jammed in very tight, as the pressure may distort the glass and thus 

vitiate the bubble reading by an appreciable amount. A reflecting 

surface of colored paper should be placed under the bubble in order 

to make the graduations more readable; a subdued green or blue 

tint is recommended.

Moimting of cross wires. For mounting cross wires a small bottle 

containing shellac dissolved in alcohol, a pinch of beeswax, and a 

pair of dividers or a forked stick are needed. The best spider web is, 

of course, a freshly spun one from a small spider, for this will be both 

clean and elastic; but as spiders are not always available, it is 

well to keep on hand a spider cocoon. Such a cocoon will furnish 

webs enough to last for years, although with age the threads become 

stiff and brittle and therefore more liable to break from a jar to the 

instrument. Most webs taken from grass or bushes are rough, coarse, 

and dirty.

To draw the reticule from the instrument, unscrew and remove 

the eyepiece slide: then take out two opposite capstan-headed 

screws and loosen the other two. Using the latter two as handles, 

revolve the cross-wire ring 90°, insert a pointed stick through the 

end of the telescope tube into a screw hole in the ring, and, using it 

as a handle, remove the other capstan screws and draw out the ring. 

To replace it in the telescope, reverse this procedure. When in 

place the cross wires should be on the side of the ring toward the 

eyepiece.

Having pressed a bit of beeswax to each prong of the dividers or 

forked stick, let a small web fall from the end of one of the prongs, 

or pick with it from a cocoon a single thread, pressing the thread into 

the beeswax, stretch the thread moderately, and attach to the wax 

on the other prong. If an old web is used, it should first be dampened by dipping in water for a few seconds. In place of the dividers

58515° 28 7
92

or forked stick, small sticks or lumps of wax may be attached to the 

web about 2 inches apart. Place the web across the reticule, using 

a magnifier to insure its coinciding exactly with the marked lines. 

Put a small drop of shellac on each end and leave until dry.

Instruments such as the prism level, dumpy level, and transit, 

which are not provided with Ys or similar devices for adjusting 

the cross wires, may be put in close adjustment by means of improvised wooden or metal Ys.

ADJUSTMENT OF TRANSIT

Plate levels. With lower plate clamped and upper plate loose, 

level carefully; revolve the instrument 180° on its vertical axis and 

bring each level bubble halfway back to the center of the tube by 

means of the screw at one end.

Collimation. Level carefully, sight on a point about 500 feet distant, raise or lower the telescope slightly, and note whether the 

vertical wire remains on the point; if not, loosen the capstan-headed 

screw and turn the cross-wire ring till the vertical wire will remain 

on the point when the. telescope is raised or lowered. Clamp the 

instrument, set the vertical wire so that it cuts the point selected, 

transit the telescope by revolving it 180° on its horizontal axis, and 

select a second point 500 feet distant in the opposite direction from 

the first. Unclamp the upper plate, turn the transit 180° on the 

vertical axis, relevel if necessary, set it on the point first selected, 

and again clamp the plate. Transit the telescope, and if the vertical 

cross wire exactly bisects the second point its adjustment is perfect; 

if it does not, bring it one-quarter of the way back to the second 

point by turning the two capstan-headed screws on the sides of the 

telescope.

Standards. Set up the transit near a tall building or other high 

object; after leveling carefully, point the telescope so that the vertical wire intersects a definite point about 60° above the horizontal, 

depress the telescope, and select a second point near the ground. 

Unclamp the upper plate, revolve the telescope and plate 180° on 

the vertical axis, clamp the plate with the vertical wire again cutting 

the upper point, and depress the telescope; if the cross wire intersects the lower point, the standards are in adjustment; if it does 

not, correct for one-half the error by the screw underneath one end 

of the telescope axis.

Object-glass slide. If an adjustment for the telescope object-glass 

slide is possible, it is made as follows: First make the collimation 

adjustment for a point about 300 feet distant, then focus on a point 

1,000 feet or more distant and again on a point only 10 or 15 feet 

distant, transit the telescope, unclamp the plate, turn it 180° on the
TRANSIT TRAVERSE 93

vertical axis, and reclamp. If the cross wire still cuts the distant 

and near points, the slide is in perfect adjustment; if it does not, 

correct half the error by means of the side screws that hold the slide 

ring in place. Next repeat the regular collimation adjustment and 

again test for the slide error; repeat both adjustments until no 

errors appear.

Eyepiece tube. The eyepiece may be put into position over the 

cross wires by turning the screws that hold the eyepiece ring until 

the cross wires appear in the center of the field; an exact centering 

is not required.

Telescope level. If there is a level attached to the telescope, it 

may be adjusted by the " peg method " after all the other adjustments are made, as follows: Level the transit and bring the bubble 

to the center of the tube under the telescope. Take a reading on a 

leveling rod or pole 300 or 400 feet distant, which is held on a stake 

set firmly in the ground. Eevolve the transit 180° on the vertical 

axis and after again bringing the bubble to the center set a second 

stake at the same distance as the first and at such an elevation that 

the rod or pole reading is the same as on the first stake. The tops 

of the two stakes will then be at the same elevation. Move the transit 

25 or 50 feet back of one stake and on a line with the other. Make 

the telescope as nearly horizontal as possible by means of the 

attached level, clamp it, and then take a reading on the rod held on 

the near stake and another reading on the distant stake. If the two 

readings agree, the telescope is horizontal; if they do not agree, turn 

the tangent screw so as to bring the cross wire while set on the distant rod nearly to an agreement; repeat the operation until an agreement is reached. The telescope is then level, and the adjusting nuts 

at the end of the level tube should be turned until the bubble is 

brought to the center.

Vertical circle or arc. The screws holding the vernier for the vertical arc should now be loosened and the vernier moved until the 

reading is 0° while the telescope is still level.

GENERAL REQUIREMENTS

Location of line. Transit traverses should always be run in circuits or tied to points previously located. In a 15-minute quadrangle, in country where routes can be readily planned, traverse lines 

should follow as closely as possible the borders of the quadrangle to 

be controlled, not departing from them more than is necessary to 

keep on roads. If there is a choice of roads, select the one in an unmapped area. An additional east-west line should be run to bisect 

the quadrangle. In areas where the country will not permit this 

plan to be followed economically and where the selection of routes
94 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

for the lines must be influenced by the location of highways, it will 

be necessary to plan the routes to meet the specific requirements.

Permanent marks. In areas where topographic conditions permit 

a tablet (see pi. 4) in a concrete post must be placed as near as possible to each corner of each 15-minute quadrangle, one on each side 

halfway between the corners, one in the center of the quadrangle, 

and others at average intervals of 3 miles along other parts of the 

lines. All such marks must be stations on the lines and unless they 

have already been marked by a levelman should be stamped " Trav. 

Sta. No. " (numbered consecutively) and also with the year of survey and the initial letter of the traverseman's surname. In areas 

that can not be traversed according to the regular plan permanent 

marks must be established at intervals not greater than 3 miles.

In cooperating States the appropriate tablet (A, pi. 4) must be 

used.

Where level bench marks have already been established along the 

route of survey, they should be tied to and stamped as above and 

thus made to serve as permanent marks on the traverse line.

It is desirable that every permanent point be tied to two or more 

witness or reference points, and the true azimuths, a sketch, and the 

approximate or exact distance to each, with description, should be 

duly recorded in the notebook.

Sites for marks. The sites for permanent marks should be selected with great care and be at points where they may be used by 

levelmen as bench marks. It should be borne in mind that the value 

of the work depends largely on the permanence and the accuracy of 

the marks. Marks that are intended to be permanent must not be 

placed nearer than 15 feet to a wagon road or a railroad. They 

should not be placed on bridges, though these may be good places for 

temporary marks. A concrete post may be placed on the right of 

way line of a railroad or highway. The right of way line at the intersection of two roads is commonly an excellent site. The marks 

should not be placed near old buildings that may soon be torn down, 

enlarged, or rebuilt. The site selected should be a place where the 

mark will not be in the way of anyone and will probably not be disturbed for many years. Marks set in earth in exposed localities 

should be surrounded by mounds of earth or stone.

Concrete posts. Where solid rock or large boulders are not 

available, the most durable objects in which to place tablets are 

concrete posts. These posts may be made by contract, or if made 

in place, proceed as follows: Provide two or three heavy reinforcing 

wires of nearly the length of the proposed post, with ends bent over 

an inch or two; also a piece of conical sheet-iron pipe 12 inches long, 

6 inches in diameter at one end and 8 inches at the other. Dig a hole
TRANSIT TRAVERSE 95

12 inches in diameter and 24 to 36 inches deep. The deepest holes 

are required in cold regions; a 24-inch hole is deep enough in 

regions where the ground seldom freezes. Place the reinforcing 

wires in the hole, and fill within 6 inches of the surface of the ground 

with concrete consisting of one part cement, two parts sand, and 

three parts broken stone or gravel, well mixed and moderately wet; 

tamp well. Set the iron pipe, large end down, over the center of 

the concrete block so as to inclose the wires, and space them an inch 

or so from the outside. Fill the pipe with cement mortar, consisting 

of one part cement and two parts clean sand; tamp well. In the 

top of the post place a tablet flush with the rounded surface of the 

cement. Any marks to be added to the tablet should be stamped on 

it before it is placed in the wet mortar. The finished post should 

not project more than 6 inches above the original ground surface. 

The post when completed should be sheltered from the sun for 

several days. If a mark must be established in soft or wet ground 

proceed as follows: Drive a wooden stake 3 by 3 inches, or larger, 

as far in the ground as it will go without splitting. Saw off the top 

about 6 inches above the ground. Place a length of glazed drain 

tile 6 inches or more in diameter around the stake, with its flange 

end at least 12 inches below the surface of the water or ground. 

Fill the tile with cement mortar, round off the top slightly, and 

set a bench-mark tablet in the top flush with the surface of the 

cement.

Azimuth marks. Whenever practicable two or more reference 

marks should be established for each permanent mark, from which 

azimuths can be found for future use. These may be church 

steeples, cupolas on schoolhouses, water tanks, corners of large buildings, or any other prominent objects. If no well-defined objects are 

visible, copper nails in large trees 50 to 100 feet distant will serve 

the purpose. The distances and the angles to near-by marks should 

be measured. A sketch helps the computer avoid errors in finished 

work. All reference marks and the azimuths to them must be 

described and reported, together with the computed results of the 

line.

Additional points. Besides the permanently marked points, a 

number of other points should be carefully located along the 

traverse, and these points should be specifically designated in the 

field notes. Of special importance are the crossings of boundaries 

of States, counties, and civil townships, and the locations of the 

principal crossroads, railroad and highway crossings, railroad stations, and township and section corners. Note should also be made 

of less important landmarks, such as road forks, mileposts, railroad 

switches, and stream crossings. These points should be so 

completely described in the notebook as to be readily identified.
96 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

Control for airplane photographs. In view of the extensive use 

of airplane photography for mapping, all points on a traverse line 

that can be easily identified from the air must be located.

Maps are most successfully compiled from aerial photographs 

when the control traverses are run after the photographs have been 

made. By this arrangement routes for traverses that will most effectively control the photographs may be selected. It is absolutely 

essential that traverse points be located near each end and the 

center of an area covered by a tri-lens photograph in order to control it properly, and the chance of getting such a combination of 

points is very much reduced if the arrangement of the areas to be 

photographed in the quadrangle is not first considered. This condition does not apply to single-lens photographs, for which the ordinary rules for the distribution of traverse lines may be followed.

Control points for aerial photographs should be selected with due 

regard to easy identification, and only such points as are clearly 

shown in the photographs should be chosen for computation. Gates, 

trees, wire fences, windmills, houses, and indefinite road intersections are unsuitable. Road forks, road intersections, well-defined 

angles in roads or streams, stream crossings that intersect roads 

at right angles, fence lines defined by a growth of trees or brush, 

sharp angles in woodland boundaries, and railroad crossings usually 

make good points for identification.

Level bench marks. The work must if possible be so arranged 

that the levelman can determine an elevation for each traverse 

mark; therefore the party that precedes should endeavor to select 

sites for marks suitable for the other party, and the descriptions 

made by both parties should agree. Copies of the descriptions should 

be forwarded daily to the party following.

Land survey corners. Diligent search and inquiry should be 

made for marks on the public-land surveys, and accurate connections should be made with each one that is found. It is very important that numerous corners be located for the topographer. In 

areas where unusual difficulty is experienced in finding corners the 

General Land Office will, on request through the Washington office, 

detail a cadastral engineer to assist in the search.

Accuracy. For all circuit closures in new work or ties between 

located points of the same or a higher order an accuracy of not less 

than 1 in 5,000 (about 1 foot to the mile) must be maintained.

For main or trunk control traverses that follow routes near the 

borders of each full degree quadrangle an accuracy of 1 in 7,500 

must be maintained that is, the initial and computed positions of 

a tie point must not show a difference of more than 1 part in 7,500 

of the length of the traverse line. To insure such a degree of accuracy especial care must be taken in making the measurements of dis-
TRANSIT TRAVERSE 97

tance. The front tapeman should be a man of experience and should 

be held responsible for proper procedure.

Highway surveys. Highway surveys may often be substituted 

for or used as transit-traverse lines. The field notes for these surveys can usually be obtained from the office of the State highway 

department, which is generally at the State capitol.

The methods of surveying highways are similar to those used in 

transit traverse, except that the true azimuths of the lines are seldom 

given; but approximate azimuths may be based on a magnetic bearing of the first course, to which has been applied the deflection angle 

at each transit station. If no true azimuths are known, it will be 

necessary to tie to at least two adjacent stations near the beginning 

of each highway survey and to observe for the true azimuth of that 

course. Additional azimuths should be determined at stations not 

more than 10 miles apart.

Field notes of highway surveys should be copied in book 9-928. 

In these notes each station is usually referred to two or three points; 

the descriptions of these points should be copied from the field notes 

and used in tying to the stations at which azimuth observations are 

to be made.

The results of each azimuth observation should be computed in 

the field as soon as the observation is made, and the bearings from 

the highway surveys should be checked between observations.

In copying field notes of highway surveys all road forks, bridges, 

railroad crossings, civil boundary lines, and junctions with other 

highway surveys should be noted for computation.

Highway surveys must always be tied to triangulation or transittraverse stations by running a traverse line from a station on the 

highway survey to a station of higher order.

FIELD METHODS

Duties of tape men. The front tape man must carefully mark off 

each tape length, if on a wagon road, with tally pins; if on a railroad 

tangent, with keel on the rail. Each time he marks off a tape length 

he registers it on his hand recorder; each time the rear tape man 

reaches the mark left by the front tape man he does likewise. When 

a transit station is established the two tape men compare their hand 

records for check on the measurement. Should they differ, the 

course must be remeasured.

Transit stations should be made at even tape lengths or even 10- 

foot marks, wherever possible, in order to simplify the work of the 

computer. They should be selected at points affording not only an 

unobstructed view back to the transit but also a clear view forward. 

Each station is to be marked, if on a wagon road, by a 10-penny
98

nail driven into the ground through a piece of paper on which the 

front tape man has written the number of the station and the distances ; if on a railroad, by a keel cross on the rail with the number 

and distance on the nearest tie.

Stations on main lines are to be numbered consecutively, beginning with zero; those on short spur lines to section corners or other 

points to be computed are to be lettered instead of numbered. Station numbers should never be duplicated in a single locality.

The two tape men must keep in book 9-929 separate records of 

the number of stations and distances between them. At noon and at 

night these records must be compared with the recorder's notes, and 

should there be a difference it must be corrected before the line is 

carried forward, the line being retraversed if necessary.

In locating transit stations the front tape man should bear in 

mind that it is desirable for the instrument man to be able to sight 

the bottom of the rod in each direction. This is especially important on short sights, for errors due to sighting the upper part of a 

rod which may be out of plumb may appreciably affect the accuracy 

of the line.

Method of measuring. When measuring along a wagon road the 

tape must be kept horizontal unless the grade is very slight; on short 

steep slopes a plumb bob must be used either to bring the tape end 

vertically over an established point or to establish a new point. 

Judgment should be used in selecting the proper length of tape on 

short slopes; no attempt should be made to use the full 300-foot 

length; about 150 feet is ordinarily all that a tape man can hold 

horizontal with the proper tension and plumb at the same time. 

On slopes that require " breaking " the tape into short sections, the 

entire tape should first be drawn forward its full length by the 

front rodman if convenient, or by the front tape man, who then returns to help " break " the tape at the proper places, until the end of 

the tape is reached. In this manner the distance is measured on the 

whole tape and does not depend on the sum of the separate horizontal 

measurements.

On long regular slopes the distance on the slope should be measured and recorded and the angle of slope measured with the transit. The corrections for slopes of 1° or 2° for short distances are 

negligible.

Test of tape. A tested tape will be supplied to each party and 

should be kept in reserve; the tape used in 'measuring should be 

compared with the tested tape each week and the results made a 

part- of the record. A tape when in use should always be stretched 

by means of a spring balance to a tension of 20 pounds.
TRANSIT TRAVERSE

Tape errors. Tests of tapes by the Bureau of Standards seldom 

disclose errors as great as 0.01 foot in 300, but occasionally for a 

patched tape the error runs as high as 0.06 foot. Great care should 

be taken when a broken tap© is patched to see that the length of 

the section is not changed. Before any tape is used in the field 

the length should be checked up by the chief of party, by comparison with an unbroken standardized tape.

A difference of 7% feet in the elevation of the ends of a 300- 

foot tape will shorten the horizontal distance 0.1 foot. A difference in elevation of 2^ feet will shorten the distance 0.01 foot.

Geological Survey 300-foot steel tapes are standardized at a temperature of 68° F. and a tension of 20 pounds. A variation of 10° 

above or below this temperature will change the length of the tape 

0.02 foot. Differences of temperature of 20° or 30° above or below 

68° are common and for such differences corrections should be made 

in the recorded figures for distance, which should be increased for 

temperatures above 68° and decreased for temperatures below 68°.

A change in tension of a Geological Survey 300-foot steel tape 

from 20 to 25 pounds increases its length 0.016 foot. A decrease 

in tension from 20 to 5 pounds shortens the tape 0.047 foot.

The correction for sag (always negative) for a 300-foot tape supported at 50 foot intervals under a tension of 20 pounds is 0.016 foot.

Errors in taping. The errors that most seriously affect the accuracy of taped lines may be grouped in two classes.

The errors of one class are due to failure to keep the tape horizontal and to careless plumbing. The instrument man should impress the tape man with the fact that the accuracy of traverse depends on the taping more than on the instrumental work, for the 

latter is checked at every azimuth observation, whereas there is no 

check on the taping until the circuit is closed.

The errors of the other class are gross mistakes, arising generally 

from carelessness in counting tape lengths. They may be eliminated by checking the count of tape lenghs by independent measurements. To do this, the instrument man should measure each distance by stadia, using the red and white transit rod or a special stadia 

rod carried for this purpose. In case the distance is too great to 

be read by a single sight, he should set up the transit between stations and read both front and rear rods. Stations should under no 

circumstances be more than 2,600 feet apart, which is about the limit 

of visibility of the rod. On a railroad an additional check on the 

taping may be had by counting rail lengths, but it should be remembered that rails may be 26, 28, 30, or 33 feet long. The counting 

should be done by both rodmen and the recorder, or by the instru-
100 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

ment man while moving from one station to the next. In other 

places a check may be had by pacing. The distance to a plus point 

should be checked, as well as the distance to the next station.

Temperature record. The transit man should carry a thermometer and record the temperature every hour.

Stadia control. Under certain conditions it is allowable to substitute stadia distances for tape-line measures in transit traverses for 

" fourth order " control of maps. Such lines should not exceed 20 

miles in length and should be well checked, either by tying to a previously determined point or by closing on an azimuth station. Points 

on stadia lines should not be used as initial points for the extension 

of transit traverses.

For work of this class a Philadelphia rod with two targets should 

be used, one target to be fixed at the 2-foot mark, the other target 

to be set from signals by the transit man.

The value of the stadia interval must be accurately determined 

for each transit by the following method: With a steel tape measure 

a base line on nearly level ground and mark stations at intervals of 

100, 200, 300, 500, 700, and 900 feet from the center of the transit, 

With the transit at station 0 read and record the rod interval at 

least five times for each station, setting the upper target carefully 

for each reading and recording intercepts to three places of decimals. 

Repeat the observation at intervals of two hours from 8 a. m. to 

4 p. m. The means of the differences between the steel-tape distances 

and those found by stadia will be the corrections to apply to stadia 

readings before recording them. Only the corrected stadia distances 

are to be recorded.

Stadia stations should not be more than 900 feet apart.

OBSERVING AND RECORDING

Deflection angles. At each station, in reading deflection angles, 

the instrument man should proceed as follows: Sight rear rod with 

transit circle set at last reading at previous station, transit telescope, 

sight front rod, and read both verniers. Turn instrument with the 

two plates clamped, the vernier remaining undisturbed; sight rear 

rod again and remeasure the angle. If the two results thus obtained 

differ more than 60 seconds, repeat the operation. Opposite vernier 

readings will not always give the same minutes and seconds; both 

must be read and recorded to the nearest second.

When the transit is carried from one station to the next, keep the 

upper plate clamped so as to retain the last vernier reading; after 

setting up the instrument verify the reading and record it as the 

first back-sight reading at the new station, but both verniers must 

be read twice at each station. By following this plan a useful check
TRANSIT TRAVERSE 101

on the readings is procured without trouble, and it also permits easy 

and quick computation of an azimuth at any station. The approximate azimuth of a line must be known at a station where daylight 

observations are to be made on Polaris, in order to determine the 

proper pointing for the star.

Computing azimuth. If the foregoing rule has been adhered to, 

the azimuth of a line at any station at which the deflection angle is 

read twice only may be found as follows:

Find the difference between the A vernier reading for the last foresight along a preceding course the azimuth for which is known and 

the A vernier reading for the last foresight along any following 

course the azimuth of which is desired; subtract the smaller reading 

from the larger and divide the difference by 2. Adding the quotient 

to the known azimuth when the later A vernier reading is greater or 

subtracting it from the known azimuth when the later A vernier 

reading is less will give the azimuth desired.

Example:

At station 10 the last A vernier reading of foresight from station 10 to 11 is 

120° 42' 00".

At station 72 the last A vernier reading of foresight from station 72 to 73 is 

94° 20' 00".

The azimuth of line 10 to 11 is 167° 25' 00". 

120° 42' 00" 94° 20' 00"=26° 22' 00". 

% of 26° 22' 00" =13° 11' 00". 

Known azimuth 10 to 11 =167° 25' 00"

 13 11 00

Azimuth of line station 72 to 73=154 14 00

The half angle is subtracted in this example because the second vernier reading is less than the first.

Tajriyents. At a railroad or highway crossing where there is a long 

tangent the distance to the farther end of the tangent should be assumed or estimated and the deflection angle to it recorded. In the 

computed results the record should be made according to the following model: " Position of a point 3 miles distant, on line with 

R. & N. Railway tangent, latitude 47° 10' 20", longitude 110° 

14' 07"." This record will afford data by which the topographer 

can accurately plot the tangent.

Azimuth observations. Observations on Polaris or the sun far 

azimuth must be made each day if the weather permits. On a 

crooked line with many short courses azimuth observations should 

be made at points not more than 100 stations apart; on a traverse 

with long tangents they should fall not more than 10 miles apart. 

When practicable an azimuth station should be placed at each 

decided change in the direction of the line and where an abrupt 

change occurs between long and short sights. These requirements
102 TOPOGRAPHIC INSTRUCTION'S OF GEOLOGICAL SURVEY

may necessitate going back over the line in order to make the essential observations. If conditions are favorable it is possible to make 

azimuth observations on Polaris in broad daylight.

Both the transit and the azimuth mark must be at stations in the 

traverse preferably not less than 500 nor more than 1,500 feet apart. 

Each point should be marked by a stake with a tack or, if on a railroad, by a nail in a tie. The azimuth mark for night observations 

may consist of a vertical slit one-eighth inch wide and 6 inches long 

cut in the side of a box or tin can containing a candle or lantern, 

the slit to be carefully centered over the tack in the stake, or of a 

nail on the marked point illuminated by a lantern or flashlight 

shaded from direct observation from the transit.

In pointing the telescope for night observations use the electric 

hand lamp to illuminate the cross wires, holding it nearly in front 

of the object glass, or allow it to shine on a piece of paper fastened 

with a rubber band in front of the object glass and having in it a 

half-inch hole.

In clear weather Polaris can be seen with a good transit telescope 

several hours before sunset, but it is necessary to know the star's 

altitude within about 10 minutes of arc and its bearing within about 

1° in order to get the star into the field of the telescope when it is 

not visible to the naked eye. The finding of Polaris in daylight may 

be facilitated by preparing a table of positions of the star for a 

month in advance. The table should give the hour angle for a 

selected hour of local time, also the altitude and azimuth of the 

star for the same time. Corrections easily applied may be found 

for other hour angles and for changes in latitude or longitude.

To find the altitude and azimuth with sufficient accuracy for this 

purpose proceed as follows:

Assume that an observation is to be made at 3h 25m p.m., ninetieth 

meridian (central) standard time, January 10, 1925, at a place whose 

latitude is 40° 10' and longitude 85° west from Greenwich, as scaled 

from a good map. As 85° is 5° east of the ninetieth meridian the 

watch is five-fifteenths hour, or 20 minutes, slower than local 

time. The observation is therefore to be made at 3h 45m local mean 

time.

The ephemeris (p. 1) shows that the nearest upper culmination 

of Polaris, which is then on the meridian above the pole, occurs at 

6h 15.6m p. m. January 10, 1925, Greenwich mean time. The correction to reduce this culmination time to 85° west longitude time is 

 0.9m.

Local time of upper culmination=6h 15.6m 0.9m ____ 6h 14. 7m 

Assumed observation time____________________ 3 45

Hour angle of Polaris______________ 2 29. 7
TRANSIT TRAVERSE 103

Always take the nearest upper-culmination time, whether it is 

before or after the observation time.

From the table on page 22 of United States Geological Survey 

Bulletin 650 the bearing of Polaris for latitude 40° 10' and an hour 

angle of 2h 29.7m (before upper culmination) was found to be 

0° 53' 07". Polaris was therefore about 53' east of true north at the 

time and place of observation. This is not the exact bearing, but it 

is near enough for the purpose. When this table is not at hand the 

bearing can be computed from the table on page 10 of the ephemeris.

The altitude of Polaris may be found from the tables on page 26 

of Bulletin 650. It may also be found by reversing the operation 

called for by the tables on page 12 of the General Land Office 

ephemeris or by means of the following formula:

Sine of altitude=sin </> sin S+cos <t> cos d cos t

where <£=the latitude of the place, 8 the declination of the star, and t 

its hour angle east or west of upper culmination.

With the transit in good adjustment set- off on the vertical arc an 

angle of 41° 03' (the altitude) ; next focus the telescope very carefully for a distant pointing. It is well to focus the telescope on a 

star at night and then mark the focusing slide so that it can be set 

at the same place at any time, for unless the telescope is properly 

focused the star can not be found in the daytime.

If an approximate true north bearing is not known, obtain it by 

compass, making proper allowance for declination. Point the telescope 0° 53' east of true north, as found by computation or by the 

needle. If the air is clear and the star can not be seen in the field of 

the telescope, turn the transit on its vertical axis slowly, without disturbing the vertical-circle setting, for a degree or two to the right or 

left to correct any imperfect pointing in azimuth. When the star 

is seen turn the tangent screws of both the vertical and the horizontal 

axis so that the cross-wire intersection will cover it, and then proceed 

with the observation for azimuth in the manner described below, 

which is applicable to observations at any hour of the day or night 

when the star is visible.

Angles may be read as follows: Set on azimuth mark, then on 

star; reverse telescope; set on star, then on azimuth mark. Each 

set of observations should consist of not less than three direct and 

three reverse measurements, the circle being shifted for each set by 

about 60°. Observations may be made at any time the star is visible but preferably when it is at or near elongation. The time of 

setting the cross wires on the star should be recorded to the nearest 

second. Observations should be made rapidly; not more than 15 

minutes need be taken to complete a set. The notes should be kept 

in the form which follows:
104 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

Date: January 10, 1925.

Azimuth observation at station 332, mark at station 333. 

Latitude 40° 10', longitude 85° west of Greenwich.

Watch 35 seconds fast of ninetieth meridian standard time (not daylightsaving time).

Mark....... __._...-._._...-.-_-.

Mark....... .................. ...

Mark..__. ....... .-..-_..___.._-.

Star-....-.....-.....-..-.-.....

Star. ... .........--.... --..--

Mark............................

Mark................ ...........

Mean.-.. __ .. _ . __ - Watch fast... ...................

Vernier A

279 06 30

333 02 30

153 01 30

99 06 00

172 02 00

225 56 00

45 55 00

352 02 30

40 56 00

94 46 30

274 46 00

220 56 00

Vernier B

99 06 00

153 03 00

333 01 00

279 05 00

352 02 30

45 56 00

225 54 30

172 02 00

220 56 00

274 46 30

94 45 30

40 56 30

Mean

99 06 15

153 02 45

153 01 15

99 05 30

172 02 15

225 56 00

225 54 45

172 02 15

40 56 00

94 46 30

94 45 45

40 56 15

Angle mark 

to star

53 56 30

53 53 45

53 52 30

53 50 30

CO AQ Ort

53 63 05

Watch time

H. m. s.

3 40 18

3 41 20

3 45 00

3 52 36

3 46 03

35

3 45 28 

3 45.5

Because of the difficulty of finding Polaris for daylight observations it is often advantageous to record the reading on the star first, 

then on the mark, and last on the star.

For daylight observations when the star is only dimly seen it is 

not advisable to shift the horizontal circle between readings, as to do 

so would make it more difficult to find the star again.

On the same page with the other records the latitude and longitude 

of each azimuth station, scaled to the nearest minute from the best 

map available, should be recorded, together with the date of observation, the watch error, and a statement as to the time zone used and 

whether or not the watch was set for daylight-saving time.

An example of computation for either daylight or night observations on Polaris is here given:

January 10, 1925, ninetieth meridian time. Latitude 40° 10', longitude 85° 00'.

Instrument on station 332; mark on station 333.

H. m. s. 

January 10, 1925, ninetieth meridian standard time of observation

(correction having been made for watch error). _ _ __ 3 45 28 

Correction for 5° east of longitude 90°___________________ + 20 00

Local mean time of observation ____ __ _ 4 05 28

(4 05.5)

The nearest upper culmination of Polaris as given in tables is 6h 15.6m 

p. m., January 10, 1925, Greenwich mean time, civil date. The correction (always negative) to reduce to local meridian is -fifs of

daily change (3.9m )=0.9m. H. m. 

Local mean time of upper culmination, January 10, 1925, p. m.

(6h 15.4m 0.9m )______________________ __ 6 14.7
TRANSIT TRAVERSE 105

H. m.

Hour angle, being the interval between time of observation (4h 05.5m )

and time of culmination_____ ___ _______ 2 09.2

With this hour angle as an argument and the declination for the 

given date (88° 54' 25"), find by double interpolation from the 

table of azimuths of Polaris of the Land Office tables (p. 10) 

the azimuth angle for the latitude and time_____________ 0° 46.9'

As the star has not reached culmination it is east of north (180°)

or, 180° being added, has an azimuth of _____________ 180° 46.9' 

Subtract from this angle the measured angle between mark and

star ____________________________ 53 53.1 

The star being east of the mark, the remainder is the true

azimuth of the mark on station 333 from station 332____ 126 53. 8

A rough check of this azimuth may be obtained by comparing it 

with the observed magnetic bearing, allowance being made for declination.

Sun observations. When it is impracticable to take observations 

on Polaris for azimuth, observations on the sun may be taken instead, 

but such observations should not be taken within two hours before or 

after noon, or when the vertical angle of the sun is less than 15°.

Set up the transit at a station in the line of survey, adjust and 

carefully level it, read the verniers and record the readings for first 

pointing on the rod. Point the telescope to the sun and allow the 

image to fall on a piece of white paper held 3 or 4 inches from the 

eyepiece. Focus the cross wires on this image. By means of the 

two tangent screws move the telescope till the vertical and horizontal 

wires bisect the sun's image, taking care to use the middle horizontal 

wire and not the upper or lower stadia wire. Read and record the 

horizontal and vertical angles. Repeat the pointing and reading at 

least five times, and after the last pointing read again on the rod. 

Should the reading on the rod not agree within 1 minute of the first 

reading, discard the entire set and make new observations.

Reverse the telescope and repeat the readings at least five times as 

before. This time should be recorded to the nearest minute at the 

first and last pointing, and the mean time should be computed.

An example of field notes for afternoon observations is given 

on the next page.
106 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

Instrument, station 624; rod, station 625.

Latitude 38° 53' 46" (as scaled from any good map).

Date, November 10, 1925. Ninetieth meridian time (standard time).

Vernier readings ^^un"*168 

Rod- 0° 00' 00" 180° 00' 00"

Sun-90 36 00 270 36 00 17° 01' Time of first pointing at sun 3h 16m p.m. 

Sun_ 90 45 30 270 45 30 16 54 

Sun_ 90 55 00 270 55 00 16 46 

Sun_ 91 02 00 271 02 00 16 40 

Sun_ 91 09 00 271 09 00 16 35 

Rod- 00 00 00 180 00 00

Reverse telescope (relevel if necessary).

RodSunSunSunSun_

SunRod0

91

91

91

91

92

00

913

Mean

0 00'

30

38

45

54

00

onuu

15

angle,

00"

30

00

00

00

30

00

30

rod

180°

271

271

271

271

272

1 OA -LoU

00

30

38

45

54

' 00"

30

00

00

00

00 30

00

to sun,

00

+91°

16°

16

16

15

15

164

15'

10

04

59

52

16

Time of last pointing at sun 3 20

6

Q£» 

ob

Mean time of observation 3h 18m

19' 33".

Mean of vertical aneles _ 16° 25' 36"

p.m.

Correct altitude of sun_________________ 16 22 22 

Refraction tables are given in Bulletin 650, page 334, but if no 

tables are available the approximate value of the refraction in seconds may be taken as 58 times the natural cotangent of the sun's 

observed altitude.

To compute the azimuth from the field notes use the formula

p ^2 azimuth angle _ sin of (S latitude) X sin (S altitude corrected for refraction) 

0 2 ~ cos S X cos (S polar distance)

ill which S = y2 (latitude + altitude -}- polar distance).

It is necessary to obtain from tables, for the hour, day, and year, 

the declination of the sun that is, the angular distance of the sun 

north or south of the Equator. The declination at Greenwich noon, 

for each day in the year, is given in a publication of the General 

Land Office entitled " Ephemeris of the sun and Polaris." This 

ephemeris is issued about December 1 of each year for the following 

year.

The polar distance is the angular distance between the sun and the 

north pole. In winter, when the sun is south of the Equator, the 

polar distance is 90° plus the declination; in summer, when the sun 

is north of the Equator, it is 90° minus the declination. Twice a 

year, September 23 and March 21, it is 90°, the declination being 

0 when the sun crosses the line.
TRANSIT TRAVEBSE 107

The procedure to find the declination of the sun in the example 

given is as follows:

Observations for November 10, 1925, 3h 18m p. m., ninetieth meridian time. When it is noon at Greenwich it is 6 a. m. on the ninetieth 

meridian (90°-=-15=:6; 12 noon 6 hours=:6 a. m.). The mean of 

the times of observation is 3h 18m p. m., 9 hours and 18 minutes after 

6 a. m. local time or Greenwich noon. In the tables showing the 

position of the sun for the year 1925 the apparent declination at 

Greenwich noon on November 10 is given as 17° 04' 43" south. The 

south declination is increasing at the rate of 42.37 seconds for each 

hour after Greenwich noon. The tables give declination for apparent (sun) time. The change from apparent to mean noon can generally be disregarded, as it will never be more than 15 seconds of arc.

The observation was made 9 hours and 18 minutes (=9.3 hours) 

after Greenwich noon; therefore the change in the declination of 

the sun since the preceding Greenwich noon was 42.37x9.3=394 

seconds=r6 minutes and 34 seconds.

Declination (south) November 10, 1925, at Greenwich noon________________________ __ 17° 04' 43" 

Correction to be added for 9.3 hours_____ ___ 6 34

Declination at 3.18 p. m________________ _ 17 11 17 

To find the polar distance, add the declination as above found 

to 90°:

Declination___________________________ 17° 11' 17"

90 00 00

North polar distance, November 10,1925, 3h 18m p. m__ 107 11 17 

To find the value of S in the formula:

Latitude________________ 38° 53' 46" 

Altitude of sun___________ 16 22 22 

Polar distance_______ __ 107 11 17

162 27 25

y2 of sum_______________ 81 13 42=S 

S_____________________ 81° 13'42" 

Latitude ________________ 38 53 46

42 19 56 = S latitude

S_____________________ 81° 13'42" 

Altitude ________________ 16 22 22

64 51 20 =S altitude of sun 

S_____________________ 81° 13' 42" 

Polar distance____________107 11 17

25 57 35 =S polar distance

There are times when the polar distance is less than S, but always 

subtract the lesser quantity from the greater. 

58515° 28 8
108 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

All the quantities required in the formula are now known except 

cot azimuth angle. To find that quantity proceed as follows:

S latitude _____ 42° 19'56" log sin__________ 9.82829

S altitude _____ 64 51 20 log sin __________ 9.95676

S polar distance __ 25 57 35 colog cos_________ 0. 04619

S ____________ 81 13 42 colog cos_________ 0. 81674

Log cot2 y2 azimuth__________________________ 0.64798

Divide log by 2 to get square root.

Log cot V2 azimuth ______________________ 0.32399 

(The cologs of cosines are the log cosines subtracted from 10.) 

Angle corresponding to log cot 0.32399=25° 22' 22" = % azimuth. 

Azimuth of thesun.____________ 50°44'44"

Angle between rod and sun____-_____+ 91 19 33

Azimuth at station 624

to station 625. ___ _____ 31925 11=S. 40° 34' 49" E.

If the angle between the rod and the sun is plus, subtract it from 

the azimuth of the sun; if minus, add it.

An example of field notes for morning observations is given below.

Instrument, station 426; rod, station 427.

Latitude, 42° 36'24".

Date, August 14, 1925. 75th meridian time.

Vertical angles 

Vernier readings to son

Rod_ 0°00'00"180°00'00"

Sun_ 312 40 00 132 40 00 38°55'00" Time of first pointing at sun 8h 40m a.m.

Sun_ 312 50 30 132 50 30 39 04 00

Sun- 312 58 30 132 58 30 39 11 00

Sun_ 313 07 00 133 07 00 39 17 30

Sun_ 313 14 00 133 14 00 39 22 30

Rod- 0 00 00 180 00 00

Reverse telescope. 

Rod- 0°00' 00" 180°00' 00" 

Sun_ 313 39 00 133 39 00 39°40'30" 

Sun_ 313 48 30 133 48 30 39 49 30 

Sun_ 313 58 00 133 58 00 39 57 00 

Sun_ 314 08 30 134 08 30 40 03 00

Sun_ 314 16 00 134 16 00 40 10 00 Time of last pointing at sun 8 44 a.m. 

Rod- 00 00 00 180 00 00

17 24

3134 40 00 395 30 00 

Mean of readings 313° 28' 00". Mean time of observation_____ 8h 42m

Subtracting mean from 360° gives mean angle, rod to sun, 

46° 32' 00" east of south.

Mean of vertical angles__________________ 39° 33' 00" 

Correction for refraction___________________ 01 10

Correct altitude of sun______________ 39 31 50 

The azimuth is computed from the field notes according to the 

formula given on page 106.
TRANSIT TRAVERSE 109

Observations for August 14, 1925, 8h 42m a. m., seventy-fifth 

meridian tune. When it is noon at Greenwich it is 7 a. m. on the 

seventy-fifth meridian (75-^-15=5; 12 noon 5 hours=7 a. m.). 

The mean of the times of observation is 8h 42m a. m., 1 hour and 42 

minutes (=1.7 hours) after 7 a. m. local time or Greenwich noon. 

In the tables showing the position of the sun for the year 1925 the 

sun's apparent declination at Greenwich noon on August 14 is 

given as 14° 27' 08" north. The declination is decreasing at the rate 

of 46.12 seconds for each hour after Greenwich noon. The observation was made 1.7 hours after Greenwich noon; therefore the 

change in the declination of the sun since the preceding Greenwich 

noon is 46.12 X 1.7=74 seconds=l minute and 14 seconds.

Declination (north) August 14, 1925, at Greenwich

noon _______________________________ 14° 27' 08" 

Correction to be subtracted for 1.7 hours___ ___ 1 14

Declination at 8" 42m a. m__________________ 14 25 54 

Subtracting the declination from 90° gives the polar distance:

90° 00' 00" 

Declination ___________________________ 14 25 54

Polar distance, August 14, 1925, 811 42m a. m______ 75 34 06 

To find the value of S:

Latitude _______________ 42° 36' 24" 

Altitude of Sun___________ 39 31 50 

Polar distance___________ 75 34 06

157 42 20

% of sum______________ 78 51 10 =S 

S ____________________ =78° 51' 10" 

Latitude _______________ =42 36 24

36 14 46 =S latitude

S ___________________ =78° 51' 10" 

Altitude___________ _ =39 31 50

39 19 20 =S altitude

S _____________________ 78° 51' 10" 

Polar distance- _ 75 34 06

3° 17' 04"=S polar distance

To find the azimuth angle of the sun from the data given, proceed 

as follows:

S latitude____ =36° 14'46" log sin __________ 9.77177

S altitude____ =39 19 20 log sin __________ 9.80187

S polar distance = 3 17 04 colog cos __________ 0.00071

S__________ =78 51 10 colog cos _________ 0.71370

Log cot 2 % azimuth__ ____ ___ __ 0.28805 

Log cot % azimuth__ __ __ 0.14402
110 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL, SURVEY

Angle corresponding to log cot 0.14402=35° 40' 10" = % azimuth. 

Bearing of sun, 71° 20' 20" (east of south).

360° 00' 00"

 71 20 20

Geographic azimuth of sun____ 288 39 40 

Observed angle between rod and sun+46 32 00

Azimuth at station 426 to station

427 ______________ _____ 335 11 40 =S. 24° 48' 20" E.

Geographic azimuths are counted clockwise from the south (0° or 

360° ; west, 90° ; north, 180° ; east, 270°).

In case unfavorable weather prevents the taking of azimuth observations leave adequate marks at a point selected, before proceed'ng 

with the line, and return later to make the observations.

Watch error. The instrument man must carry a reliable watch 

and keep it in good condition. He should ascertain its error daily by 

comparison with telegraphic time, which is sent over Western Union 

lines once a day. In case he has no opportunity to make this comparison daily while running the line, he should do so as often as possible, figure the rate, of error per day, and record the proper correction for each azimuth observation made. A watch error of 20 seconds 

or less will not appreciably affect the accuracy of the determination.

Magnetic declination. A careful reading of the needle for magnetic declination should be made at frequent intervals and recorded 

opposite the proper station number in the notebook. Such determinations should be made at each azimuth station and at favorable 

points along the line where the needle is not likely to be affected by 

rails, electric wires, or similar disturbing elements. At azimuth stations determine the magnetic bearing of the azimuth mark at the 

time it is established. If the line follows a railroad, magnetic determinations should be obtained from a parallel line at a distance of 25 

yards from the rails or wires.

Field record. Complete notes must be kept by the recorder in book 

9-928, to be written in a plain, neat hand with a No. 4 pencil. The 

blanks in the title-page should be filled in the first day the book is 

used.

The recorder must take down the vernier readings as they are 

called off by the transit man and compute the mean pointings and deflection angles, giving proper signs to the angles. He must keep up 

with the instrument man in these computations, as they enable him 

to note by inspection whether the instrument man has made errors 

in his readings and to call attention to them before the instrument is 

removed from the station. He should take special pains to see that 

the degree and minute numbers for the two verniers are consistent 

and are recorded in the proper columns. A single line should be 

drawn through erroneous records, which must never be erased.
TRANSIT TRAVERSE 111

The notes are to be kept in the following form.: 

Date, September 9, 1925. Line from Pikeville to Dayton, Mo.

Station 

No.

326 

327 

327+ - 

327+ 

328. ......

Distance 

(feet)

{;;;;;;;

900

{=

1,320 

90 

430

260

Vernier 

A

316 51 30 

275 06 30 

233 21 00

o 233 21 00

279 04 30 

324 48 30

Stream cros 

Crossroad s 

 =324 4830 

3420800 

359 27 00

Vernier 

B

136 52 30 

95 07 00 

53 2200

53 2200

99 05 00 

144 49 30

ssing. 

it Tanbark. 

144 49 30 

162 09 00 

179 2800

Mean

316 52 00 

275 06 45 

233 21 30

233 21 30

279 04 45 

324 49 00

324 49 00 

342 08 30 

359 27 30

Deflection 

angle

0 , 

41 45 15 

41 45 15

-41 45 15

45 43 15 

45 44 15

+45 43 45

17 19 30 

17 1900

+17 19 15

Azimuth

0 / //

« 123 35 00

» 81 49 45

« 81 49 47

* 127 33 30

 127 33 34

» 144 52 45

"144 5243

Stadia

Stadia 905 ...

/Sta. 327-328... 

\N. 59° 30' W..

Stadia 1,330 ...

Stadia 260 _ ..

Vertical 

angle

0 Written in red ink.

* Written with black pencil.

« From actual readings; not copied from the preceding record.

The record must contain also a description of the starting and 

ending points of the line, of each permanent mark established along 

the line, of each point which is to be computed for the use of the 

topographer, and of all crossings and other landmarks that may be 

of value to him. Such descriptions should be concise, yet full 

enough to leave no possible doubt as to the identity of the points 

described. Each should be supplemented by an explanatory sketch, 

if necessary, showing the deflection angles to the reference marks, 

as the true azimuths to these marks are required. The description 

should begin on the next line after the angle record.

Example of description of permanent mark:

Station 1025, bench-mark tablet stamped "Trav. Sta. No. 4, 1912," set in 

sandstone ledge, top of Walden Ridge, 3 miles northwest of Dayton, Mo., at 

junction of Dayton, Pikeville, and Morgan Springs roads, 325 feet west of 

residence of John Neilson. Reference marks: Cross cut in ledge 60.25 feet 

N. 25° 30' E.; spike in root of white-oak tree 14 inches in diameter, 75.60 feet N. 

45° 15' W.

Examples of description of points to be computed and other landmarks :

Station 625+730 feet, center of crossroads at Antioch Church. 

Station 720+320 feet, east abutment of bridge over Glade Creek. 

Station 732, road fork at Johnson blacksmith shop.

Station 926+210 feet, center of track opposite semaphore, Lee station. 

Station 936+300 feet, road crossing half a mile east of Sequatchie railroad 

bridge.

Each point to be computed should be marked with brackets in ink 

immediately upon its selection by the instrument man.
112 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

As soon as the records in a field book are completed, it should, if 

not needed for reference, be sent at once to the Survey office in Washington by registered mail. Tape man's books should be sent separate from other notes and on another day.

TRUNK-LINE TRAVERSES

The foregoing instructions apply also to trunk-line traverses, for 

which an accuracy of 1 in 7,500 is required. The only difference in 

methods between the two grades of work is that much greater care 

will be required for each operation, in both the field and the office, 

for the trunk lines. Temperature corrections must be made, and 

computations carried to tenths of a foot.

TRANSIT-TRAVERSE COMPUTATIONS

The steps in traverse computations are set forth below. The computations are made in books 9-928 and 9-931. The abstracts of 

results are placed on long sheets of paper. Each azimuth computation is to be made in the field notebook on the same page with the 

observations, and the results written in red ink in the azimuth column of notebook (see pp. 101, 111) on the line with the station 

occupied.

Computers should read carefully the " Suggestions to computers " 

on pages 86-87.

Field computation of azimuth. Azimuth notes must be computed 

as soon as possible after observations are made and the results applied to the deflection angles. These computations must be made 

at odd times, when they will not interfere with other work. Errors of closure in azimuth should not be distributed until checked 

by a second computer either in the field or in the office. Allowance 

must always be made for convergence of meridians.

Computation of de-flection angles. The mean deflection angle is 

combined according to its sign with the azimuth from the preceding 

station, and the result placed in pencil opposite the deflection angle 

used. This process is repeated until the next computed azimuth, 

written in red ink, is reached.

The last azimuth in pencil will probably not agree with the observed azimuth. For any line not running due north or south there 

will be a discrepancy between observed and computed azimuths, due 

solely to convergence of meridians, which for latitude 30° will be 0.5 

minute for each mile run east or west. For latitude 49° the amount 

will be 1 minute. For any latitude the convergence in minutes of arc 

will be the difference in minutes of longitude between the ends of the 

line multiplied by the sine of the middle latitude. For lines running 

east the computed azimuth should be less than the observed. For 

lines running west it should be greater.
TRANSIT TRAVERSE 113

Adjustment of closing errors. If no large errors appear in the 

results, the discrepancy between computed and observed azimuths at 

the closing station is to be divided by the number of stations and 

a proportional correction applied to each penciled azimuth, the corrected figures being written in red ink. When a large closing error is 

found in a transit-traverse line look first for a compensating error 

of 1° or 10° in the azimuths or angles.

Computation of latitudes and departures. Latitudes and departures are to be computed in book 9-931, as shown below:

Line from Pikeville to Dayton, Mo.

Station

326 to 327---.-.- ..... _ ..--..-.

327+430 feet ._....._. _ _ ...

527+430 feet to 328.......... ..

Azimuth

0 / //

81 49 47

127 33 34

Distance

Feet 

900

430

890

Sine

0.990

.793

.793

Cosine

0.142

.610

.610

North

Feet

262

262 

128

134 

543

South

Feet 

128

East

Feet

West

Feet 

891

341

1,232

706

Natural sines and cosines for the azimuths given are written in 

the appropriate columns. By means of Crelle's tables the products 

of these quantities by distances are found and placed in the proper 

columns. The sines multiplied by the distance give departures east 

or west. When the sine is positive, the new point is west; when negative it is east. Cosines multiplied by distances give latitudes north 

or south. When the cosine is negative, the new point is north; when 

positive it is south. The direction of the new point can readily be 

determined by noting the azimuth, remembering that 0° azimuth is 

for a line running due south, 90° for a line due west, 180° for a line 

north, and 270° for a line east. In the example given in the above 

table the azimuth 81° 49' 47", being between due south and due west, 

will be to a point southwest. Four decimal places in sines and cosines should be used when distances are greater than 1,000 feet.

When the Gurden traverse tables for distances 1 to 100 for single 

minutes of arc are available, the latitudes and departures may be 

written in the north, south, east, and west columns direct for each 

azimuth and distance.

Whenever a point is reached for which the latitude and longitude 

are desired, as at 327-J-430 feet in the example, leave six blank spaces 

for the computation. The data for the computation for such a point 

are found from the record on page 111 as follows: For the crossroad at 

Tanbark post office, which is on the line between stations 327 and 328, 

the azimuth is the same as to station 328. The distance by measurement is that given, 430 feet from station 327. In order to make the 

computations continuous, station 328 is taken as 1,320 430=890 feet
114 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

from the intermediate point used, the azimuth being the same for 

both points.

Computation of latitude and longitude. The next step in this 

work is the computation of latitude and longitude. These should be 

determined for important points a mile or less apart. Assume, for 

illustration, that for station 326 (p. Ill) the coordinates have been 

completed, and that 327+430 feet is the next location desired. Each 

of the four columns north, south, east, and west is summed; the 

difference between the sums of the north and south columns is placed 

in the column of the greater, and the difference between the east and 

west columns is placed in the column of the greater. The computations of latitude and longitude and the descriptions of the points 

are placed on the right-hand page of the book opposite the group of 

stations.

The logarithms of the geodetic constants for metric measures, 

called " the A, B, G factors," are on pages 219-290 of " Geographic 

tables and formulas." x Factors A and B are used to five decimal 

places only. These will be practically constant for a distance of 10 

or 15 miles north and south, the value for the middle latitude being 

used.

For the example on page 113:

Log distance 134 (north)______________________ 2.12710 

Log to reduce feet to meters__ _ ____ _______ 9. 48402

Log B for latitude 39° 00'____________________ 8. 51093

0.12205

The sum, 0.12205, is the logarithm of change in latitude in seconds between station 326 and 327+430 feet=1.32" (north). 

For change in longitude:

Log distance 1,232 (west)____________________ 3.09061 

Log to reduce feet to meters___________________ 9. 48402 

Log A for latitude 39° 00' 00"__________________ 8.50914 

Log secant of middle latitude__________________ 0.10950

Log of change in longitude in seconds________ 1.19327 

New point west_ ___ _ _ 15. 61"

These differences are to be added to the latitude and longitude of 

station 326.

When the Survey tables of M and P factors, prepared by D. H. 

Baldwin, are available the computation of changes in latitude and 

longitude may be materially shortened by adding log M to the log 

of distance north or south for change in latitude and by adding 

log P to the corresponding distance east and west for the change of 

longitude.

1 U. S. Geol. Survey Bull. 650.
TRANSIT TEAVEESE 115

The foregoing computation would then be written as follows: 

For the latitude change:

Log distance 134 (north)_____________________ 2.12710 

Log M for latitude 39° 00'___________________ 7. 99495

Log of change in latitude in seconds-__ _ a 0.12204 

For the longitude change:

Log distance 1,232 (west)______________ __ 3.09061 

Log P for middle latitude_____________________ 8.10266

Log of change in longitude in seconds. ___ 1.19327

To check the plotting of positions on topographer's field sheets 

the distance between successive positions must be computed. As 

few lines are as much as 1 mile in length and none over 2 miles, the 

latitude and departure can with sufficient accuracy be taken as the 

base and perpendicular of a plane triangle. The distance sought 

will then be the hypothenuse, and its square will be equal to the sum 

of the squares of the base and altitude. For distances less than 

10,000 feet Barlow's tables should be used in finding squares or 

square roots. The distance should be written in red ink, inclosed 

in a circle, on the right-hand page of the computation book in the 

blank space between the entries for the two stations referred to. 

After the record is complete its accuracy may be tested by computing a side from the given distance (hypothenuse) and the other 

side.

Adjustment of closures. These operations are repeated for each 

selected point until the traverse line closes back on itself or ties to 

another point previously determined. The errors of closure for a 

15-minute quadrangle, if not in excess of 1 second in latitude or 1^4 

seconds in longitude, may be distributed proportionately between 

initial and closing points, provided the error is not greater than 1 

in 5.000 parts of the distance between them for ordinary lines or 

1 in 7,500 for trunk lines.

Errors. Where so many operations are involved, errors are likely 

to creep into the computations. Therefore each step of the work 

should be checked as well as possible. The azimuth computation may 

be compared with the observed magnetic bearings, but because of the 

possibility of local variation little dependence can be placed on this 

comparison as a check. If the computed and observed azimuths for 

a line differ about 10 minutes, look for an error of that amount in 

the deflection angle or in the adding and subtracting of deflection

2 The difference in the fifth place is the result of carrying forward decimals from the 

sixth place in the first computation.
116 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

angles to azimuths. If the difference is larger, it is very likely that 

a wrong sign has been used for a deflection angle. To find the 

error, divide the difference by 2 and look for a deflection angle with 

an incorrect sign equal to the quotient. Errors of about 180° result 

if the recorder places the vernier readings in the wrong columns. 

By a careful inspection of the records it is sometimes possible to 

detect such an error. Many errors are due to incorrect multiplication by the distance, to the decimal point being in the wrong place, 

or to the product being written in the wrong column in the north 

column when it should be in the south column, etc. The latitudes 

and departures, as well as the other steps in the work, should be computed by two persons working independently of each other; after 

each has completed each step of the work the results should be compared and differences corrected and verified.

A plat must be made by the computer on an approximate scale 

of 5 miles to 1 inch, on one or more pages of book 9-931, for each 

group of traverse notes. In the center of the plat of each circuit 

write the length of the circuit and the closing error.
D. LEVELING

Compiled by E. M. DOUGLAS

GENERAL FEATURES

RESPONSIBILITY

The following instructions are formulated to assist the levelman 

in obtaining accurate results. Before he undertakes any work for 

the Geological Survey he must familiarize himself with these instructions in every detail, for he will be held strictly accountable for 

any deviation from them and personally responsible for the proper 

execution of his work. In order to be sure that the instructions have 

been received and are understood, a postal-card acknowledgment is 

required from each levelman at the beginning of his season's field 

work. He must understand that elevations of bench marks are published for the use of engineers outside of the Geological Survey and 

are sometimes used for large engineering projects. They must be 

reliable, or the Geological Survey may be subject to severe criticism. 

The proper contouring of topographic maps depends wholly on the 

character and the accuracy of the vertical control. The levelman 

must therefore realize the vital importance of his work and must 

give to it from the start such care and attention as will insure its 

thorough accuracy.

Levelmen working in the same area with topographers should so 

arrange their work as to satisfy in every way possible the requests 

and needs of the topographers in respect to priority and sequence of 

the work. The topographer in charge of mapping an area should 

be certain that a copy of these instructions is in the hands of every 

levelman in the area and that the instructions are understood by the 

levelmen. In the technical details of execution of his work, however, the levelman is directly responsible to the Washington office.

When a levelman is sent to any area for work he will be furnished 

with special instructions and all necessary data pertaining to that 

area. In "an area where his work has been preceded by transit 

traverse he must follow the traverse route if practicable, but in 

any area he must utilize all permanent traverse marks as bench 

marks, which must be turning points in the line, and he must tie his 

work to any permanent or substantial marks of other organizations 

that he may find along the line, making them turning points also.

117
118 TOPOGRAPHIC INSTRUCTIONS OP GEOLOGICAL SURVEY 

TYING NEW WORK TO OLD

Every bench mark from which new work is to be started must be 

checked by leveling to an adjacent established bench mark before the 

work proceeds. If the closure error between those two bench marks 

is not within the limits allowed, the section should be releveled, and 

if the closure is still out of limits the line must be continued until 

two old bench marks are found between which the closure comes 

within the limits. The initial elevation of the new work must be 

derived from one of two bench marks that agree. For the end of the ' 

line a tie to one bench mark will be sufficient, provided the closure 

is within the limits; otherwise the line must be run to a second or 

third mark. \

A complete description must be given of all previously established 

bench marks to which new work is tied. Whether beginning or 

ending a new line, or touching older lines in any part of the new 

work, these junction bench marks must be so fully described that 

there can be no uncertainty as to which marks have been used. If 

the results of the older work have been published, give bulletin number and page. If the bench mark has been recently established give 

page references to the field book where it has previously been recorded or show from what source its data have been obtained. Give 

in parentheses the old elevation. Make a note describing the condition of the old mark and stating whether it shows signs of having 

been disturbed.

When a levelman finds a previously established permanent bench 

mark broken or in bad condition he must replace it or reset it. If 

a new tablet is used it should be stamped like the one replaced, 

except that if the elevation has been adjusted the new figure should 

be used, and a full report, including change in elevation, if any, 

should be sent promptly to the Washington office.

If the bench mark is also a transit-traverse mark and a horizontal 

change in its location is found necessary, the magnetic bearing must 

be taken and the distance from the original position accurately measured with steel tape. The descriptions of both the old and the new 

marks, their elevations, and a sketch showing their positions must 

be promptly transmitted to the Washington office. If the tablet 

previously set is incorrectly stamped the erroneous figures should be 

carefully cut out with a chisel and the correct figures stamped in 

their place and verified. This action, together with a description 

and a sketch of the bench mark, must be promptly reported.

DISTRIBUTION OF VERTICAL CONTROL

The act of Congress providing for the sundry civil expenses of the 

Government for the fiscal year 1896-97 contains the following paragraph :
LEVELING 119

For topographic surveys in various portions of the United States * * * 

Provided, That hereafter in such surveys west of the ninety-fifth meridian 

elevations above a base-level located in each area under survey shall be determined and marked on the ground by iron or stone posts or permanent bench 

marks, at least two such posts or bench marks to be established in each township or equivalent area, except in the forest-clad and mountainous areas, 

where at least one shall be established, and these shall be placed, whenever 

practicable, near the township corners of the public-land surveys; and in 

the areas east of the ninety-fifth meridian at least one such post or bench 

mark shall be similarly established in each area equivalent to the area of a 

township of the public-land survey.

The most advantageous locations of level lines for a 15-minute 

quadrangle are near the borders of the quadrangle and from east 

to west through the center, the same arrangement as is required 

for transit-traverse lines. If additional leveling control is needed 

by the topographer the lines should be run by the levelman as 

a good grade of fourth-order levels, but without setting any permanent bench marks. Permanent bench marks should not be established by means of any level lines of a grade less accurate than that 

described on page 130 as " third order."

PERMANENT BENCH MARKS

Distribution. Permanent bench marks should be placed along 

level lines at intervals of approximately 3 miles, unless the levelman is otherwise instructed, and the distance between bench marks 

should nowhere exceed 4 miles. They should be established if 

practicable at township corners of the public-land surveys; near all 

large lakes and reservoirs; at crossings of the larger streams and 

divides; in the vicinity of active mines; and in every city, town, or 

large village traversed. In county seats and cities that have a population of 10,000 or more two permanent bench marks, some distance 

apart, must be established. Along public highways and railroads 

bench marks should be located where practicable at road junctions 

and crossings.

Best locations. Permanent bench marks should be so located 

that they will not be liable to injury or disturbance, yet they should 

be so prominent as to be easily found. Along a railroad or highway they should be placed, if practicable, outside the right of way 

but close to it. If such a location is impracticable and they are located within the right of way care should be taken for their preservation in the event of future changes in road location. Bench-mark 

posts must not be set close to trees, telegraph poles, or fence posts, 

or in front of gateways. They should not be set in swampy soil.

Tablets must not be set in boulders within the right of way of 

any well-established highway, or in any part of a bridge structure.
120 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

Permission* of landowner. Before a bench mark is set on private 

property permission should be obtained from the owner or agent, 

but if this is impracticable Written notification, explaining the necessity for the mark should immediately be sent to him.

Bench marks on Federal buildings. If the custodian of a Federal 

building objects to the placing of a bench-mark tablet in the building, the exhibition of the following copy of a letter from the Assistant Secretary of the Treasury should induce him to give the necessary permit.

TREASURY DEPARTMENT, 

Washington, December %2, 1920. 

The honorable the SECRETARY OF THE INTERIOR.

SIR: By direction of the Secretary, the receipt is acknowledged of a letter 

from the First Assistant Secretary of the Interior, dated December 20, 1920, 

requesting that permission be granted to the officers of the United States 

Geological Survey of your department to place on the Federal buildings under 

the control of this department small inscribed metal tablets, which are to be 

used as bench marks in connection with the system of leveling, the custodians 

of the buildings to designate where the tablets are to be placed.

No objection will be interposed by this department to the placing of such 

tablets on the various Federal buildings as desired, and this letter or a 

copy thereof, upon its presentation to the custodian of a Federal building, 

is to be considered by him as his authority for permitting the placing of one 

of the tablets on the building in his custody.

(Signed) J. H. MOYLE,

Assistant Secretary.

Form, materials, and construction. The tablets that form permanent bench marks are fastened with cement in large boulders, in 

solid rock in place, in permanent masonary structures, or in the 

top of concrete posts. (See pi. 4.) The tablet should be countersunk so that its lettered surface is flush with the surface of the rock 

or concrete in which it is set.

Portland cement in air-tight cans is supplied from the Washington 

office for use in setting tablets in rock or in masonary already in 

place. If good clean sand is available it can be mixed with the dry 

cement in equal parts. The drill hole for the tablet must be well 

cleaned and wet. The cement and sand, or cement alone if pure 

sand can not be conveniently procured, should then be thoroughly 

mixed with water to a thick paste, which should be packed into the 

drill hole. The stem of the tablet should then be pushed into the 

hole, when the excess cement will be forced out and the cement will 

fill completely the space under the tablet. In order that the cement 

may set well, it should be kept damp and protected from the sun 

for at least a day, and for 12 hours it should not be allowed to freeze. 

Damp earth or a piece of sacking will probably be sufficient protection. If a tablet is set in a vertical wall a prop may be necessary to hold it in place until the cement sets.
LEVELING 121

Suitable concrete posts may be made by contract in a town where 

materials are available, or they may be made by the levelman at the 

place where they are needed. They should generally be long enough 

to extend below frost line, and may be square or round in section; 

their sides should taper, and the top should be at least 6 inches and 

the bottom about 12 inches across. The post should be reinforced 

by three or four pieces of heavy galvanized-iron wire. The top of 

the post should not project more than 6 inches above the natural 

surface of the ground. The concrete should consist of 1 part cement. 

2 parts sand free from loam or clay, and 3 parts coarse gravel or 

broken stone. The upper 12 inches of the post should be made of a 

mixture of 2 parts sand to 1 part cement, without any gravel or 

stone, and the tablet should be put in position in the top of the post 

when the post is made. The mixture should be made up with just 

sufficient water to moisten it thoroughly, and it must be well tamped 

in the mold. An excess of water is harmful. The post, when 

completed, should be sheltered from the sun for several days and 

wetted frequently if practicable.

The point of elevation on all ^tablets, whether set vertically or 

horizontally, is the intersection of the cross lines inside of the 

triangle.

Reference marks. A reference mark, which shall be made a turning point in the line or be on a checked spur line, must be established 

near every permanent bench mark. Reference marks should conform 

to the instructions given for supplementary bench marks and should 

be described with equal care.

Establishing marks after line is i^un. If conditions make it necessary to leave the setting of a permanent bench mark till after the 

line is run, two temporary bench marks (both of them turning points 

in the line) must be left near the point selected, one of which is to 

be a reference mark. The elevation of the permanent bench mark 

must be determined by readings on both of the temporary marks 

from two different set-ups. A single " side shot" is never sufficient 

in establishing the elevation of a bench mark.

Pavnted elevations. The letters " U. S. B. M.," together with the 

determined elevation to tenths of a foot, arranged when practicable 

thus:

U.S.

[figures]

B. M.

must be neatly painted in letters and figures 4 inches high on some 

convenient object near every permanent bench mark in order to insure 

its being readily found by the topographer or traverseman. When 

no suitable object is found on which to paint, a mound of rock or
122 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

earth large enough to attract attention must be left. The painted 

elevations must be in no way objectionable or offensive to the owners 

of property or to travelers. Prominent trees along public highways 

must not be defaced by blazing except as a last resort.

Sta/mping. To facilitate the identification of permanent bench 

marks, an individual letter will be assigned by the chief of division 

to each levelman, which he must stamp on all tablets set by him. He 

will also stamp on each permanent bench mark a number, which will 

be serial for all tablets set by him in any one State during one season, and this number must be followed by figures showing the year 

in which the work was done. For example, " C-10-1920 " means 

that the line was run by levelman C and that it was the tenth permanent bench mark set by him in that State in 1920. These letters 

and figures will be stamped beneath the space left for the figures 

showing the elevation and must be stamped before the bench mark 

is set; they should be in two lines, the figures for the year on the 

second line. If the mark is both a transit-traverse mark and a 

bench mark, the control man who first establishes the mark should 

stamp it with his letter and serial number. The second man should 

not add his own stamping to this but should use the first man's letter and number to identify the mark.

Figures of elevation must not be stamped on metal bench marks 

until the level lines have been adjusted and the final elevations supplied by the Washington office. Usually the elevations can not be 

stamped until the field season after the marks are set, and the stamping may be done by a different engineer from the one who set the 

marks.

Stamping must be neatly done, so that the figures are perfectly 

legible. Metal bench marks are to be stamped only to the nearest 

foot of the adjusted elevation, as indicated below:

Elevation Stamping

1328.675 1329

1474.428 1474

1492.501 1493

1237.500 1238

1238.500 1238

If the decimal .500 follows an even number, disregard it. If itfollows an odd number, add 1 to the number.

A list of marks to be stamped is furnished to the engineer. Write 

in ink on this list the figures of elevation as stamped, also make an 

impression on the margin of the list or on a separate piece of paper 

of the elevation stamped and the identifying letter, number, and 

year. An impression of all markings can be made by first smearing 

the surface of the tablet with printer's ink and then applying to it
LEVELING 123

and rubbing down a piece of white paper, or by holding the paper 

firmly on the tablet and rubbing over it with a soft lead pencil.

If a tablet is wrongly stamped, as soon as the error is discovered 

cut out with the small cold chisel supplied the erroneous figures and 

restamp the correct ones. If the erroneous figures have been reported to the Washington office the correction should also be reported.

The list should be returned to the Washington office as soon as the 

stamping is completed.

SUPPLEMENTARY BENCH MARKS

As descriptions of supplementary bench marks are published in 

level bulletins and their elevations are given on topographic maps, 

careful attention must be given to their character and location, in 

order that they may be made as permanent as possible and easily 

accessible. They should be placed where they are least likely to be 

disturbed and yet can readily be found from the descriptions.

Supplementary bench marks must always be turning points in the 

main line and should be set at intervals of half a mile to a mile 

on all lines. On railroads and highways they should be set at the 

principal crossings, crossroads, and road intersections. They may 

consist of well-defined chiseled marks, preferably forming a square, 

on solid rock in place or on permanent structures of concrete or 

stone, or bolt heads surrounded by painted rings on steel structures, 

or copper nails with lettered washers in exposed roots of suitable 

trees. No other form or material less substantial than those above 

specified should be used for supplementary bench marks.

The elevations of all supplementary bench marks as at first determined by the levelman must be painted to tenths of a foot on some 

convenient object near by, as explained on page 124.

USEFUL ELEVATIONS

The levelman should bear in mind that his work is not an end in 

itself but a preparation for the work of others and that the accuracy 

with which his circuits check, though of paramount importance, 

is not the only feature that determines its usefulness.

Besides the elevations of the permanent and supplementary bench 

marks a number of other elevations are required for the use of the 

topographer, and they should be distributed with a special view to 

their usefulness in topographic mapping. For instance, an elevation painted on a summit will be of great value to the topographer, 

whereas one painted below it, simply because a turning point can 

more easily be made there, is of far less value.

The points for which elevations are particularly useful are the 

tops of rails at railroad stations, junctions, sidings, and crossings; 

58515° 28 9
124 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

the center of the road at crossroads, road forks, bends, and summits; 

points near schoolhouses and other public buildings, lone houses, 

active mines and quarries, and oil, gas, and artesian wells; the 

water surface of streams under bridges, at stream crossings, and 

above and below dams; and the water surface of lakes and reservoirs. The date and hour when the measurement of a water-surface 

elevation was made should be recorded.

The number of these elevations should differ according to the 

nature of the country and the contour interval used for the map. 

Thus, in rugged regions mapped with 50 or 100 foot contour intervals relatively few elevations are required, but in areas of gently 

rolling surface they should be more numerous.

Elevations should be determined to the nearest tenth of a foot 

for such of these points as are of a definite nature for example, 

the top of a rail or a bridge floor.

Ground elevations (to the nearest foot only) should be neatly 

painted in conspicuous places along the sides of roads and on 

fences, telephone poles, trees, or rocks. If practicable, all such marks 

along a road should be placed on the same side of the road. On 

a bridge the elevation of the floor should be painted on the railing 

or truss immediately above it, not on the floor itself.

NOTES AND RECORDS

The fly leaf of every field book should be filled in before any other 

records are put in the book. Instrument and rod numbers must be 

given.

Notes should be kept as neatly as possible, and all figures should 

be clear and plain, so that there can be no possibility of misreading 

them. Ink or hard pencil may be used. Do not erase an incorrect 

figure or record, but draw a single line through it, and write the 

correct entry above it. Do not use separate loose sheets of paper 

for recording notes; all records must be set down directly in the 

books, so that there can be no possibility of losing a part of them.

The description of a bench mark should begin directly opposite 

the entry indicating elevation. Notes should not be crowded, and 

if two descriptions occur close together, the records for the second 

mark should be started enough farther down on the left-hand page 

to clear the description of the first mark.

There are a number of items that should be recorded in addition 

to the rod readings and elevations. Weather conditions and temperature, details of rod and instrument tests, brief statements of unusual 

incidents that may affect the results, page cross references at junction 

points, and other such details form a necessary and important part 

of the records and should be written on the right-hand page of the
LEVELING 125

notebook, commencing opposite the entry for the point in the line 

to which they apply. Every page heading should be filled in with 

the date and a brief description of the line.

In short, the levelman should remember that his notes are made 

for the purpose of transmitting information to the office and therefore should be in such shape as to be clearly understandable not 

only by himself but by others.

Forward the records to the Washington office by registered mail. 

Field books and bench-mark books should be sent in different packages on different days, so that if one package is lost the other may 

furnish the data for the line. It is very unlikely that both packages 

would go astray. A letter or card should also be sent, stating that 

the books have been mailed.

DESCRIPTIONS OF BENCH MARKS AND USEFUL ELEVATIONS

Complete descriptions of all bench marks and useful elevations 

must be entered in the field notebook and should be copied in the 

description book (9-916) at the end of each day's work. A comprehensive sketch should be made in both notebook and description 

book showmg the correct position of each bench mark in relation to near-by objects, such as streets, roads, and railroads, and 

indicating by arrows the direction of the line that is being run 

and the true north. Such a sketch must accompany the description 

of every permanent bench mark. Sample pages of the field notebook 

and bench-mark description book are given on pages 135 and 136.

Descriptions are of the greatest importance in all level records, 

and the levelman must therefore take particular care to make them 

comprehensive, concise, clear, neat, and legible and to arrange them 

in proper form for publication. The items of the descriptions should 

be written in the following order:

1. Name of the nearest post office, town, village, or other wellImown locality, with direction and distance from it to the bench 

mark, in miles and tenths; or the township, range, and section in 

which the bench mark stands, with direction and distance from 

the nearest corner. When a new reference point is cited in the 

description give the distance to the former point as well as to the 

new one, thus affording data for total mileage.

2. Position with reference to buildings, bridges, mileposts, and 

streets or road corners; if along a road, state on which side. Give 

compass directions; do not use " right" or " left."

3. Description of object on which the bench mark is placed, such 

as boulder, tree, or concrete post.

Items 2 and 3 should be written in direct (uninverted) form. 

Items 1, 2, and 3 answer the question "Where?" and should be 

followed by item 4, which answers the question "What?"
126 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

4. Nature of the bench mark tablet, chisel mark on rock, copper 

nail with washer, iron pipe, etc. and how marked or stamped; 

the object on which the figures of elevation are painted should 

also be named.

Old bench marks to which the line is tied must be fully described 

and shown on a sketch, and the old elevation and source of information must be given.

If a previously set transit-traverse mark is used for a bench 

mark, the description must be the same as the traverseman's unless 

that is found to be erroneous; in that event a correct description 

must be entered in the description book, and a copy sent to the 

Washington office.

The levelman who sets a permanent bench mark should make a 

pencil copy of his description on a loose sheet of paper to transmit 

to the traverseman if one follows. This should be done each day. 

so that the set is up to date when the line is finished.

Descriptions should be written in the order in which the bench 

marks occur along th© line. If standard bench marks are not established when the line is first run, spaces should be reserved for them 

in their proper order in both the field notebook and the description 

book. A brief description of the line should be given as a page 

heading, and when the direction of the line is changed the distance 

and direction froln the reference point along the route of the line 

should be given, not the air-line distance and direction. For example, if the line runs in a general easterly direction for 6 miles 

from the reference point and then changes to a northerly direction, a 

bench mark set 3 miles beyond the bend should not be described as 

" about 7 miles northeast of" the reference point but as " 6 miles 

east, thence 3 miles north from."

If any correction is made to the field-book elevations when they 

are copied into the description book, a full explanation should be 

written in the description book, including the data warranting the 

change.

A neat and legible diagram of all lines and circuits must be "made 

on a page near the back of the description book. Boundaries of 

quadrangles should be shown, and if the area is covered by publicland surveys the position of each line with reference to township 

and section lines should also be shown. The direction in which each 

line was run must be indicated by arrowheads placed on the line, and 

the number of the page on which the record was made must be placed 

at the beginning and end of each circuit and line; the location of all 

permanent bench marks must be indicated by crosses; and all towns 

and villages and the crossings of the larger streams must be shown. 

The records in the description* book are incomplete without this 

diagram.
LEVELING 127 

CLOSURES AND BEBUNITING

Formulas are given for the limits of error and closures on the 

different types of lines hereinafter described. If a circuit fails to 

close within the specified limits, and if the levelman is in doubt what 

to do, he should immediately notify the Washington office, giving 

details of the line, descriptions of the initial and final bench marks, 

his rod numbers and tests, and any other information that may enable the office to verify data regarding older lines or to arrive in any 

way at an explanation of the excessive closure. Rod error is a 

common cause of failure of field results to close. Meanwhile, if 

additional lines that will intersect the line of error are conteniplated, 

they should be run by the levelman before he attempts any releveling 

over the erroneous line. These intersecting lines may show which 

part of the erroneous line is weak, and that part should then be 

investigated. If no explanation for the excessive closure can be 

found either in the office or in the field, the weak link or line should 

be rerun. This work should be done by a method as accurate as that 

by which the line was run at first, but in the opposite direction. If 

the line to be rerun is of the second order and has thus already been 

run twice, a single additional running, with the same care and refinements as in the original work, will suffice if it checks one of the 

two former lines. If the line is long it should preferably be rerun 

by a different levelman. Complete details of all rerunning should 

appear in the bench-mark description book.

When there is a large discrepancy between two runnings of any 

section of a line, a third running of the section is required in order 

to prove whether it is the first or the second running that is in error. 

If the third running agrees within the permissible limit with one 

of the other two their mean shall be used to carry forward the elevation, the discordant one of the three being eliminated.

For example, suppose a circuit from A to B, with seven^jnterrnediate bench marks, closed 1 foot out of limits. Begin at B and 

rerun back toward A to locate the error. Between bench marks B, 

7, 6, and 5 the new line checks with the old, but between bench 

marks 5 and 4 a divergence between the two lines is found which 

is nearly equal to the closure error. Continue the line, however, to 

another bench mark (3) to verify this divergence. When it has 

been verified go back and rerun the line in either direction between 

bench marks 4 and 5, where the large divergence occurred. If a 

large discrepancy is found on rerunning a line between any two 

bench marks, that part of the line must be run a third time to discover which running was in error and to obtain two records that are 

in close agreement.
128 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

If as the rerunning progresses no error approaching the allowable 

closure limits is found between any two bench marks but the divergence between the new and old lines continues, the error is shown 

to be cumulative, and in that case the rerunning must be continued 

to the end of the circuit or loop. If the closure is then satisfactory 

no third running of such a line is necessary. Before releveling any 

part of a large circuit on account of a large closure error, it is best 

to run a cross line if the additional bench marks will be useful or 

the probable amount of releveling thereby be reduced. This will 

localize the error in a smaller circuit.

Every effort should be made to have all lines closed satisfactorily 

before the leveling party leaves the locality, as faulty lines may 

prevent the adjustment and publication of the work. Lines may 

fail to close on account of error of two kinds gross errors and slight 

inaccuracies that accumulate through the line. Methods of minimizing the cumulative errors are discussed in the detailed instructions for 

the different kinds of work (pp. 131-133). Gross errors are usually 

due to carelessness, but occasionally even the most careful and painstaking man may make such an error. Failure to close a line may 

perhaps be due to no fault of the levelman. Sometimes the starting or ending elevations may be incorrect, or there may be other 

understandable causes for the failure. In any case, if the levelman 

has been conscientious, painstaking, and careful, he need feel no 

embarrassment in occasionally failing to close a line and in recording the circumstances fully in his books. Field notes should not be 

erased or altered, even to effect neatness in the books. Alteration 

to disguise or conceal an error or falsifying the records in any manner is evidence of fraud and of course will not be tolerated. To 

avoid all question, therefore, it is best never to make an erasure of 

any sort in a field book, as any evidence of such a change will immediately arouse suspicion when the notes reach the computer.

CARE OF INSTRUMENTS

Responsibility for damage. The effectiveness of instruments may 

be maintained by proper care in handling and transportation. This 

care is highly necessary} and everyone who is intrusted with instruments is expected to see that they receive such care and protection 

that when returned to the custodian they will be in fit condition for 

further use. Damage or injury to leveling instruments is often the 

result of carelessness or negligence of the levelman or the rodman. When evidence of such carelessness is discovered any expense 

incurred for repairs will be charged to the person who is fesponsible.

Level. When the level is not in use it should be kept in its wooden 

case, with the top fastened; that is the only way to insure it against 

being tampered with or knocked over.
U. S. GEOLOGICAL SURVEY BULLETIN 788 PLATE 7

INSTRUMENTS USED IN LEVELING

a. Wye level; &, New York level rod; c, prism level; dt yard rod
LEVELING 129

When the level is being transported to and from work in the field 

it should not be subjected to bumps or jars from riding unprotected 

on the floor of the conveyance. The safest way to carry it is in the 

lap, but if it is carried in its case the box should rest on a padded 

support. It should not be unnecessarily exposed to damp or rainy 

weather and must be kept in a dry place at night.

When the level is shipped by express it must be securely packed 

in its case with paper to protect it from jarring or its parts from 

shaking loose. Old newspaper makes excellent packing; excelsior 

or hay must not be used for this purpose. The wooden case containing the level must be packed inside another box.

Rods. It is very important, particularly for areas where differences of elevation are considerable, that an accurate value for the 

length of the leveling rod be determined not only from tests by 

the Bureau of Standards but also from field tests by the levelman. 

At the beginning of each field season and at least every two weeks 

thereafter the levelman should make several measurements of each 

leveling rod he is using, with an invar test tape or a tested steel 

tape kept for that purpose, and record in proper order in his notebook the mean of the result to thousandths of a foot for each graduation tested. State definitely the length of the rod interval tested, 

and give the rod number and test tape number. The tape should be 

held as nearly as possible at the tension for which it is tested, which 

should be 10 or 15 pounds. If an ordinary steel tape is used, 

special attention must be given to the reading and recording of 

the temperature. The comparisons should be made under the same 

conditions as those prevailing when the rod is in use. As invar 

strips are easily damaged by bending or by coiling too tightly, 

they must be handled carefully. Corrections for rod error need not 

be made in the field except in a rough way when needed to check 

circuit closures.

A levelman is responsible for the safety of the rod; he must see 

that the rodman takes proper care in handling and transporting it 

in the field. Particular care must be exercised not to expose the 

face of the rod to anything that may deface or mar it. The face 

of the rod must not be laid on the ground nor exposed unnecessarily 

to the weather. When not in use the rod must be kept in its canvas 

cover, and it must be stored in a dry place at night. When it is 

being transported to and from work it must be carried in its case 

and must be fully protected from rubbing or blows. When a ISTew 

York rod is shipped by express it should be either packed in a 

box or fastened to a board extending 2 inches beyond each end. 

The target should not be removed from the rod but should be 

fastened securely to a flat board and protected with hay or excelsior.
130 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

If the rod is not shipped in a box its face should be thoroughly 

protected and the entire rod should be wrapped in canvas or burlap. 

Precise rods must always be shipped in the boxes made especially for 

them.

Neither level nor rod should be left overnight in the care of a 

person not connected with the Geological Survey merely to avoid the 

inconvenience of taking them to headquarters.

A levelman who is careful with his instrument will be careful with 

his work.

Minor repairs. Each levelman should provide himself with a 

few simple tools and supplies, such as a small pair of pliers with 

side wire cutter, screw drivers of two sizes, small flat and round 

files, a spool of soft copper or brass wire, some assorted brass nails 

and screws, a bottle of oil, a bottle of liquid shellac, spider web, and 

plaster of Paris, all of which may be used for minor repairs to 

the instruments.

Field work should not be delayed by sending an instrument away 

for repair if the levelman can possibly repair it himself. Even 

crude repairs may often be made to serve until a new instrument 

can be procured. A piece of hardwood may be used temporarily 

to replace a screw that is accidentally broken.

In leveling or adjusting an instrument tighten screws to a snug 

bearing only, using but little force.

If it becomes necessary to separate the two lenses that make up 

the object glass, which should seldom be done, insert three pieces of 

paper about one-eighth inch in length, equally spaced, near the edge 

when putting the lenses together. If this is not done color rings will 

probably form and interfere with the vision.

GRADES OF WORK

The permissible limits of error in the three grades of work required in leveling are indicated below.

. , f__-___ feet__ 0. 017 Vlength of section in miles

"[millimeters-- 4 Vlength of section in kilometers

Second order f- ----- feet- _ 0. 035 Vlength of section in miles

[millimeters-- 8. 4 -y/jength of section in kilometers 

Third order ______ ______ feet-_ 0. 05 Vlength of circuit in miles

Whichever grade of work is attempted these limits of error must 

not be exceeded. The grade of work classed as third order should 

not be extended more than 30 miles from work of higher accuracy. 

Second-order lines, double run, must be used as trunk lines for 

expanding the work over distances too great to be covered by un-
LEVELING 131

supported lines of third-order accuracy. No standard bench marks 

should be established on lines less accurate than those of the third 

order.

THIRD-ORDER LEVELING WITH WYE LEVEL AND

TARGET ROD

PERSONNEL AND EQUIPMENT

The level party consists of a levelman; one or two rodmen, one 

of whom may act as chauffeur and be used to set permanent marks 

in advance of line; and in some areas a bubble tender. The equipment issued (see pi. 7) is as follows:

One 20-inch wye level.

One or two New York rods.

One or two plumbing levels.

Two steel turning pins.

One set dies (figures and letters).

One pocket compass.

One 25-foot steel tape.

One special invar strip testing tape.

Thermometer.

Bench-mark tablets.

Copper nails and washers for intermediate bench marks.

Cement in cans.

Two paint cans.

Level notebooks, 9-903 in black covers to be used by levelman; 9-903A

in yellow covers to be used by rodman. 

Bench-mark description book 9-916. 

Two book bags. 

Small cold chisel ( a/4 inch).

*

Other accessories, to be obtained in the field, are as follows:

One or two hatchets or Boy Scout axes.

One drill hammer.

One post-hole digger.

Two stone drills, 1%-inch bit.

CHARACTER AND ACCURACY

Third-order leveling should be run as single lines forming circuits wherever practicable; otherwise the lines must be checked by 

rerunning, preferably in the opposite direction. No work is complete until it is checked in some way. Lines should be connected 

with near-by bench marks of railroads, cities, highways, and other 

organizations either by making these marks turning points in the 

main line or on a spur line leveled twice.

The closure error, in feet, of a circuit should not exceed

0.05 Vlength of circuit in miles.
132 TOPOGRAPHIC INSTRUCTION'S OF GEOLOGICAL SURVEY 

BEADING OF TARGET BOD

Both the levelman and the rodman must read each target setting 

independently and keep complete separate field notes.

When the target is set for the back-sight reading, the rodman must 

immediately read the rod and set down his reading in his notebook. 

He should then bring the rod forward to the levelman without changing the setting. The levelman then reads the rod, recording his result. They must not compare figures until their respective records 

for a given sight are completed. If the difference between the records 

exceeds 0.002 foot each must read the rod again before further comparison is made.

When the fore-sight target is set, the rodman must immediately 

read the target and record his reading. The setting should remain 

undisturbed till the levelman can come forward and make an independent reading, and he should record the result in his book before 

making comparison with the rodman's reading.

When a New York rod is lengthened beyond 6.5 feet both the rodman and the levelman must examine the setting of the target as well 

as the reading of the rod vernier. When the rod is closed they 

should see that the rod vernier indicates 6.5 feet, not depending on 

the abutting ends to bring it back to place.

LENGTH OF SIGHT

The maximum length of sight permissible under the most favorable conditions is 300 feet, except across rivers or deep ravines. In 

such places reciprocal observations must be made as follows: Just 

before reaching the river or ravine the levelman should see that all 

excess in total distance by either fore sights or back sights is eliminated. He should then establish a turning point (A) near the edge 

of the river or ravine, approximately opposite and level with a point 

(B) to be established on the opposite side. Next he should test the 

adjustment of the instrument. Then, with the instrument set up 20 

to 50 feet from the point A, he should take a back sight on it and a 

fore sight on point B. He should then move across the river, set up 

the instrument 20 to 50 feet from the point B, and take a back sight 

on point A and a fore sight on point B. The mean of the two elevations determined for the point B will be accepted as correct. For 

very long sights at least four readings on the distant rod should be 

made and the average adopted. To minimize the refraction it is 

advisable to read the rod on the distant sights 3 feet or more above 

the ground.

EQUALIZATION OF FOBE-SIGHT AND BACK-SIGHT DISTANCES

In order to eliminate instrumental errors and errors caused by 

curvature and refraction the lengths of fore and back sights should
LEVELING 133

be equalized at each set-up, but if this is impracticable because of an 

abrupt change in grade, enough unequal sights to balance should 

be taken as soon as the grade is passed, before another permanent 

bench mark is reached and before any change in the instrument adjustment is made. The difference between sums of back-sight distances and fore-sight distances should not exceed 1,000 feet.

If the adjustment of the level is changed before balancing sums, 

any attempts to eliminate instrumental errors by taking unequal 

sights to balance former sights are useless.

The failure to balance sights may allow a large inclination of 

line of sight to affect results if not corrected by the determination 

and application of a slope factor (C). The levelman should make 

observations for this factor by the peg method (p. 141) at all places 

where it is found impracticable to balance the sights. The values 

of C should be recorded on the right-hand page of the notebook 

opposite the entry for the point at which they were determined, 

and reference should be given by page numbers to the computation 

and the section of the notes to which each factor is to be applied. 

The application of this factor need not be made in the field.

MEASUREMENT OF DISTANCES

Distances may be measured by stadia readings on the rod or by 

counting rails along a railroad. The distances in miles or feet of 

both fore sights and back sights must be recorded in the notebooks 

in the proper columns by both the rodman and the levelman. When 

stadia distances are used, the reading for distance on the back sights 

should be taken before and on the fore sights after the level readings 

are taken, in order to prevent disturbing the bubble.

BOD LENGTH AND CLAMPS

Rods must be tested for length as explained on page 129. The long 

rod clamps and the target clamp should be kept working smoothly 

so that close settings can be promptly made. The bottom of the 

rod must be kept clean and free from clinging dirt.

PLUMBING LEVELS

Plumbing levels must be used, tested at frequent intervals, and 

kept in adjustment.

TURNING POINTS

The regular steel turning-point pin should be used where no rock 

or other suitable point is available. When the line is being run 

along a railroad the higher edge of the rail or a spike may be
134 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL, SURVEY

used, and. the point occupied must always be distinctly cross marked 

with keel before the rod is held on it.

Care should be taken not to choose for a turning point a sloping 

surface, on which there is a possibility of the rod slipping to a lower 

position between sights. The turning point must be firm and free 

of dirt.

Do not depend on a single stake or pin driven the night before 

as a starting point in the morning.

RECORDING

All level notes must be recorded directly in books 9-903 and 

9-903 A. The black-covered books are for the levelman's notes, and 

the yellow-covered ones are for the notes to be kept independently by 

the rodman. One set of notes must not be merely a copy of the 

other. Each set must be taken directly from the rod.

For a given point in the levelman's notes the rodman's notes must 

be at least two lines lower down the page than the levelman's, 

and the two men must not turn over a leaf at the same time. Erasures of rod readings with rubber or knife are not permissible; a 

single line should be drawn through an erroneous record and the 

corrected figures written above it.

Both the levelman's and the rodman's books must be balanced 

daily. At the bottom of each page and at the end of each day's 

work the sums of columns of fore-sight and back-sight readings 

must be recorded and the difference determined. This difference 

should agree with the difference between the first and last elevations 

on the page, and the figures for this page check must not be omitted. 

The sums of the distance columns should be recorded for each page of 

notes, also the difference of sums of back-sight and fore-sight lengths 

and the accumulated excess.

The two sets of notes should be mailed to the Washington office 

in separate registered packages on different days.

Sample pages of the notebooks are given on pages 135-136.
Field notes, third-order leveling with wye level and New York rod (book 9-903)

Date, October 18-20, 1924

Dist. 

B. S.

200

195

165

50

205

200

200 

200

170

210

210

210

210

205

120

50

70

160

200

55

3,285

Dist. 

F. S.

200

200

80

150

200

210

200 

200

150

200

200

200

200

150

120

65

55

185

190

205

3,450

3

OQC

, ^oO

105

Back sight

°

4.630

1.885

.890

4.934

7.673

1.642

5.203 

8.457

10. 724

4.327

1.691

0.184

6.235

2.896

2.071

.775

2.671

3.385

1.965

.916

82. 154

H.I.

741. 508

739. 594

729. 698

728. 370

735. 004

730.406

729. 931 

735. 457

743. 867

744. 605

737. 363

742. 451

745. 098

745. 306

737. 794

731. 073

725. 183

723. 490

722. 534

712. 127

Fore sight

3.799

10. 786

6.262

1.039

6.240

5.678

2.931 

2.314

3. 589

9.033

3.996

3.588

2.688

9. 583

7. 496

8.561

5.078

2.921

11. 323

11. 740

118. 645 

82. 1,54

36.491

Elevation

736. 878

737. 709

728. 808

723. 436

727. 331

728. 764

724. 728

727. 000 

733. 143

740. 278

735. 572

732. 267

738. 863

742. 410

735. 723

730. 298

V22. 512

720. 105

720. 569

711. 211

700.387

736. 878

on 401 oo. rtyj.

Check.

Total miles

0.00

P. B. M.

0.45

T. B. M.

1.00

P. B. M.

1.05

Ref. M.

1.28

Name of line, From quarter corner between sees. 31 and 32, T. 38 N., R. 11 E., east 

along highway to Salem. John Doe, levelman

T. 38 N., E. 11 E., near quarter corner on W. side of sec. 32, in NE. angle of crossroads,

10 ft. N. of fence corner; top of iron post, stamped "Prim. Trav. Sta. No. 4, 1919,

111. 737." (See Bull. 567, p. 75.)

728.9, top of west rail of C., B. & Q. E. R.

T. 38 N., R. 11 E., about 0.13 mile S. of corner of sees. 22, 23, 26, and 27, in SE. corner of 

crossroads, at fence corner, in root on S. side of a 10-inch box elder tree (marked 727.0);

copper nail and washer.

745, top of hill.

715, floor of bridge over Canoe Creek.

T. 38 N.,R. HE., at corner of sees. 26, 27, 34, and 35; 22 ft. N. and 20ft. E. from T road to E.,

inside of NE. fence corner, top of concrete post; bronze tablet stamped "Prim. Trav.

Sta. No. 2, K 1924, 111. 61 D."

Ref. mark is 240 ft. E . of concrete post, on N. side of road, inside of field fence, in root on

S. side of a 3^-ft. cottonwood tree; copper nail and washer.

[NOTE. The above descriptions are fictitious and do not fit the distance recorded.

A location sketch for each P. B. M. should be given.]

00
I a

1 si

£

_,) Oo cf m S VJ T

[Columns omitted here are used for computations, comparisons, and corrections.]

Closure error -....---.----.--- .....

'

1

 .059 Closure error. 

Willow Springs, 1.00mile east of,100feet of1side ofroadat fence line,nroot o suthide of

nail andwasher (marked 675.1). 

Orlando, atnortheast corner of Main andFirst Stn

table atsouthwest corner of Orlando National tablet stamped "627 111.1920." (Note: SeBu

Elevation bythisline---.-.---.. ....Elevation byBull. 672.. ____ ._

lid t|

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0,P CD p g

885s<= 4 I

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SS «g So

0010 g - S

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S n * cr

T. 38N.,R. 11 E.,atquarer corner between sees and 30feeteas from crossroads; 65westof concrete post;bronze tablet stamped "Prim. 1

111. 60 D."

Reference mark, 60 feetwest and25north finnorth and30feet west fromcrossroads, inrooto 

box eldertree; copper nail andwasher.

Ref.llB.M. x||x

r

Willow Springs, northcorner of Wentworth and

northwest endofstone doorstep, 8feetsoutheast c 

on southwest sidofHenry B.Koller's brickt

vertically (U.SCorps ofEngineers P.BM. 12 

616. 503 616. 444

"Pg^S ' I 3 S §J3

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T. 38N.,R. 11E.,near quarter corner owest si<angle ofcrossroads, 10feetnorth fence corner; " Prim;Trav. StaNo4, 1919,111. 775." (Bull. 

II N HX T

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Description (tobewritten inpublication fo

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Line fromquarter corner between sees. 31 and32,

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IJEVELING 137 

CAUSES OF ERROR

The use of an instrument that is slightly defective or out of 

adjustment will cause errors unless care is taken in balancing backsight and fore-sight distances, which reduces errors of this kind 

to a minimum. Other causes of error to guard against are unfavorable atmospheric conditions, the settling of turning-point pin or 

instrument, failure of rodman to hold on the pin, carelessness or 

roughness in setting rod on pin or in closing the rod, slipping of 

target or long-rod clamps before a reading of the rod is made, poor 

adjustment of rod bubbles, refraction when taking a sight too close 

to the ground, "boiling air," attempting to take sights of excessive 

length. A levelman must exercise continual vigilance to foresee and 

avoid conditions or incidents that may impair the accuracy of his 

line. Do not take a sight over 100 feet in length passing within 2 

feet of intervening ground.

Work on third-order lines should not be carried on during high 

winds or when the air is "boiling" badly, because such conditions 

will affect the accuracy of the work.

CONDITION OF INSTRUMENTS

Although all instruments are adjusted and tested before they are 

shipped from Washington, complaints are sometimes made, even by 

experienced levelmen, that good results can not be obtained with 

the levels furnished. The levelman should, therefore, immediately 

on receipt of an instrument, look it over carefully and thoroughly, 

and if any parts are lacking or so defective as to preclude an adjustment by him he should immediately telegraph for another level. 

The adjustment of the level must be tested at the beginning of each 

day's work and corrected if found materially in error. It niust be 

tested and the necessary adjustments made before taking long sights 

by reciprocal leveling across rivers or deep ravines. However, 

though it is desirable to keep the level in good adjustment in order to 

obtain the best results, unnecessary tampering with the adjustable 

parts of the instrument should, of course, be avoided.

When the line is being run the levelman should not take it for 

granted that the level bubble will stay centered while the level is 

being revolved for fore sight, but he should examine it, and if he 

finds it off, he should relevel it. An error of even a single division 

of the scale neglected in leveling up a sluggish bubble introduces an 

appreciable error in the rod reading on an ordinary sight. However, even though the level may be out of adjustment, satisfactory 

work can be done if all parts are screwed up snug but not too tight 

and fore and back sights are kept equalized.
138 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY 

DEFECTS OF INSTRUMENTS

Any of the following instrumental defects may produce bad results, especially if the sights are not equalized. The remedies are 

almost self-evident.

1. Glass level vial loose in its case or level-tube adjusting screws 

loose.

2. Glass level vial defective. Sometimes small crystals collect on 

the inside of the tube and make the movement of the air bubble 

sluggish or irregular. When this occurs insert a new vial and be 

sure to set it with the marked (curved) side uppermost.

3. Object glass loose in its cell or cell partly unscrewed.

4. Cross-wire adjusting-screw threads worn out, or screws too 

tight or too lose, or cross wires themselves too loose.

5. Tripod points or tripod leg-clamp screws loose.

6. Leveling screws too tight or too loose.

Two other possible sources of error are not so easily found, but 

fortunately they need seldom be considered:

1. The two telescope rings, which rest on the wyes, may be of 

different size or of irregular shape.

2. The object-glass slide may be out of adjustment.

If the instrument has either of the two defects last mentioned 

another instrument should be ordered by telegraph and the defective 

one returned to the Washington office.

ADJUSTMENT OF INSTRUMENTS

The customary adjustment of the wye-level should be taken up 

in the following order: (1) Collimation, (2) motion of object-glass 

tube, (3) horizontality of thread, (4) eyepiece slide, (5) level-vial 

direction, (6) level-vial inclination, (7) wyes.

Collimation. Remove all parallax by focusing the eyepiece with 

the sky as a background until a distinct image of the cross wires is 

obtained. Loosen and raise the wye clips, focus, and set the intersection of the cross wires on a point, such as a nailhead, 300 feet or 

more away, revolve the telescope halfway around in the wyes, and 

note whether or not the intersection of the cross wires moves away 

from the point. Should the horizontal wire be found above or below 

the point, bring it halfway back by the capstan-headed screws perpendicular to it. Repeat the operation until it will reverse correctly. 

Proceed in the same manner with the other wire until the adjustment is complete. Erecting telescopes require a movement of the 

reticule screws as if to increase apparent error.

Motion of object-glass tube. When the collimation adjustment 

is perfected for distances of 300 feet or more as described above,
LEVELING 139

proceed to test it for a distance of 20 or 30 feet, and if coincidence 

is not obtained after revolving the telescope on the near-by point 

it is evident that the object-glass slide is out of adjustment. To 

correct the error remove the bubble tube and the ring near the 

middle of the telescope and with a screw driver turn the screws, 

each pair in succession, until the cross-wire intersection will coincide 

with the near-by point while the telescope is revolved 180° in the 

wyes. When the collimation is perfect for both long and short 

sights, replace the telescope ring and the level-bubble tube. This 

adjustment is seldom required.

BorizontaHty of thread. Level the instrument carefully with wye 

clip pins in place, and select or set some point at the exact elevation 

of one extremity of the horizontal wire; clamp the spindle and with 

the tangent motion turn the instrument on its vertical axis until 

the opposite side of the field of view is reached; note whether or 

not the opposite extremity of the horizontal wire now coincides with 

the point selected. If it does not, it can be made to coincide by 

loosening one vertical and one horizontal capstan-headed screw and 

turning the reticule until perfect horizontality is obtained. A plumb 

line on the vertical edge of a building may be used to test the verticality of the vertical wire. Always retest and correct any derangement to the line of collimation which this movement of the reticule 

may have caused before proceeding further.

Eyepiece slide. The adjustment of the eyepiece tube so that the 

cross-wires will appear in the center of the field, is not essential to 

the accuracy of the work but may be effected by means of the 

screws underneath the ring just back of the cross-wire screws. 

Loosen one and tighten the opposite one of these screws with a screw 

driver until the wires appear centered.

Level-vial direction. When the bubble has been carefully centered, with the instrument clamped parallel to opposite leveling 

screws, loosen the clips and rotate the telescope around its horizontal 

axis in the wyes about 20° each way from the normal position, making sure that the wyes are free from dirt; if the bubble moves away 

from the center toward opposite ends alternately, bring it all the 

way back by the side or azimuth adjusting screws by loosening one 

and tightening the other. In the ordinary wye level the two rings 

on the telescope tube that rests in the wyes are assumed to be circular and exactly equal by construction, but if they are not the 

bubble will run toward the same end when the level is rotated either 

way from the normal position. Under such conditions an inclination of the line of sight will exist after the usual adjustments are 

apparently satisfactory, and the only course left open is to treat 

the instrument like a Dumpy level and to adjust the level to the

58515° 28 10
140 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL, SURVEY

telescope by the peg method described on page 141. This is a more 

direct adjustment and gives a positive useful measure of the inclination of the line of sight.

Level-vial inclination. When the bubble has been carefully centered with telescope in normal position but with clips open, lift the 

telescope out of the wyes, reverse it end for end, and replace it in 

the wyes; if the level bubble has moved away from the center bring 

it halfway back by means of the capstan adjusting nuts at one end of 

the level tube and the rest of the way by the lower leveling screws. 

Repeat this operation until the adjustment is perfect, and close the 

clips.

Wyes. After each of the foregoing tests and adjustments have 

been made, the wyes can be adjusted. This is done by turning the 

telescope and level 180° on its vertical axis; if the bubble, which was 

at first in the center, moves away, bring it halfway back by changing 

the setting of the pair of large capstan nuts under one wye and the 

remainder of the way by the base screws. This wye adjustment is 

relatively unimportant and is made more as a matter of convenience 

than of necessity.

SPECIAL ADJUSTMENTS

All instrumental errors may be compensated in each set-up by the 

exact equalization of back-sight and fore-sight distances, but as this 

can not always be done it is important to know the amount of error 

introduced when a balance is not maintained. The level and collimation adjustments are the most important of the regular wye-level 

adjustments, but a large deviation of the line of sight from parallelism with the level vial, due to unequally worn or deformed rings or 

unequal pressure of clips, may exist and will not be revealed by the 

usual adjustments. Information as to this deviation is desirable, 

however, and should be obtained, in order to show the condition of 

the instrument and to take it into account when sights have not been 

well balanced. The existence of this deviation is ascertained by 

means of the peg-method test for the determination of C.

Peg-method test for determination of C. Use two turning points 

about 300 feet apart and at nearly the same elevation. Set up the 

level about 30 feet from one point, and with the bubble centered 

take readings on the rod for both points. Repeat the operation from 

a set-up 30 feet from the other point. From these readings and distances determine the inclination of the line of sight per 100 feet of 

distance, which is the constant C. The value of C is expressed by 

the following formula : C= (sum of near-rod readings minus sum of 

distant-rod readings less 0.004 feet for curvature and refraction )-^ 

(difference between sums of long and short sight distances-KLOO). 

Example:
LEVELING 141

Distant rod

Distance

299 

298

597 

67

530

Readings

Turning 

point A 

4.520

Turning 

point £ 

3.580

a 100 

.004

8.096

Difference

0.256 

.282

Near rod

Readings

Turning 

point B 

4.264

Turning 

point A 

3.862

8.126 

8.096

+.030

Distance

35 

32

67

+0.030-«-5.30 = +0.0057= C.

This is equivalent to an error of 0.01T foot on the rod at a distance 

of 298 feet (0.0057x2.98=0.017), which is the amount that would 

be required to raise the line of sight on the distant rod to make it 

level.

The computation should be carried to the fourth decimal place, 

and the parts of the notes to which the value determined applies 

should be plainly indicated. The value of C should be recorded on 

the right-hand page of the notebook opposite the entry for the point 

at which the test was made, and a page reference to its computation should be given.

Peg-method adjustment. The adjustment by the peg method is 

necessary when the rings are unequally worn or deformed and is a 

direct method of bringing the line of sight parallel to the vial. It is 

accomplished by taking up the amount of error disclosed in the pegmethod test by raising or lowering the reticule while keeping the 

bubble centered. The reading on the rod at the distant point corresponding with a level line of sight at the instrument is found by 

increasing or decreasing, according as the constant C is plus or 

minus, the last reading made on the rod so situated by the product 

obtained by multiplying the distance to the rod in feet by C divided 

by 100. If, after making the usual wye-level adjustments for level 

and collimation, a peg-method test reveals so large a value for the 

constant C that this adjustment is required, the usual collimation 

adjustment should be abandoned and this peg-method adjustment 

used instead. This will leave the level-vial and wye adjustment 

undisturbed and repeatable and take up the other instrumental errors 

by moving the reticule. In the prism level the error is taken up 

more conveniently by the vial adjustment screw, as the level is not 

reversible. If an adjustment is made after a value for C has been 

determined a new determination is required.
142

THIRD-ORDER LEVELING WITH PRISM LEVEL AND

YARD RODS

PERSONNEL AND EQUIPMENT

A prism-level party consists of one levelman, two rodmen, a recorder, and a general utility man. The instruments and outfit (see 

pi. 7) consist of the following:

One prism level.

Two yard rods, each to have plumbing level and thermometer attached.

One steel tape (25 feet).

One special invar testing tape.

Two steel turning-point pins.

Two rawhide mallets.

One pocket compass.

One Locke level.

One set of dies (figures).

Bench-mark tablets or posts.

Copper nails and washers for temporary bench marks.

Cement, paint can, keel, and other accessories.

Two book bags.

Prism level notebook 9-940 or 9-940A.

Bench-mark description book 9-916.

CHARACTER AND ACCURACY OF LINES

Third-order levels executed with a prism level ordinarily need be 

run in one direction only but must be checked by closing circuits 

or releveling or otherwise. Circuits must close with an error in feet 

not exceeding 0.05 V length of circuit in miles. Steps to be taken 

if the closure is in excess of this amount are explained in the first 

part of these instructions (p. 127).

GRADUATION OF ROD

The rods used are graduated to yards, tenths, and hundredths and 

are read by estimation to thousandths. Each yard has a different 

and distinctive color, which must be recorded for each reading. One 

edge of the rod has also graduation in tenths of feet, numbered, for 

use as a check on yard readings, and some rods have "double yard " 

graduations to be used as a check. These rods are of the " selfreading " type and have no targets.

METHODS OF OBSERVATION

Third-order lines of levels may be run in two ways with the prism 

level by reading all three horizontal cross wires on the rod, or by 

reading the middle one only. The three-wire method gives more 

accurate results and makes available a greater number of checks
LEVELING 143

against errors, but the keeping and computation of the field notes 

are somewhat more cumbersome. The one-wire method has a slight 

advantage in speed and simplicity.

THKEE-WIRE METHOD

In the three-wire method the program at each set-up is as follows : After the tripod is firmly set and the clamp screws tightened, 

level approximately by the circular level, which has been adjusted 

by comparison with the long level. Point the instrument toward the 

back rod and clamp; bring the level bubble to the center of the tube 

by means of the micrometer screw. Read on the rod and, first, call 

off the color initials for the lesser and greater extreme readings; 

second, call yards and tenths for each wire, taking the smallest reading first; third, repeat and read yards, tenths, hundredths, and estimated thousandths; fourth, for additional check on the yard number, 

read the middle wire on the tenths of feet scale on the back of the 

rod, estimating and recording to hundredths of a foot. When the 

recorder has checked the back sight he signals the rear rodman to 

come ahead. Meanwhile the levelman sights the front rod and takes 

the fore sight as soon as the recorder has checked the back sight 

but does not move his instrument until the recorder has also checked 

the fore sight. The front rodman remains at his turning point, 

guarding it carefully against disturbance. The levelman moves forward to his next set-up, and the free rodman advances to a new 

turning point. Hodmen should never exchange rods.

Prism-level notebooks (9-940A) should be used when readings are 

to be made on all three cross wires. The horizontal lines in these 

books are in groups of four, and the bottom line of each group 

is red. Each group is intended to cover a single set-up of the instrument, the back sight on the left and the fore sight on the right. 

Sample pages of level notebooks are given opposite page 144.

The seven columns on the left-hand side of the book, from left 

to right, are used as follows: In the left part of column 1 are written 

the yard color initial of the first and last yard readings and the 

check reading in hundredths of a foot, the last figure being estimated; in the right part of the same column are placed the three 

yard readings to thousandths of a yard. In column 2 are given the 

interwire intervals, found by subtracting the least yard reading 

from the middle and the middle from the largest. If the three 

cross wires are equally spaced these two interwire intervals should 

be within 0.002 or 0.003 yard of being the same, thus giving a check 

on the yard readings. The wires are so spaced that either one of 

these intervals, as read on a yard rod, will give a stadia distance 

to the rod in feet that is, the interval between the middle wire and
144 TOPOGRAPHIC INSTRUCTIONS OP GEOLOGICAL, SURVEY

either one of the others will subtend 0.1 yard on the rod for every 

100 feet of distance to the rod. The continuous accumulating sum. 

of the interwire intervals between the least yard reading and the 

middle is carried along from set-up to set-up, starting with zero at 

each permanent bench mark. This sum of back-sight distances, 

which is written on the fourth line of each group, may then be compared at any time with the sum of fore-sight distances to see how 

nearly fore-sight and back-sight distances agree. If the continuous 

sum of interwire intervals is not carried along in this manner the 

net excess of the page sums of interwire intervals for one column 

down to the bottom of each page should be placed at the top of 

the same column on the next succeeding page. Added together these 

amounts give the distance run from the last permanent bench mark. 

Column 3 is for the sum of the three yard readings, which is equivalent to the mean of these three readings converted to feet, and it 

is checked by the readings in hundredths of a foot taken on the 

back of the rod. Column 4 is used for H. I. and elevation.

The space above the short black line is for the H. I., and that 

below the line for the elevation. Columns 5, 6, and 7 are for 

the fore sight, and are used in the same way as columns 3, 2, and 1, 

respectively. Thus in each fore sight or back sight there are three 

independent checks: The color initial checks the first figure of the 

yard readings, the inter-wire intervals check the difference of the 

yard readings, and the foot reading on the back checks the sum of 

the yard readings. These three checks must be made for the back 

sight before the back rodman moves his turning-point pin, and for 

the fore sight before the instrument is disturbed. When a bench 

mark is reached, the page sums of columns 3 and 5 should be completed, and the levelman should also make corresponding sums of 

the foot readings in columns 1 and 7 as a check. Also, either the 

recorder or the levelman should add the middle-wire yard readings 

in both columns 1 and 7, and multiply each sum by 3. This will 

check the sums for columns 3 and 5 if the algebraic sum of the 

discrepancies of the inter-wire intervals is considered. If column 

4 is filled in, the usual page check should be made, the difference of 

the sums of columns 3 and 5 being used to check the difference of 

the first and last elevations on the page. Show all such computations in full.

If in the body of the page the record is reached of a point for 

which the elevation is to be computed, the H. I. and elevation must 

be entered throughout the page. Otherwise it is permissible to 

carry the elevation through the page by means of the totals of 

columns 3 and 5, using the total of column 3 as a back-sight reading 

to be added to the elevation brought forward from the preceding
Field notes by prism level and yard rod and three-wire method (book 9-940A}

Date: June 8, 1925. John Smith, recorder

Back sight

Thr. Rdg.

B 0. 365 

1.34 0.447 

B 0. 528

B 0. 363 

1.35 0.448 

B 0.533

B 0. 277 

1. 07 0. 359 

B 0.441

B 0. 563 

1.91 0.636 

B 0. 707

B 0.017 

0. 75 0. 248 

B 0. 478

' O 2. 394 

8. 17 2. 727 

Y 3. 058

Y 3. 184 

10. 02 3. 339 

Y 3.493

Y 3. 094 

9. 67 3. 226 

Y 3. 356

R 1.913 

6. 57 2. 191 

Q 2. 463

Thr. 

Int.

782

82 

81

85 

85

167 

82 

82

249 

73 

71

322 

231 

230

553 

1,443

333 

331

886 

155 

154

1,041 

132 

130

1,173 

278 

272

1,451

Sum 

T. R.

1.340 

1.344 

1.077 

1.906 

0.743

feet = 

8.179

10. 016 

9.676 

6.567

Sums for page

13. 621 

3

40.863 40. 848

H.I. (feet)

Elev. 

(feet)

327. 861

329. 201

318. 641 

319. 985

310. 089 

311. 166

301. 804 

303. 710

297.246 

297. 989

294. 257 

0. 27 mile

302. 436

300. 953 

310. 969

308. 574 

318. 250

317. 201 

323. 768

315.911

Elev. Elev. 

11. 950

B CJ T? Ci

11. 950

Fore sight

Sum 

T. R.

Thr. 

Int. Thr. Rdg.

(Elevation brought forward from 

page ..-.)

10. 560 

9.896 

9.362 

6.464 

3.732

1.483 

2.395 

1.049 

7.857

89 

89

76 

75

165 

86 

85

251 

269 

265

520 

370 

370

890

175 

173

1, 065 

115 

113

1,180 

186 

185

1,366 

263 

263

1,629

3. 431 Y 

3. 520 10. 56 

3.609 Y

3.223 Y 

3. 299 9. 89 

3.374 Y

3. 035 Y 

3. 121 9. 36 

3.206 Y

1. 887 R 

2. 156 6. 47 

2. 421 G

0. 874 B 

1. 244 3. 74 

1. 614 R

0. 320 B 

0. 495 1. 47 

0. 668 B

0. 684 B 

0.799 2.40 

0. 912 B

0.164 B 

0. 350 1. 06 

0. 535 B

2. 356 Q 

2. 619 7. 86 

2. 882 O

Sums for page

52. 798

17. 603 

3

52. 809

Line from Troutdale, via . _ , to Essex

Miles

24.45

24.72

Descriptions (including elevations)

Clear; strong wind; 65°.

Union City, 4 miles NW. of, at foot of long hill, 100 feet E. of road forks to N., 

on E. end of head wall of small concrete bridge; chiseled square.

Road turns to NE.

T. P. on south rail at R. R. crossing.

782 -178

604 excess B. S.

3,080 feot=0.58 mile; 25.03 total miles.

58515° 28. (Face p. 144.)
LEVELING 145

page and the total of column 5 as a fore-sight reading to be subtracted from the result of this addition to obtain the elevation to 

carry forward to the next page.

If a bench-mark description falls in the middle of a page, it is 

advisable to skip one of the four-line spaces before continuing the 

notes, thus giving room for distance totals, etc. The bench-mark 

descriptions are to be written in book 9-916 in the same form as 

for wye-level results. (See p. 136.)

In using two rods on alternate turning points, give the number 

of each rod occasionally alongside the record of a fore sight on 

which it was used.

ONE-WIRE METHOD

In the one-wire method rods having the double yard graduation 

on the back should be used. The program at each set-up is the same 

as described for the three-wire method, except for the reading and 

recording. The stadia distance is first read while the instrument is 

being leveled. Then, by the middle wire only, are read, first, the 

yard color initial; second, the yard, tenth, hundredth, and estimated 

thousandth; and third, the "double yard" reading estimated to 

thousandths. These readings are recorded in field book 9-940. A 

sample of field notes is given on page 146. The horizontal lines 

are in groups of two, each group covering one set-up. The upper 

line of the two should be used for recording the back and fore sights 

and the H. I. for the set-up. The elevation of the forward turning 

point should appear by itself on the lower one of the two lines. In 

column 1 are entered the color initial of the middle wire reading 

and the distance to the rod in feet, obtained by reading stadia on the 

rod. Column 2 is for the check reading in " double yards," column 

3 for the yard reading, column 4 for H. I. and elevation placed as 

noted above. Columns 5, 6, and 7 are for the fore sight and are 

used like columns 3, 2, and 1, respectively, for the back sight. The 

recorder should mentally multiply each double-yard reading by 2 

and compare the result with the corresponding yard reading, thus 

obtaining a check of not more than 0.001 yard above or below, 

before the next sight is taken or the turning point or instrument disturbed. The yard readings are used to compute the H. I. and elevation in column 4 through every page. These values are therefore in 

yards. Computations of bench-mark elevations in feet are to be 

placed on the right-hand page. The usual page check must be made 

for every page by comparing the difference of the sums of columns 

3 and 5, multiplied by 3, with the difference between the beginning 

and ending elevations for the page, converted to feet, this computation to be shown in full. The sum of the distances in columns 1 and 7,
146 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

converted to miles, is entered to show the total miles from the last 

permanent bench mark. A two-line group should be skipped before 

continuing the record after establishing a bench mark. Bench-mark 

descriptions are written in book 9-916 in the same form as for wyelevel lines. (See p. 136.)

LENGTH OP SIGHTS

The length of fore and back sights should be equalized with the 

prism level as with the wye level. The maximum length of sight 

with the prism level is 360 feet except at river crossings, where the 

mean result of reciprocal observations should be taken between one 

pair of pegs at nearly equal elevations on opposite banks.

Mount the instrument first near one peg and then near the other 

so that the center wire will fall near the middle of each rod; if the 

distance is too great to read the three wires, use improvised targets 

of cardboard held in place by rubber bands or some other simple 

device, and make several settings by raising and lowering them an 

equal number of times. Hodmen should be provided with field 

glasses if necessary to read signals. From bench marks on each 

bank the elevation of the adjacent water surface should be determined as an additional check.

MEASUREMENT AND USE OF BODS

Testing of the rods in the field for length is very important. On 

wooden yard rods small metal plugs are set into the faces at intervals, each bearing a fine graduation; these are for use in testing the 

rods. These tests are made as explained on page 129.

The rods must be kept covered when not in use. The painted 

sides must not touch the ground. Should difficulty be found in 

holding a rod steady because of wind, two pieces of bamboo or other 

light poles, 8 feet long, may be held by the rodman against the rod, 

so as to make a triangular brace against the wind. Plumbing levels 

must frequently be tested and kept in adjustment.

ADJUSTMENT OF PRISM LEVEL

When the work is cotamenced, and at least once each day thereafter, the adjustment of the level must be tested by the "peg 

method," either by making two separate set-ups, apart from the line, 

as described for testing the wye level (p. 148), or by utilizing 

one of the sights of the line itself, thus saving one set-up. If the 

latter procedure is used care must be taken not to get the extra
Field notes by prism level and yard rod and one-wire method (book 9-940}

Date: Jan. 9, 1925. John Doe, Lev. ___ . Rec.

Back sight

Color Dlst.

B 160

R 300

Y 270

R 200

Y 200

Y 200

Y 200

0 190

Q 100

B 40

B 100

B 90

B 200

R 40

R 30

Double 

yards

0.050

0.777

1.505

0.566

1.835

1.669

1.725

1.488

1.040

0.483

0.358

0.390

0.171

0.903

0.749

Yards

0.100

1.554

3.010

1.131

3.670

3.339

3.450

2.977

2.092

0.965

0.716

a 792

0.342

1.806

1.499

Sums for page

13. 721

2

2, 320 27. 442 27. 443

H.I.

(yards)

Elov. 

(yards)

395. 200

395. 320

392. 150

393. 704

393. 514

396. 524

395. 596

396. 727

395. 612

399. 282

399. 046

402. 385

401. 210

404. 660

404. 480

407. 457

406. 653

408. 745

407. 534

408. 449

405. 779

406. 495

403. 731

404. 523

401. 852 

402. 194

399. 844

401. 650

399. 900

401. 399

399. 926

Elev. Elev. 

4.706

B.S.-F.S.

4.706

Fore sight

Yards Double 

yards Dist. Color

(Elevation brought forward from

page ....)

3.170

0.190

0.928

1.115

0.236

1.175

0.180

0.804

1.211

2.720

2.764

2.671

2.350

1.750

1.473

1.585

0.095

0.464

0.557

0.118

0.587

0.090

0.402

0.606

1.360

1.382

1.336

1.175

0.875

0.736

300 Y

280 B

360 B

80 R

50 B

130 R

150 B

70 B

40 R

190 0

140 Q

150 G

160 G

20 R

30 R

Sums for page

11. 368

2

22. 737 22. 736 2, 150

Line from point near Crownovcr ranch, via roads S., E., N., to Marble Falls

Elev. (feet)

1, 185. 660

1, 222. 602

1, 199. 778

Descriptions

T. B. M., Beakley's ranch 1.5 miles SE. of, on W. side of road at turn, in 

root on N. side of forked cedar tree; copper nail in washer; "T. B. M.

1222.6" painted on tree.

[Give usual sketches]

P. B. M., Beakley's ranch, 1.8 miles SE. of, about 0.7 mile NW. of the corner 

of Burnet, Blanco, and Llano Counties, in SE. angle of cross roads; iron

post stamped " C-7-1925."

Page check

4. 706 2, 320 3. 51 miles

3 2, 150 . 85

14.118 14.118 4,470 4.36

58515° 28. (Face p. 146.)
LEVELING 147

sights confused and introduced into the line, in place of or in addition to the regular sights. To do so would introduce a gross error.

Peg-method test and computation of C. At some convenient 

set-up, having a full-length fore sight, after the usual back-sight and 

fore-sight readings have been recorded, copy the fore-sight reading 

on the right-hand page for use as a long test sight. Set an extra 

turning point about 30 feet back of the instrument, and read the rod 

on it for a short test sight. Move the level forward to an extra set-up 

about 30 feet back of the regular fore-sight pin, and read the rod on 

it for the second short test sight. The rod is read also on the extra 

turning point, for the second long test sight. The test sights are now 

all obtained, and the extra turning-point may be moved, the instrument carried forward, and the line continued as usual from the 

regular turning point. The two long test sights, recorded one under 

the other on the right-hand page, and the two short sights, similarly 

recorded, should be marked "Determination of C." Test sights 

should be taken in the same manner as the regular sights, three wires 

or one wire being used according to the way the line is being run.

The constant C, which is a factor of the adjustment correction, 

must then be determined. It is the sum of readings on near rods in 

feet minus that on far rods (corrected for curvature and refraction) 

in feet divided by the difference between the sum of the greater and 

that of the lesser distances in feet and multiplied by 100. It is 

the amount, in feet per 100 feet of distance, that the line of sight 

slopes when the bubble is centered. 1

When the sum of the readings on the near rods is the greater, the 

sign of C is plus and the line of sight is too low. Care should be 

taken to give the proper sign and proper position of decimal points. 

Curvature and refraction correction for the sum of the long sights in 

feet is obtained by the formula 0.00041 (mean length of long sights 

~ 100) 2 . This correction is of such sign as to be always subtracted 

numerically from the long-sight readings. Examples of the computation of C are given below. In the expression for C by the threewire method the approximate sums and difference of sums of lengths 

of long and short sights in hundreds of feet are derived from the 

corresponding sums and difference of sums of lower or upper thread 

intervals in yards by moving the decimal point one place to the right.

1 C as used by the U. S. Coast and Geodetic Survey is the amount of slope, in meters, 

per meter of total rod intercept or interval between the stadia wires. This is not the 

same as the amount in meters per 100 meters or feet per 100 feet, because the stadia 

constant of the levels used by that bureau is 0.003. Therefore the numerical value 

of C as used under these instructions represents a slope 3.33 times the slope corresponding 

to the U. S. Coast and Geodetic Survey formula., The difference should be borne in mind 

when comparing the limits of instrumental error allowed without readjusting. The 

U. S. Geological Survey prism level stadia constant is 0.006,
148 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY 

Determination of C for three-wire method

Long sights

Wire 

reading 

(yards)

2.781 

3.103 

3.426

1.638 

1.956 

2.276

Interval 

(yards)

0.322 

.323

.318 

.320

.643 

.063

.580

Sum 

(feet)

I 9. 310 

5. 870

15. 180 

o.004

-15. 176 

+15. 140

-.036

Short sights

Sum 

(feet)

5.893 

9.247

+15. 140

Interval 

(yards)

{

0.032 

.033

\ .029 

I .030

.063

Wire 

reading 

(yards)

1.932 

1.964 

1.997

3.053 

3.082 

3.112

0 Curvature and refraction.

15.140-15.176^-0.036 0 6.43-0.63 ~TSO=-0-0°62.

Determination of C for one-wire method

Long sights

Distance 

(feet)

320 

318

638

638 

60

578

Double 

yards

1.551 

0.978

Yards

3. 103 

1.956

5.059 

° 15. 177 

\ 004

-15. 173 

+15. 138

-.035

Short sights

Yards

1.964 

3.082

5.046 

15. 138

Double 

yards

0.932 

1.541

Distance 

(feet)

30 

30

60

Feet.

Curvature and refraction.

 15.138-15.173 -0.035 _ {-J "^ ^ oo n at\ ==3 ErTO=3 0.0060.

6.38-0.60 6.78

Peg-method adjustment. If the resulting value for C numerically 

exceeds 0.005, an adjustment should be made by changing the position of the level bubble only, as follows:

. Point to a distant rod with the bubble in the middle of the tube 

and read; move the telescope (by micrometer screw) so as to raise 

or lower, by an amount derived by multiplying the distance to rod in 

feet by C-^-100. This amount is in feet, and it should be reduced to 

yards in order to set it off more conveniently on the rod. While holding the telescope in this position, bring the bubble to the middle of 

the tube by raising (or lowering) one end of the level vial with the 

adjustment wrench. After the adjustment has been made, its accuracy should be tested by redetermining the value of C.
LEVELING 149

In case the cross wires break and the level-tube adjustment has 

not been disturbed, insert new spider threads and determine value 

of C, as above directed. Compare with the last determination of C, 

and adjust for the difference by changing the position of the crosswire ring only not the level bubble.

When both level and cross wires have been disturbed the cross 

wires can be put in proper position by means of improvised wooden 

wyes in which the telescope is turned while watching a clearly defined point through it, the operation being the same as for the collimation adjustment for a wye level. The length of the air bubble 

in the graduated level vial can be regulated by means of the air 

chamber in one end of the glass tube. There is a small passageway 

in the lowest part of the tube between the air chamber and the main 

level tube; when one end of the telescope is held considerably lower 

than the other, with the leveling screws uppermost, if the air chamber end is then the lower, bubbles will be seen rising through the 

liquid; these added to the large bubble will make it still larger, 

but if no bubbles appear and the large bubble grows smaller, it indicates that the air chamber is in the upper end. Note the effect at 

the first trial and act accordingly in future. When the level is being 

carried from station to station, if the tripod is held nearly vertical 

the bubble will not change in length.

When leveling up at the beginning of a day's work, set the telescope parallel to two leveling screws and level; turn it 90° and 

again level. Turn the level 180° and then 90° and test in both positions. If the bubble moves away from the center, bring it halfway back by means of the leveling screws and the remainder by the 

micrometer screw. When the leveling is perfect adjust the circular 

level to agree with the other level and note the reading of the micrometer head. The reading should be maintained for the day as 

nearly as possible to that thus found. The instrument should be so 

carefully leveled with the leveling screws at each set-up that there 

will be no material difference between the readings of the micrometer head for fore and back sights; a failure to observe this precaution may introduce uncompensating errors.

CARE OF INSTRUMENT

When the level is on the tripod, be sure that the central tripod 

clamp screw is tight. Keep the telescope off the micrometer-screw 

bearing while carrying it between stations. Leave the three tripod 

wing nuts loose when carrying; clamp tight when tripod is in place 

for work. The micrometer screw should be cleaned and oiled slightly 

every two or three days.
150 TOPOGEAPHIC INSTRUCTIONS OP GEOLOGICAL, SURVEY

If the level can not be shaded from direct sunlight by an umbrella when in use, a piece of white cloth or frosted celluloid about 

8 inches square may be fastened over the top of the instrument with 

rubber bands, so as to allow only diffused light to reach the bubble 

and prisms. While not being used and still on the tripod, the instrument should be set in the shade or a cloth hood thrown over it.

In running lines by the one-wire method there is danger of error 

through reading the wrong horizontal wire, as all instruments have 

stadia wires. This possibility may be avoided by revolving the 

reticule a quarter turn so as to bring the single wire horizontal, and 

the instrument may be regularly used in this manner. If this is 

done the rod'may be held horizontal for the stadia reading.

TURNING POINTS

With the yard rod having a hemispherical foot serious errors 

may result if turning points are taken on the highest point of a 

rock or nail, as it is difficult to set the rounded shoe in its highest 

position on such a point. It is better to find a slight nick or depression into which the rounded shoe can settle to a definite position. 

It is always best, however, to use the regular turning-point pins 

made for the purpose, wherever there is a chance to drive them into 

a firm position, even if other hard surfaces are available. A wooden 

or rawhide mallet should be used to drive the pins. Rods should 

be set upon the pins gently, so as not to cause them to move or 

settle.

Certain unfavorable conditions and other causes of error, mentioned on page 137 in connection with work when a wye level is 

used are also applicable to lines run with a prism level.

SECOND-ORDER LEVELING

PUBPOSE

Trunk lines of second-order leveling must be run as a framework 

upon which to base third-order leveling where first-order lines are 

too far apart to give effective control. These lines should follow 

as nearly as possible the trunk lines of transit traverse that is, 

in lines not over 50 miles apart, so that no point will be over 25 

miles from a main control point of second or higher order.

The prime requisites of through trunk lines are accuracy and reliability, and if there is a choice of route, that route should be 

chosen which will assure the most accurate line rather than the one 

that may give more conveniently located control for the topographer. 

The topographer's needs may be satisfied by side loops of a lower
LEVELING 151

grade. Every effort, both in office planning and in field work, 

should be made to have these trunk lines run and subjected to a 

preliminary adjustment, before other work is based upon them. 

If the trunk line can not be completed in advance, that part of 

the local work that is run over the route of a planned trunk line 

should be run in the manner prescribed for the trunk line, thus 

making a completed link that may later be connected up as a fullweight part of the trunk line.

PERSONNEL AND EQUIPMENT

For second-order leveling the instrumental outfit and the number of men in the party are the same as for third-order leveling 

with prism level, except as hereinafter noted. Some refinements of 

field methods are necessary beyond those required for third-order 

leveling, in order to insure the required accuracy. The work should 

be done with the prism level, by the three-wire method.

CHARACTER, ACCURACY, AND PROCEDURE

Lines must be run independently in both the forward and the 

backward direction.

The back runnings may start from points on the forward-run line 

and may be run in such sequence as may be convenient, except that 

they should not be allowed to lag too far behind the forward running. When the allowable error, in feet, for sections between 

bench marks exceeds 0.035 \/distance between bench marks in miles 

the forward or backward measurement is to be repeated until a 

pair run in opposite directions is obtained between which the 

divergence falls within this limit. It is especially desirable to 

make the backward measurement in an afternoon if the forward 

measurement was made in the forenoon, and vice versa. The observer should make the two measurements under atmospheric conditions as different as possible without materially delaying the work 

for that purpose.

The last set-up of one running must not be copied nor used as the 

first set-up of a return running that is, the instrument must be 

moved so that an independent reading can be obtained.

Whenever a blunder, such as a misreading of 1 yard or one-tenth 

or an interchange of sights, is discovered and the necessary correction is applied, the running containing it may be retained, provided 

there are at least two other runnings over the same section which 

check it and are not subject to any uncertainty.

The field work must in general conform in the instructions 

for third-order leveling with the prism level by the three-wire
152 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

method. (See pp. 143-145.) In order to insure the increased accuracy required, such precautions as careful rod and instrument tests, 

equalization of fore and back sight distances, and care in selecting 

turning points must receive particular attention. Yard rods having 

graduations on an inlaid invar strip instead of on wood are to be preferred. An umbrella should be provided to shade the instrument 

when it is set up, and a cloth hood should protect it from the sun 

when moving from one set-up to the next. The instrument should 

be very carefully handled and must not be subjected to jars and jolts 

such as those resulting from riding uncushioned on the floor of an 

automobile.

RECORDING

Two sets of field books should be used, one for forward running, 

which should be kept as an unbroken continuous line, and the other 

for backward runnings, which should show each section complete and 

continuous in itself. The sections can not be shown in any particular order in the backward-running books, as their sequence will depend upon the field program adopted in the rerunning. Bench 

marks need be described only in the forward-running books, but they 

should receive consecutive numbers and letters, which should appear 

in the backward-running books also, in order to identify the corresponding marks in the two books. The consecutive numbers should 

be the same numbers as the identifying numbers stamped on the 

bench marks. For a supplementary bench mark the same consecutive 

number should be used as for the next preceding permanent or 

stamped mark, and consecutive subordinate letters added until the 

next permanent mark is reached; thus the sequence might be, for 

example, C-23-1925, 23A, 23B, etc., C-24-1925, representing permanent 

mark 23, two supplementary marks following it, and permanent mark 

24. In addition to the use of these numbers, careful and complete 

book and page cross references should be made between the two sets 

of books, in order that no confusion or doubt may arise in finding 

the proper pair of runnings for any given section.

SECTION CHECK

In the forward-running book the difference of elevation should be 

computed for each section of the line between bench marks, permanent or supplementary, and should appear, with the complete computation, on the right-hand page near the end of the space allotted to 

the section. The full computation of the difference of elevation obtained by the backward running should appear with the notes for 

that running, and the difference itself should be brought over into 

the forward-running book for comparison. These differences must
LEVELING. 153

be in agreement within the limits prescribed above, or it will be necessary to make additional runnings, which should be recorded in 

the backward-running books, even though the runnings may be in 

the forward direction.

In running lines with the prism level and the three-wire method 

the elevation and H. I. need not be computed throughout the page. 

Differences of elevation should be computed by means of the page 

totals from bench mark to bench mark, and elevations carried forward by means of these differences, great care being taken to apply 

them in the proper direction.

DESCRIPTION BOOK

Descriptions must be copied into the bench-mark book (9-916) in 

consecutive order, as in third-order leveling. Field-book elevations, 

however, are not to be copied into the bench-mark book, but instead 

the differences between bench marks are to be copied. These should 

appear in a column to the right of the elevation column, one under 

the other, beginning just below the line upon which the elevation 

of the first bench mark is shown. The mean of these two differences 

is then set down in the next column to the right, and this mean is 

applied to the first elevation to obtain that for the second bench 

mark. Thus in the bench-mark book the mean line elevation is carried forward by means of the differences between bench marks. The 

mean line elevations should then be copied into the forward field 

book, on the right-hand page above the description of the bench 

mark to which they apply, and a circle drawn around them to distinguish them from the field-book elevations. If field-book elevations have been carried through in the forward-running book in the 

usual manner, rough comparison with the mean line elevations will 

serve to check the proper use of the sign in applying the differences 

between bench marks.
Record in description book (9-916)

Level No. 163. Rod Nos. T-32, T-42. Levelman, John Doe

Date 

(1925)

June 2

2 

3

2

3

2

3

2

Interpol

2

2

4

4

5

Outoflii

5

5

(5

Level book

No.

3F

3B

3F 

3B

3F

3B

3F

3B

3F

ited or

3F

3B

3F

3B

3B

aits; t

3F

3B

3B

Page

21

41

22 

46

23

44

25

43

26

i first i

27

42

28

48

43

sethir

29

42

42

Miles by 

route

0

0.3

0

1.2

2.0

2.7

unning.

3.3

4.5

d running

5.7

Instrum

7.3

elevation

(feet)

428.96

431. 286

431. 278

520.716

529.811

627.1

483. 217

422. 987

in place oi

402. 615

jnt tested;

385. 017

Differences of 

elevation

(feet)-

2.330

2.322

89. 451 

89.425

9.087

9.103

46. 610

46. 578

60. 238

60. 222

20. 384

20. 360

second.

17. 629

17. 567

C=-0.0

Mean differences

(feet)-

+2.326

+89. 438

+9. 095

-46. 594

-60. 230

-20. 372

-17. 598

)21).

Bulletin elevation.

Check.

Bulletin elevation.

Line from Troutdale via Highway 24 to Essex. Quadrangle, Newman

Description (in publication form)

[Location sketches should also be given]

Troutdale, on south side of Corning Street, between High and River Streets, at east front 

corner of courthouse, on east end of sill of basement window; chiseled square. (Bull

621, p. 18.)

Troutdale, in west corner of intersection of Corning and Mission Streets, on east end of

second granite step to the main entrance of the First National Bank Building; bronze 

tablet, stamped " C-32-1921 431." (Bull. 621, p. 18.)

Troutdale, at south city limits, on west side of Mission Street, 100 feet south of center of 

Lenox Street, on stone curb 17 feet south of fire hydrant; chiseled square.

Troutdale, 2.3 miles southeast of courthouse, opposite junction of road to west, in south

root of 24-inch maple tree, about 2 inches above the ground; copper nail. Tree painted "B.M."

South rail at crossing of Denver & Rio Grande Western Railroad.

Troutdale, 2.3 miles south and 1.3 miles east from, at south corner of small cemetery,

just inside the angle of the stonewall, in top of concrete post about 3 inches above the

ground; bronze tablet stamped "D-17-1925. "

T. 5 N., R. 4 W., at quarter corner on south side of sec. 8, on north side of road, at T corner of stone wall, on south projecting corner of lowest corner stone; chiseled square;

wall painted "B.M."

T. 5 N., R. 4 W., at east sixteenth corner on south side of sec. 9, 0.25 mile west of crossroads, on north side of road, on south corner of concrete base of lamp post; chiseled square.

Essex, at Denver & Rio Grande Western Railroad station at foot of Meadow Street,

near east end of main building, at southeast corner of grass plot, in concrete curbing;

bronze tablet, stamped ' ' N-20-1902 385. " (Bull . 621 , p . 28.)

Elevation by this line ___ .385. 017

Elevation by bulletin ______ 385. 085

Closure ___________ .068

' These column headings are not printed in book 9-916 but may be added in the space provided for such computations.
LEVELING 155 

FIRST-ORDER LEVELING

Leveling of the first order has heretofore been called " precise 

leveling." The net that more or less fully covers the United States, 

made up of lines run by the United States Coast and Geodetic Survey and other organizations, was last adjusted as a whole in 1912, 

thus forming a consistent datum for the area, known as the standard datum. In adjusting this net and in fitting subsequent lines to 

it. work of the first order has been found to require corrections, 

> owing to the distribution of errors in closure, in general less than 

0.2 millimeter per kilometer. Work of this type will not ordinarily 

be done by the United States Geological Survey, but if the necessity 

for it arises, the detailed instructions given in Special Publication 

18 of the United States Coast and Geodetic Survey should be 

followed.

COMPUTATION AND ADJUSTMENT OF LEVEL CIRCUITS

GENERAL CORRECTIONS

©

In the computation and adjustment of level circuits the notes are 

first examined for errors in field computations or records. Corrections are next made for rod errors, including those due to changes in 

temperature; these corrections are products for each difference of 

elevation by the rod correction per foot. Corrections are applied if 

. required for collimation, curvature, and refraction for unbalanced

sights.

ORTHOMETRIC CORRECTION

On long lines at high elevations a correction is required to take 

account of the fact that level surfaces at different altitudes are not 

parallel except at the Equator and at the poles. This correction, 

which depends on meridional distance, latitude, and altitude, may be 

found from the following formula: x

 <fts) sin

659,000 

in which

C = correction in feet. 

/tm =mean height of line in feet.

<£ 8 and<ft n =the latitudes of the south and north ends of section, respectively. 

(<£ n <£ 8) = difference of latitude in minutes of arc.

In applying the formula the lines must be divided into sections 

of not over 100 miles each, and a division should be toade where the 

general direction changes materially. The corrections thus found 

are applied to the several sections so as to lower the elevations at

1 Coast and Geodetic Survey Kept, for 1899, p. 875, 1900 ; Special Pub. 18, p. 49, 1912. 

58515° 28 11
156 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

successive division points going northward. Although orthometric 

corrections may at times lead to apparently absurd results, such as 

giving a lower elevation for the north end than for the south end 

of a large lake having no outlet, yet in order to insure agreement 

between different lines and to obtain results of the greatest theoretical 

accuracy, they must be applied if appreciable.

After all the foregoing corrections are made to the original results, 

the remaining closure errors are those which are to be removed by 

adjustment.

ADJUSTMENTS OF FIRST-ORDER AND SECOND-ORDER LEVELING

The net of lines in the United States of the first and second orders 

of accuracy run prior to 1912 by various organizations was adjusted by the United States Coast and Geodetic Survey and is 

described in that organization's Special Publication 18, " Fourth 

general adjustment of the precise-level net in the United States and 

the resulting standard elevations." By that adjustment the previous 

general adjustment of 1907 was held fixed for points east of ai^ 

imaginary line joining Shreveport, La.; Little Bock, Ark.; St. 

Louis, Mo.; Savanna, 111.; and Marquette, Mich.; and the portion 

of the 1907 net west of that line was readjusted to include the orthometric correction and additional lines. The elevations thus derived 

are assumed to be standard elevations and are expected to be held 

fixed. The lines subsequently added to the net have been merely 

fitted in by prorating the closure error. New lines will be similarly 

treated except that if several connected new lines are considered 

jointly, a special computation for the new junction points will be 

made before the errors of each new link are distributed.

ADJUSTMENT OF THIRD-ORDER LEVELING

All adjustments of third-order are to be made in the Washington office in the bench-mark description book (9-916), in which abstracts from the field books, which include the description and elevation of each bench mark as determined by the levelman, are written 

by him in regular order for each line as run.

All the level lines associated with one another should be considered at one time, and in order to obtain a better comprehension of 

their arrangement they should first be plotted on the office progress 

maps as accurately as possible, and from these maps tracings should 

be made on paper, to be used in the adjustment and later filed with 

the description book as part of the record. The diagram should show 

the approximate relation of all the lines, including the first-order 

or previously adjusted lines forming the base of the system, and the
LEVELING 157

work of different grades or different men should be represented by 

different-colored inks or pencils or in some other manner, a suitable explanatory legend being attached. The names of a sufficient 

number of towns should be given to identify the location readily, 

and beside each line reference should be made to the page in the 

description book where the bench-mark elevations for that line are 

given. On each line a > is to be placed to show the direction 

in which it was run. For small areas the diagram of routes prepared by the levelman in the description book will probably answer 

in place of the tracing.

The field notes should be examined to see whether the work was 

in accordance with the instructions; whether fore and back sights 

were equalized, rod readings properly summed, balances checked, and 

elevations properly copied from page to page. The entries in the 

description book should be systematically checked to see that all 

elevations, including those at starting, junction, and closing points, 

and all breaks and second runnings are properly copied. Where 

two runnings of equal weight are made over one course, the mean 

result should be accepted for adjustment and written with the appropriate statement in a separate column, the divergence being given 

alongside.

Before proceeding further the rod and orthometric corrections, if 

considerable, should be applied as explained on page 155.

At each junction point on the diagram should be written the difference between the recorded elevation by some one of the lines and 

those recorded in the description book for each of the other lines 

for the same bench mark, with an arrow alongside and plus or minus 

signs added to indicate that the elevations as recorded by these lines 

are greater or less than the selected elevation. Also, as an additional 

aid in the adjustment, the closure error for each circuit should be 

written in the center of its position on the diagram, the sign being 

computed in counter-clockwise order. Next ascertain by inspection 

of the diagram which of the unknown junction points may be determined with the greatest apparent accuracy OP by the greatest number of independent lines. From three or more lines connecting this 

point with the points of known elevation obtain three or more possible corrections to the recorded elevation for one of the lines. Estimate and record relative weights for these corrections, the weights 

to be based on the reciprocals of length, class of leveling, instrument used, number of times leveled, and relative standing of observers if two or more are involved. Weights should not be influenced greatly by closure errors. If corrections from different sources 

are computed partly through a common line the length of this part 

of each route should be doubled in fixing the weight of each 

correction.
158 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL, SURVEY

From the weights adopted compute the weighted mean correction 

to the selected elevation of the new point as follows: Multiply the 

correction computed for it through data for each route from known 

points in turn by the weight of the line; divide the algebraic sum 

of these products by the sum of the weights. The quotient is the 

correction to apply algebraically to the assumed elevation; it should 

be written in the diagram at the proper junction point in a small 

loop or rectangle with proper plus or minus signs. In complicated 

nets it may be necessary to assign a preliminary correction to a subordinate junction point in order to obtain a direct approximate correction from it for some other point; after fixing the correction for 

the second point from the various lines a final correction is determined and substituted for the preliminary value of the first point.

In this manner weighted values are found for each junction point 

in turn, and corrections are distributed between the points thus fixed

2'M. | ISM. J 4M. 

FIGURE 3. Method of adjusting a level net

in proportion to the distance. A line once thus adjusted should not 

be readjusted for a slight change only.

Figure 3 illustrates the method of adjusting a level net. By inspection of the diagram, junction point E seems to be the most favorably situated for adjustment first. The line run from A through B 

and E to D closed at D 0.060 foot low; from H through I to E 0.120 

foot low. The correction to the recorded elevation for E on the line 

from A is 0.00 by that line itself, -fO.060 computed from D by reversing the closure, and 0.120 from H. The distances to be used 

in assigning weights are taken as A through B to E:^:-3*^+8=13 

miles (A to B being a double-run line is given double weight by 

dividing the length of the line by 2); D to E, 5 miles; H through I 

to E, 10 miles. The weights to be assigned should be in inverse proportions to the length of the lines, or nearly so. To determine the 

weights, take the reciprocals of the lengths or else divide a con-
LEVELING 159

venient number as 13 in this example by the computation distances 13, 5, and 10 each in turn, obtaining 1, 2.6, and 1.3 for the 

weights of the respective lines. These weights are each to be multiplied by the corresponding assumed corrections 0, +0.06, and 0.12, 

giving products of 0, +0.16, and 0.16. Divide the algebraic sum 

of these products by the sum of the weights (4.9) ; the quotient will 

be the weighted correction; this is 0 for the point in question, but as 

there is another line to this point which has not been considered this 

correction must be accepted as preliminary only. The foregoing 

data may, if desired, be assembled in tabular form, thus:

From 

point 

A......

D...___ 

H......

Miles

13

5 

10

"Weight

1.0

2.6 

1.3

4.9

Correction

0.000

+.060 

 .120

Weight 

X correction

0.00

+ 16 -.16

.00

The preliminary correction for point B is now taken as 0, as found 

from three lines, two lines from A and one from E, and a preliminary 

correction of +0.02 foot for I can be obtained by taking a proportionate part of the closure error at E (one-fifth). Junction point F depends for its elevation on values from several lines. The corrections 

from E, B, and I are, respectively, 0.00, 0.32, and 0.26; the corresponding distances are 12, 10, and 26; the weights 2.2, 2.6, and 1.0; 

the resulting preliminary correction for F is 0.19. A final value for 

E may now be found from B, D, I, and F, to include the effect of F, 

and by the foregoing method it is found to be 0.03. G is found from 

lines from B through C, F, F through C, F through J, and I, with 

the computation distances 38, 7, 44, 28, and 38, respectively; in this 

case the distances C to G and J to G, which are common to two lines, 

should be doubled in order not to give them undue weight. The 

final corrections to the various selected elevations are now found in 

a similar manner, the computations for B, I, and F being repeated 

to obtain the effect of the additional lines, and are as follows: B, 

0.00; C, -0.30; E, -0.03; F, -0.18; G, -0.3T; I, +0.02; and J, 

 0.19, two places of decimals only being used for junction points. 

Each of these corrections is placed in a rectangle on the diagram 

near the point to which it belongs.

After the corrections for the junction points are fixed, corrections 

proportioned to the distance are found for intermediate points along 

the several lines.

For high altitudes the orthometric corrections (see p. 155) should 

be applied before adjustment.
160 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

Lines on which the closure error is over the permissible limit 

should not be used in adjustment unless they are indispensable in 

making the best approximation from existing data. Such an adjustment must be regarded as preliminary, pending releveling, and so 

used for map control. Elevations that are suspected to be grossly 

in error must not be published unless the data are urgently needed 

and a caution as to their probable error is expressed.

The computer should report to the division engineer in writing 

any failure on the part of the leverman to comply with instructions; 

he should also report all circuit-closure errors in excess of the allowable limit. A copy of these data should also be written on the last 

inside page of the bench-mark book.
E. TOPOGRAPHIC MAPPING

By W. M. BEAMAN

CHARACTER OF TOPOGRAPHIC MAPS

Definition of a topographic map. A topographic map is a representation on paper that is designed to portray certain selected 

features of a section of the earth's surface plotted on some form of 

projection and to a certain scale; that primarily depicts the relief 

of the country mapped but shows also its drainage and cultural 

features; and that delineates all features in true latitude and longitude 

and therefore all parts in a rigidly correct relative position. A 

reproduction of a part of a topographic map is shown in-Plate 17.

Quadrangles. The topographic maps of the United States Geological Survey are designed to constitute a topographic atlas of the 

United States for an engineering and geologic base. For the purpose 

of this atlas the country is divided into quadrangles bounded by 

parallels of latitude and meridians of longitude. Each sheet of the 

atlas is a map of some quadrangle. The quadrangle maps are 

printed on paper of approximately uniform size, about 16 J^ by 20 

inches, and the maps themselves are about 17 ^ inches long and 12 

to 15 inches wide according to latitude.

Field and publication scales. Standard quadrangle maps are 

published on different scales, which have been selected as best 

adapted for use in the development of different parts of the country. 

The difference in scale involves a corresponding difference in the 

size of the area represented. The relation between the field and 

publication scales of Geological Survey maps and the area represented 

is shown in the table below.

Relation between scale of maps and area represented

Size of quadrangle

1° by I0 .. 

30' by 30'-.--... ___ - __ . __ . ___ .-..-.

15' by 15' 

TW by iyt ......... ...........................

Field scale

Fractional

1:192,000 

1:96,000 

1:48,000 

/ 1:24,000 

\ 1:31,680

Feet to 1 

inch

16,000 

8,000 

4,000 

2,000 

2,640

Publication scale

Fractional

1:250,000 

1:125,000 

1:62,500

} 1:31,680

Miles to 

linch

04 

°2

° 1

X

Area of 

quadrangle 

(square 

miles)

3, 200-4, 200 

800-1, 050 

200-262

50-66

' Approximate.

161
162 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

About 98 per cent of the topographic maps prepared by the Geological Survey have been published on one or another of the four scales 

listed above.

The large range in quadrangle areas is due to the convergence of 

the meridians toward the pole; the areas given represent the differences (in round numbers) between the area of a quadrangle near 

the Canadian border and one in southern Texas or Florida. (For 

areas of quadrangles in different latitudes see Bulletin 650.)

Standard topographic surveys for the United States proper and 

the resulting maps have for many years been divided into three 

types, differentiated as follows:

1. Surveys of areas in which there are problems of great public 

importance relating, for example, to irrigation, reclamation of 

swamp areas, or mineral development are made with sufficient 

accuracy to be used in the publication of maps on a scale of 1:31,680 

(1 inch = half a mile), with a contour interval of 1, 5, or 10 feet.

2. Surveys of areas in which there are problems of average public 

importance, -such as most of the basin of the Mississippi and its 

tributaries, are made with sufficient accuracy to be used in the 

publication of maps on a scale of 1:62,500 (1 inch = nearly 1 mile), 

with a contour interval of 10 to 50 feet.

3. Surveys of areas in which the problems are of minor public 

importance, such as much of the mountain or desert region of Arizona 

or New Mexico, are made with sufficient accuracy to be used in the 

publication of maps on a scale of 1:125,000 (1 inch = nearly 2 miles), 

with a contour interval of 20 to 100 feet.

A scale of 1:31,680 is used instead of a scale of 1:31,250 (half of 

1:62,500) because all the township plats of the public-land surveys 

of the General Land Office have been made on the 1:31,680 scale, 

upon which 1 mile is represented by exactly 2 inches.

Some areas are surveyed on special scales for special purposes, 

as for mineral, power, or urban development and special military 

use. Among such scales are 1:24,000, 1:20,000, 1:12,000, and 

1:10,000, and the field and publication scales are in general identical. In the early days of the Geological Survey maps of large 

areas were published on the scale of 1:250,000, but now this scale 

is used for reconnaissance maps.

Projection. In mapping large areas the engineer is confronted 

with the problem of representing accurately on the plane surface of a 

map the details that exist on the earth's spherical surface. As it is 

impossible to do this exactly, he must resort to the use of some convention that will represent the earth's surface with the least distortion. The systematic drawing on a plane surface of lines that represent reference lines on the spherical surface of the earth is called a 

map projection. There are many systems of projection, each of
TOPOGRAPHIC MAPPING 163

which fulfills certain desirable conditions but none of which is ideal. 

The choice of the proper projection to use for a certain map is not 

always easy but depends largely on the extent of the area to be represented and on the use to which the map will be put. The best treatise 

on map projection published in English is United States Coast 

and Geodetic Survey Special Publication 68, "Elements of map 

projection."

The topographic engineer needs a projection which is simple in 

construction, which can be used to represent small areas on any part 

of the globe, and which, for each small area to which it is applied, 

preserves shapes, areas, distances, and azimuths in their true relation 

to the surface of the earth. The poly conic projection meets all these 

needs and was adopted for the standard topographic map of the 

United States, in which the 1° quadrangle is the largest unit (fig. 4) 

and the 15' quadrangle is the average unit (fig. 5). Misuse of this 

projection in attempts to spread it over large areas that is, to construct a single map of a large area has developed serious errors and 

gross exaggeration of details. For example, the poly conic projection 

is not at all suitable for a single-sheet map of the United States or of 

a large State, although it has been so employed. Its greatest advantage lies in the fact that it represents a small area on any part of the 

earth's surface just as well as one on any other part.

The poly conic projection takes its name from the fact that it is 

based on the development of a large number of cones conceived to be 

tangent to the spheroid at each parallel of latitude to be represented 

on the map. It has been computed for every minute of latitude from 

0° to 90°, and existing tables make its construction very easy. It 

was devised by Ferdinand Hassler, the first superintendent of the 

United States Coast and Geodetic Survey, and has been computed 

by that bureau. The theory of the projection and tables for 

its construction are given in Coast and Geodetic Survey Special 

Publication 5.-

In this projection a central meridian is drawn as a straight line, and 

the intersections of the parallels are spaced true to scale along this 

central meridian. Each parallel is then laid down separately by means 

of a cone whose base is tangent to the earth's surface at that parallel, 

with the vertex of the developed cone on the extension of the central 

meridian. The arcs of the parallels thus drawn are subdivided to 

true scale, and the meridians are drawn through these subdivisions. 

As a result the central meridian is shown as a straight line, and theoretically all other meridians are shown as curves. As the meridians 

and parallels nowhere intersect at right angles, except along the centraT meridian, and as all the other meridians are drawn as curves 

concave toward the central meridian, it is theoretically impossible to 

fit together in a row east and west two maps, each of which is
164 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

drawn on its own poly conic projection, as their joining edges are 

curved in opposite directions. However, in practice and within 

certain limits these conditions do not exist. It is impossible for 

a draftsman or an engraver to draw the limiting meridians of a 1 ° or 

smaller quadrangle within the latitudinal limits of the United States 

other than as straight lines. Therefore, a row of maps east and 

west will join perfectly, although as the north edge of each map 

is shorter than the south edge the row will form a curve. A tier of 

maps north and south will also join perfectly. Theoretically, there 

will be small gores between the edges of each east-west row of maps 

and the next row to the north or south, but in actual practice the 

distortion of map paper due to changes in atmospheric conditions is 

greater than the error of joining, so a moderate number of maps 

say live or six each way can be joined as perfectly as any maps 

can be joined. Seldom, if ever, will a map user wish to join more 

than five or six quadrangle maps in any direction. The size of 

tables or wall space makes further extension impracticable, so that 

the theoretical weakness of this projection can be ignored so far as 

maps of small quadrangles are concerned.

Features shown. The data shown (pi. 17) are essentially the same 

for all maps of the topographic atlas and differ only with the limitations of the different scales. They comprise cultural features, such 

as all buildings, routes of communication, and other works of man that 

are permanent in character; the boundaries of civil divisions, reservations, and grants; the lines of the public-land surveys; the elevation of bench marks and other accurately determined useful elevations; drainage features; relief features; and so far as is practicable 

the names of all features, cultural and natural. Further descriptions 

of the three principal classes of features shown on topographic maps 

are given on pages 229, 242, and 245.

Relief expression. For the cartographic representation of land 

forms several systems are available, but that which Has proved most 

useful and has become the standard in Geological Survey work is the 

system of contour lines. The superiority of this system lies in the 

fact that "hot only is the vertical interval between the lines capable 

of being regulated to suit the character of the relief, but each contour, 

being a line of constant elevation, is projected upon the plane of the 

map with a minimum of distortion. It appears for all practical purposes with its true length and true deflections and consequently 

represents with exactness the contour of the ground at a given level.

A contour line may be variously defined as representing (a) an 

imaginary line on the ground every point of which is at the same 

height above sea level; (6) a level or grade line; (c) a line of constant 

elevation; (d) a coast line or other shore line of level water; (e) an
TOPOGRAPHIC MAPPING 165

assumed shore line resulting from, assumed rising of a body of level 

water.

Contour interval. Standard contour intervals are 1, 5, 10, 20, 25, 

50, 100, and 200 feet. Intervals of 40 and 250 feet have occasionally been used, but these intervals are not now standard. Other 

contour intervals may be used for special purposes, as in the international map of the world, where the contour interval is expressed 

in meters.

The approximate distribution of contour intervals in their relation 

to Geological Survey map scales is shown in the table below representing the 3,167 maps published up to June 30, 1926.

Relation of scale to contour interval in topographic maps published by the Geological 

Survey up to June SO, 1926

[Figures indicate number of maps]

Scale

1:125,000. .............. -.

1:62,500- 

1:31,680. .. .

1:24,000-----. __ .-- .

1:21,120-- 

1:12,000- 

Contour interval (feet)

250

29

29

200

37

37

100

12 

345 

24 

1

1

383

50

1 

252 

273 

2 

5

3

8

544

40

10

10

25

1

25 

107

1

4

4 

4

140

20

145 

1,230

4

4 

8

1,391

10

I 

248 

_5

2 

2

258

5

1 

33 

258 

10

13

315

1

35

35

None"

19

19

Total

80 

779 

1,934 

302 

23 

13 

13 

23

3,167

° Entire area less than 5 feet above sea level.

Colors. Cultural features and names are shown in black, drainage 

features in blue, and relief features in brown. (See pis. 18-23.) 

Transparent overprints of green and red are used to designate woodland areas and a road classification respectively on certain maps.

PREPARATION FOR FIELD WORK 

INSTRUCTIONS AND PERSONNEL

Each permanent employee will receive a letter of instructions 

signed by the chief of the topographic division to which he is assigned 

and covering each assignment of field work. In the temporary absence 

of a division chief or in other emergencies such instructions will be 

signed by the chief topographic engineer. The field instructions 

should specify the area to be mapped and the scale and contour interval for the survey, and as a rule they should outline the general 

method to be employed. The personnel for the party should be 

stated, or authority should be given for the employment of additional 

assistants. The letter should also include such other instructions as 

may be needed. Supplemental instructions may be issued during the 

progress of the field work.
166 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

A topographic field party will consist of a topographic engineer 

(of appropriate grade) as party chief, assisted by one or more engineers, each of whom will usually have a personal assistant serving 

as rodman, as recorder, or in some similar capacity. In country of 

certain types each engineer will have two rodmen and in addition a 

recorder and sometimes an umbrella man. Where appropriate, axmen, boatmen, and laborers are employed. Necessary camp hands 

are included in the personnel.

The instructions given below are for the guidance of party chiefs 

preparing their own field sheets and assembling their own field material prior to taking the field. Party chiefs are urged to be methodical and thoughtful in their field preparations and to foresee the 

season's needs so far as practicable. If the field sheets are prepared 

in the Washington or other headquarters office for shipment to a 

party chief in the field, similar care and judgment should be used in 

preparation, and the interests of the field party should be fully kept 

in mind.

PREPARATION FOR NEW TOPOGRAPHIC SURVEYS

Before starting for the field the topographer should prepare his 

field sheets in the form best suited to the conditions under which his 

work is to be carried on. He should make all necessary requisitions 

for instruments and field supplies and should by inquiry and search 

collect all available data that may prove helpful during the field 

season.

PLANE-TABLE PAPER

All topographic maps made by the Geological Survey are plotted 

on a plane-table sheet that is mounted on a plane table. The planetable sheet consists of two sheets of drawing paper that have been 

specially prepared and mounted on both sides of a sheet of cloth, 

with the gram of the paper on one side at right angles to the grain of 

that on the other side. When such a double-mounted sheet is well 

seasoned it will hold its shape and will withstand the ordinary effects 

of weather conditions that are likely to be encountered in field work. 

The recent experimental use of drawing paper mounted on thin metal 

sheets indicates that by this device the distortion of the paper due to 

changes in atmospheric conditions is reduced to a minimum.

GENERAL FEATURES

Polyconic projections may be constructed by hand, using the instructions and tables published in United States Coast and Geodetic 

Survey Special Publication 5, which gives the required values in 

meters on the surface of the spheroid, or using the instructions and
TOPOGRAPHIC MAPPING 167

tables published .in United States Geological Survey Bulletin 650, 

which gives the measurements in inches on the map scale desired; 

or they may be constructed mechanically by means of a Bumstead 

projection plate. (See p. 175.) The practice of the Geological Survey 

indicates preference in the reverse order from that given above, but 

the theory is best explained by describing the methods in the order 

given. In general a central meridian is assumed upon which the intersections of the parallels are plotted to scale. Each parallel is then 

drawn separately as an arc of a circle with its center lying in the 

extension of the central meridian. The arcs of the parallels are subdivided to scale, and the meridians are drawn through the subdivisions. However,in actual practice on projections of small quadrangles, 

the parallels are not drawn as arcs of circles, but their intersections 

with the meridians are plotted from the computed x and y values, 

and the sections of the parallels between adjacent meridians are 

drawn as straight lines. In polyconic projections of quadrangles of 

1° or smaller meridians may be drawn as straight lines, and in largescale projections of small quadrangles in low latitudes both meridians 

and parallels may be drawn as straight lines. For example, the curvature of the parallels of a projection of a 15' quadrangle on a scale of 

1 :48,000 in latitudes from 0° to 30° is so small that it can not be 

plotted, and for a 7% ' quadrangle on a scale of 1:31,680 or larger 

the curvature can not be plotted in any latitude.

The meridional distances given in the tables apply to the central 

meridian of the projection, but for any standard quadrangle the differences in the curvature of the several parallels are so slight that the 

distances given for the central meridian can be taken for all other 

meridians.

Whichever method of construction is used, each projection must be 

subjected to a thorough test by some person other than the one who 

did the plotting. It is not sufficient merely to check the plottings 

with the figures first used. A true check consists of independent 

computations and measurements throughout. The verifier should 

therefore enter the tables anew, replot the coordinates, and, as a 

final test, measure the over-all dimensions of the projection and 

compare the lengths of its diagonals.

For identification, the latitude and longitude must be clearly 

marked in pencil at each of the four corners of the projection.

COAST AND GEODETIC SURVEY METHOD

For making a polyconic projection by the Coast and Geodetic 

Survey method the following materials are required: A metal straightedge graduated in centimeters with one centimeter at one end subdivided into tenths of a millimeter, the scale being standardized and 

the straightedge being as long as the longest dimension of the pro-
168 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

jection; a good rigid-beam compass with micrometer movement; 

a hard chisel-point pencil; a plotting needle; and Coast Survey Special 

Publication 5. As an example the construction of a polyconic projection on a scale of 1 : 250,000 of the degree quadrangle lying between 

latitudes 40° and 41° north and longitudes 88° and 89° west is 

described.

89°00'

FIGURE 4. Diagram illustrating 1° polyconic projection

Draw the central meridian miW4 (see fig. 4), and at the middle 

point ra draw the construction line ab perpendicular to the central 

meridian. As the accuracy of the entire projection depends largely 

on this operation, it is advisable to swing several arcs as a check on 

one another. From the point m lay off the latitude intervals mmi 

and mm4, taking the distances from the table of meridional arcs. 

(Seep. 91, Spec. Pub. 5.) The value of mmi (the arc of the meridian

JQ go' is found to be
TOPOGRAPHIC MAPPING 169

55,518.8 =55,523.6 meters. Likewise the value of rora4 is 55,518.8 

0 = 55,518.8 meters.

These values represent meters on the spheroid, and to reduce them 

to the scale of the projection it is necessary to multiply them by the 

representative fraction 2 & 0*0 0 0 . The length of the arc mmi in meters 

on the map is found to be 0.22209 meter, or 222.09 millimeters. Likewise the length of the arc mm4 is found to be 222.08 millimeters. 

It is therefore evident that for a map of this size on this scale it would 

have been as well to use the value in meters opposite the argument 

"30 minutes" from the column "continuous sums of minutes from 

latitude 40 degrees" for both of these values, as it is impossible to 

plot 0.01 millimeter. (In preparing to construct a projection it 

is always best to make a small sketch and set down all the measurements before beginning actual construction. Fig. 4 serves as 

such a sketch.) The values of mlm2 and m2m are each found to belli .04 millimeters (by computation from the table or by taking onehalf of the value of mm^}, and of course the values of mm3 and m3m4 

are practically the same. The plotting should be checked by testing 

the length of the degree arc m\m±, which should be 444.17 millimeters.

At the points mi, m2 , ra3 , and ?n4 draw the construction lines cd, 

gh, ij, and ef parallel to the line ab and perpendicular to the central 

meridian. These construction lines must be absolutely parallel to 

each other and all perpendicular to the central meridian. The best 

results can be obtained by striking arcs from points near the extremities of the line db, using the same settings of the beam compass that 

were used in laying off the distances mm1} mm4 , etc., and then drawing the lines cmid, em4f, etc., through the proper points on the central 

meridian and tangent to the proper arcs.

On each one of the construction lines lay off from the central meridian the proper abscissae of the developed parallel, selecting from the 

table "Coordinates of curvature" the value of x opposite the proper 

longitude interval and taking care to interpolate for the desired 

latitudes not given in the table. As this table for coordinates of 

curvature is computed for latitude 40° 00', and the values of x change 

appreciably between 40° and 41°, the values taken directly from the 

table can be used only for m4x4 on the line ef. The value m^x should 

be taken from the table on page 93 of Special Publication 5 and 

values for mx, m^, and m3x3 should be interpolated between the 

values given in these two tables. Or these three values can be taken 

from the table of "Arcs of the parallel in meters" on page 90, by 

multiplying by 6 the value of 5' of longitude given for the proper 

latitude. For example, on the line ef the interval m4cc4 corresponds 

to 30 minutes of longitude and the x value is found to be 42,697.8 

meters, which is 170.75 millimeters on the map.
170 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL. SURVEY

At the point x4 erect a perpendicular representing the ordinate of 

the developed parallel, selecting from the table "Coordinates of 

curvature" the value of y opposite the proper longitude interval. 

No interpolation is necessary, as the values of y change so slowly for 

differences of latitude that the values given in the table may be considered the average for the latitude interval from 40° to 41°. The 

value of y4 is found to be 119.8 meters, or 0.47 millimeter on the map. 

The two points thus constructed (to the left and right of the central 

meridian) are the lower corners of the projection. It remains to 

construct the two points atav- These coordinate for 15' of longitude 

is found to be 21,349.0 meters, or 85.4 millimeters on the map, and 

the y coordinate is 29.9 meters, or 0.12 millimeter on the map. This 

y value is so small that it can scarcely be plotted, and the two plotted 

positions of x4> may be taken as the proper position of the intersection of the 15-minute meridians with the parallel of 40° 00'. In 

theory this parallel is curved, but as the curvature can not be drawn 

on a map of a small quadrangle, straight lines are drawn joining all 

the plotted positions on this parallel. Similarly all the other parallels 

are developed, and the meridians are drawn through the plotted 

points. It will be discovered that these points fall exactly on a 

straight line for each meridian, and the meridians are therefore 

drawn as straight lines.

To test the construction of the projection set the beam compass to 

the diagonal distance from the lower right to the upper left corner 

of the projection and then check the measurement from the lower 

left to the upper right corner, which should be the same. Continue 

these diagonal tests in various combinations of small projection 

blocks equidistant from the central meridian, so as to check the plotting of every point. Add the proper figures showing latitude and 

longitude, as shown in Figure 4, and the job is completed.

The Coast and Geodetic Survey employs metal plotting scales 

giving the values in meters on the spheroid directly in terms of millimeters on the map for each of the map scales used.

GEOIOGICAL SURVEY METHOD

For making a poly conic projection by the Geological Survey 

method the following materials are required: A metal straightedge 

graduated in inches with one inch at one end subdivided into hundredths of an inch, the scale being standardized and the straightedge being as long as the longest dimension of the projection; a good 

rigid-beam compass with micrometer movement; a hard chiselpoint pencil; a plotting needle; and Geological Survey Bulletin 650.

To illustrate this method the construction of a poly conic projection on a scale of 1: 48,000 of the 15' quadrangle lying between latitudes 40° 15' and 40° 30' north and longitudes 88° 00' and 88°
TOPOGRAPHIC MAPPING 171

15' west is described, (See fig. 5.) The projection wijl show each 

5' meridian and parallel. The central meridian of the projection 

will represent the meridian of longitude 88° 07}^' and will be used 

for construction only. Likewise the perpendicular crossing the central meridian at latitude 40° 22^' will be used for construction only. 

The geometry of the construction given below is slightly different 

from that given in the preceding example, owing principally to an

, 

F V :

' V 

aoe

88

^ .W \S 2 8S7" *

F * *

F' / \

^'l\ 

v i \

§.

N| 0

I 0

1 *

|

S^iy

H 7 ^

/

/

D 

3s"

a.9OO"

^2.902"

\ ,, r c"\ »>^ \oo/ i\ . ,001 -^

**\

i

i n

I C

i =

s!

1 ! 

\ |

2.9O4-"

D

0

X

0 5.794" \i

<

J. SO/ *

-S.706 -^ 

/ ^' 5.304" _^

 °°6^

5.808"

Control . 

Point A

*- 40*30'

25'

20'

^ ' /> A'\ ' 0 "I 

°I5' 10' A 5' 88°00'

FIGURE 5. Diagram illustrating 15' polyconic projection

effort to eliminate the plotting of the small ordinates of curvature, 

a task so difficult to perform in the projection of a small quadrangle. 

In Table 10 on page 81 of Bulletin 650 the upper group of ordinates 

and meridional distances are computed for latitude 40° and may 

safely be used for latitudes between 39° 30' and 40° 30' without 

interpolation between the values given therein and those given in 

the second group, which are computed for latitude 41° 00'. By interpolating in the upper group so far as necessary the meridional distance 

58515° 28 12
172 TOPOGEAFTTIC INSTBT7CTIONS OF GEOLOGICAL SURVEY

for iy^' of latitude is found to be 3.796 inches, for 5' 7.588 inches, 

for 7^' 11.383 inches, for 10' 15.178 inches, and for 15' 22.766 inches. 

(New tables are being computed in which the meridional distances, 

ordinates, and abscissas are given without interpolation for all the 

latitude and longitude intervals needed in the construction of a 

projection of a standard quadrangle.)

In the part of the table headed "Abscissas of developed parallel" 

the x values for 2%' and 7^' of longitude in latitude 40° 15' are 

found to be 2.908 inches and 8.723 inches, respectively. The x values 

for latitudes 40° 20', 40° 22^, 40° 25', and 40° 30' are shown in 

Figure 5.

In the upper group of "Ordinates of developed parallel" the y 

value for 7^' of longitude is found to be 0.006 inch. The ordinate 

for 2^' of longitude is not given, but as the ordinates vary as the 

square of the distance from the central meridian the y value for 2 J^' is 

one-fourth of that given for 5' or one-ninth of that for 7^' that is, 

0.0007 inch, or approximately 0.001 inch.

These are all the measurements needed to proceed with the construction of the projection. It is impossible to plot the y value for 

2}^' of longitude and difficult to make an individual plotting of the y 

value for 7}^' of longitude, but 0.006 can be added to or subtracted 

from other measurements of meridional arcs and the resultant distance measured on the metal scale, and this is done in the following 

description :

Draw the central construction meridian AB in vertical position near 

the center of the map, select the middle point C as the center of the 

projection, and lay off from C the meridional distances for 2^' and 

7^j' of latitude, CE (3.796 inches) and CB' (11.383 inches) above 

and CD (3.796 inches) andCA' (11.383 inches) below. The over-all 

distance A'B' (22.766 inches) for 15' of latitude should be used to 

check the plotting. At the point C erect the perpendicular FG, using 

the points A' and B' as centers for long arcs and the points D and E 

as centers for short arcs. Lay off on the construction line FG the 

abscissas of the developed parallel for 2^' and 7^' of longitude, CH 

and CI (2.902 inches) and OF' and CG' (8.706 inches).

With the points F' and G'.as centers and a radius equal to the 

meridional distance for 7^' of latitude plus the ordinate for 7^' 

of longitude (11.383+0.006 = 11.389 inches) strike arcs at J and K. 

Then with the same points as centers and a radius of 11.377 inches 

(11.383 0.006) strike arcs at L and M. In striking these arcs use 

the metal point of the beam compass rather than the pencil point 

and either scratch the paper lightly or place under the metal point a 

small piece of carbon paper made by rubbing a piece of thin tracing 

paper with a hard pencil. This obviates the inaccuracy of using the
TOPOGRAPHIC MAPPING 173

pencil point of the beam compass to take an exact measurement from 

the scale.

With the points H and I as centers and a radius equal to l}/2 of 

latitude (11.383 inches) measured along the central meridian, strike 

arcs at N and O above P and Q below. The true meridional distance 

as here used should always be taken in constructing the inner meridional distance for 7^' of latitude on a scale of 1:48,000, or larger, 

as it is impracticable to use the small ordinate for 2^' of longitude. 

However, should the more rigid construction be required, it may be 

done in the folio whig manner: With points H and I as centers and 

a radius equal to 7 y% of latitude measured along the central meridian 

plus the ordinate for 2^' of longitude (11.383+0.001 = 11.384 inches) 

strike arcs at N and O. Then with the same points as centers and a 

radius equal to the meridional distance minus the 2J^' ordinate 

(11.383-0.001 = 11.382 inches) strike arcs at P and Q.

With the points B' and A' as centers and radii equal to the proper 

abscissas, strike arcs at J, K, L, M, N, O, P, and Q. Check the length 

of the diagonals JM and KL, which should be exactly the same. Draw 

the straight lines JL and KM through the intersections of the arcs at 

J, L, K, and M. These lines represent the limiting meridians on the 

projection. Draw the straight lines NP and OQ through the intersections of the arcs at.N, P, O, and Q. These lines represent the two 

inner meridians on the projection, and the four intersections at the 

top and the four at the bottom of the projection are the exact intersections of the four meridians with the limiting parallels.

With the beam compass set at the length of the meridional arc for 

5' of latitude, plot along all four meridians down from J, N, O, and 

K and up from L, P, Q, and M, and check the middle 5' sections of 

the meridians, thus locating the intersections of the four meridians 

with the parallels 40° 20' and 40° 25'.

All the necessary intersections for the projection of this 15' quadrangle have now been plotted without trying to make an individual 

plotting of 0.006 inch from the points F' and G', which only the most 

skilled draftsmen can accomplish, and the same setting of the beam 

compass has been used for all equal measurements, thereby strengthening the construction. Check the construction by measuring overall distances and by testing corresponding diagonals of all combinations 

of projection blocks.

Although it is customary to show only the 5' intervals on a projection for a 15' quadrangle, it may be desired to develop the central 

parallel, which, in the projection under construction, would fall on 

latitude 40° 22}^'. With the beam compass set at the meridional 

distance for 7^' and plotting along the meridians down from J and 

K and checking by plotting up from L and M locate the points F" 

and G", which are the intersections of the limiting meridians with
174

the central parallel at latitude 40° 22^r . The points H and I already 

determined are the intersections of this parallel with the inner meridians, as no ordinates can be plotted at these intersections.

Draw the parallels as straight lines between the plotted intersections. This practice is permissible as the curvature of the parallels 

of any standard quadrangle within the limits of the United States 

is too small to be drawn as a curve. Insert the figures for latitude 

and longitude as shown hi Figure 5, and add the scale, the name of the 

quadrangle, and the initials or name of the person making the construction. The projection is then completed, but it should be checked 

carefully by another person.

In any projection where the ordinate of a developed parallel at the 

limiting meridians is less than 0.005 inch it is impracticable to plot 

the curvature, and the parallels should be represented as straight 

lines perpendicular to the central meridian. This will be true of 

projections of maps of standard quadrangles on the scale of 1:48,000 

between latitudes 0° and 30° and on scales of 1:31,680 and larger 

in any latitude.

Bulletin 650 does not give projection tables for all the map scales 

that are used by the Geological Survey. For example, tables are 

given for the scale of 1:48,000, which is the field scale for maps 

published on the scale of 1:62,500, but no tables are given for the 

scale of 1:96,000, which is the field scale for maps published on the 

scale of 1:125,000. New tables are being prepared to cover all the 

scales used in standard mapping and all latitudes from 0° to 50°, but 

until these are available and within certain limitations a particular 

projection table can be used for a scale half as large or twice as large. 

The abscissas of developed parallels and the meridional distances are 

both practically in direct proportion to the scales, so that the abscissa for ly^ of longitude at latitude 40° on the scale of 1:48,000 is 

the same for 5' of longitude at latitude 40° on the scale of 1:96,000. 

Likewise the meridional distance given for a latitude interval of 2^' 

on the scale of 1:48,000 is the same for 5' on the scale of 1:96,000.

The ordinates of developed parallels are also directly proportional 

to the scales, but the ordinates are also proportional to the squares of 

the distances from the central meridian, and this may lead to confusion in interpolation for a different scale. For example, the 

ordinate of developed parallel for a longitude interval of 5' in latitude 

40° on a scale of 1:48,000 is 0.003 inch. The ordinate is not the 

same for a longitude interval of 10' on a scale of 1:96,000, but is 0.006, 

or twice as much.

The following rules may disclose discrepancies in the third decimal 

place, but these discrepancies will be too small to plot: To double the 

scale for example, to make a projection on a scale of 1:24,000 from 

tables for the scale of 1:48,000 use correct arguments for the
TOPOGHAPHIC MAPPING 175

scale desired and multiply all values given hi the table by 2. To 

halve the scale for example, to make a projection on a scale of 

1:96,000 from tables for the scale of 1:48,000 use correct arguments for the scale desired and divide all values given in the table 

by 2.

USE OF BUMSTEAD PROJECTION PLATE

Projections for 15' quadrangles on a scale of 1:48,000 may be made 

without the use of projection tables by means of the Bumstead projection plate (pi. 8), which consists of a heavy metal plate 29 inches long 

and 25 inches wide, smooth on the under surface and carrying on the 

upper surface 20 graduated scales, 16 of which, arranged in rows of 

four each, are placed in such positions as will give the 5' latitude and 

longitude intersections of a 15' quadrangle when the index line of a 

small separate key plate is successively placed opposite the appropriate lines on the 16 latitude scales. The other four scales give the 

intersections of a straight line joining the middle points of the 

limiting meridians of the quadrangle with the four 5' meridians of the 

projection, so that the projection can be constructed in two half 

sheets. For all practical purposes on large-scale projections this 

straight line can be considered the middle parallel. Each scale is 

graduated for ranges in latitude from 25° to 50°. As the longitude 

interval will be the same for all 15' quadrangles in the same latitude, 

only latitude figures are given on the plate. Each degree of the four 

scales marking the four corners of the projection and each degree of 

the two intermediate outer scales on both sides (eight in all) is divided 

into quarters of a degree (15' spaces), and each degree of the eight 

inside scales is divided into half degrees (30' spaces). The other 

four scales (middle latitude) are divided into quarters of a degree on 

the two outer scales and half degrees on the two inside scales.

Example: To construct a 15' projection for a quadrangle between 

parallels 40° 00' and 40° 15' and meridians 90° 00' and 90° 15', 

weight the plate on the paper sufficiently to avoid slipping. Place 

the index line of the separate key plate (pi. 8, B} opposite latitude 

40° 00' on each of the four scales on the lower margin of the plate, 

and at each 40° 00' setting run a needle down the triangular channel 

of the key and through a slit in the plate and the needle points in the 

paper will mark the southwest corner, the southeast corner and the 

two 5' intersections on the south edge of the projection. Similarly 

place the index line of the key successively opposite latitude 40° 05' 

on each of the four scales next north by interpolation of thirds on the 

two outer scales and by interpolation of sixths on the two inner 

scales, and at each setting make a needle point on the paper as before. 

On the four scales next north make the settings at latitude 40° 10', 

and on the last or upper row of four scales at latitude 40° 15'; cm the 

upper line the points marked will be the northwest corner, the north-
176 TOPOGKAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

east corner, and the two 5' intersections on the north edge of the 

projection. These 16 plottings give all the 5' intersections of latitude and longitude for a 15' quadrangle. If a middle latitude line is 

desired, or if the projection is to be macle in halves, plot the 40° 07' 

30" intersections at the four scales across the middle of the plate.

A projection that is made as described above will correctly show a 

slight curvature of the parallels.

Projections for 7^' and 30' quadrangles on scales of 1:24,000 and 

1:96,000 respectively may also be made by means of the Bumstead 

projector, by assuming that the 16 scale settings give 2^' and 10' 

intersections respectively. Theoretically this is not true, for although 

the abscissa of a parallel on the ground the x value is directly proportional to the distance from the central meridian and therefore the 

representation of half or twice its abscissa on projections half or 

double the scale of the projection plate will be the same as for the 

unit length on the scale of the projection plate, nevertheless the ordinate of the parallel the y value varies as the square of the distance 

from the central meridian. Therefore use of a projection plate made 

for the scale of 1:48,000 will theoretically result in plotting too much 

curvature in the parallels on a scale of 1:24,000 and too little on a 

scale of 1:96,000. For all practical purposes in latitudes below 50° 

this discrepancy may be neglected for a 1:24,000 projection, in 

which the parallels should be drawn as straight lines connecting the 

outer needle points, for the reason that no curvature can be shown on 

that scale within the limits of a 7^' projection. For a 1:96,000 projec.tion the parallels may be drawn through the upper side of the dots 

at the outer needle points and then through the lower side of the dots 

representing the inner intersections of the same parallel, as here the 

curvature is still small and not otherwise readily plottable.

CONVERGENCE OF MERIDIANS

The convergence of the meridians can not be appreciably plotted 

within the limits of standard quadrangle maps in latitudes below 

50° that are drawn on a scale of 1:31,680 or on any larger scale. On 

a scale of 1:62,50*0 (or on the corresponding field scale of 1:48,000) 

the convergence is just plottable within the limits of a 15' projection 

representing a quadrangle in southern Florida or Texas, but the convergence is increasingly appreciable as the latitude increases. No 

convergence can be shown on maps of 15' quadrangles in Hawaii. 

On maps representing 30' and 1° quadrangles that are published on 

scales of 1:125,000 and 1:250,000, respectively, the convergence is 

considerably larger, for the reason that the eastern and western 

limits of the quadrangle are at greater distances from the central 

meridian.
TOPOGRAPHIC MAPPING 177

The amount of the convergence, if any, is shown on published maps 

at the two northern corners of the projection (pi. 15), where it is represented by the spaces between the meridians and the neat lines, the 

latter being drawn parallel to the central meridian of the map. Neat 

lines are not to be drawn on field projections.

CONTROL DATA

All the horizontal and vertical control data that are available for 

any quadrangle will be furnished by the chief of the section of computing on requisition, which should be submitted in duplicate. The 

section of computing will return one copy of the requisition containing a sketch showing the approximate position of all triangulation, 

transit-traverse, and level lines that fall within the area to be mapped 

and the necessary descriptions for these triangulation, traverse, and 

level positions. Data thus supplied will be carefully examined and 

should be returned intact with the field sheets when the sheets are 

forwarded to the office.

PLOTTING HORIZONTAL CONTROL

A triangulation or transit-traverse control point may be plotted 

by computing the proportional parts of the arcs of the limiting meridians and parallels of the small projection block in which the point 

falls that conform to the latitude and longitude of the point. For 

example, it is desired to plot on a projection on the scale of 1:48,000 

the position of a point whose latitude is 40° 16' 35".75 and longitude 

is 88° 01' 27".55. This point will faU in the lower right-hand 5' 

block of the projection illustrated in Figure 5. The sides of this 

projection block represent parallels 40° 15' and 40° 20' and meridians 88° 00' and 88° 05', and the block covers 300 seconds of latitude 

and longitude. The 5' arc of parallel 40° 15' is represented by a 

length of 5.816 inches and that of parallel 40° 20' by a length of 

5.808 inches. The 5' arc of each limiting meridian is represented 

by a length of 7.588 inches. The point falls 1'35".75 = 95".75 above 

the parallel 40° 15'. The proper distance to be plotted along the 

limiting meridians above the line on the projection representing this 

parallel is given by the proportion 95.75:300 : :y:7.5S8 inches, and 

y is found to tie 2.242 inches. . Similarly the proper proportional 

parts of the two limiting parallels to the left of the intersections with 

the meridian 88° 00' are found by the following proportions: For 

latitude 40° 15', 87.55:300 : :x: 5.816, from which x is found to be 

1.697 inches; for latitude 40° 20', 87.55:300 : :x': 5.808, from which 

x' is found to be 1.695 inches. These values should be plotted on 

the proper meridians and parallels, and the intersection of the two 

lines joining corresponding latitude and longitude positions on the
178 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL STJRVEY

limiting meridians and parallels will be the location of the control 

point.

The method described above is laborious, and the plotting of control points is facilitated by use of latitude and longitude plotting 

scales so subdivided that the proper readings in minutes and seconds 

may be plotted without computation. The plotting scales are available for all standard projection scales and are made slightly longer 

than the corresponding dimensions of the individual projection blocks 

in the lowest latitude for which their use is intended. The scales 

are used diagonally between the limiting parallels and meridians, 

and thus the same plotting scale can be used for a wide range of latitude. At least two plottings of both latitude and longitude positions 

are so made as to embrace the position of the point, and the intersection of the lines joining the corresponding plottings will be the 

position of the point. The plotting scale for 1:48,000 is shown in 

Plate 9, A.

MAP BORDERS

It is of prime importance that contiguous topographic maps shall 

join perfectly, so that when they are laid edge to edge the lines on 

them shall pass without break or offset from one to the next. For 

this purpose the engineer, before beginning field work on a new quadrangle, should procure photographs, photolithographs, or tracings 

of adjoining edges of all previous maps (including woodland) that 

are on the same or larger scales. Data that are on a different scale 

from the new field work should be reduced to that scale by photography. The strips so furnished should be preserved as a part of the 

field material and returned for the office files. The data on the 

strips should be transferred to the field sheets. (See "Map borders," p. 227.)

DATA FROM OTHER SURVEYS

Source of material. Existing map material of Federal, State, and 

municipal surveys and other authenticated organizations should be 

diligently sought, both before leaving the office and after reaching 

the field. The files of the map information office of the Federal 

Board of Surveys and Maps (Interior Department Building) should 

be consulted freely.

Maps of the General Land Office (see p. 179), the Coast and Geodetic Survey, the Hydrographic Office of the Navy, the Corps of 

Engineers of the Army, the Mississippi River Commission, the survey of the Great Lakes, the national boundary surveys, State boundary surveys, boundaries of national parks, forests, monuments, game 

and bird preserves, Indian and military reservations, land grants, 

surveys made by the Bureau of Reclamation, Forest Service, and 

Bureau of Soils should be obtained, and such of them as prove,
TI. S. GEOLOGICAL SURVEY BULLETIN 788 PLATE 8

BUMSTEAD PROJECTION PLATE 

A, Face of plate; B, Key plate
U. S. GEOLOGICAL SURVEY BULLETIN 788 PLATE 9

PLOTTING SCALES 

A, Latitude and longitude B, Burklaud alidade; C, 1: 31,680
TOPOGRAPHIC MAPPING 179

on field examination, to be adequate, should be incorporated in the 

field sheets, with proper recognition. (See " Credit for outside data," 

p. 307.) All such material will, upon requisition, be reduced by 

photography to the field scale.

Land Office data. Before reaching the field party chiefs must provide themselves with copies of the latest plats of the public-land 

surveys, if any, of the assigned areas, and if practicable these plats 

should be reduced to the scale of mapping. It is important that 

the data furnished should be the latest available and that they 

should include any resurveys or retracements and any exterior notes 

of townships not yet sectionized that fall within the limits of the 

quadrangle to be surveyed. Inquiry should also be made to ascertain whether any of the plats are under suspension by the General 

Land Office.

Before starting work in national forests topographers should check 

off on forest maps the Land Office corners that have been found by 

the Forest Service and also corners that have been looked for and 

not found; such information is on file at the headquarters of each 

supervisor and also at each district office. Inquiry may also often 

be advantageously made of county surveyors, deputy mineral surveyors, and local engineers as to the existence and location of known 

corners or ties.

Other reference data. The following additional maps and data 

should be assembled for field use: Post-route and rural-delivery maps; 

Geological Survey index circular, corrected to date, together with 

copies of engraved maps or advance sheets of all maps of areas 

adjoining the proposed new quadrangle; list of incorporated places 

given in Census reports; alinement maps of railroad valuation surveys; 1 :500,000 scale State map; State highway and other route 

maps.

ENDING OFFICE SEASON

At the end of the office season turn in to the section of inspection 

and editing all map material pertaining to the office season that is 

not needed for field work. Clear desk and map file cases. Turn 

in to the division of field equipment all office instruments not needed 

in the field. Submit office report.

PREPARATION FOR REVISION OF TOPOGRAPHIC MAPS

FIELD SHEETS

The field revision of a topographic map will be made upon a reproduction of the latest print of the map, printed for the purpose on 

double-mounted drawing paper. The field sheets for revision are 

printed in relatively weak colors, often referred to as nonphotographic, 

in order that the revision corrections, where inked in the standard
180 TOPOGEAPHIC INSTRUCTIONS OF GEOLOGICAL, SUKVEY

strong colors, may be reproduced photographically and thus furnish 

copy for transfers to the plates which are afterward to be corrected. 

Such field sheets may be prepared under one of the three plans 

described below:

1. A printed copy of the map may be reproduced by photolithography, enlarged to the usual field scale, and printed in faint blue, 

which is only weakly photographic. This process should not be 

used, however, where distortion of the paper on which the'map has 

been printed has so changed the map projection that its dimensions 

are long or short in one direction and not proportionately so in the 

other direction. The projections of maps selected as camera copy 

for reproduction by this method should be carefully tested before use.

2. Transfers to stone may be made from the three copper plates 

on which the map was engraved and a special print of the map made 

in three different weak colors, such as faint blue for culture, light 

gray for drainage, and light pink for contours, each printing being 

as carefully registered as for a map printed in the usual way. Such 

a revision field sheet has the advantage of true scale and of the same 

use of distinctive colors for the three principal classes of features as 

is shown on a printed map; but the advantage of the usual field 

scale is lacking. Plotting scales are provided graduated to both 

miles and feet on the usual publication scales.

3. The process described in paragraph 2 may be varied to provide 

for enlargement to field scale before transferring to the printing 

stones. Revision sheets prepared by this process combine all the 

advantages of the other two; that is, they are on true scale, are on 

the field scale, and are printed in three distinctive colors.

The first process described above is the cheapest of the three, and 

the third is the most expensive. The selection will be based on field 

and office conditions, the nature of the county represented, and the 

usual relation between field and publication scales.

CONTROL DATA

A complete set of control notes, both horizontal and vertical, must 

be obtained before starting field revision. The control data should 

be requested from the section of computing on a form provided for 

the purpose.

OTHER REVISION DATA

So much of the material described under "Data from other surveys" (p. 178) as will apply to the revision work that is to be undertaken should be assembled. Of especial importance are post-route 

map, Land Office data, reservation maps (national forest, etc.), 

index circular, and maps of adjoining quadrangles.
TOPOGRAPHIC MAPPING 181

FIELD WORK 

STANDARDS FOB FIELD WORK

ACCURACY

Accuracy defined. A topographic map, irrespective of scale, is 

accurate if it is based upon a sufficient amount of well-distributed 

and well-adjusted control, to which the carefully considered topographic features appropriate to that scale have been tied with a 

maximum of refinement in field measurement and in plotting. (See 

"Definition of a topographic map," p. 161.)

Accuracy in a topographic map can be truly measured only by a combined appraisal of the character and amount of its control, its adjustment, the accuracy with which the field measurements have been 

taken and plotted, the ease with which the features mapped can be 

identified, its amount of detail or degree of generalization, the consistency of its parts, its freedom from errors and omissions, and its 

date of survey.

Control factor in map accuracy. The control that is necessary for 

accuracy in a map embraces first the primary control of first, 

second, or third order both horizontal and vertical, upon which 

the survey for the map must rest. Of this control but a relatively 

small amount is needed, for the reason that initial control is expanded 

and supplemented by further topographic control of another kind, 

obtained by means of the topographic mapping operations themselves, such as plane-table traverse and plane-table triangulation, 

as a result of which the area under survey is so gridironed or covered 

by lines and locations that no essential map feature is so far from a 

traversed line or located point that it can not be satisfactorily seen 

and delineated.

Careful judgment will be required to cover the entire quadrangle 

adequately to the end that no part of the area be mapped that is 

not properly seen and that too much control and time be not devoted 

to portions of the area that happen to be easy of access and too little 

given to other portions that happen to be difficult of access.

Accuracy of adjustment. If a map is in accurate adjustment then 

all its parts are in correct relative position. This important and 

desirable quality in topographic maps is insured through the use 

of control and by means of adjustment. The initial primary control 

for a map is so tested by the geodetic engineer that it may be accepted 

as accurate by the topographic engineer, but its plotting on the field 

sheets must be checked before it is used. Inasmuch as all single 

observations, such as the measurement of a distance or an angle 

or the determination of an elevation, are inherently subject to error, 

however slight, and as continuous lines are subject to errors of accu-
TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL, SURVEf

mulation, both in distance and in direction, such map measurements and observations must be adjusted in order to distribute the 

small unavoidable errors in such a way that they may be eliminated 

or made negligible.

An area may therefore be adequately covered by supplementary 

control and be thoroughly mapped so far as map features go, and 

yet the map may be out of position locally through the presence of 

accumulated errors of survey that remain unadjusted. A common 

source of unadjusted error is the use of unchecked lines of planetable traverse that may contain unsuspected errors and thus result 

in the false location on the map of the area affected by the errors; 

and inasmuch as errors in unchecked lines often result in the forcing 

of other features into a remaining space on the map paper, topographers are cautioned to run spur lines with the utmost care. 

Another example of possible error through unchecked spur lines 

appears when each of the opposite sides of a ridge or mountain is 

mapped from a traverse line that has been run without closure and 

where the effect of the error on one or both sides of the ridge remains 

undetected through lack of intervisibility. Obviously large errors 

are not subject to adjustment and must be located and corrected, 

and if they can not be located that part of the survey must be rerun 

or remapped. (See "Errors and omissions," p. 185.)

Accuracy of observations and oj plotting. As it is a waste of effort 

and expense to execute surveys on the ground with an accuracy 

greater than can be plotted on the scale of the field sheets, and as 

it is a failure to get full value from effort and expense already incurred 

to plot the results of field work with an accuracy less than that of the 

observations themselves, the topographic engineer should think of 

ground features in terms of scaled map distances and dimensions and 

then correctly plot his measurements under all the favorable plotting 

conditions, such as light, magnification, needle point, and the avoidance of parallax. Refinement in paper accuracy is therefore quite 

as important as care in field measurements.

Identification of features. One of the simplest tests of the accuracy 

of a topographic map is to examine it in the field and note the relative ease or certainty with which the features represented on the 

map may be identified on the ground or the ease with which features 

seen on the ground may be recognized on the map. In the hands 

of a trained map reader such a test is one of the most severe to which 

a map may be subjected, and for this reason it is the preliminary 

basis for a Geological Survey field inspection of topographic mapping, either in progress or completed. Inasmuch, however, as the 

topographic engineer sees more on the ground than he can plot on 

his map, so will the field inspector observe more on the ground than 

he can find on the map; and inasmuch as the map maker must
TOPOGRAPHIC MAPPING 183

learn to abstract what he sees, so must the inspector or the map 

reader learn to read the abstract.

If the features shown on the map and the features seen on the 

ground are thus readily recognized and if several corresponding 

features appear to be in the same relative position, each to the others, 

the map may be regarded as accurate in the degree that the map 

user is himself versed in maps and their interpretation. Correct 

interpretation of a map is therefore a factor in its best use. To 

interpret a map it is necessary first to visualize its scale and contour interval .and become very familiar with them and with their 

possibilities and limitations. Familiarity with the scale of a map 

may be acquired in several ways for example, by identifying points 

in common on the ground and on the map; by orienting the map 

by means of the points thus identified and sighting others for additional identification; where the identification of a first point is uncertain, by orienting the map by needle, allowing for magnetic 

declination; by measuring a distance on the ground and plotting 

the corresponding distance on the map; or by traveling a road or 

other recognizable route and comparing ground and map appearances, 

checking on recognized points or places. The mistaken identification 

of a map feature is a common source of discouragement to a map 

user and will tend to increase his perplexity until he locates himself. 

A map that is found to be accurate by an expert critic will obviously 

be found accurate by map users who are less critical and less observant, but the reverse is not necessarily true.

Detail and generalization. In measuring the accuracy of a map 

by the faithfulness with which ground detail has been represented on 

it or appraising it by the success that has been attained in the 

generalization of such detail as is beyond the scale of the map, it is 

necessary to understand the uses and the meaning of the terms 

"detail" and "generalization" and their application to Geological 

Survey maps. These terms describe two relative conditions that 

are opposite or complementary. "Detail" implies a refined treatment and suggests literal mapping; "generalization" signifies a 

broad treatment and involves an abridgment. The use of the terms 

may be further defined by an example. A map drawn on a scale of 

1 :24,000 should represent a region in detail as compared with a 

map of the same region drawn on a scale of 1 : 48,000, on which 

the representation must be confined to a broad generalization of the 

same features.

"Detail" may refer to a ground topography that is intricate as 

well as to its refined representation on a map, but "generalization" 

distinctly refers to a process. When referring to the country rather 

than to a map we may speak of detailed topography but not of 

generalized topography. When we speak of generalized topography
184 TOPOGEAPHIC IlSrSTETJCTIONS OF GEOLOGICAL SURVEY

on a map we mean that abridged, condensed, or abstracted treatment of a detailed ground topography that is made necessary by the 

limitations of scale, contour interval, and expediency. Ground 

detail may range in degree or amount from the excessive detail of 

city culture and bad-land relief to the relatively negligible detail of 

smooth broad or coastal plains.

Inasmuch as the published topographic maps of the Geological 

Survey represent greatly reduced abstracts of nature, the topographic 

engineer must determine what proportion of the ground detail can be 

adequately shown on the scale of publication. The smaller the 

publication scale and the more intricate the ground detail the more 

complicated is his problem; the larger the publication scale and the 

less intricate the ground detail the larger will be the proportion of it 

that can be delineated and the simpler will be his task. But whatever 

the scale or whatever the amount of the ground detail, the resulting 

map must in a large degree represent a generalization, and his problem is first how much must he generalize and second how can he best 

do it.

Generalization can be further explained by an example: On the 

larger scale of 1 : 24,000 a stream may be plotted to show all its bends 

and all its tributaries; on the smaller scale of 1 : 48,000 the smaller 

bends and the shorter tributaries will be omitted. This example 

comprises two phases of map generalization: The smallest tributaries 

have been omitted because they would not show on the small scale, 

being only microscopic ticks or specks against the main stream; but 

the smaller bends in the main stream have been disregarded because 

they are difficult to draft on the small scale and are equally difficult to 

find on the map, and instead a stream line is plotted in which no attempt is made to show them. One phase of generalization involves 

omission; the other substitution. The contour system that is dependent on the drainage likewise becomes successively generalized as it is 

mapped on smaller scales. In a similar sense, a small hill may be a 

conspicuous feature on a detailed map of small contour interval 

(5 or 10 feet) and yet not be shown on a small-scale map of larger 

contour interval (50 or 100 feet). Generalization, then, means 

elimination, and the greater the generalization the more drastic must 

be the process.

Consistency in accuracy. The map should be as consistently 

accurate in all its parts as is practicable. If two or more topographers are responsible for the mapping of independent areas on the 

same or adjoining quadrangles, they should compare their maps not 

only at their common borders but throughout, in order that they may 

reconcile any differing interpretations of the country or of the instructions under which they are working. Such comparisons should 

include examination of drainage, road and woodland classification,
TOPOGRAPHIC MAPPING 185

and the names of features in common, as well as the discussion of any 

unusual features.

Errors and omissions. The most obvious source of inaccuracy in a 

map is error. A map error may be caused by an erroneous measurement or erroneous plotting of a distance, by the erroneous measurement of an angle, or by an error in a field computation. A map error 

may also result from the misinterpretation of the shape of a distant or 

otherwise veiled feature seen in perspective. If an error is followed by 

another error that is made in the opposite direction the errors are 

termed compensating, in that one tends to balance the other. Where 

compensating errors are nearly equal the results under certain conditions, as in running a traverse line, may have a false appearance of 

accuracy in that the line may check out and yet be in error in two 

places. Small compensating errors may usually be disregarded, but 

where such errors are large they are a source of perplexity until found 

and corrected.

In order to provide against error all traverse lines so far as practicable should be run in circuits closing on themselves or run from one 

located point to another; and, barring compensating errors, a line 

that "closes" or checks is assumed to be correctly plotted. The 

errors to be chiefly guarded against are therefore those that may 

result from isolated measurements unrelated to other features and 

the possible accumulation of errors in unchecked lines.

The plane-table methods employed in topographic mapping enable 

the topographer to detect and correct most errors in the measurement 

of distances and most errors in plotting, because such errors usually 

produce erroneous mapping that will not fit other data that are 

correctly placed from other control. The topographer can therefore 

often detect errors in mapping through the appearance of the map 

alone, because the map is plotted in the field with the country that 

is being mapped directly in front of him. The check on the accuracy 

of the map that is thus afforded by its constant comparison with the 

features themselves as they are being mapped is a test that should be 

repeatedly applied by topographic engineers.

Inaccuracies in a map may also result from omissions. A house or 

a name may be omitted through inadvertence, and a spur or a tributary stream may be omitted because of lack of sufficient supplemental 

control. In the first case there has been lack of care, and in the second 

case the standard of accuracy is deficient. A feature that has been 

plotted in the field may be lost before it is inked because of faint 

penciling, or it may be lost during the inking through inadvertent 

erasure; and a feature that has been inked may be omitted in the 

engraving or inadvertently brushed off in the transfer operations 

prior to printing. Firm penciling, care in cleaning the sheets, and 

faithful proof reading are the safeguards against such omissions.
186 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

The omission of essential features from a map because they were 

not seen or recognized as such during the progress of the field work 

can be guarded against only by close observation combined with a 

control that is fine enough to close up all unseen gaps.

Date of survey. Map accuracy must be considered in terms of the 

date of the survey. This date is stated on each published map, and 

the accuracy of the cultural representation must be considered as of 

that date. Although reasonable effort should be made to obtain 

information as to all important changes in culture, even though the 

area affected has been passed by in the survey operations, the policy 

of the Geological Survey is to plot no feature that has not been 

constructed on the ground and to show no proposed features. Such 

features as roads and railroads under construction may be plotted so 

far as actually graded, but unless they are known to be in use when 

the map is inked they should be shown on the final drawing in red, as 

features not to be included on the published map.

SPEED

Speed may be expressed in terms of elapsed time or rate of progress. 

For example, a quadrangle covering an area of 225 square miles may 

be reported as mapped in five months or at the rate of 45 square miles 

a month. The rate at which mapping should progress will differ 

more for different kinds of country than for different individuals, 

and in general it will differ more for different mapping scales than for 

different kinds of country, and to a less extent it will differ with different 

contour intervals.

Differences in speed between individuals are accounted for in part 

by differences in natural and developed ability and in part by different conceptions of the standards of accuracy. Speed is increased 

by the use of the most efficient mapping methods, through cooperation, by the advance planning of work, by experience, and by diligence. 

Speed is reduced by inclement weather and by errors.

Speed through efficient methods. Experience justifies the use of 

different mapping methods for different types of country and to some 

extent for different scales. Although the engineer will know in advance 

and usually before reaching his field of work what general type of 

topography to expect, he can not anticipate the detailed types to be 

found, nor anticipate how often or abruptly these types may change 

within the same quadrangle. The topographic engineer should therefore have so good a working knowledge of all field mapping methods 

in approved Geological Survey practice that he may be ready to use 

those methods that are locally best suited to the varying types of 

country he is called upon to map. There are also many short-cut 

devices applicable to all methods of mapping, and topographers
TOPOGKAPHIC MAPPING 187

are encouraged to become familiar with them through contact with 

others and through personal experience.

Speed through cooperation. A topographic engineer seldom works 

alone, being usually assisted by a rodmanor by a station assistant. He 

is frequently further assisted by traversemen, each working separately 

and each in turn assisted by a rodman. The map work of the 

traverseman is transferred and adjusted into the topographer's map 

and becomes a part of it. The output of the combined party is 

credited to the topographic engineer as party chief and is measured 

in terms of the number of square miles completely mapped each month. 

Party chiefs therefore should not overlook the possibilities of increasing the efficiency of their assistants and thereby increasing not only 

the accuracy but also the speed of the output of the party. Assistants 

acquire efficiency more rapidly through personal attention and training given to them than through unaided experience. Assistants, 

including junior engineers, should be fully instructed in their duties 

and should be kept as fully occupied as the nature of their work and 

their fitness for added duties justifies.

Speed through advance planning. A material factor in the speed 

of topographic mapping is a well-considered and reasonably complete 

plan of work for the season, augmented by a daily and weekly laying 

out of work in advance. The work of engineering assistants, working 

separately, should be similarly outlined well in advance, in order that 

it may proceed without delay and that the party chief may have 

the prompt use of the work of his assistants when he needs it.

Planning involves the selection of areas for initial and subsequent 

work, selected in the most advantageous sequence in which the work 

can be taken up for survey and mapping; the advance assignment of 

tasks and areas to assistants who are working separately; and the 

appropriate assignment of method to country and to the available 

personnel in order that the relative strength of supplemental control 

on which to adjust the completed survey may be maintained in 

advance. It also provides for the availability of essential outfit 

when and where it is needed. Planning should include a consideration of the party personnel, as to whether it is sufficient, too small, 

or unnecessarily large, and if men can be spared for other work or if 

further assistance is needed timely notice should be given, in order 

that there may be the fullest adjustment to the needs of all.

Speed through experience. Experience should be rated in terms of 

work performed as well as by length of service; and in considering 

work performed, its variety as well as its amount should receive consideration. At the outset of an engineer's career a part of his tune 

will be spent in acquiring a working experience, and in order that he 

may build soundly his speed at this stage should, be. Q£ secondary

58515° 28 13
188 TOPOGRAPHIC INSTBUCTIONS OF GEOLOGICAL SURVEY

importance, but as experience is gradually gained his rate of progress 

should increase. Party chiefs have in this respect a responsibility 

and a constructive opportunity in the proper guidance and instruction 

of the newer men.

The rate at which mapping experience may be acquired may 

obviously be increased through close observation and the application 

of mapping principles and also through the discussion of mapping and 

its problems with others. Topographers are encouraged to get 

together in all appropriate ways for the interchange of thought 

and experiences in connection with the furthering of their work.

Speed through diligence. Diligence is a prerequisite for speed. 

Diligence, however, must first be used in attaining thoroughness and 

accuracy, but when these essentials have been adequately acquired 

further diligence should be directed toward the expedition of the 

work rather than toward a refinement of the mapping that would be 

beyond the scale of the field work. Inasmuch as topographic field 

work is generally done at considerable distances from any office 

headquarters and involves the expensive maintenance of a party in 

the field, topographers are expected to prosecute their work with zeal 

and perseverance and to try so far as possible to overcome the obstacles that will always in some measure confront them. Among such 

obstacles are inclement weather, short days, extremes of heat or 

cold, and country that is difficult of access. The Geological Survey 

utilizes the favorable working seasons and conditions to the fullest 

degree practicable, but the exigencies of the public needs frequently 

demand that topographic work be carried on under less favorable 

working conditions, and at such times the resources of the engineer 

should be diligently used in devising ways and means to keep the 

mapping in progress, even though at reduced speed.

LEGIBILITY

Legibility in general. The relations between the legibility of a 

field sheet, that of an inked office drawing, and that of a printed map 

are so close that the need for legibility in field penciling can be best 

understood when it is considered in connection with the similar need 

for legibility in inking and in reproduction. The readability of a 

printed map depends upon the clearness of its reproduction, the 

detail of its treatment, and the ability of the map user to read it. In 

meeting demands for detailed maps there is always danger lest more 

time be spent in obtaining detailed representation in surveys, in 

drafting, and in reproduction than the scale of the reproduction 

warrants on the one hand or than the legibility of the resulting map 

warrants on the other hand. Less detail of treatment, however, 

does not imply less accuracy (see "Accuracy," p. 181), but it does 

mean further generalization, and proper generalization is accurate
TOPOGRAPHIC MAPPING 189

in so far as correct placement of the generalized features is concerned. 

The engineer therefore will do well to consider map generalization 

(see "Detail and generalization," p. 183), and largely in the degree in 

which he can apply its principles will his map serve its purpose by 

being readable.

Standards in map legibility must needs be largely set by the legibility attainable in map reproduction. To attempt to reproduce 

a map that contains more detail than can be legibly engraved or 

otherwise reproduced is obviously uneconomical, and in consequence 

a topographic map should be inked with the possibilities and limitations of engraved or other reproduction well in mind and with full 

allowance for the scale of reproduction. To plot more detail in the 

field than can be legibly inked in the office or legibly reproduced in 

the press room is likewise uneconomical, and as a consequence the 

field engineer should make his survey, plot his observations, and pencil in his map with the probabilities and limitations of office drafting 

and inking fully in mind and also with due allowance for the appearance of the final map when printed.

Legibility of map reproduction. First consideration should be 

given to the possibilities of engraving or other form of reproduction to 

be used. Most of the topographic maps published by the Geological 

Survey are engraved on copper, separate plates being used to represent the culture, relief, and drainage. Transfers from the three 

engraved plates are made to three printing plates (either stone, zinc, 

or aluminum), from which the map is printed in three colors. The 

legibility of the printed map is increased in part by the sharpness of 

the engraved lines, which are faithfully reproduced in the printing, 

and in part by the contrast afforded by the three colors used to distinguish the principal classes of map features. Legibility of reproduction is further increased by good lettering that has been placed 

in favorable positions for reading and so placed as to avoid unduly 

covering the map features. The legibility of a printed map is 

decreased by excessive detail in map expression and by inferior map 

reproduction.

The legibility with which engraved lines may be reproduced (pi. 17) 

determines the character of the engraving. For example, if engraved 

lines are cut too close together their printed reproduction will be 

"mashed," and if lines are cut too lightly there may be uncertainty 

in their transfer and printing. Engraving must therefore conform to 

that which can be legibly reproduced. It is possible, however, to 

engrave and to print so much detail that the final map may be overloaded and its legibility impaired. This possible condition should 

be foreseen and prevented so far as practicable, and field work should 

ordinarily not be executed in more detail than can be reproduced 

with legibility on a map that is easily readable.
190 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

Legibility of office inking. The standard of legibility for the inking 

of topographic maps should be based wholly upon quality for reproduction. If the map is to be engraved the inked copy for the engraver 

need be accurate and legible only, and as a consequence finely executed and expensive drafting may for the greater part be avoided. 

If the map is to be reproduced by photolithography for regular publication the inking must be done with the utmost care and refinement, 

inasmuch as any defect in the drawing will be repeated in the photolithograph.

The engraver's need for inking legibility is twofold. First, the map 

should be so legibly inked that when it is transferred to copper a 

process involving photography, transfer to zinc, and a wax impression 

from the zinc to the copper plate the transfer itself will be legible 

to the engraver. Second, the map should be so legibly inked that the 

engraver can easily read it as he constantly refers to it and also that 

he can pick out with certainty those features that are to be engraved 

separately on the plates representing the culture, drainage, and relief, 

inasmuch as the entire map is transferred to each plate.

Inking legibility is increased by the use of the best paper and inks. 

The inks used must have strong photographic value and should not 

smear or run. The symbols used, especially those representing the 

culture, should be so drawn and spaced that when they are transferred to the copper plates they will be of approximately the standard 

gage for engraving. Legibility for the engraver is further increased 

by the omission of certain lines in the inking not needed as copy and 

only tending to clog up the transfer. (See last paragraph under 

"Character" [of inking], p. 278, and ''Cliffs," p. 295.) The inking 

topographer will do well to bear in mind that he is preparing copy 

for the engraver rather than an artistic drawing for an exhibit.

Legibility of field 'penciling. The standard of legibility for field 

penciling should be based first upon furnishing clear copy for the inking topographer or draftsman, and then upon furnishing only such 

copy as can be legibly engraved and reproduced. The field sheet 

should be so legibly penciled that the office inking may proceed with 

assurance and dispatch, with no doubt as to the interpretation of the 

copy. The engineer who excels in ability to draft fine lines, however, 

should be watchful lest he overrefine in detailed expression and produce intricate pencil copy that will call for more skill in inking than 

may be available or for more detail in engraving than can be legibly 

reproduced. The topographer should also bear in mind that illegibility in field penciling can be overcome in the office only at the 

expense of accuracy, and that any overrefinement in detail can be 

overcome only at the expense of a forced generalization of features in 

the inking, or in the reproduction, or both. Legibility in penciling 

requires sharp, fine lines that can be made only by a sharp hard pencil,
TOPOGHAPHIC MAPPING 191

evenness of appearance in each line, avoidance of crowding, avoidance 

of dirt or other soiling of the paper, and the use of such spacings and 

symbols as will most nearly approximate those that are to be inked 

on the final drawing. The engineer will also need to learn to use a 

rubber eraser with a minimum of injury to the surface of the paper. 

Legibility through neatness. The legibility of a penciled field sheet 

may be strikingly increased by neatness and care in the handling of 

the paper. The use of cover paper of a soft color such as manila will 

not only aid in keeping the sheet clean but will also relieve the eyes 

from the glare that is reflected from a wide exposure of clean white 

drafting paper. If the plane-table sheet is kept mostly covered and 

portions exposed by means of openings cut into the cover paper only 

where needed for the day's work (and afterwards pasted over), much 

dust and dirt will be excluded. Additional dust protection may be 

obtained by having the cover paper a little larger than the plane-table 

sheet and folding the edges under the drawing paper. The hands and 

fingers should touch the paper as little as possible, inasmuch as 

moisture and oil from the skin may either leave permanent marks 

or serve as a collecting agent for dust that may afterwards be rubbed 

in. A sheet of paper or a dry handkerchief may be advantageously 

used as a rest for the hand, and in warm weather this precaution is 

imperative in order to keep the sheet clean. Grease spots, dirt, and 

superfluous soft penciling are all highly photographic and in addition 

to obscuring the legibility of the essential penciling are serious hindrances in photography, first in the advance-sheet photolithography 

and finally in the photographic processes used in transferring the map

to copper.

CARE OF INSTRUMENTS

Too much emphasis can not be laid upon the importance of care 

in the handling and transportation of instruments. Every employee 

intrusted with instruments in the field will be expected to keep them 

clean and in adjustment, to protect them from undue wear, and to 

return them to the custodian in fit order for use.

Minor repairs. Each topographer should provide himself with a 

few simple tools and supplies, such as a small pair of pliers with side 

wire cutter, screw drivers of two sizes, small flat and round files, a 

spool of soft copper or brass wire, a few assorted brass nails and 

screws, a bottle of oil, a bottle of liquid shellac, spider web, and plaster 

of Paris, all of which may be used for minor repairs to instruments. 

Field work should never be delayed by sending an instrument away 

for repair if the topographer can possibly repair it himself. Even 

crude repairs may often be made to serve until a new instrument can 

be procured.

Setting of bubbles. For setting level bubbles a small supply of 

plaster of Paris should be kept on hand. For use the plaster should
192 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

be mixed with water to the consistency of a thick paste. If plaster is 

lacking, strips of paper may be used, but these should never be 

jammed in very tight, as the pressure may distort the glass and thus 

vitiate the bubble reading by an appreciable amount. A reflecting 

surface of colored paper should be placed under the bubble in order 

to make the graduations more readable; a subdued green or blue tint 

is recommended.

Mounting of cross wires. For mounting cross wires a small bottle 

containing shellac dissolved in alcohol, a pinch of beeswax, and a 

pair of dividers or a forked stick are needed. The best spider web 

is of course a freshly spun one from a small spider, for this will be 

both clean and elastic; but as spiders are not always available, it is 

well to keep on hand a spider cocoon. Such a cocoon will furnish 

webs enough to last for years, although with age the threads become 

stiff and brittle and therefore more liable to break from a j ar to the 

instrument. Most webs taken from grass or bushes are rough, 

coarse, and dirty.

To draw the reticule from the instrument, unscrew and remove the 

eyepiece slide; then take out two opposite capstan-headed screws and 

loosen the other two. Using the latter two as handles, revolve the 

cross-wire ring 90°, insert a pointed stick through the end of the 

telescope tube into a screw hole in the ring, and, using it as a handle, 

remove the other capstan screws and draw out the ring. To replace 

it in the telescope, reverse this procedure. When in place the cross 

wires should be on the side of the ring toward the eyepiece.

Having pressed a bit of beeswax to each prong of the dividers or 

forked stick, let a small web fall from the end of one of the prongs, 

or pick with it from a cocoon a single thread, pressing the thread into 

the beeswax, stretch the thread moderately and attach to the wax 

on the other prong. If an old web is used, it should first be dampened 

by dipping in water for a few seconds. In place of the dividers or 

forked stick, small sticks or lumps of wax may be attached to the web 

about 2 inches apart. Place the web across the reticule, using a 

magnifier to insure its coinciding exactly with the marked lines. Put 

a small drop of shellac on each end and leave until dry.

Cleaning instruments. Instruments having working parts exposed 

to air and dust require cleaning from time to tune. Such exposed 

parts as the threads of tangent screws are particularly liable to collect dust and grit and should be wiped frequently with an oily rag 

and then rubbed dry. Only the best quality of clock or watch oil 

should be used for this purpose. Steel tapes should be cleaned and 

oiled after use. All moisture or grit must be wiped from them each 

time they are reeled, or they will deteriorate rapidly. Neither the 

object glass nor the eyepiece of a telescope should ever be rubbed 

with rough cloth or with the fingers, as the glass may thus be per-
TOPOGRAPHIC MAPPING 193

manently scratched. The lenses should never be removed from the 

cell that holds them nor separated from one another.

Packing and shipping. In shipping instruments by freight or 

express alidade boxes must be filled in with paper or cloth, so that if 

any part of the instrument should jar loose during the journey it 

will not roll around in the box and damage other parts. Heavy 

articles, such as compasses, aneroids, or other small instruments, 

should never be placed in the instrument box. On no account should 

any instrument be shipped by express or freight in its own case only. 

A wooden box, large enough to permit a generous amount of excelsior, 

hay, or other padding around the instrument case, should be provided. The same precautions should be taken when these instruments are to be transported by pack train. Under such circumstances the instrumental outfit is most conveniently carried in a pair 

of canvas pack bags (alforjas), which must be properly balanced. A 

canvas pack cover should be thrown over the whole and tucked in 

on all sides.

Protection. When in camp instruments, plane-table boards, tripods, and rods should never be allowed to remain outside overnight, 

exposed to dew or rain. It should be the regular practice in every 

field party to place all instruments under shelter as soon as they are 

brought in at the end of the day.

ADJUSTMENT OF INSTRUMENTS 

PRECAUTIONS

The object glasses and eyepieces of all instruments must be properly 

focused. The cross wires projected against a distant object should 

appear immovable when the eye only is moved. Before the adjustments are commenced the instruments must be firmly set up and 

leveled. An instrument may appear to be out of adjustment 

simply because some part is loose. The object glass may be partly 

unscrewed or an adjusting screw may be only partly tightened; level 

bubbles or cross wires occasionally become loosened. Therefore, 

before commencing the adjustment of an instrument look out for 

such defects. When it is thought that an adjustment has been 

completed, always test it before using the instrument. All adjusting 

screws should be screwed tight enough to hold, yet not so tight as 

to injure the threads or put a severe strain on any other part. Especial care should be taken not to strain the cross-wire screws.
194 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

TELESCOPIC ALIDADE

The principal adjustments for the telescopic alidade (pi. 11, A) 

are for level and collimation. These should be tested daily.

Level. Whenever a new vial is inserted in the tube of the striding 

level an adjustment for side swing should be made. Unscrew the 

pin that holds the level on the telescope; place the striding level in 

position, and bring the bubble to the center of the tube by means of 

the tangent screw; rock the striding level from.side to side through 

an arc of about 10°. If the bubble stays in the center the adjustment is perfect, but if not, bring it to the center by means of the 

side adjusting screws. Then replace the pin.

Clamp the telescope, bring the bubble to the center of the tube 

with the tangent screw, lift up the level carefully, reverse, and 

replace it on the telescope. If the bubble runs away from the 

center, bring it halfway back by means of the tangent screw and 

the other half by the adjusting screw at one end of the level tube. 

Repeat this operation till the bubble stays in the center after reversal.

Collimation. With the alidade standing on a level surface test 

the verticality of the vertical wire by setting the wire on a near-by 

point and raising and lowering one end of the telescope to see if the 

point remains on the wire; or by setting the wire on a vertical 

corner of a building or on a plumb line and raising and lowering 

the telescope to see if the wire always coincides with the vertical 

line. If the wire is found not to be in true vertical position, loosen 

the screws and by a slight shift in the position of the cross-wire 

ring bring the vertical wire into true vertical position. Point the 

telescope on a small but well-defined object about half a mile distant and while watching this through the telescope revolve the 

telescope 180° in its supporting sleeve. If the intersection of the 

cross wires remains centered on the object, the adjustment is perfect; 

if not, change the cross wires for half the error and repeat the operation until they stay on the point selected.

Ruler. So long as but a single alidade and but one edge of the 

ruler are used, it makes no difference in the results whether the edge 

of the ruler is parallel to the line of sight or not, except for use with 

the Baldwin solar chart, when a correction must be applied if 

appreciable.

Circular level. Place the alidade on a level surface. Bring the 

bubble to the center of the glass by means of one or two of the three 

adjusting screws.1

Side level with adjustable vernier. A type of alidade now on the 

market, which in the near future may be generally adopted (pi. 11,

» The second table on p. 407, Bulletin 650, is erroneous. The right-hand column should be minutes and 

seconds instead of degrees and minutes.
TI. S. GEOLOGICAL SURVEY BULLETIN 788 PLATE 10

PLANE TABLE AND TRIPODS 

A, Plane table; B, Johnson tripod head; C, Traverse tripod head
IT. S. GEOLOGICAL SURVEY BULLETIN 788 PLATE 11

H V

503

iG^ee

-60! 

G 5S

20= H

.B

®

TELESCOPIC ALIDADES 

A, Staadard alidade; B, Stadia arc graduations; C, New standard alidade
U. S. GEOLOGICAL SURVEY BULLETIN 788 PLATE 12

STADIA ROD AND ROPE 

A, Stadia rod; B, Stadia-rod aheet; C, Twisted rope
U. S. GEOLOGICAL, SURVEY BULLETIN 7S8 PLATE 13

ANEROID BAROMETER 

A, Face of aneroid; B, Internal mechanism
TOPOGRAPHIC MAPPING 195

(7), has a movable vernier arm with a side level attached. The advantage of this type is that in reading vertical angles only one setting is 

necessary and the level reading is always the same generally 30°. 

To adjust this vernier level, place the alidade on a horizontal surface. 

Level the telescope by means of the striding level which has been 

previously adjusted. Set the 0 of the vernier opposite the 30° 

mark on the arc. Turn the adjusting screw at one end of the level 

tube until the bubble is in the center. The 0 position for some alidades may be opposite the 15° mark and capstan-headed nuts may 

be used in place of screws.

To fix an accurate level surface, proceed as follows: Place the 

alidade on a plane-table board or other adjustable surface which is 

approximately horizontal. After having adjusted the striding 

level, place it on the telescope and bring the bubble to the center 

by means of the tangent screw. Turn the alidade 180° and then 

90°. If the bubble remains in the center of the tube for both positions the adjustment is perfect and the surface is level. If not, 

bring the bubble halfway to the center by the tangent screw and the 

rest of the way by moving the plane-table board. The circular 

and side levels may then be adjusted if necessary.

COMPASSES

Compasses will usually be out of balance when transported to a 

different locality. The sliding weight must be moved when it is so 

much out of balance that one end of the needle is near the glass cover 

when the box is leveled. Many complaints have been made that 

compasses were worthless, when the only trouble was that the needles 

were so badly out of balance that they rubbed against the glass covers.

It should be a strict rule with everyone using a compass to lift the 

needle from the center pin immediately after use. Under no circumstances should a compass be carried from one station to another with 

the needle resting on the center pin. Party chiefs should lay special 

emphasis on this rule when instructing new field assistants.

TOPOGRAPHIC MAPPING METHODS <

CONTROL

The initial control as outlined below, upon which the surveys for 

topographic maps are based, is described in detail in parts B, Triangulation; C, Transit traverse; and D, Leveling. (See also "Standards for field work," p. 181.)

Surveys for topographic maps must be horizontally controlled by 

means of locations that have been determined either by theodolite 

triangulation of the first, second, or third order or by transit traverse,
196 TOPOGKAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

and some maps are controlled by means of both triangulation and 

transit-traverse locations.

Surveys for topographic maps must also be vertically controlled by 

means of elevations that have been established by lines of spirit levels 

of the first, second, or third order.

The further horizontal control on which the survey of the details 

of the map is to be based will be obtained by means of plane-table 

triangulation (p. 197) or plane-table traverse (p. 205) or by both combined. These forms of control also provide supplementary vertical 

control through the use of vertical angles measured with the telescopic 

alidade. Supplemental horizontal control may also be obtained by 

means of the aerial photographic methods referred to below.

Part F, "Map compilation from aerial photographs" describes 

aerial photographic methods for obtaining supplemental control, a 

partial culture and drainage base, and nearly complete woodland and 

marsh outlines for topographic maps. Such procedure promises increasing usefulness as the photographs and the methods of using them 

are further improved. The initial horizontal control needed for the 

adjustment of aerial photographic map data is similar to that specified above for the control of topographic surveys. (See "Mapping 

on aerial photographic base," p. 254.)

TOPOGRAPHIC MAPPING INSTRUMENTS

Theodolites, transits, and levels, as described in parts B, C, and 

D of this manual, are not employed in detailed topographic mapping 

but are used in the initial control operations. Exceptions may occur 

where a control level party is attached to a topographic party or 

where there may be need for spirit levelling of the fourth order, sometunes referred to as "fly" levels. The instruments used in topographic mapping are chiefly the plane table (pi. 10), telescopic and 

sight alidades (pi. 11), stadia rod (pi. 12, A), compass, aneroid (pi. 13), 

tape, field glasses, and plotting scales (pi. 9). Complete lists of instruments and accessories needed for different kinds of topographic mapping will be found on pages 44 and 45 of part A.

Plane table. The surveys upon which the topographic maps published by the Geological Survey are based are executed by means of 

some form of the plane-table method. The plane table (pi. 10, A] consists essentially of a drawing board that is supported by a tripod and 

used in connection with an alidade (pi. 11). The board can be leveled 

and also turned in any horizontal position and can be clamped when 

properly set. When in use the plane table and its support must never 

move; and the greatest care must be taken that when it is once set
TOPOGRAPHIC MAPPING 197

or oriented it shall not be disturbed in position. The engineer must 

not lean on it or against it. On the board is fastened the drawing 

paper upon which the map is to be plotted. (See "Plane-table paper," 

p. 166.) Detailed topographic mapping is usually executed on a planetable board that measures 18 by 24 inches (pi. 10, A); plane-table 

triangulation is done on plane-table boards that measure 24 by 31 

inches; for plane-table traverse boards either 15 by 15 inches or 18 by 

24 inches are employed, although some traversing in dense timber 

or in brushy areas is done on a board that measures 9 by 9 inches.

Two types of alidade are used, the telescopic (pi. 11, A) and the 

sight (pi. 9, B}. The sight alidade is used only for paced or tape 

traverses; for all other mapping the telescopic alidade is used. The 

alidade is used as a means of sighting the direction of topographic 

details which are to be located on the map, and immediately after 

each sight is taken the corresponding direction line is drawn on the 

plane-table sheet by running a pencil edge against an edge of the 

ruler which is rigidly attached to the sighting part of the alidade.

Two types of tripod are used. The one in most common use 

(Johnson type) (pi. 10, A, B} has a universal leveling movement for a 

rapid leveling of the plane-table board and combines rigidity of construction with comparative lightness. A lighter form (pi. 10, C] is 

also used for foot and tape traverses for which the leveling is done 

with the tripod legs.

Other instrumental outfit. Stadia rods (pi. 12, A) are used in connection with stadia wires that are set in all telescopic alidades. 

Stadia rods are divided into feet and suitable graduations thereof, 

and the rods are generally used in 10, 12, or 14 foot lengths and may 

be hinged in the middle for convenience in carrying. The stadia 

wires of the alidade are set to intercept 1 foot on a rod 100 feet in 

front of the object glass of the telescope.

A box compass is fastened to the ruler of each telescopic alidade. 

The compass is used as a means of orienting the plane-table board in 

traverse work and also as an approximate means of orienting the 

table prior to the determination for position by the three-point 

method.

The use of the aneroid (pi. 13) is fully described on pages 21.4-219. 

Two types of tape are used, a 50-foot metallic tape for miscellaneous 

use and a 300-foot or 528-foot linen tape or braided rope for certain 

traverse lines. (See "Tape traverse," p. 211.)

PLANE-TABLE TRIANGULATION

Definition. Plane-table triangulation consists in the location of 

many points on a plane-table sheet (representing tie points distributed 

over the area that is to be mapped) through the use of the so called 

pure plane-table methods. (See pi. 10, A.} These methods, in
198 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL, SURVEY

principle, involve only the use of the plane table and the telescope 

alidade, and in theory the operations may be executed by one man. 

In practice one or more assistants are employed and auxiliary methods 

such as stadia are used. The area that is to be mapped is outlined on 

the plane-table paper by means of a projection (seep. 166) on which 

the initial horizontal-control points have been plotted.. Plane-table 

triangulation starts from these control points, and by means of the 

plane-table methods of intersection and resection the necessary points 

on which to tie the topographic details of the map are "cut in" or 

located on the paper.

How used. The results of plane-table triangulation are utilized 

under one of two general plans, or both combined, (a) The points 

that have been located on the paper by the plane-table triangulation 

are transferred to smaller plane-table sheets (usually one-half size) 

on which the final map is to be drawn, and the subsequently executed 

plane-table traverse lines are tied to the points thus transferred. 

(6) The original plane-table triangulation sheet may become the 

final sheet on which the map itself is drawn, and this procedure is the 

practice in mountainous areas that are sufficiently open to permit 

detailed topographic mapping by plane-table methods alone, (c) In 

regions that are sufficiently open for detailed plane-table triangulation the two plans outlined above may be combined, the details of 

mapping being obtained by traverses and by stadia measurements, 

and supplementary control being obtained where it is needed by 

means of additional plane-table triangulation.

Preparation. Before the projection for the map under consideration is prepared a thorough study of all the geodetic positions available for the control of the area should be made, and the position of 

the projection on the paper should be so arranged as to include the 

greatest possible number of desirable positions.

Projection. The projection should be made with the utmost care 

on seasoned double-mounted paper, and the positions should be plotted thereon as accurately as possible. The projection and all positions should be satisfactorily checked. Metal-mounted sheets should 

be used for plane-table triangulation whenever practicable. (See 

"Plane-table paper," p. 166; "Construction of projections," p. 166; 

and "Plotting horizontal control," p. 177.)

Precautions. In the field the plane-table sheet should be protected 

by cover paper as much as practicable and should be firmly attached 

to the plane table by brass thumbscrews or tacks, to reduce to a 

minimum the expansion or contraction caused by changes in climatic 

conditions. In windy weather a weight should be suspended from 

the head of the tripod to steady the plane table and to prevent a 

possible accident. The use of a large umbrella, if the sun is bright,
TOPOGRAPHIC MAPPING 199

facilitates the work and is a protection to the eyes and the paper. 

The instrument and paper should be kept clean of sand and grit.

Alidade. The adjustment of the alidade for collimation (seep. 194) 

and parallax should be carefully inspected before commencing work 

and watched thereafter to be assured of its good condition at all 

times. (See "Adjustment of instruments," p. 193.)

Signals. Substantial signals, of whatever material is at hand, 

should be erected on the main triangulation stations and on other 

prominent hilltops according to necessity. If the use of flags is 

essential, red and white cotton make good material. Use white if 

the flag is to be observed against a dark background and red if it 

stands against the sky. While the signals are being placed every 

opportunity should be utilized to learn the topography of the country, 

to select the best subsidiary stations, to mark their approximate location on the guide map, and to fix in mind the distinguishing features 

of objects most likely to be seen from the stations to be occupied.

Choice of station. In choosing the first station to be occupied it 

is best to select one of the most prominent triangulation stations, 

located preferably in the southern part of the quadrangle, so that 

when most of the sights are taken the observer will be looking away 

from the sun. In this way objects may be more clearly seen and 

peculiarities noted. Clear atmosphere is essential when the first 

stations are occupied.

On the station. After leveling the plane table, place the alidade on 

a line connecting the station occupied with one of the triangulation 

points farthest away (the other end of the base), revolve the table 

until the farther signal is bisected by the vertical wire of the alidade, 

and clamp the table. Verify the orientation by sights to additional 

visible triangulation stations. Now make the circuit of the horizon 

systematically and take foresights to prominent objects, such as 

signals, cupolas, towers, chimneys, flag poles, monuments, windmills, 

church steeples, and definite points on schoolhouses, dwellings, barns, 

silos, trees, hilltops, or spurs. Draw the lines of sight with a chiseledged 9-H pencil, to considerable length along the square edge of 

 the alidade, being careful always to hold the pencil at the same angle, 

and to see that the contact of rule and paper is perfect. Get azimuths 

of long, straight stretches of road and railroad whenever possible. 

Stadia may well be used to locate road forks or objects in the immediate vicinity of the station. From time to time while making observations and on the completion of the work at each station check the 

orientation of the plane table in order to see if there has been any 

movement.

Magnetic declination. While the plane-table sheet is oriented, 

determine and draw the line of magnetic north through the station, 

and repeat the operation at several other widely separated stations.
200 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

Vertical angles. After all the sights have been taken adjust the 

striding level of the alidade (see "Adjustment of instruments," p. 193) 

and read vertical angles to the points whose elevations are desired. 

Angles that are read to the principal control points in the scheme 

should be checked. (See "Station elevation," below.)

Station elevation. The elevation of each plane-table station should 

be determined by means of vertical angles taken either to specially 

located spirit-level bench marks or to other plane-table stations whose 

elevation has been previously determined. In general, the principal 

stations from which the greatest number of vertical angles are to be 

taken should be connected by means of reciprocal vertical angles taken 

under differing conditions, and then the final elevation for each station in the net should be determined by means of a weighted adjustment of the observed differences in elevation. This adjustment 

should be made in conjunction with such ties with level bench marks 

as have been made. In measuring important vertical angles, such as 

those to other stations or to points on spirit-level lines, all readings 

should be checked by reversing both striding level and telescope and 

by using different positions of the vertical arc, which may be accomplished by placing a plotting scale or some other flat object under one 

end of the alidade ruler.

Records and computations. Plane-table stations may be designated 

by Roman numerals (I, II, III, etc.), and each line of sight drawn on 

the plane-table sheet by an Arabic numeral. Such designations should 

be written on the plane-table sheet and also entered in a suitable 

notebook. Brief descriptions of objects sighted may be noted on the 

plane-table sheet and written along the line of sight, and complete 

descriptions should be recorded in the notes. The notebook should 

also contain the vertical-angle records.

Distances between stations and between stations and located 

points whose differences in elevation are to be computed will be scaled 

by means of a boxwood scale of miles provided for the purpose and 

graduated for the field scale. Computation of differences in elevation is facilitated by the use of prepared tables. Care should be 

exercised in noting and in allowing for the height above ground both 

of the alidade and of the point sighted. The proper corrections for 

refraction should be applied wherever appropriate.

Other stations. When the work on the initial station is completed, 

repeat the operation on the station at the other end of the base and 

on as many additional stations as may be necessary to complete 

the work. If practicable all triangulation stations that have been 

plotted on the sheet should be occupied. The point of intersection 

of lines drawn to the same object determines its location, but all 

intersections should be verified by a sight from a third position.
TOPOGRAPHIC MAPPING 201

Additional stations may be made at intersected points (see below), 

at points to each of which a single foresight has been drawn on the 

plane-table paper (see "Location by resection," below), and at points 

whose location may be determined by the "three-point method" 

(see p. 202).

Suggestions. A signal should be erected where necessary to mark 

the place of a station for future reference. Care should be taken to 

prolong on the plane-table sheet a line that may later be used for 

an orientation. In areas of great relief and of difficult access advantage should be taken of every opportunity to contour, even 

approximately,' topographic features, such as bottoms of canyons, 

rock exposures along canyon walls, ground surfaces in heavily timbered, inaccessible mountain gaps, and indefinite slopes of mountain 

masses that may not practically be occupied by the plane table.

Number of points. Enough locations should be made to furnish 

satisfactory control. The number necessary is determined by consideration of the character of the country, the amount of supplementary plane-table traverse, and the scale of the work.

STATIONS AT INTEESECTED POINTS

In occupying a point whose location has been determined by means 

of sights taken from previously made plane-table stations the orientation should be made on the stations from which the foresights were 

taken. If the exact point that has been located can not be occupied 

proper allowance must be made for any plottable distance between 

the new station and the located point.

LOCATION BY RESECTION

The location of a plane-table station may be obtained by the 

method of resection, which in general is stronger than the threepoint method. Location by resection involves two separate operations performed on two different stations, and in practice any length 

of time may elapse between the two operations. The resection 

method is of limited use, however, inasmuch as it involves a foresight 

from a previous station and the erection of a signal on the proposed 

station point or the positive identification afterward of the point or 

direction sighted. Foresight lines that are to be used for a location 

by resection should be drawn on the plane-table paper exactly 

through the point representing the station from which the sights are 

taken and to the full length of the alidade ruler. The line through 

the point representing the occupied station should be light, and care 

should be taken to hold the chiseled pencil point directly against 

the ruler. The foresight line need be drawn only through the approximate position of the new station and at the extreme end of the
202 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

ruler in order not to add unnecessary lines to the paper. After 

drawing the line look through the telescope again and also test the 

plane-table orientation in order to insure that the table has not 

moved, Similar foresights may be taken to other prospective station 

points whose locations it is desired to obtain at some future time by 

resection.

To locate a new station which is being occupied and to which a 

long foresight has been previously drawn, orient the plane-table 

sheet by placing the alidade ruler in the reverse direction on the line 

sighted and swinging the plane-table board until the station from 

which the foresight was drawn is seen behind the center wire, and 

clamp the plane-table board. The station being occupied is on this 

foresight line, and the location is determined by resecting from other 

plane-table stations whose directions are most nearly at right angles 

to the foresight line that they are to intersect and whose distance is 

less than that of the station from which the foresight line was drawn. 

Center the ruler on the plotted position of one of these stations, 

swing the telescope until the signal mark at that station is behind 

the center wire, and draw a line against the ruler to intersect the 

foresight line. The intersection marks the location of the occupied 

station. This intersection should be checked by at least one other 

resection from another station. The two resected lines should cross 

the foresight line at the same point.

THREE-POINT METHOD

A plan frequently adopted for the location of plane-table stations 

is that known as the "three-point method." It can be used advantageously when three or more previously located points properly 

distributed are visible. Before making three-point stations a compass line should be drawn on the sheet and used for approximate 

orientation.

In Figure 6 the triangle formed by the three fixed points is called 

the great triangle, and the circle passing through them the great 

circle. When the plane table is imperfectly oriented, the lines 

drawn from the projected points (rays) will not intersect at one 

point, except when the table is on or near the great circle, but will 

form a triangle of error. The term "new station" means the place 

on the ground where the plane table is set up, and the term "point 

sought" its true projected position on the sheet.

The angle formed by the intersection of the rays drawn from any 

two of the fixed points is the correct angle, the problem being to 

shift the orientation of the plane table so that the vertices of the 

several angles come together in a common point, which will be the 

point sought. This fact is the basis for the tracing-paper solution 

of the three-point problem, which is described under the next heading.
TOPOGRAPHIC MAPPING 203

If more than three known points are visible, select the three that 

will give the best results, preferably the three that will form a triangle 

embracing the new station. Do not try to use more than three at 

once. Orient the plane table by magnetic compass, and draw rays 

from the three known stations. If a compass line is not available 

or if there is considerable magnetic attraction, adopt an approximate 

location of the point sought, place one end of the alidade ruler on 

the point thus adopted and the other end on the most distant of the 

points used, revolve the plane table, sight the most distant point 

used, clamp the table, and draw rays from all three points. On 

the first trial a triangle of error will undoubtedly result, owing to 

improper orientation of the table.

If the new station is on or near the great circle, its position can 

.not be determined from the three fixed points selected, and one of the 

three should be replaced by a fourth. (See fig. 6, 2.)

FIGURE 6. Graphic solution of three-point problem

If the new station is within the great triangle, the point sought is 

within the triangle of error and in the same relative position in the 

triangle of error as this small triangle bears to the great triangle. 

(See fig. 6, 1.)

If the new station falls outside of the great triangle, the point 

sought is either to the left of all the rays or to the right of them all. 

Of the six sectors formed by the rays, there are only two in which 

this condition is fulfilled.

If the new station falls within one of the three segments of the 

great circle formed by the sides of the great triangle, the ray drawn 

from the middle point lies between the point sought and the intersection of the other two rays. (See fig. 6, 3.)

If the new station is without the great circle, the point sought is 

always on the same side of the ray from the most distant point as 

the point of intersection of the other two rays. (See fig. 6, 4.)

Under either of the two conditions stated just above, where the 

new station is outside the great triangle, the exact position of the

58515° 28 14
204 TOPOGRAPHIC INSTRUCTIONS OP GEOLOGICAL SURVEY

point is determined by the condition that its distance from the several 

rays must be proportional to the length of the respective rays. Make 

a new approximation of the point sought and repeat the process, 

orienting on the most distant point. If the second trial results in 

a larger triangle of error, the trial point has been taken in the wrong 

direction from the ray from the middle point if within a segment and 

from the most distant point if without the great circle.

In practice the topographer estimates the relative distances of the 

three fixed points from him and marks the position of the trial point 

a proportionate distance from the three rays that form the triangle 

of error. The alidade is then so placed that it exactly cuts this 

trial point and the plotted position of the most distant point, and the 

plane table is turned so that the line of sight bisects the most distant 

point. The table is then clamped. A short ray is drawn through 

the trial point, and the other stations are sighted and short rays 

drawn toward them. If the three intersect in a common point, it 

is the point sought, and the plane table is oriented. If a new triangle of error is formed by the rays, the operation must be repeated. 

The final location should always be checked where possible by 

sighting a fourth point.

Points whose location has already been determined and which can 

be seen from any one point are usually few. However, where the 

available control is sufficient to permit a choice of points, a selection 

of three points that will place the new station within their great 

triangle will give the most accurate location of the point sought. 

The next best location is obtained where the new station is nearly 

on a line between two known stations, one of which is at a considerable 

distance, so that the two rays will nearly coincide, and where a third 

known station lies at a moderate distance and in such a position 

that the ray drawn toward it will be at approximately right angles 

to those toward the other two. Where these conditions do not exist 

the selection of three points of which the middle one is nearest to 

the topographer will place the new station definitely outside of their 

great circle and will eliminate the danger of an indeterminable 

location.

Bessel's, or the Italian method, as it is sometimes known, and the 

inverse triangle method, used by the French, offer no advantages 

over the methods already described and involve the use of more 

construction lines. They are therefore not used.

For a detailed discussion of plane-table methods, see "Plane-table 

manual" (United States Coast and Geodetic Survey Special Publication 85), or standard texts on surveying, such as "Higher surveying, volume 2," by Breed and Hosmer, or "Topographic surveying," 

by Herbert M. Wilson. For mathematical solution of the threepoint problem, see United States Coast and Geodetic Survey Report
TOPOGRAPHIC MAPPING 205

for 1880, appendix 13; idem for 1897-98, appendix 13; or United 

States Geological Survey Bulletin 650.

TRACING-PAFER SOLUTION

 By another method a piece of tracing paper is fastened securely 

to the plane table, and the three or more located points visible are 

sighted and rays drawn toward them from a fine point upon which 

the alidade is carefully centered for each ray. The alidade is then 

removed. The tracing paper is released and so shifted over the 

plane-table sheet that the rays drawn toward the points sighted pass 

through their respective plotted positions simultaneously. The 

point at the intersection of the rays (the pivot point) is then exactly 

over the position on the plane-table sheet of the point sought and 

should be pricked through the tracing.

Locations made by the tracing-paper method are likely to be less 

accurate than those made by the graphic method, described above. 

They should be checked after they are pricked through to the planetable sheet before using them in the location of other points. In 

general, this method should be used only when special conditions make 

it necessary, or as a means for locating a trial point for the graphic 

method.

PLANE-TABLE TRAVERSE

METHODS

Traversing consists of much more than getting direction and distance, though these are absolutely essential features. All the essential topographic features on each side of the line are to be obtained 

at the time the traverse is made.

Accuracy of plane-table traverse depends on two factors namely, 

the obtaining and plotting of distances and the orientation of the 

plane table.

Distances are obtained by stadia, wheel, tape, or pacing, and the 

orientation is made by magnetic needle, by back and fore sights, 

by the Baldwin solar chart, or by other approved solar apparatus.

When the needle is used the accuracy of orientation is dependent 

on the freedom from local attraction and the length of the needle. 

For these reasons it is well to avoid the use of the compass near railroads, electric-transmission lines, or large bodies of steel or iron, and 

in volcanic regions. No plotted line should be greater than the 

length of the needle.

The method employed in determining distances will be governed 

by the character of the country and the scale of the work. Traverse 

lines should be run along roads, ridges, or streams, or at intervals in 

timbered country when necessary; the method in general practice
206 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

when the needle is used is to set up at alternate stations, using intermediate stations as turning points. Sights should be taken from 

these stations to prominent hilltops, spurs, houses, windmills, lone 

trees, and other conspicuous objects, and these should be intersected 

at subsequent stations. Following this plan, the traverseman should 

locate all railroads, roads, trails, houses, churches, schools, and bench 

marks, all State, county, township, and city boundaries, also all cultural features as listed on page 229.

Streams near the roads should be mapped as accurately as the 

skill and experience of the traverseman will permit. Especially 

should stream crossing and recrossing roads traversed in ravines or 

gulches be located and junctions shown with side streams.

In traversing railroads frequent locations by the three-point 

method should be made if possible, and the line extended by means 

of fore and back sights. If this is not practicable and it becomes necessary to rely on the needle, it is important to set up the plane table a 

sufficient distance from the rails to prevent their influence on the 

needle. The distances can be obtained advantageously by measuring a rail and counting the number of rails between stations.

Where traverse is extended along roads over which levels have 

been carried, note elevations marked on fences, at summits, bridges, 

corners, etc., and record them on the traverse sheet. Names of 

villages, streams, hills, etc., should be obtained in the field as far as 

possible especial care being taken to get correct spelling and 

should be written plainly on the traverse.

Traverse should not be made to close but should show the two 

tie points by a double arrow between them; such junctions should 

not be made in towns or villages.

Traverses should extend a sufficient distance beyond the edge of 

the quadrangle to overcome any possible error that may occur in the 

adjustment.

Single-mounted paragon paper is ordinarily used, though celluloid 

may be substituted to advantage in wet weather. Before using the 

sheet the name of the State and quadrangle, the date, the name of 

the traverseman, and that of the chief of party should be written 

in the lower left-hand corner.

The proper method of plotting is to place the fractional scale division on the old point and prick the new location with the needle at 

the even division at the end of the scale. This operation should be 

performed with the greatest care, as more closure errors are to be 

attributed to careless plotting than to any other cause. (See pi. 9.) 

When aneroids are used the elevations should be recorded on the 

sheet at road and stream crossings, divides, and traverse stations. 

To insure accuracy the aneroid should be compared and corrected 

with bench-mark elevations whenever possible.
TOPOGRAPHIC MAPPING 207 

STADIA TRAVERSE

In plane table and stadia traverse instrumental measurement of 

distances and elevations gives sufficient control to permit considerable sketching to be done on either side of the line.

Determination of elevations. If the elevations are determined by 

means of vertical angles taken from the plane table ground elevations 

may be carried by using a mean height of instrument (4^ feet) as a 

turning point on the rod, or ordinary level notes may be used with 

H. I. computations. Accurate distance readings are essential, and 

sights for turning points should not be over 1,000 feet, unless under 

exceptional circumstances. In large-scale detailed work 300 feet 

is a better limit. When the lower hair comes near the ground on 

long sights serious errors are liable to occur at certain hours of the 

day through refraction. The Anderson or Johnson stadia tables are 

probably the most satisfactory for computing differences of elevation 

and horizontal correction. On scales of 1:48,000 or larger the horizontal correction can be readily shown in plotting. On larger scales 

it becomes important. Angular measurements exceeding 15° should 

be avoided.

In setting with any tangent screw (whether setting for a zero reading of the arc or sighting a point) turn in the direction that compresses 

the spring against which it works. If the screw needs to be turned 

back, instead of turning it to the exact setting, turn it back too far 

and then bring it up to the accurate setting with a clockwise or 

right-hand motion, thereby insuring a firm bearing of the spring 

against the screw. Failure to observe this rule is the cause of many 

errors in elevation.

Wherever possible, as in regions of low relief, elevations should be 

determined by using the alidade as a level and the rod as a level rod.

Beaman stadia arc, The use of vertical angles may be avoided by 

the use of the Beaman attachment to the telescopic alidade. (See 

pi. 11, A, B.) This attachment consists of a stadia arc, which is 

screwed on the outer side of the old arc and which carries two separate 

double scales having coincident zero points marked 50 and 0, respectively. Either scale is read by reference to the common adjustable 

index, which, when the telescope is level, must be set at the zero 

point of the scales before the stadia arc is used. The two scales 

(pi. 11, B) are:

To the right, next to the index, a multiple scale,' with zero point 

marked 50, which indicates multiples for obtaining differences in 

elevation. To get desired multiple, subtract 50 from scale reading 

and use algebraic remainder for example, if scale reads 56, multiple 

is 56-50= +6; if scale reads 47, multiple is 47-50= -3.
208 TOPOGRAPHIC INSTRUCTIONS OP GEOLOGICAL SURVEY

To the left, a reduction scale, with zero point marked 0, which gives 

percentages of correction that may be used, if desired, to reduce 

observed stadia distance to horizontal.

To determine differences in elevation read the distance subtended 

on the rod and express in feet (for example, 8.7 = 870 feet). Clamp 

the telescope and level it. Set the index exactly at 50, by means of 

the tangent screw back of the arc, and do not touch this tangent 

screw again.

Then, by means of the customary clamp and tangent movement, 

raise or lower the telescope until there is brought exactly opposite the 

index such a graduation on the multiple scale as will throw the 

middle stadia wire somewhere on the rod, it does not matter where. 

The arc reading, minus 50, multiplied by the observed stadia distance gives the difference in elevation between the instrument and 

a known point on the rod that is, the height on the rod indicated by 

the middle wire. Settings of both index and arc should be made 

carefully under a reading glass.

Example: Suppose the observed stadia distance is 6.3 (630 feet) 

and the telescope is so inclined that the multiple scale reads 58; at 

this exact setting the middle wire on the rod reads 7.2 (7.2 feet above 

base of rod); then multiple is 58 50 = + 8, and computation for a 

foresight would be

6.3

+ 50.4 

 7.2

+ 43.2 feet=base of rod above H. I.

If the middle wire were set on H. I. or on the top or other fixed 

point on the rod and the arc were read by estimation (for example, 

54.2) to obtain a multiple, the result would be approximate only; 

therefore this method is not to be used with this attachment.

If the half-wire interval is read and this reading is then doubled to 

get the stadia distance, it occasionally happens that no even multiple 

arc setting that will throw the middle wire on the rod can be found. 

In this case make an arc setting that will throw the lower wire anywhere on the rod; the middle wire will then be somewhere above the 

top of the rod. Then take the multiple as read on the arc, but 

compute the position of the middle wire above the base of the rod by 

adding one-half the expressed stadia distance (in feet subtended) to 

the reading of the lower wire.

Example: If the half wires subtend 7.2 on the rod, the distance 

would be 7.2x2 = 14.4 (1,440 feet). If the lower wire cuts the rod 

8.7 feet above its base, the computed middle-wire reading would be
TOPOGRAPHIC MAPPING 209

8.7+7.2 = 15.9 feet above the base of the rod. Then compute as 

before.

The reading of the left-hand arc from the same arc setting, used to 

obtain the difference in elevation, will give the correction, expressed 

as a percentage, needed to reduce observed distances to horizontal.

Example: If a multiple-arc setting of, say, 70 has been made for 

difference of elevation work, the reading of the reduction scale would 

be 4, or 4 per cent. (Reading to the nearest unit per cent is usually 

sufficient.)

If the observed distance was 12.0 (=1,200 feet), then 4 per cent of 

1,200 =48 feet; 1,200-48 = 1,152 = corrected horizontal distance.

Stadia-arc notes. Form 9-913A has been prepared especially for 

Beaman stadia arc notes. The arc reading or multiple (expressed as 

above or below 50) is placed under the appropriate heading, as in the 

example below, and all sights are to be regarded as foresights except 

those taken to determine H. I. The column headed "Product" is 

for multiple times distance for example, 4X4.2 = 16.8. The column 

headed "Rod correction" is for the final reading of the middle wire 

on the rod.

Date, April 29,1916. Traverse from Takoma to Sligo.

2--........-.. ____ ...........

3. ..............................

4.... ....................... ....

5..............................

Distance

4.2

6.3

9.2

Beaman 

arc or 

steps

48 or 2

57 or 7

Product

-16.8

-12.6

+55.2

+110. 6

Rod correction

+8.2 -4.9

+4.3

Difference in 

elevation

-8.6

-17.5

+59.5

+96.8

H.I.

646.1

688.1

Elevation

654.7B.M.

628.6

784.9

The signs to be affixed to "Product" and "Rod correction" are 

determined according to whether the observation is a backsight or 

foresight, by following a rule of universal application, namely:

Product

Rod

correction

+

The arc reading 54 indicates +; therefore here the sign of the 

product is for a backsight and + for a foresight. Another way 

of determining the sign to be affixed to "Product" is to consider 

whether the telescope is inclined upward or downward in the direction in which the line is being run when the middle wire is set on 

"Rod correction." If the angle is upward in the direction in which 

the line is being run, the sign of "Product" is +. If the angle is 

downward in the direction in which the line is being run the sign of
210 TOPOGEAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

"Product" is . Note that the sign of "Rod correction" is the 

same as in leveling. When the line of sight is level the arc reading is 50, and therefore the only entry is rod reading, entered as 

"Rod correction," whose signs follow the above rule.

Micrometer eyepiece. A micrometer eyepiece for the telescopic 

alidade has been used for determining distances, and under some 

conditions, on small scale or reconnaissance work, it has proved of 

great value. The principle of this attachment is that if two angles 

and one side of a triangle are known, the remaining parts may be 

found. The length of the base is known by previous measurement, 

being a known space on a stadia rod or the distance between two 

signals left on the ground. The micrometer is used to measure the 

angles between the lines of sight to opposite ends of the base, and 

the result is in divisions of the micrometer head. Constants for 

each instrument are determined,2 and tables have been prepared to 

show the number of turns of the micrometer head on different bases 

to give distances in feet or hundredths of a mile. These tables and 

constants should be tested on measured horizontal bases of different lengths at the beginning of the season.

In establishing a base for use with the micrometer eyepiece its 

bearing should be placed on the sheet for future reference. At new

station (fig. 7) if the line of 

sight is not perpendicular to 

the established base, orient 

as closely as possible, and 

draw a Jme toward one of

FiGUEET.-DiagramillustratmgcorrectionofbaseliBe plofc

long as the paper will permit. Erect a perpendicular to the line of 

sight at one end of the plotted base (a). Draw a line parallel to 

the first line of sight through the other end of the base (6). Measure the distance of the perpendicular from a to the intersection with 

the line through & on the same scale as the base was plotted. This 

distance (#&') is the corrected length of base to be used; then 

ab' = ab sin y. The solution depends on the fact that the angle 

between the lines of sight to opposite ends of the base is so small 

as to be disregarded, and angles V and W are practically 90°. A 

protractor may be used to make the angle y between the plotted 

base at 6 and the line lib' the same as the supplement of the angle 

V+cc between the plotted base and the perpendicular erected at a.

The same principle applies to a vertical base, which may be above 

or below the station occupied.

Instruments. The instruments needed for stadia traverse consist 

of a telescopic alidade (pi. 11, A), with compass attached, a plane 

table (pi. 10, A) not smaller than 15 by 15 inches, with a Johnson

3 See formula for computing these constants in U. S. Qeol. Survey Bull. 650, p. 12, 1924.
TOPOGRAPHIC MAPPING 211

tripod (pi. 10, B), and a standard stadia rod (pi. 12, A). Establish 

the magnetic north line on the sheet at the beginning of work for 

future orientation.

It is necessary that the stadia wires give the correct reading on 

the rod. Therefore, before work is commenced they must be tested 

on a measured base not less than 500 feet in length, and if an error 

is found a correction must be applied to each distance measured. 

It is not desirable to graduate rods to fit the peculiarities of individual instruments.

Correct adjustment for collimation and striding level must be 

maintained. The eyepiece should give a clear-cut image, free from 

parallax. To obtain this throw the object glass out of focus and 

adjust the eyepiece so that the cross wires are perfectly distinct and 

stationary at every position of the observer's eye.

WHEEL TRAVERSE

Revolutions of the wheel may be used for obtaining distances 

along the traverse line. Tables are furnished to facilitate reduction. A hand recorder may be used as a check on long sights. A 

record of distances should be kept until closures are made as a check 

on plotting.

TAPE TRAVERSE

In some parts of the country dense forest and undergrowth make 

it impracticable to carry stadia or wheel traverse, and the lack of 

open tops puts a narrow limit on triangulation methods. Under these 

conditions a form of tape traverse depending on aneroid elevations has 

been devised for obtaining the topography. (See "Aneroid barometer." p. 214.) It is applicable only to scales of 1:48,000 or smaller.

A plane table 9 inches square, with compass attached, and Bumstead tripod are best for the .work. A sight alidade, 300 to 528 feet 

of linen tape or cotton rope (pi. 12, (7), and a pocket compass are the 

instruments required. The tape or rope should be marked at 100- 

foot intervals with red ink in a manner to be clearly understood. 

It should then be run through hot paraffin and the rear end stiffened 

to avoid catching and tangling in the brush. It will be necessary to 

paraffin the tape frequently, especially the rear end, and it should be 

thoroughly dry to have the best effect. Knots and weak places 

should be promptly mended with needle and thread.

The chainman should carry a pocket compass, light ax, and marking crayon. He blazes one or more trees at the end of each tape 

length, and the topographer occupies the point as his next station, 

thus setting up at every station instead of alternate ones. The sights 

are taken in the direction shown by the tape and the signal of the
212 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

tapeman. It is well to number the stations to avoid error in making 

closures. Lines should follow natural features, such as ridges, valleys, and spurs, rather than gridiron the territory. The greatest 

error of the lines comes through the tapeman not keeping a straight 

course.

Adjustment of aneroid elevations should be made daily (see 

"Aneroid barometer," p. 214), and the contours altered to agree, care 

being taken to preserve topographic shape and detail. Adjustment 

of horizontal errors should not be made on traverse sheets.

FOOT TRAVERSE

The method of obtaining distances by foot or animal paces is 

resorted to in timbered countries and mountainous regions without 

roads. Careful measurements of the average pace of an animal or a 

traverseman on a level or a slight incline should be made, and a table 

prepared in hundredths of a mile.

ADJUSTMENT OF TRAVERSE LINES

Large closing errors of traverse lines indicate either a swing in 

direction due to incorrect orientation or a gross error in reading or 

in plotting one or more distances. Gross errors in distance should 

be located between intermediate points of a traverse by running additional traverse lines from them to closing points. By first transferring the lines that fit between control points, the gross error can 

often be located within a short portion of the line, and that portion 

can then be rerun. In areas that have been subdivided by surveys 

of the General Land Office the traverse should be tied to the land 

lines as indicated by corners or by roads and fence lines. A comparison of distances on the traverse with the same distances as indicated by the plats of the General Land Office will often indicate the 

gross error of a traverse within a certain mile and sometimes within 

a less distance. Cumulative errors due to a stadia interval other 

than 100 should, as stated before, be provided against by testing the 

alidade to be used before field work is started. If there is an appreciable error in the interval a table should be prepared so that the 

error may be eliminated in plotting the distances. The adjustment 

of errors that can be eliminated by proper action is not advisable.

The errors in wheel and tape traverses will generally tend to make 

them too long. Foot traverse may be either too short or too long, 

the error depending on the accuracy of calibration and on the character of the area under survey. Plotting errors are usually all in one 

direction for any individual and result in a cumulative error. A 

tendency to plot too long or too short should be overcome as quickly 

as possible.
TOPOGEAPHIC MAPPING 213

Cumulative errors may readily be adjusted by the method of similar 

triangles. Through the end points of the traverse (fig. 8) draw a 

straight line (AB). Measuring from one end, lay off on this line the 

distance (indicated by the control on the regular field sheet) which 

should be the end to end distance of the traverse. Call the end 

which does not coincide with the end of the traverse & or &' according 

to whether the distance laid off is respectively shorter or longer than 

the traverse. Take any convenient point (O) at one side of the 

traverse and at a sufficient distance away to avoid sharp angles of 

intersection with the line AB, and draw lines OA and OB. If the 

traverse is too long, draw a line from & parallel with the line OA and 

intersecting the line OB at point B'. Through point B' draw the 

line B'A' parallel to the line AB. Line A'B' gives the desired length 

of the traverse Ab, as parallel lines intercepting parallel lines are 

equal. From point O draw lines through road corners and the several 

angles of the traverse represented by points 1, 2, 3, etc. The end 

points of the adjusted traverse are represented by points A' and B'. 

To locate other points on the adjusted traverse, begin at either end A' 

or B' and through them draw A'l' parallel to Al, B'5' parallel to 

B5, 5' 4' parallel to 5-4, etc. Point 2, any point on the traverse, 

may be located directly on the adjusted traverse by paralleling the 

direction of A2 through point A' to the line O2 the intersection 2' 

being the desired point. Because of the successively similar triangles 

constructed, the same proportional reduction of distance is carried 

through for each segment as was applied to the end to end length of 

the traverse.

If the traverse is too short by any distance B&' draw a line through 

point &' (fig. 8), parallel to the line OA to intersect line OB extended 

at point B" and proceed as before. A" and B" represent the ends 

and 1", 2", etc., the intermediate points of the adjusted traverse.

In the actual use of the similar triangles method, it is not necessary 

to draw the whole lines from the point O. A segment of each line, 

through points of the traverse slightly longer than will be necessary for the enlargement or reduction, will suffice. By fastening 

tracing paper over the traverse, the construction lines and the 

adjustment can be made directly on the tracing paper and so be ready 

without further effort for transfer to the final field sheet. With 

only a moderately large error to be adjusted, it will be found that a 

careful adjustment of the intermediate road corners or principal 

pouits on the traverse line will suffice. The segments of traverse 

between such points can then be adjusted into place without appreciable error by shifting a tracing of the original traverse line.

The similar triangles method of enlargement or reduction is applicable to plats of other than traverse lines.
214 TOPOGEAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

Adjustments of traverse lines should be made as field work progresses and not allowed to accumulate. Prompt adjustment of travFIGURE 8. Graphic adjustment of traverse

erses will enable the topographer to place a larger proportion of 

future traverse work in final position as it is run and thereby save 

avoidable transfer work with its consequent local adjustments.

ANEROID BAROMETER

CHARACTER

Field of use. In certain classes of work in different parts of the 

country the aneroid, properly supported by spirit-level and verticalangle elevations, may be used to great advantage in the completion 

of topographic detail. In some regions, as in heavily timbered areas 

of moderate relief and especially where distances are determined by 

means of a cloth tape or braided rope (see " Tape traverse," p. 211), 

the aneroid affords the only practicable economical means of deter-
TOPOGBAPHIC MAPPING 215

mining elevations. In order to obtain the best results from its use, 

however, the topographer should realize its limitations as a result of 

its delicate mechanism and its susceptibility to meteorologic influences.

Construction. The aneroid barometer or the aneroid, as it is 

usually termed (pi. 13), consists essentially of a corrugated-metal 

box (vacuum chamber) which has been nearly exhausted of air and 

hermetically sealed. The corrugated metal is so thin and elastic 

that it expands and contracts with the slightest changes in atmospheric pressure. Inasmuch as there is a direct relation between 

elevation above sea level and atmospheric pressure it is only necessary to measure the amount of the movement of the top of the vacuum 

chamber in order to obtain a corresponding difference in elevation. 

The rise and fall of the corrugated top is greatly multiplied by 

transmission through a lever and chain to an index pointer moving 

over the scales as shown upon the face of the instrument. One 

scale (the inner) is graduated to indicate inches corresponding to 

inches of mercury in the tube of a mercurial barometer, and the 

other scale is graduated to indicate elevations in feet corresponding 

to the atmospheric pressure as measured in relative inches of mercury 

shown on the inner scale.

Each aneroid is constructed for use only to the limit of pressure 

for which its scales are graduated and for which nearly the complete 

circumference of the aneroid is used in order to give the largest 

graduations possible. Aneroids are kept in stock in the Geological 

Survey for elevations up to 3,000, 5,000, 6,000, 8,000, 10,000, 12,000, 

16,000, and 20,000 feet, and no instrument should be used or transported beyond the elevation for which it is made.

Scale relations. All Geological Survey aneroids have movable 

elevation scales. Aneroids of the "Tycos " type have elevation scales 

with a uniform spacing of the graduation intervals, but all other 

Geological Survey aneroids have elevation scales with slowly diminish - 

ing graduations. The zero or any graduation of the "Tycos" elevation scale may be correctly used for any elevation setting, but for 

all other types the scales are graduated for a zero elevation scale 

setting of 31 inches on the inner scale and give theoretically correct 

readings of differences in elevation only when the zero of the elevation scale is set at 31. The zero of the elevation scale is placed at 

31 inches in order that all the readings on this scale may be positive, 

although the normal atmospheric pressure at sea level is nearer 30 

inches than 31 inches.

TESTS

Office tests. EachOmeroid is examined in the Geological Survey 

instrument shop before it is issued. The aneroid is placed in a glass 

case, which is also connected with an air pump and standard mer-
216 TOPOGKAPHIC INSTEXJCTIONS OF GEOLOGICAL SURVEY

curial barometer; the inch-scale readings of the two barometers are 

compared for several widely differing pressures, and, if found necessary, the aneroid is reset to its true reading by means of the screw 

in the back of the metal case. The mechanical parts of the transmission are likewise examined and are cleaned and repaired if such 

attention is needed.

Field tests. The best field test for an aneroid is one that is made 

between points whose differences in elevation are known. A sensitive 

aneroid should show a small difference in reading between a horizontal 

and a vertical position of the face. This difference may amount to 

several scale divisions and is due to the extreme sensitiveness of the 

transmission and multiplying devices. If in further doubt as to 

whether the aneroid is working or not, exert a slight vertical pressure 

on the adjusting screw, using a hard point (not a pencil point), and if 

the needle responds by a movement equivalent to several scale 

divisions and moves back when the pressure is released the aneroid is 

probably working. The aneroid should not be opened nor should the 

screw in the back be turned by the topographer. Do not blow into 

the aneroid, to test its sensitiveness, as the breath may rust the chain 

and spring.

USE

The aneroid may be used in several ways as described below, 

depending upon the method of setting the movable altitude scale of 

feet.

Elevation differences. For the most accurate results the aneroid 

should not be used for reading elevations above sea level direct, 

but only for recording differences of elevation, much the same as a 

spirit level. For such use the zero of the elevation scale should be set 

at 31 inches, and this setting should be checked whenever the aneroid 

is read in order to guard against a slipping of the outer scale. Readings should be taken both on arrival at and departure from a station or 

any point where a stop of considerable length is made. Aneroid 

readings should be checked by comparison with previously determined 

elevations whenever opportunity is afforded, as well as at the beginning and end of each day's work. Notes should be kept on a form 

similar to that shown on page 217, for which a card can be obtained 

on requisition.
TOPOGBAPHIC MAPPING 

Record of barometer readings

217

9.915 U. S. Q. S.

Date

Sept. 1...

Place

B. M. 743

Station 1 

1

2 

2

B. M. 857

Time

9 am 

10 am

11 am

12 m

Barom. 

reading

750

870 

860

920 

900

820

Diff. 

elev. by 

barom.

+120

+60

-80

Apparent 

elevation

863

923

843

Adjusted 

elevation

743

870

932

857

Record time and barometer reading on arrival and when leaving a station. 

Never change the barometer adjustment by means of the screw in back.

Elevations direct. In using aneroids with elevation scales graduated 

into unequal parts (all Geological Survey aneroids except those of the 

"Tycos" type), where a scale error of 10 or 20 feet in 1,000 feet can be 

disregarded and especially where the range in elevation between 

resetting points is considerably less than 1,000 feet, scale settings to 

give very close elevation readings referred to sea level may be used as 

described below.

Set the zero of the elevation scale at 31 inches and note the scale 

reading at the occupied station, which in average weather will be 

many hundred feet in excess of the known elevation of the station. If 

this excess is less than 500 feet, use the zero of the elevation scale as 

the true zero and set the scale to read the known elevation. If, however, the excess is greater than 500 feet (in general it will be nearer 

1,000 feet) add a fictitious 1,000 feet to the elevation of the known 

station and then set the elevation scale to indicate it. This device 

will more nearly bring into use those parts of the elevation scale that 

are intended for use and will tend to keep the zero of this scale near 

31 inches, where in theory it should be at all times. The fleur-de-lis 

reading on the elevation scale must be recorded at each new setting of 

this scale and examined before each new reading for elevation as a 

check against possible slipping of the scale.

Example: Assume a station elevation of 1,020 feet above sea level 

and an aneroid reading of 1,850 feet for a scale setting of zero at 31 

inches. Here the scale reading excess is 830 feet. Move the elevation scale to a 2,020-foot scale setting and thereafter assume that the 

1,000-foot graduation is the zero. This expedient is easily kept in 

mind, and further unknown differences in elevation will be known 

within any possible error of 1,000 feet.

Use of " Tycos" type. Aneroids of the "Tycos" type may be used 

for reading direct elevations (referred to sea level), inasmuch as the 

elevation scale is graduated into equal parts and may be moved until 

it indicates the known elevation at any point, such as the initial
218 TOPOGEAPHIC INSTRUCTIONS OF GEOLOGICAL SUBVEY

station or subsequent known elevations reached in the course of mapping. In order to guard against a slipping of the elevation scale during the interval between the readings of the aneroid, a check reading 

of the fleur-de-lis on this scale should be recorded and examined before 

each reading for elevation.

Reading the aneroid. The aneroid should always be held in the 

same position when it is read, and inasmuch as all shop tests and settings are made for a horizontal position, that position should invariably be used. The aneroid should be lightly tapped before each 

reading, using a pencil point or a finger nail. The aneroid should be 

tapped with the same force whenever it is read, and in the same place, 

preferably in the center of the face. A tap on the side or back of the 

instrument will often give a different reading.

Although the aneroid is compensated for changes in temperature of 

its metallic parts, sufficient time should be permitted to elapse for 

the parts to adjust themselves to any large differences in temperature 

between indoors and outdoors. Corrections for air temperature may 

be considered negligible in connection with Geological Survey determinations of differences in elevation by aneroid, as such corrections 

are appreciable only when large extremes of temperature and elevation are combined.

Whenever a station is occupied for a considerable length of time 

the usual record should be supplemented by an additional reading 

made just before departure, for a possible correction. After long 

ascents or descents the aneroid should be allowed a little extra time 

to settle. In general the aneroid responds less quickly to a descent 

than to an ascent.

Care of the aneroid. The proper care and handling of the aneroid 

is the most important factor in its successful use. The aneroid is more 

delicate than a watch, and, because of the screw hole in the back, there 

is constant danger lest dirt or moisture gain access into interior transmission. (See pi. 13, #.) For these reasons the aneroid should be 

transported and handled with care and should be protected from all 

sudden jars and from rain, fog, and dust. It should be carried preferably in a closely fitting vest or small pocket secured by a string. 

This pocket should be periodically cleaned to remove dust. The 

aneroid should not be left loosely on a table or in a drawer with other 

things, but when not in use should be placed in its case and the case 

left where it will be least liable to jar or meddling. The aneroid 

should never be oiled. The transportation or shipment of aneroids 

across country whose elevation is beyond the limits of the aneroid 

range should be avoided.

"Weather influences.~Inasmuch as changes in weather conditions 

are accompanied by considerable fluctuations in barometric pressure, 

topographers dependent upon the aneroid for elevations should be 

on the lookout for changes in local pressure, whether rapid or
U. S. GEOLOGICAL SURVEY BULLETIN 788 PLATE 14

' /../-../-../- ~/\ _/_/_/_ - / - JTO-eo- i-o-tpoo- Jo- LA? ----/--- -- ft BALDWIN SOLAR CHAR7

PLANE TABLE: OR/ENTAT/ON 

U. S. GEOLOGICAL SURVEY

/ /_/_/_/_ _/x/ /__/__/

ros s fig, S cfraw a straight h'n* from point A 

Co tfif proper l*titudi gr#cJutitiGn. Upon tbi'i: fine r;nc/*pvint

four-den the et.rttf.t-//M& of the arrow, one ttirmctJy 

another an *quat <Ji*t*rtc

BALDWIN SOLAR CHART
TOPOGRAPHIC MAPPING 219

gradual, and should make such allowances or corrections as may be 

necessary. Readings obtained during periods of most rapid or 

irregular increase or decrease in the pressure for example, immediately before or after a thunderstorm should usually be thrown out 

altogether. Although a steady barometer affords the best working 

condition, a slowly rising or falling barometer if recognized as such 

will in general afford a working condition practically as good.

BALDWIN SOLAR CHART 

OBJECT

The Baldwin solar chart (pi. 14) is designed to supply a means of 

obtaining true north, particularly for the orientation of the plane 

table in regions where the local conditions will not permit the usual 

determination by compass. When it is so turned that the proper 

pivot point on the arrow and the sun-time point on the local latitude 

ellipse are on a line parallel to the shadow cast by a plumb line upon 

a level table the arrow will point true north.

To use the chart some form of stylus or gnomon that will cast 

a good shadow must be provided. Either a sight alidade with an 

extra long sight vane or a carpenter's 2-foot rule that folds in 6-inch 

sections is suitable for the purpose.

EXPLANATION

The chart consists of elliptical lines indicating the sun's path for 

different latitudes from 30° to 90° N., at intervals of 5°, intersected 

by straight sun-time lines at 5-minute intervals. A separate chart 

is provided for use in latitudes 0° to 30°. The hour lines are heavy, 

and on them are shown intersections of elliptical lines for each degree 

of latitude. The respective hour figures are marked near the ends 

of the hour lines. The 30-minute and 15-minute lines are also solid 

but are lighter in weight and are marked with their proper number 

of minutes after the hour. The 5-ruinute intervals between the 

quarter hours are shown by dashed lines, the ends of the dashes 

being points on the elliptical lines for whole degrees of latitude, thus 

aiding in the interpolation of the line for the sun's path for any particular latitude. The points where the tune lines intersect latitude 

lines are called sun-time points. Figure 1, Plate 14, represents the 

portion of the chart not completely shown in the section between 

4.30 and 7.30 o'clock on the chart proper; it is an auxiliary diagram 

to aid in finding sun-time points between these hours. It is divided 

into segments, representing the tune before and after 6 o'clock, on 

each of which the local latitude is to be interpolated between the 

radial lines and the sun tune between the 5-minute lines shown. 

Points located on Figure 1 must be projected upon the local latitude 

ellipse in a direction at right angles to the sun-tune lines of the 

58515° 28 15
220 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

chart to locate the sun-time points for use. Guide lines are drawn 

on Figure 1 with extensions on the chart proper so that points may 

be projected by eye with, sufficient accuracy.

Figure 2, Plate 14, is a diagram for rinding the correct daily pivot 

points on the arrow. The positions of these points vary according 

to the sun's declination and the latitude of the observer. Morning 

and afternoon pivot points are equidistant from the middle point 

((7) of the arrow.

Figure 3, Plate 14, is a diagram by means of which local mean 

time may be converted into local apparent ,tune. Below it are 

given directions regarding Figures 2 and 3 and the conversion of 

standard to local apparent time.

It will be found convenient in surveying an area of small extent, 

say less than 20' in latitude, to emphasize, by drawing in pencil or 

colored ink on the chart, the curve of the middle latitude of the area, 

producing the curve so as to complete it to the 6 o'clock point. 

Draw on Figures 2 and 1 the lines for the same latitude, radiating 

from points marked "A" and "6," respectively. In Plate 14 such 

lines are drawn for latitude 43° N. Similar lines will be required 

for any material change in latitude.

A convenient device for fixing the daily positions of pivot points 

may be provided by sticking a narrow cardboard strip on the chart 

with one edge directly on the center line of the arrow, by means 

of shellac-alcohol adhesive, and marking on the strip in the form of 

a scale the positions of pivot points for the latitude of the locality 

for selected dates, so that the points for any intermediate dates 

can be found by interpolation. Cut away the portion of the strip 

representing all previous dates and use the corner of the strip at the 

point representing the current date as a stop against which the alidade 

is placed. A strip for each astronomical season should be provided, 

but only the one for the current season should be attached. Whiter 

and spring strips should be placed on the outer side of the center line 

of the arrow and summer and fall strips should be placed on the inner 

side of the arrow, each in their proper turn for use.

When the chart is to be used on the west edge of the plane-table 

sheet it may be more convenient to turn the chart 180° from its 

regular position (that is, point the arrow south), so that the arrow 

will be directly over the projected meridian. The pivot points as 

found in normal position apply in this position also, but the relative 

position of pivot point and sun-time point will be reversed.

A tracing of the essential parts of the chart may be used instead 

of the chart itself. Those parts would consist of the elliptical curve 

for the latitude of the area (with its projection in the auxiliary diagram; see pi. 14, fig. 1), the time lines intersecting this curve, and
TOPOGRAPHIC MAPPING 221

the north-south arrow. As the chart is designed to be used with 

local apparent time and to provide for daily change in declination, 

Figures 3 and 2 on the chart would necessarily be used for converting 

standard time to local apparent time and for fixing from day to day 

the pivot points.

In Figures 2 and 3, Plate 14, the day lines intersect the month's 

curve at date points corresponding with the noon values of declination and equation of time, respectively, for the year 1924 at Greenwich, England. For other years and places a date correction must 

be made as tabulated on the chart under Figure 3. Figure 2 is used 

to obtain pivot points on the arrow, two being required for each day. 

The north one is the a. m. pivot point and the south one the p. m. 

pivot point for any day falling in the half year between March 22 

and September 21, inclusive (that is, when the position of the sun is 

north of the Equator); the relative positions are reversed during the 

other half of the year. When the arrow is pointing north the line 

from the a. m. pivot point to the sun-time point is directed toward 

the sun, and the line from the p. m. pivot point away from the sun.

Example: On July 20, 1925, find pivot point (a) and sun-time 

point (6) at 10 a. m., latitude 43° N., longitude 85° 40' W.

As indicated below Figure 3 of the chart, the time correction for 

85° 40' west longitude is +% day (85% divided by 360). The 

correction for the period March to December in the year 1925 is 

 34 day. The net correction (the algebraic sum of the two corrections) for use both in finding the equation of time and in finding the 

pivot point is zero. The day lines as drawn on the chart are therefore correct for the year and date given. Follow the 20th day line 

through Figure 2 of the chart to its intersection with the July curve. 

From this point of intersection follow an imaginary line perpendicular 

to the day lines to intersect the diagonal latitude line for 43°. From 

this intersection follow an imaginary line parallel to the day lines to 

the central white space of the arrow. That point on the arrow is a 

pivot point for the date given, and, as July 20 is between the spring 

and fall equinoxes and the sun is north of the Equator, it is the a. m. 

pivot point (a). At an equal distance on the other side of point C 

of the arrow will be the p. m. pivot point (a') for the same day. If 

the date had been after the fall equinox and before the spring equinox, 

the first pivot point found would have been the p. m. pivot point. 

To find the sun-time point at 10 a. m. follow the hour line (10) to 

its intersection with the latitude curve 43°, as shown at point 6. 

When the arrow points true north the line ab is in the direction cast 

by a vertical object upon a horizontal plane at the time and place 

given. When the plane table is level and is so turned that the shadow 

cast by a vertical object (the gnomon) falls along the line ab or parallel to it the arrow will point true north.
222 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

The sun-time point for 2.25 p. m. for the same date and place is 

shown at &' having been located on the latitude curve for 43° in the 

same manner as the point for 10 a. m. The line b'a' will be in the 

direction of a shadow cast by the gnomon at 2.25 p. m. when the plane 

table is leveled and turned so that the arrow of the chart points true 

north.

To find the sun-time point at 6.28 a. m. for the same latitude use 

the auxiliary diagram. (Fig. 1, pi. 14.) Follow the radial latitude line 

for 43° from the point 6 to a point three-fifths of the way from the 

6.25 time line toward the 6.30 time line. Project this point horizontally to the curve for 43° latitude; the intersection (e) is the sun 

time point for 6.28 o'clock. All sun-time points between the hours 

of 4.30 and 7.30 are found in the same manner.

For the year 1926, for the same place, month, and day as used 

in the examples given, the net correction to be applied in using Figures 

3 and 2 of the chart would be % day; recede along the month 

curve to a point corresponding to date point 19% before proceeding 

to find the equation of time or the pivot points for the day. For a 

given latitude sun-time points for the same hours on any day are the 

same, but pivot points change daily.

Figure 3, Plate 14, is used to obtain the correction necessary to 

convert local mean time to local apparent (sun) time. This correction combined with the correction for longitude, gives the total correction to convert standard to sun time. To convert standard time 

to local mean time a correction of 1 minute must be made for each 

quarter of a degree of longitude east or west of the center of the time 

belt in which the work is being done, the correction to be added if 

east or subtracted if west. Standard-time meridians ordinarily are 

multiples of 15° of longitude east or west of Greenwich, England. 

Those crossing the United States proper are at longitude 75°, 90°, 

105°, and 120° W. and are central meridians of the eastern, central, 

mountain, and Pacific standard-time belts, respectively. The 

Hawaiian standard-time meridian is 157° 30' W., and there are some 

other exceptions.

To convert local mean time to local apparent time, locate on 

Figure 3 of the chart a day line in exactly the same manner and 

applying the same corrections as in finding the pivot point by means 

Figure 2. Follow this day line, parallel to the day lines drawn, to 

its intersection with the proper month curve. This intersection is 

the date point for that particular day, and the corresponding time 

correction can then be read on the minute scale at the top of the 

figure.

Example 1: For July 20, 1925, longitude 85 ° 40' W. (same date 

and position as in previous examples) find the correction to convert 

standard time to local apparent time for use with the chart. Longitude 85° 40' W. is 4M° east of the center (90°) of the central time
TOPOGRAPHIC MAPPING 223

belt. Applying the correction of 4 minutes for each degree of difference in longitude gives a correction of 17^ minutes, and, as the locality is east of the center of the time belt, the correction is to be added 

to standard time. The result is the mean time for the locality. To 

convert it to local apparent time for use with the chart, the equation 

of time as found from Figure 3 of the chart must be applied as a 

further correction. As the data used are the same as were used in 

finding the pivot points, the net correction to the day lines of Figure 

3 is the same that is, zero. On following the day line for the 20th 

to its intersection with the July curve, it is seen that this date point 

is opposite 6)4 minutes to subtract on the minute scale. (Note that 

in pi. 14 day lines are drawn on fig. 3 only for each fifth day. Quarterday corrections to day lines would therefore be expressed by twentieths 

of the space between the day lines shown.) The total correction to 

standard time to convert it to local apparent time (the sun tune to be 

used with the chart) is the algebraic sum of the two corrections found 

 that is, + 17% 6%, or + HTJ minutes. In applying such a correction it should be approximated as closely as possible although that 

will probably be with more error than ^ minute. It will be found 

convenient to write on the chart, for daily reference, the constant 

corrections to be applied in a given locality. For the locality indicated 

in this example they would be " + 17^± equation of time" and 

"No correction to date lines."

Example 2: On September 12, 1925, at longitude 96° 30' W., convert standard time to local apparent time. The correction on account 

of longitude will be 26 minutes, and the correction for equation of 

time will be +3^ minutes, a combined correction of 22}/£ minutes 

to subtract from standard time.

Other examples are given on the margin of the published chart.

Standard time can be obtained at most railroad stations or telegraph offices and at certain hours of the day by radio. The watch 

used should be set each day to apparent time by applying the constant 

correction for longitude and the daily correction for equation of time.

To orient the plane table by use of the chart, attach the chart to 

the plane-table sheet so that the arrow will be parallel to the line on 

the sheet representing the local meridian, with the point of the arrow 

in a northerly direction. The chart should have been prepared for use 

in the locality in which the work is to be done and the pivot points 

for the day plotted. Level the plane table at the station, select the 

sun-time point for the instant of observation, place the edge of the 

base of the gnomon so that it cuts the sun-time point and the proper 

a. m. or p. m. pivot point, and revolve the plane table until the shadow 

of the gnomon falls parallel to the edge of its base. The gnomon must 

be in a plane perpendicular to a level line at right angles to its base
224

edge that cuts the points on the chart. This may be accomplished 

by fixing a small bubble on the base of the gnomon at right angles 

to its edge or by utilizing the circular-plate bubble on the telescopic 

alidade and exerting just enough pressure on the plane table to center 

the bubble-in the desired direction at the instant of observation. 

When the shadow falls as described, the arrow of the chart points 

true north; the plane table is oriented and should be clamped.

If a carpenter's 2-foot rule is used as a gnomon, open it so that its 

two end sections are together and approximately at right angles to 

the center two sections. Use the center two sections as the base and 

the end two sections as the upright part of the gnomon. The end 

two sections may be spread just enough to leave a narrow slot between 

them, and paper may be pasted on the upper side of the part used as 

a base, with the center line marked upon it. The plane table is then 

 revolved until the sunlight falls through the slot upon the center line 

thus marked. Or the free ends of the rule may be kept together, and 

the plane table revolved until the slightly spreading shadow of the 

upright portion falls equally on the two sides of the base. The line 

from the morning pivot point to the sun-time point is directed toward 

the sun and the line from the afternoon pivot point away from the 

sun. To obtain best results it is necessary to use accurate time and 

to plumb the shadow plane carefully. A long gnomon gives more 

accurate results than a short one.

Example: To orient the plane table at 10 a. m. July 20, 1925, 

latitude 43° N., longitude 85° 40' W., place the edge of the base of the 

special gnomon or of a sight alidade (using the open-sight vane as a 

gnomon) on pivot point a and sun-time point &, with the shadowcasting end toward point a. Revolve the plane-table board until the 

shadow is bisected by a line parallel to the edge used, drawn from the 

center of the base of the gnomon; then the arrow points true north, 

and the board is oriented.

It must be remembered that an orientation using the chart as 

described is a true orientation. In order that lines sighted and 

drawn on the map shall be in their true direction, the line of sight of 

the alidade used must be parallel to its ruler edge. Any angular 

error between the line of sight and the ruler edge will result in a 

closing error for a traverse line that will be directly proportional to 

the distance of the closing point from the starting point. To test 

whether the line of sight and the ruler edge are parallel, stick two 

pins or needles against the ruler edge of the alidade and near its ends 

and sight then on a point about a thousand feet distant. If, without 

moving the alidade, its line of sight also cuts the same point the line 

of sight is parallel to the ruler edge. If the line of sight of a Burkland 

alidade is not parallel to its edge, it can be made so by shifting the 

sight vanes forward or backward from the old screw holes and reset-
TOPOGRAPHIC MAPPING 225

ting them. In order to correct an appreciable error found in a telescopic alidade, place the arrow line of the chart parallel to the line 

joining the pins, then shift the alidade over the chart till the line of 

sight cuts the point sighted over the pins. Now draw a meridian line 

on the chart along the alidade edge. In use, the meridian so drawn 

must be placed parallel to the meridian of the field sheet. When the 

plane table is oriented the angular error in orientation will then equal 

and compensate the error due to the use of that particular alidade.

The length of sight on the field sheet should not exceed the distance 

on the chart between the sun-time point and the pivot point or the 

length of the shadow of the vertical gnomon in use. This will vary 

with the time of day and the season of the year.

ERRORS

The error in azimuth caused by errors in latitude, time, and level 

can be found graphically upon the chart for various conditions, but 

the error m azimuth due to error in time is most likely to be serious. 

At the pole an error in time of 4 minutes causes an error in azimuth 

of 1°. Elsewhere, if the sun time used is not over 3 minutes in error, 

the error in azimuth will usually be less than 1° before 10 a. mi. and 

after 2p.m. and will be least at low latitudes, but at low latitudes the 

error changes more rapidly near these hours than at high latitudes 

and at and near noon is greatest. On June 22 at latitude 30° N. 

an error of 3 minutes in time at noon will cause an error in azimuth of 

about 6°, but at 10 a. m. and 2 p. m. it will cause only 0.5°. At 

latitude 40° N. the error at noon will be less than 2.5°, whereas at 

10 a. m. and 2 p. m. it will be about 1°. To obtain good results with 

the chart in plane-table traverse, the error in time should not exceed 

3 minuteSj and near noon in low latitudes it should not exceed 1 minute. Fast time increases the measured azimuth of a course, and as 

the error is greatest at noon a straight course run throughout one 

day would appear as a slight reversed curve, the morning curve to the 

right and the afternoon curve to the left.

TIME CORRECTION

Sun time can be found as described in the foregoing text. It can 

also be found directly from watch time (whether that is fast or slow) 

if the plane table can be reliably oriented each morning by known 

points by placing the alidade edge against the proper pivot point and 

toward the sun. The edge of the alidade will then cut the true 

latitude curve at sun time, and the difference between that and watch 

time will show the correction to be applied.
226 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

NAMES 

NAMES WITHIN THE MAP

Name sheets. All names that are thought to be appropriate for the 

final map should be assembled on sheets of tracing paper or linen and 

registered over each plane-table sheet. Name sheets must be kept 

current and preferably should be combined into two tracings for the 

north and south halves of the quadrangle map. The importance of 

a complete and authentic record of feature names is so great that 

nothing should be left for memory. All necessary notes should be 

made and all names recorded as soon as they are obtained.

Authority for names. The topographer should utilize local opportunities for obtaining the correct names of all features shown on the 

map and not depend upon correspondence on this subject after his 

return to the office. The general policy should be to conform to 

local usage, but at least two independent authorities for each name 

and spelling should be obtained; and in case of differences in usage, 

spelling, or application, a definite effort must be made to obtain all 

pertinent facts, so that a just decision may be reached in the field or 

made the basis for further reference.

New names. In unsettled or sparsely settled regions it may be 

found desirable to give names to the larger land and water features as 

a means of reference. As such names, by Executive order of January 23,1906, must be referred to the United States Geographic Board 

for consideration and approval before publication, they should be 

submitted by party chiefs, through their division engineer, for action 

by the board before being used. Requests for consideration of new 

names should be accompanied by full information as to their appropriateness. The selection of new names should not be a mere matter 

of whim but should be made with due consideration of their geographic value and significance.

Names to be shown. The map should show names of the following 

features:

.Cities, towns, villages, and other settlements, including all country post offices 

and railroad stations. Where the name of a railroad station differs from that of 

the corresponding post office, both names should be shown, the one most widely 

known being given the greater prominence and the other being followed by " P O " 

or "Sta" as the case may be.

Country schoolhouses.

Country churches, where used as locality names.

Isolated ranches constituting important landmarks in sparsely settled districts.

Important public institutions, such as universities, colleges, and State hospitals.

Railroads (steam or electric). In addition to the name of the railroad, it is 

desirable, as a rule, to give the name of the branch, line, or division, for complete 

office identification.

Highways, turnpikes, and boulevards.

Bridges, ferries, and fords.
TOPOGBAPHIC MAPPING 227

Through trails.

Principal steamboat routes on large lakes and rivers. 

Large canals, ditches, aqueducts, etc. 

Tunnels, dams, lakes, reservoirs, and other public works. 

Lighthouses, lightships, and life-saving stations. 

Parks and cemeteries, if scale will allow. 

Isolated mines, quarries, prospects, and oil wells. 

Isolated furnaces and smelters. 

Civil divisions. 

Reservations. 

Hydrographic features.

Springs, wells, and tanks, especially in arid regions where these features are of 

vital importance. 

Relief features.

MAEGINAL NAMES

The name sheet should be complete copy for all marginal lettering 

(pi. 15) that pertains especially to the map in hand. Data that are 

common to all sheets may be omitted.

The names of the topographers engaged in the mapping of the 

quadrangle must be listed in the margin of the name sheet. (See 

"Topographic authorship," p. 306.) It is not enough that the separate field sheets carry the names of the topographers responsible for 

their mapping.

Each name sheet must carry a diagram showing the area mapped 

by each topographer named in the author legend.

The date or dates of survey should be entered on the margin of the 

name sheet.

The contour interval used on the map and a statement of any 

changes in interval at any given contour should be recorded on the 

lower margin of the name sheet.

MAP BORDERS

Adjoining unmapped areas. If any of the adjoining quadrangles 

have not been mapped, the field work should be carried across the 

border into such quadrangles far enough to obviate the possibility of 

later work not joining it. To insure this joining the over-edge topography should be carried to a road, stream, or ridge, if such a feature 

is near at hand, but if not the topography must be carried at least a 

quarter of an inch beyond the border on the field sheet and will seldom 

need to be carried more than half an inch. Failure to use good judgment in connection with this requirement may make it necessary to 

correct the copper plates where the borders affected are afterward 

joined by future work or to readjust future work slightly in order to 

avoid making corresponding changes on the plates.

Joining previous work. Procure copies of such map borders covering adjoining areas as may be needed. (See "Map borders," p. 178, 

and "Border corrections," p. 302.) Should it appear in the progress
228 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

of field work that the older maps contain inaccuracies or are not up 

to date in the representation of culture, the new work shall be considered standard and the older work revised for such a distance over 

the border as may be necessary to effect a good joining. Should the 

older sheets prove so deficient in quality or so out of date in the 

representation of cultural features that a radical revision would be 

required to make them join the new work, the topographer must at 

once report the failure to join to the division engineer. Where new 

work practically though not exactly joins engraved or published work, 

expediency warrants a slight readjustment of the new work to fit 

the old.

Datum of previous work. Where the horizontal datum upon which 

the map of an adjoining quadrangle has been published differs from 

that upon which the map of the new quadrangle is drawn, proper 

corrections to the projection lines must be made before comparing 

the joining of the topography on the two maps.

OTHER QENERAL FIELD INSTRUCTIONS

Protection of field sheets. Field sheets should at all times be protected from injury or loss. When a field sheet is in use on the plane 

table it should so far as practicable be protected by heavy cover 

paper supplied for the purpose, in which a hole may be cut for each 

day's work.

Identification of field sheets. Each separate piece of map manuscript, oversheet, or map material should be marked with the names 

of the State and quadrangle, the date, scale, contour interval, coordinates, authors' names, and other appropriate information. If more 

than one engineer works on a single sheet the areas covered by the 

several men should be indicated on the field sheet.

Information tracing. The use of an information tracing is to be 

encouraged. On it should be assembled, over the map features 

for which added information is to be given, all data that can not be 

legibly penciled on the original. Such information is especially 

needed where the original has been rubbed and sharp penciling is 

difficult, where only the inked colors will clearly differentiate between 

closely spaced features, where detached contours might be mistaken 

for water features or the reverse, or where the desired treatment of the 

feature may be beyond the map scale and yet, because of the apparent 

need of showing it, the topographer wishes to leave its proper delineation for office determination.

Separation of oversheet data. Separate tracings should be prepared 

and submitted for names (p. 226), woodland outlines (p. 255), road 

classification (p. 256), elevations (p. 241), and information, and no 

two or more of the classes of data above listed should be submitted 

on a single tracing. The placing of more than one class of data, as
TOPOGRAPHIC MAPPING 229

listed above, on a single tracing will cause delay and confusion in 

the office operations and may be the cause of the inadvertent omission 

of essential data on the final sheets. The data on oversheet tracings 

should be kept current and not allowed to accumulate.

Monthly field report. Monthly reports of field work (one copy to 

division chief, one to section chief, and one to chief topographic engineer) should be mailed not later than the first day of the succeeding 

month. The name of the sheet or project on which work has been 

done should be plainly indicated. A separate report should be submitted for each sheet or project. (See "Monthly field reports," 

p. 272.)

Field inking. No inking on final sheets should be done in the field 

unless authorized. Where an explanation is necessary, it should be 

placed on the information tracing.

MAPPING OF CULTURAL FEATURES

Definition. The cultural features are those features of the terrain 

that have been constructed by man, such as roads, buildings, and 

canals; those features designated by man but only partly constructed 

on the ground, such as boundary lines; and all names and legends.

Features to be mapped. The following cultural features are to be 

shown on all topographic maps, either by the standard symbols 

shown in Plates 18-23 or by means of other conventions, which are 

described in the text.

Aqueducts, water and oil pipes.

Artificial depressions.

Bench marks.

Boundary monuments.

Bridges.

Buildings.

Canal locks.

Canals and ditches.

Cemeteries.

Civil boundaries.

Coke ovens.

County subdivisions.

Cuts and fills.

Dams.

Ferries.

Fords.

Furnaces and smelters.

Levees.

Life-saving stations.

Roads. Roads should be penciled as final copy for inking according 

to the distinctions given below.

(a) Good public motor roads should be indicated by solid double 

parallel lines. Good motor roads are defined as those, public roads

Lighthouses, etc.

Location monuments.

Mine dumps.

Mines and quarries.

Mineral monuments.

Oil and gas wells.

Power-transmission lines.

Public-land lines.

Railroads.

Reservoirs.

Roads.

Steamboat routes.

Trails.

Transit-traverse stations.

Triangulation points.

Tunnels.

Useful elevations.

Wharves, etc.
230 TOPOGKAPHIC INSTBUCTIONS OF GEOLOGICAL SUKVEY

that may be used for automobile travel the greater part of the year 

and include all Government, State, county, or other public roads in 

such condition as to be available for such travel; all main or through 

roads in sparsely settled regions, regardless of condition; and all city 

streets and park drives open to the public.

(&) Poor public motor roads and private roads should be indicated 

by dashed double parallel lines. Poor motor roads are defined as 

those public roads which through disuse or neglect have become 

impassable for automobile travel or can not be traveled without risk 

to an automobile. Public roads that are passable for wagons but are 

not good for motor use should be classed as poor motor roads.

Public roads are defined as those built or maintained by the Federal 

Government, a State, or a subdivision thereof. Private roads include 

all neighborhood roads in rural districts (except those of sufficient 

length and importance to be regarded as through routes, as defined 

above); all lanes and stub roads to farms, country houses, or institutions; and cemetery drives and race tracks. Private roads are 

further defined as those roads built or maintained by private or 

neighborhood funds.

It should be especially noted that public roads should be shown by 

full or dashed lines according to their condition as good or poor for 

motor use, whereas private roads should be shown by the dashed 

symbol irrespective of condition.

Lumber or wood roads are in general to be omitted, but any principal through lumber roads that may be properly considered permanent cultural features are to be shown by the dashed symbol. In 

regions where winding roads are numerous and where there are few 

recognizable map features, the occasional plotting of the forks of a 

prominent lumber road is advisable if the two roads at the forks are 

of nearly equal prominence.

On the 1:192,000 scale no distinctions are to be made between 

roads of different classes. They are all to be drawn as solid double 

parallel lines.

Field penciling of roads. Roads should be penciled with a uniform 

width which will reduce approximately to the width used by the 

engraver on the scale of publication. As few draftsmen can legibly 

ink on any scale a double-lined road with a space between the parallel 

lines less than that representing the space between two lines about 

75 feet apart when plotted on a scale of 1:48,000, such a plotting 

may be taken as a standard for penciled road copy, unless the map 

scale or width of the road is such that a greater width can be plotted 

to scale. Pikes, drives, and boulevards materially wider than the 

limit above specified should be shown to scale. On maps drawn on 

large special scales all roads should be shown with their individual 

widths wherever they can be plotted.
TOPOGKAPHIC MAPPING 231

Buildings in general. The map must show all buildings of a permanent character, such as dwellings, public buildings, shops, factories, 

and other industrial establishments; it should be reliable not only as 

to their location but also as to their orientation that is, the way 

each building is set with respect to the points of the compass.

Uninhabitable dwellings, whether farmhouses or miners' or lumbermen's cabins, are to be shown only where they constitute landmarks in regions of sparse culture.

The conventional black square is to be used for all buildings except 

those whose dimensions plotted to scale exceed the size of the symbol, 

which should be shown with their individual plan outlines. On 

large-scale maps all houses may have to be thus shown.

On the 1:192,000 scale only isolated houses in the country should 

be shown; those in towns and cities should be shown by a conventional symbol representing the solidly built up area.

Houses should not be shown as contiguous to the roads unless the 

distance that separates them from the edge of the right of way is so 

small that it can not be plotted on the scale of publication.

House Hocks. Detached houses in residence portions of cities, 

suburbs, and villages are to be shown separately wherever possible. 

If the scale does not permit individual houses to be shown indicate 

the group by a solid block, in accordance with the following specifications. Distances between houses are to be understood as from 

center to center, and length of street blocks as between building lines 

and not from center to center of streets.

1:48,000 scale field work for publication on. 1:J$2,500. Houses, where evenly or 

nearly evenly distributed, should be blocked where the distance between 

them is less than 100 feet for example, in a 500-foot street block six houses 

evenly distributed should be blocked, but five houses or less should be shown 

separately.

1:24,000 or 1:31,680 scale field work for publication on either scale. Houses 

should be blocked where the distance between them is less than 50 feet for 

example, in a 500-foot street block 11 houses evenly distributed should be 

blocked, but 10 houses or less should be shown separately.

1:24,000 scale field work for publication on 1:62,500. Houses less than 100 feet 

apart should be blocked.

1:96,000 scale field work for publication on 1:125,000. Houses less than 200 

feet apart should be blocked.

These specifications are set up in order to standardize the blocking 

of houses, to reduce the cost of field work in areas of heavy culture, 

and to afford specific copy for inking and for engraving. The decision as to the blocking of houses should be made in the field, and the 

data should be properly penciled«on the field sheet.

Business and residence blocks. Business and residence blocks 

should be distinguished by the width of the block, the residence 

blocks being made distinctly narrower than the business blocks.
232 TOPOGKAPHIC ItfSTKTJCTIONS OF GEOLOGICAL SURVEY

Churches and schoolhouses. Churches are to be distinguished by 

a cross and schoolhouses by a pennant, so attached to the house 

symbol as to point at right angles to the roadway. In centers of 

dense culture these distinctive symbols should be omitted. Buildings used both for schools and "for religious services should bear the 

school symbol.

Railroads. Railroads, whether operated by steam, electricity, gasoline, or other motive power and including all railroad lines listed in 

the Official Railway Guide should be shown by the broad-spaced 

symbol representing a railroad of any kind.

Electric trolley lines carrying passengers only and not issuing 

tickets with baggage-checking privileges should be shown by the 

close-spaced symbol.

Double tracks, railroad yards, spur tracks, and switches should be 

shown so far as the scale will permit. Separate railroad lines in 

juxtaposition and parallel tracks belonging to the same road should 

be differentiated by placing the crossties as shown on the symbol 

chart.

Tramways should be shown by the broad-spaced symbol. Aerial 

tramways should be shown by a broken line and with the name where 

there is space.

Railroads or electric trolley lines within a roadway should be shown 

by fine cross lines having the same spacing as those on the corresponding line outside of the road.

Railroad surveys. A railroad alinement is made up of tangents 

and curves; most curves are compound, and many leave the tangent 

on an easement curve. Reversed curves usually have 200 feet or 

more of tangent between them. In traversing railroads these facts 

should be kept in mind, and the resulting plot should show a line free 

from abrupt deflections that are not found on the ground. Railroad 

azimuths should be well checked, by fore and back sight methods 

when necessary.

Railroad crossings. Grade crossings should be shown by continuous 

railroad and road symbols; a railroad crossing over a road by a broken 

road symbol; and a road crossing over a railroad by a broken railroad symbol. Do not use the words "overhead" or "underhead.' '

Railroad station buildings. A railroad station building is to be 

treated like other buildings, except where its symbol is carried conventionally across the track to indicate the location of a train stop 

that is not otherwise clearly indicated by the position of the station 

name or by the culture. The conventional station symbol should 

not be drawn across the track where there is no station building, and 

its use should generally be confined to small villages or cities.

Bridges. Symbols should be used to show all road bridges across 

double-line streams and all road bridges across single-line streams
TOPOGRAPHIC MAPPING 233

in sparsely settled regions or wherever the existence of the bridge is 

vital to the use of the road. Bridge ends should not be shown for 

viaducts over railroads, railroad yards, roads, or streams except on 

large-scale maps (1:24,000 or larger). Names of large viaducts, 

however, should be shown.

Drawbridges on roads and railroads should be shown by a separate 

symbol. Ordinary bridges and trestles on railroads are to be omitted. 

The bridge symbol should also be omitted wherever its presence 

would impair the legibility of the map.

The footbridge symbol should be used only where the bridge is of 

local importance in general only where it is isolated and only where 

the scale permits. Footbridges should always be shown on large-scale 

maps.

Ferries. Ferries are to be shown by symbol wherever the stream 

is wide enough to permit; where it is too narrow the word "Ferry" 

should be written. Names of ferries must be put on the map.

Fords. The symbol for a road ford is similar to that used to 

represent a private road; the symbol for a trail ford is similar to 

that used for a fence of any kind. On large-scale special maps the 

route of the ford, if difficult to follow, should be shown accurately.

Trails. Distinction should be made between good pack trails and 

poor pack or foot trails, the former being indicated by short heavy 

dashes and the latter by small dots. In mapping trails the topographer should consider their relative importance as a means of communication. Thus in mountain and desert regions, especially in 

the far West, where traveling is done largely by trail, he should take 

pains to map every trail in use, giving its name, if known; in the 

more densely populated districts, where railroads and wagon roads 

are plentiful, he should show only such trails as lead up mountains 

or through unimproved areas not readily accessible otherwise. A 

mere "way through" not regularly traveled does not constitute a 

trail.

Steamboat routes. All steamboat routes on lakes and rivers over 

which a regular public service is maintained by ferries or passenger 

boats should be indicated by fine dashed lines and the words "Steamboat route."

Canals and ditches. Canals, whether for navigation, irrigation, or 

drainage, should be shown by double-line symbol if their actual 

width can thus be indicated on the scale of publication; otherwise, 

by a single line. Abandoned trunk canals constituting prominent 

topographic features will be indicated by the long-dash symbol.

The mapping of irrigating ditches is to be restricted to the main 

feeders; laterals are not to be shown except on large-scale maps. On 

smaller scales only those ditches that constitute important landmarks in regions of sparse culture are to be indicated.
234 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

Canal locks. The lock symbol should point upcurrent. The 

symbol showing both the upper and lower gates will be used only on 

scales large enough for their individual plotting.

Aqueducts; water and oil pipes. Only the principal aqueducts 

and pipe lines should be mapped.

Power-transmission lines. The alinement of high-voltage (100,000 

volts or more) trunk power-transmission lines should bo obtained in 

the course of the field survey and shown on the topographic maps. 

Sections of power-transmission lines within corporate limits and 

lateral distribution systems should be omitted. Trunk lines are in 

general built on private rights of way and in most parts of the country 

are placed on steel towers.

Tunnels. Tunnels of all kinds, whether on railroads, roads, or 

canals, should be shown by the tunnel symbol; the route of the tunnel should be indicated by double broken lines.

Dams. Permanent dams on streams, lakes, or reservoirs should 

be indicated by a heavy line. Where a wagon road follows the top 

of the dam, the road is to be shown in its correct place, the road line 

on the upstream side being thickened to represent the dam.

Reservoirs. The shore line used to represent a reservoir should 

correspond to the normal full stage of the reservoir that is controlled 

by the dam. Where the penciled copy for reservoirs and the adjacent 

contouring are not clear, these details should be explained elsewhere 

by means of a large-scale sketch.

Levees. Levees may be represented by the hachure symbol alone 

where the levee is too small to be shown to scale by the contours, 

but such representation should be confined to large-scale maps or 

to levees that are conspicuous or important features.

Cuts and fills. The rule as to the use of hachure symbols for the 

representation of levees also applies to cuts and fills, but inasmuch 

as cuts and fills are in general sufficiently shown by the contouring 

and by the presence of roads, railroads, or waterways their further 

representation by hachures should be confined to special cases or 

scales.

Artificial depressions. Artificial depressions, such as are found 

above railroad and highway fills, should be indicated by hachured 

contours. (See "Depressions," p. 251.)

Mine dumps. The use of the hachured mine-dump symbol should 

be chiefly confined to large-scale special mining maps where all dumps 

are to be hachured. On standard-scale maps only those mine dumps 

should be hachured that for some reason constitute important 

topographic features not indicated by the contouring. It is impossible to frame a specific rule for general application, and instructioDS 

should be obtained for each map.
TOPOGRAPHIC MAPPING 235

Wharves, etc. Wharves, docks, jetties, breakwaters, and similar 

structures should be indicated by firm sharp lines and shown with 

such detail as the scale of the mapping permits.

Lighthouses, etc. Lighthouses and light ships should be located 

on all maps, whatever the scale.

Life-saving stations. Life-saving stations in general should be 

shown by the symbol followed by the letters "LSS," but life-saving 

stations of the Coast Guard should be shown by the same symbol 

followed by the letters "CG."

Cemeteries. Cemeteries should be shown with .^heir actual outlines, and the name should be used if it is well known and there is 

space, otherwise a cross within the outline or the letters "CEM" 

alongside. Small private cemeteries that are too small to plot to 

scale may be conventionally shown by a small square inclosing a 

cross but should be omitted unless they constitute landmarks in a 

thinly settled country.

Mines and quarries. Relatively important commercial mines and 

quarries should be indicated by the pick and hammer symbol, which 

should be engraved. The commercial character of a mine may 

usually be judged by its possession of railway switches or docks to 

facilitate transportation or of permanent equipment. Lack of these 

would exclude from the engraved maps mines or pits worked only to 

supply neighborhood demands.

In sparsely settled regions, where there is little culture to be 

represented, isolated mines, quarries, and even prospects (sawbuck 

cross) that constitute landmarks and are widely known should be 

shown with their names, which should be engraved.

Mineral prospects exceeding 10 feet in depth, country coal banks 

or mines worked only for local supply, and abandoned mines should 

be plotted (hiked in red) for the advance sheet only. The copy 

should clearly distinguish between mines that are to be inked in 

black for publication and those that are to be inked in red for the 

advance sheets only, and this distinction is usually most clearly 

indicated on the information tracing.

On special-scale mining maps aU mining features including prospects 

may have to be engraved. It is for this purpose that the special 

mine symbols for shafts, tunnels, drifts, etc., are provided.

Oil and gas wells. Producing oil and gas wells should be indicated 

and engraved. Where such wells are so abundant as to be practically 

indistinguishable, only the approximate outline of the pool (by 

dashed lines) is to be shown.

Furnaces and smelters. No additional conventional sign is used 

to represent furnaces, and in many areas it will not be practicable or 

desirable to name them. In many sparsely settled regions, however,

58515° 28 16
236 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY l!

the furnaces are the most important and persistent landmarks. 

They have well-recognized names, which cling to the localities even 

after the practical disappearance of the furnace itself. In such areas, 

therefore, it is desirable that the names be given, even if nothing 

remains but a ruined stack. The same rule applies to smelters, 

except that those located should be restricted to smelters in active j 

or prospective operation. |

Coke ovens. Only coke ovens connected with mines in operation \ 

are to be shown on the engraved maps. I

Civil boundaries. All civil boundaries, whether national, State, i 

county, district, civil township, reservation (national or State parks, 

forests, monuments, bird and game preserves, Indian, military, or fi 

lighthouse), land grants, corporations (city, town, or borough), ( | 

parks, and cemeteries, are to be shown on the map by their respective / 

symbols. Special effort should be made by field parties to locate 

such boundaries with accuracy and directly from triangulation points 

or transit-traverse lines if practicable.

Necessary descriptions, survey notes, and plats of all lines of 

importance should be consulted or procured. Data on national or 

State reservation boundaries should be obtained at or through the , 

Washington office prior to the beginning of the field work. Data ( 

on minor civil subdivisions can best be procured locally, while the 

survey is in progress. Many boundaries are obscured or obliterated 

by natural causes or artificial works; some were indifferently marked 

to begin with; others have lost some or all of their marks. Information from local settlers may often prove of value and save time 

and effort in the search for such obliterated lines. The topographer 

will do well to avail himself of such information; at the same tune 

he should bear in mind that the word of a resident is not to be taken 

as authoritative, but merely as supplementing information from 

official sources.

Where lines are found incorrect in azimuth and distance as the 

result of field errors, it is a fundamental principle that the line marked 

on the ground is the de facto boundary and is to be shown on the , 

map in its actual position, regardless of what the statute calls for. ; 

This principle may necessitate the accurate locating of a number of 

monuments, so that each error in the alinement may be designated 

at the particular spot at which it exists.

Some civil boundaries are defined by statute to follow natural 

boundaries, such as streams or divides between drainage basins. 

Those following large rivers should be given special attention, as 

they may be variously defined as following the middle of the stream, 

its main current, or one of the banks. (For descriptions of national 

and State boundaries see Bulletin 689; see also references listed 

separately by names of boundaries, pp. 322-328.)
TOPOGRAPHIC MAPPING 237

Boundary monuments. All monuments on national, State, and 

national park boundaries must be located in the field and represented 

on the map with the side of the open square oriented with the 

direction of the boundary line and with its designating number 

alongside. On other boundaries monuments occupying controlling 

positions, such as corners or important crossings, should be located.

County subdivisions. The policy of the Geological Survey is to 

show only such county subdivisions on its topographic maps as 

appear reasonably permanent in character and in location, and to 

exclude from its maps any representation of county subdivisions that 

are subject to frequent changes at county elections. Topographic 

engineers should therefore become familiar with the legal system of 

county subdivision in the States in which they are working and 

should seek local advice and facts upon which to base appropriate 

action or a request for instructions.

In general, counties are divided into smaller units that bear different designations in different States or even different designations in 

different counties in the same State. In the States organized from 

the public domain and surveyed under the public-land system the 

so-called congressional township has usually been taken as the organization unit. In New England and in parts of the country affected 

by New England migration are found town units, in which are vested 

many of the powers that in the South and in the newly settled West 

pertain to the county. Some counties in Maine, New Hampshire, 

and Vermont, in addition to the towns and cities that are the only 

regular subdivisions, have partly organized or unorganized territory 

laid off by the States as plantations, gores, grants, purchases, locations, and islands.

The following summary, taken from Census reports, gives the names 

of the primary divisions of the county in the several States and outlying Territories:

Alabama.________________ Election precincts.

Alaska.__________________ Recorders' districts.

Arizona._________________ Election precincts.

Arkansas.._______________ Townships.

California._______________ Judicial townships.

Colorado.________________ Election precincts.

Connecticut__-_______-_-_ Towns.

Delaware._______________ Representative districts.

District of Columbia. _____ None.

Florida._________________ Election precincts.

Georgia__________________ Militia districts.

Hawaii._________________ Election districts.

Idaho..__________________ Election precincts.

Illinois.___________________ Townships and election precincts.

Indiana_.________________ Townships.

Iowa--_ Townships.
238 TOPOGKAPHIC INSTRUCTIONS OP GEOLOGICAL SURVEY

Kansas__________________ Towns-hips.

Kentucky ________________ Magisterial districts.

Louisiana- ______---___--_ Police jury wards.

Maine___________________ Towns and cities.

Maryland._______________ Election districts.

Massachusetts____________ Towns and cities.

Michigan._______________ Townships.

Minnesota______--____-_- Civil townships and townships and ranges.

Mississippi _______________ Beats.

Missouri _________________ Townships.

Montana.________________ School districts, townships, and election

precincts.

Nebraska ________________ Townships and election precincts.

Nevada __________________ Townships and election precinc ts.

New Hampshire __________ Towns and cities.

New Jersey ___---_-_--__ Townships.

New Mexico._____________ Election precincts.

New York-1 ______________ Towns and cities.

North Carolina ___________ Townships.

North Dakota ____________ Civil town ships, election precincts, school

townships, and school districts.

Ohio..___________________ Townships.

Oklahoma.-.-----------.- Townships.

Oregon __________________ Election precincts.

Pennsylvania.____________ Townships, cities, and boroughs.

Porto Rico_____---____-_- Barrios.

Rhode Island.____________ Towns and cities.

South Carolina ___________ Townships.

South Dakota-___________ Civil townships, election precincts, school

townships, and school districts.

Tennessee ________________ Civil districts.

Texas____________________ Commissioners' precincts and justices' precincts.

Utah.___________________ Election precincts.

Vermont______----__.__-_ Towns and cities.

Virginia..________________ Magisterial districts.

Washington ______________ Election precincts.

West Virginia.._ __________ Magisterial districts.

Wisconsin________________ Towns.

Wyoming-_______________ Election districts and election precincts.

Public-land lines. In the so-called public-land States all lands 

that have at any time been subdivided or " sectionized" by the 

General Land Office must be shown on the topographic maps of the 

Geological Survey by indicating such township and section lines as 

have been run and have been approved by the Land Office and are 

not under suspension, and by showing by a distinctive symbol such 

public-land survey corners as have been found in the course of the 

topographic survey, after a reasonably diligent search and through 

inquiry. The relative strength or weakness of the land net will be 

indicated by the proportion of found to unfound corners. All corners 

are theoretically marked on the ground, but in practice many are
TOPOGRAPHIC MAPPING- 239

difficult or even impossible to find. (For a description of the publicland survey system see pp. 368-376.)

In settled country, where land lines often become property lines, 

there are section-line roads and fences, and there the construction of 

a public-land survey net is usually simple. But in unsettled country 

or in settled areas where the roads or fences seldom conform to section lines it is necessary to find on the ground and locate on the map 

enough section corners to enable the engineer to construct a land 

net built up from the Land Office plats and notes and tied to the 

section corners found. Such a land net when superimposed upon a 

topographic map will indicate the true, theoretical, or approximate 

location of each land line and corner with respect to the topography, 

according as corners are found or are only located from the plats and 

notes.

The land net should be completed in the field and compared with 

published maps of adjoining areas, and not left for office adjustment. 

If the Land Office plats can not be reconciled with the topography, 

even though a few isolated corners may be found, the section or 

township lines or both may be omitted, and a note added to the map 

to this effect. The note will be engraved and will list the omitted 

townships. (See "Land lines and topography," p. 307.)

Search j'or public-land corners. The tune warranted in search for 

obscure corners will be generally determined by the probable regularity or irregularity of the net and the proximity of corners already 

found. The less local information is at hand obviously the greater 

the necessity for pioneer hunting for the needed land ties. Diligent 

search must be made on the ground for all corners believed to exist 

near the line of survey. Hence the best judgment must be used 

before giving up the search.

In a region where there are few roads on section lines assistance in 

finding corners may be had by using an oversheet of tracing paper or 

linen upon which has been laid out to field scale either a single 

typical township or an entire land net covering the area to be mapped, 

built up in advance from the Land Office plats and notes. Such is 

a tracing, placed in position over a field sheet as soon as the first 

land corner has been plotted, will indicate graphically the theoretical 

location of all other corners; and as more corners are found the further 

placements of the tracing become more serviceable as a guide.

The topographer should be thoroughly conversant with the system 

of rectangular land surveys and the intricacies peculiar to it. 

Acquaintance with the standard monuments used for the several 

classes of land corners, their marks, and their bearing trees, as well 

as with the manner in which blazes on trees become overgrown with 

bark, will prove most useful both in searching for corners and in
240 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL, SURVEY

determining their authenticity where this is in doubt. (For a discussion of the public-land survey system see p. 368.)

Location and mineral monuments: Monuments erected as permanent reference marks for the location of mineral and other claims 

(often designated as USLM's or USMM's) must be located with the 

same accuracy as land-survey corners and if practicable by planetable triangulation and should be shown on engraved maps with their 

designating numbers.

Authority is vested in the United States mineral surveyors to 

establish "mineral monuments" where no land-survey corners exist 

in the immediate vicinity of claims and to number them serially in 

each State. A former practice was to establish so called "location 

monuments" in each separate mining district, numbered serially in 

each district, and those already established are still so designated. 

A careful distinction must be made between the two systems, and 

the numbers of the monuments must be obtained; the abbreviations 

used are, for example, "USLM 2," "USMM 237."

Triangulation points and transit-traverse stations. The triangulation points and transit-traverse stations to which the topographic 

mapping of the quadrangle has been tied must be accurately indicated 

on the topographic maps with the open triangle and dot symbol, 

which will be engraved. Wherever practicable the elevation of each 

of these points and stations should be determined by levels, stadia, 

or vertical angles and be stamped on the tablet or post that constitutes the permanent mark. If vertical angles have been used, the 

letters "V A" are to be stamped below the elevation figures.

Level bench marks. All permanent and supplementary bench marks 

must be diligently looked for and accurately located on the field 

sheets with a view toward inking them on the final office drawings. 

Topographic field parties should not rely upon finding bench marks 

by search alone but must locate them systematically with the aid of 

printed or typewritten descriptions or of notes furnished by the level 

parties. Bench marks should not be shown where in areas of heavy 

culture, their representation on the map would be illegible.

Indicate the exact position of the bench mark with a small needle 

hole and right-angle cross in order that its true relation to the side of 

the road, cross roads, railroad, or house may be evident. Indicate 

all bench marks, both permanent and supplementary on the field 

name sheets, with letters "BM" for the permanent bench marks and 

with elevations for all.

Vertical-angle bench marks. Where it is not expedient to run lines 

of third-order levels into or across mountain areas provision is made 

for the establishment of vertical-angle bench marks and for their 

permanent marking on the ground. Such bench marks must be well 

tied to one or more level bench marks by a system of well-checked
TOPOGEAPHIC MAPPING 241

reciprocal vertical angles from plane-table stations within the main 

plane-table control triangulation net of the quadrangle. Verticalangle bench marks should be located at triangulation points or other 

conspicuous summits so far as practicable and should be kept away 

from roads or other routes of travel. Where, however, a verticalangle bench mark is established near a road it should be designated 

"VABM" in order that there may be no doubt of its character, but 

on summits the designation will be the same as level bench marks, 

"BM."

Reporting bench marks not found. Bench marks must be found or 

reported as not found. Therefore, report promptly to the chief topographic engineer any bench marks (permanent or supplementary) 

that have been looked for and either not found or found to have been 

disturbed, in order that the office records and the level-bulletin 

manuscripts can be corrected. Also indicate them on the field name 

sheet as not found.

Control points adjacent to cultural features. In plotting cultural 

features adjacent to horizontal-control points or in plotting bench 

marks adjacent to cultural features the copy for inking should be 

accurate and clear as to the relation between the culture and the 

control shown.

Useful elevations. In addition to the permanent and supplementary 

bench marks, reliable elevations that have been determined by means 

of leveling or stadia at road corners, summits of mountains and hills, 

water surfaces of lakes, ponds, and wide rivers, prominent high points 

in roads, section corners, boundary monuments, and other appropriate places should be penciled on the field sheets. In selecting these 

elevations for the maps, the topographic engineer should bear in 

mind that it is the policy of the Geological Survey to publish, either 

on the advance sheets or on the engraved maps, only such elevations 

as have a definite working value; therefore only those elevations 

should be finally penciled on the field sheets that can be identified 

on the ground and on the map both in elevation and in location.

The distribution of useful elevations on the final field sheets should 

be based on a spacing of about half a mile apart for maps plotted on a 

field scale of 1 :48,000 and about 1 mile apart for a £eld scale of 

1 : 96,000, and in proportion for other field scales. Shorter spacings 

should be used, however, wherever features of unusual importance 

or large differences in elevation are involved; and under certain 

conditions, when specially authorized, even more elevations may be 

indicated.

Elevation tracing. If the field sheets are drawn on a scale of 1 : 31, 

680 or on a larger scale, all elevation data must be assembled on an 

oversheet tracing in the field, as the small elevation figures that have 

been placed on the field sheets themselves are ever in danger of being
242 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

erased or so obscured as to be illegible. The point of application for 

the elevation given should be clearly indicated on the tracing.

MAPPING OF DRAINAGE FEATURES

Drainage features defined. The drainage features of the terrain 

are those features representing water, such as flowing streams, lakes, 

and shore lines, and those features indicating some degree of wetness, 

such as intermittent streams, marsh, and glaciers.

Features to be mapped. The drainage features to be shown on all 

topographic maps, by standard symbols (see pis. 18-23) or by means 

of other conventions as described in the text are listed below.

Glaciers. 

Lakes. 

Marshes. 

Shore lines.

Sand.

Springs.

Streams.

Wells and water tanks.

Tidal shore lines. On all topographic maps of the Geological 

Survey the line of mean high tide is considered to be the shore line. 

In determining the margin of mean high water, exclude the highest 

(semimonthly) tides and take the average of the usual high tides as 

generally marked by the limits of vegetation.

Use of Coast and Geodetic Survey charts. The fullest practicable use 

should be made of the charts of the Coast and Geodetic Survey in 

mapping coastal areas. The charts should be photographed to the 

scale of the field work, and where they represent recent work on a 

scale as large as Geological Survey field work, or larger, the shore-line 

data should be transferred to the field sheets. The data taken from 

charts must be instrumentally checked to insure their correct adjustment and tie to the Geological Survey topography, and afterwards 

they must be examined in detail for possible changes.

MarsJies in general. Both fresh and salt marshes should be represented by the symbol for marsh in general, and no distinction should 

be made between them in field work. Marsh or swamp land is defined 

as land that is not suitable for cultivation without first being drained. 

The outlines of marsh areas should be indicated in dashed lines and 

inked but will be engraved only under certain conditions, which are 

described on page 291.

Marshes on low coasts are as a rule traversed by a network of 

tidal channels. Unlike the rills in mud flats, these channels are 

fairly permanent in location, and those that exist at mean high tide 

should be mapped individually so far as the scale permits.

Submerged marsh. Marsh lands that are partly submerged for 

many months each year are to be differentiated from ordinary 

marshes and represented by a symbol combining water and marsh 

tufts. The inking copy should be clearly indicated.
TOPOGRAPHIC MAPPING 243

Wooded marsh. No symbol has been provided for wooded marsh 

other than that offered by the green woodland overprint over the 

marsh symbol. Areas of wooded marsh should therefore be included 

in the areas shown on the woodland tracing, but with a note alongside so that they will not be inadvertently stricken out in the office.

River shore lines. Broad rivers offer a perplexing problem to the 

topographer, as, owing to their periodic fluctuations, their width 

often varies considerably with their stage. The general rule is that 

the width shown should correspond to the normal stage. The normal 

stage may be defined as that water level which remains nearly stationary for the greater part of the year, and therefore it excludes all stages 

of relatively short duration resulting from floods, whether periodical 

or out of season, and all low-water stages resulting from exceptional 

run-off. The normal stage will, in general, be found to exist for 

about 9 to 11 months for most streams. If any other stage of water 

other than the normal has been mapped by other Government 

agencies instructions should be sought as to the availability and best 

use of the material. The elevation of the plotted shore line should 

be indicated at short intervals, and the figures of elevation should be 

placed in the space indicating water surface where they can be made 

readable.

In areas where the flow of rivers, though active for brief periods, 

dwindles or ceases altogether for many months the normal or prevailing stage is very low. Thus, rivers like the Platte are normally 

braided streams and should be represented as such on the map. 

Many rivers in the desert regions are most of the time nothing more 

than broad sandy washes and should be shown by strips of sanding.

River banks. If the contour interval is too large to permit the 

delineation of river banks by contour lines, hachures may be used, 

a single row being sufficient.

Natural lakes. The shore line used to represent a natural lake or 

pond should be that corresponding to a normal stage of water and 

not necessarily the shore line that is found at the time of the survey, 

which may be during periods of flood or extreme drought. An 

effort should be made to ascertain the shore line of the normal stage, 

as usually marked by a line of permanent land vegetation. The 

shore line used to represent a large lake that is subject to a gradual 

rise or fall over long periods should be that found at the date of survey. This date should be indicated on the water surface and be 

inked, and it will usually be engraved.

Artificial lakes. The shore line of an artificial lake should be the 

line that represents the water surface at the full normal stage of the 

lake, as controlled by the dam.

Island shore lines. The shore line that is to be mapped for an 

island must be that corresponding to the stage of water used for the
244 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

adjoining mainland shore line. Islands exposed only at a stage of 

water below that used for the mainland shore line should therefore 

not be mapped.

Drainage classification. The field sheets should clearly classify all 

streams as perennial or intermittent; this classification is defined 

below, and as it can not be accurately made in the office it must be 

completely made in the field.

Perennial streams. A perennial stream is one that flows throughout 

the year. It should be represented on the field sheets by a solid 

penciled line, firm enough to avoid confusion with the light penciled 

drainage that is drawn simply as a basis for contour construction. 

The topographer should show all perennial streams and leave for 

office decision the possible omission of any that may be considered 

not within the publication scale. Although the map should not be 

overburdened with insignificant rills and forks, such as abound in 

well-watered countries, the perennial drainage symbol should be 

penciled in all cases of doubt. As the purpose of this symbol is to 

show where running water may be found, it should be indicated on 

the field sheets only where the perennial character of the stream is 

reasonably established; and to this end occasional inquiry should be 

made to supplement field observations.

Intermittent streams. An intermittent stream is one that is dry 

for a considerable time each year, say for three months or longer. 

It should be represented on the field sheets by a firm penciling of the 

dash and three dot symbol. In regions where both perennial and 

intermittent streams abound the penciling should be complete and 

clearly distinct as to each kind, but if the proportion or amount of 

intermittent drainage is so large that the field drafting of the dash 

and three dot symbol becomes burdensome the copy can be made 

clear for inking by means of an overtracing (information sheet) 

showing only the perennial streams with a statement that all other 

streams are intermittent.

Double-lined streams. No stream should be double lined unless its 

actual width can thus be shown on the scale of publication without 

need of exaggeration.

Drainage lines as contour control. All drainage lines should be 

lightly penciled in on the field sheets, as they constitute a controlling 

element of all normal erosion topography and serve as a natural 

skeleton for the construction of the contours. Indeed, the systematic 

tracing out of the drainage net can not be too strongly recommended; 

the earlier the topographer begins to cultivate the habit the more successful he is likely to be in his work. Even in volcanic, sand-dune, or 

glaciated areas, where the topographic features have been shaped by 

agents other than running water, the drainage lines will often be 

invaluable to the topographer in making clear the real nature of
TOPOGRAPHIC MAPPING 245

slopes and irregular surfaces that are in themselves deceptive to the 

eye.

Disappearing streams. Many streams in limestone regions abruptly 

sink into caverns and continue their courses for long distances through 

subterranean channels. Special care should be given to the mapping 

of streams of this type. The points of disappearance and reappearance 

should be accurately located.

Springs. The importance of representing springs on a map is 

dependent on their relative usefulness as a part of the water resources 

of the region. Thus springs should be shown on maps of desert 

regions, where they are literally of vital importance and theii omission 

or erroneous location may have the gravest consequences to those 

dependent on the map. In such regions the name by which each 

spring is known should be indicated. Intermittent, alkali, or undrinkable springs should be so designated on the map. Springs should 

usually be omitted from maps of well-watered regions, but even there 

conspicuous springs may be shown by symbol and by name if locally 

recognized. The inking copy must be clear, and if necessary the 

presence of springs should be noted on the information sheet.

Wells and water tanks. The importance of wells and tanks, like 

that of springs, depends entirely on their relative usefulness as a part 

of the water resources of the region. In semiarid regions both wells 

and tanks must be shown. Wells, if artesian, should be so designated. 

The presence of wells and tanks should be shown on the information 

sheet if the field-sheet copy is not clear.

Intermittent and dry lakes. Shallow lakes and ponds that are dry 

for many months each year are typical of some regions, and all those 

not too small for the scale must be shown. Dry salt lakes and alkali 

flats, although not intermittent in the usual sense, are so closely 

related to intermittent lakes in appearance and formation that they 

should be shown by the symbol for intermittent lakes. Both types 

should therefore be shown by a dashed outline with the surface indicated by hatching.

Glaciers. The area of each glacier should be outlined by a dotted 

line, and its surface should be contoured (blue on the final map) with 

the same contour interval as that used for adjoining land surface 

and with the same degree of accuracy.

MAPPING OF RELIEF FEATURES 

. CONTOUR LINES

The relief on all topographic maps is expressed by contour lines. 

(See "Relief expression," p. 164.)

One contour interval. The contour interval that should be used on 

any map will be stated in the field instructions that are issued to
246

topographic engineers for each separate field assignment. If, in the 

course of field work the use of a different interval appears to be 

advisable, prompt recommendation should be sent to the division 

engineer.

Two contour intervals. Where the lower or valley parts of a quadrangle are to be contoured with a smaller contour interval than is to 

be used in the higher or hill parts of the quadrangle the change 

from one contour interval to the other should be made on one of the 

emphasized contours. For example, in changing from a 5-foot to a 

25-foot interval the change should be made on one of the 100-foot 

contours. Where, however, the border line between the valleys and 

the foothills represents a line that is rapidly rising or falling the 

emphasized contour on which the interval is changed should itself be 

correspondingly changed, in order to give the greatest possible 

expression with the small contour interval to the natter country and 

to avoid the unnecessary use of a small contour interval in the bolder 

country.

Where intermediate contours are needed to show detailed relief in 

certain small parts of a quadrangle, as in small valleys or flats, such 

contours may be added in dashed lines without interfering with the 

sequence of the regular heavy and light contours on the map.

CONTOURING METHODS

Contours may be mapped from plane-table set-ups that are made 

directly over or adjacent to the country that is to be mapped, as along 

a traversed road; or from a table that is kept stationary while it is 

circled by one or more moving rods; or from plane-table stations that 

overlook the distant country that is to be contoured. These three 

methods of contouring are described below.

Contouring from a traverse line. In regions where the principal 

control is obtained by different kinds of traverse (which in general are 

extended along public highways), the usual procedure is first to plot 

the contour crossings and other contours on or near the traversed 

road or other traverse line and then to extend the contouring out on 

both sides of the traverse line as far as good visibility and locally 

established control warrants. Where the visibility from a traverse 

line is poor all necessary advantage should be taken of such relatively 

good view places as are passed; and if good sketching points are noted 

off the line but near it, such points should be occupied as the work 

progresses. Contouring from a traverse line may also be advantageously supplemented by having the rod held occasionally at 

salient points in the topography off the line.

When aU sides of a road circuit or other large traverse circuit have 

been thus traversed and mapped, traverses should be extended into 

or across the unmapped interiors, giving sufficient traverse control to
TOPOGRAPHIC MAPPING 247

enable the topographer to complete the mapping. Such interior 

traverses may be run across open country or along ridges or streams, 

or the topographer may occupy favorable interior viewpoints with 

the plane table and resect from previous traverse locations in order to 

obtain a plane-table location.

Contouring from radial rod readings. In open country' of low 

relief where little contouring can be done from single plane-table 

set-ups one or two rodmen and a recorder can be advantageously 

used. Where two rodmen are employed each holds a rod on different 

sides of the plane table and at the salient points in the topography, 

and each rodman advances in the direction of the proposed mapping. 

As soon as the sights become too long or are about to be obscured 

both rodmen should hold their stations, and these points should be used 

as turning points in the line and the mean of the two readings used in 

determining the elevation of the new plane-table station that is made 

beyond the points held by the two rodmen. The rodmen then 

advance as before. Plane-table locations may be obtained as in 

"Contouring from a traverse line" (above) or as in "Contouring 

from stations" (below).

To use this method to advantage the topographer should employ 

such signals as may be found necessary between the table and the 

rod and between rods and should fully instruct the rodmen in their 

duties, as much depends upon their activity and resourcefulness. 

The readings that result from the successive rod sights may be plotted 

as fast as they are taken, or they may be allowed to accumulate and 

be plotted after the series has been completed, as local conditions 

may dictate.

Contouring from station. In open country of bold relief, where all 

the features are plainly visible, contours can be best delineated from 

plane-table stations overlooking the country to be contoured, without 

the running of a traverse line or the use of a rod. The method of 

contouring from plane-table stations involves the use of plane-table 

triangulation (p. 197) and the three-point method (p. 202). Woodland country as well as open country may be contoured from stations 

provided a sufficient number of outlooks can be found from which a 

satisfactory view and a good determination of position can be obtained. In the construction of contours from a station the location 

and use of drainage lines is important. (See "Drainage lines as 

contour control," p. 244.)

Contouring from a station is dependent upon supplemental control that is obtained by the location on the plane-table sheet by 

intersection methods of many of the salient points on the surface 

that is to be contoured; and for this reason little sketching can be 

done from the first station other than that of form lines, which are 

afterwards converted into placed contour lines. (See "Form lines,"
248 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

p, 249.) In planning the order in which plane-table stations should 

be made, careful consideration must be given to the need for the 

sighting of many points ahead, so that a sufficient number of such 

sights may be intersected from subsequent stations and used as a 

basis for contour construction. Vertical angles may be taken to the 

points when they are first sighted, or after the points that have been 

sighted have been intersected, or at both times, as circumstances 

may warrant, but in either procedure the elevations must be computed and the contours placed on the map as soon as the intersections 

are obtained.

The elevation of plane-table stations must be determined from a 

carefully executed series of reciprocal vertical angles taken between 

the principal stations in the quadrangle, and at least one station 

must be directly connected with a level bench mark by means of 

reciprocal vertical angles measured under different conditions.

Contour skeleton outline. Before mapping the contours that are to 

represent a distant relief feature a skeleton outline of that feature 

should be prepared, and on the degree with which this is adequately 

accomplished depends much of the accuracy, speed, and ease with 

which the contours themselves are placed on the map. Although it 

is true that lacking such an outline an experienced topographer will 

make a more faithful contour sketch than one less experienced, it is 

equally true that the best and most experienced topographers make 

a suitable skeleton outline of the drainage and ridge lines before 

attempting the construction of the contour lines themselves.

The landscape that is to be contoured should be first divided into 

its separate features or unit masses, such as mountains, hills, and 

spurs, and then, after sufficient control has been established through 

intersection methods, each feature thus segregated should have its 

natural drainage-line boundaries sketched in, tangents drawn to 

salient points as well as located points being used as control for the 

placing of the drainage lines. Similarly, ridge and crest lines may be 

outlined. It is best, as a general rule, to use convex forms such as 

spurs and lateral ridges as unit masses, the intermediate drainage 

lines being used as boundaries. (See also "Drainage lines as contour control," p. 244.)

In determining elevations based on vertical angles it is well to 

remember that large angles must be supplemented with accurate 

measurements of distance but that small angles based on measurements of distance that are approximate only will yield useful elevations for contour work.

Each separate unit mass as above described should be completely 

contoured, so far as control and visibility permits, before the contouring of another feature is begun. Should control alone be lacking, 

form lines (see below) should be lightly sketched in and advantage
TOPOGRAPHIC MAPPING 249

thus taken of a favorable viewpoint, effort being made subsequently 

to cut in the lacking control. By treating each mass as a separate 

unit, each can be best delineated with its own characteristic shape.

Form lines. Form lines are short detached sections of contour 

lines that are based on little or no control and on approximate contour intervals only. Form lines serve as a temporary expedient in 

expressing the relief of a small area until the necessary control can be 

obtained; they can then be readily converted into contour lines. 

Advantage is thus taken of a favorable point of view, and another 

visit to the same station is often avoided. Jn regions of moderate 

relief, where each feature takes but a few contours or where the mapping is done at short range, provisional sketching by form lines is 

not needed, but in many regions of intricately sculptured mountains 

it is a necessity.

Distances from which contouring can be done. Where the topographic method used is that of mapping the country from a distance, 

as in station work by plane-table methods alone, the distance will 

vary according to the proposed mapping scale and contour interval. 

In general, the smaller the map scale the more distance should the 

country be from the stations in order that it may be properly seen, and 

the larger the map scale the nearer should the stations be to the detail 

that can be properly mapped only at short range. Where small-scale 

mapping is confined to country that is near the station, less area will 

be covered and more detail will inadvertently be attempted than is 

needed for the scale, with the result that only a small paper area will 

be mapped in a given time; where the large-scale mapping of a too 

distant country is attempted the needed detail is not well seen and 

inferior work will result. On the selection of the best distance for 

work and on the choice of stations depends much of the success of 

the topographer.

Effective working distances in the mountains may be as great as 5 

to 10 miles with a 100 or 200 foot contour interval on a scale of 

1:192,000, as great as 2 to 5 miles with a 100-foot interval on a scale 

of 1:96,000, and may range from a quarter of a mile to 1 mile with a 

20-foot interval on a scale of 1:48,000. The cultural features of a 

country of bold relief should in general be separately traversed, and 

where they dominate the country the plane-table station method may 

become secondary.

DRAFTING OF CONTOURS

Penciling. Contour lines should be drawn with the hardest pencil 

that can be used under field conditions, and this in general will be a 

9H pencil in dry weather and a 7H pencil in damp weather or in a 

wet climate. The pencil lines should be drawn fine, sharp, and of 

even strength and should give as uniform an appearance as possible,
250 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

but under no circumstances should the lines dent the paper or leave 

grooves in its surface. Erasures should be made gently and only when 

the paper is perfectly dry, lest the surface be broken. As the same 

sheet will later be inked in the office, it should at all times be kept covered save where the day's work is being done, for which a small hole 

can be cut in the cover paper.

Emphasized contours. Inasmuch as every fifth or fourth contour, 

according to the contour interval, will be later emphasized by inking 

it in a heavy line (see " Strength of contour lines," p. 294), the penciled 

contours that are to be made heavy in the inking should be indicated 

clearly, by adding contour figures at short intervals and by placing 

little penciled crosses on them rather than using dashed or dotted lines 

or heavy penciled lines. For steep slopes whose relief is expressed in 

emphasized contours alone no mark of identification is needed other 

than the drawing in here and there of a band of intermediate contours.

Contour numbers. Contour numbers should be added to contours 

that are to be emphasized wherever such numbers may be helpful to 

the inker and should be placed here and there on the intermediate 

contours wherever they may be essential or helpful in the interpretation of the copy.

Uniform steep slopes. Where the slope is both steep and uniform 

only the contours to be accented should be penciled, for the reason 

that the inker can interpolate the intermediate lines as readily as the 

topographer can pencil them in on the field sheet and for the additional 

reason that the inker's copy is the clearer for their omission. (See 

"Uniform steep slopes," p. 295.)

Steep slopes that are not uniform. Where the slope is steep but not 

uniform a sufficient number of intermediate contours should be added 

to define clearly the positions of the changes in slope. If this is not 

done an unnatural "banded" expression will be given to the map in 

those places where the inker inadvertently uses an even spacing of 

intermediate contours between the unevenly spaced heavy contours.

Drainage and ridge slopes. Along lateral stream channels and ridges 

that have been contoured in heavy contours alone the intermediate 

contours should be penciled in wherever a uniform interpolation can 

not be made; otherwise an erroneous interpolation may be made in 

the office with resulting improbable slopes, illegible copy, or both.

SPECIAL FEATURES

Railroad grades. As railroads are constructed on known and definite grades they should be so represented in contours. The distances 

given in the following table apply to standard service roads and should 

be regarded as approximate only. Few main lines use grades in excess 

of 1 or 2 per cent, and few branch lines in excess of 3 or 4 per cent. 

For grades of 5 and 6 per cent unusual precautions are necessary, such
TOPOGKAPHIC MAPPING 251

as heavy motive power and short trains; grades of 7 per cent or more 

require safety switchbacks.

Distances, in feet, between contour crossings on railroads for different contour 

intervals and different railroad grades

Railroad 

grade 

(percent)

1 

2 

3 

4 

5 

6 

7

Distance between crossings for contour interval of 

5 feet

500 

250 

167 

125 

100 

83 

71

10 feet

1,000 

500 

333 

250 

200 

167 

143

20 feet

2,000 

1,000 

667 

500 

400 

333 

286

50 feet

5,000 

2,500 

1,667 

1,250 

1,000 

833 

714

100 feet

10,000 

5,000 

3,333 

2,500 

2,000 

1,667 

1,429

Cuts andfiUs. Cuts and fills that have straight and smooth slopes 

should be ruled in rather than drafted free hand. Cuts and fills 

paralleling cultural features should be drawn rigidly parallel to those 

features. Where the lines of a fill, plotted to scale, are so close together 

that the separate lines can not be shown by ordinary drafting, the 

contours should be slightly separated, provided that there is room on 

the map and no undesirable crowding of other map features is introduced thereby.

Depressions. Natural depressions or sinks, such as occur in limestone regions, and artificial depressions, such as are inclosed by embankments, should be indicated on the field sheets by the addition of 

hachures on the downhill side of the contours inclosing them. Large 

depressions can be adequately shown without the hachures by placing 

rows of contour figures on the inclosing contours. In areas of intricate topography or in deep depressions bottom figures of elevation 

should be added wherever the contouring can not be legibly drafted. 

Hachures should be freely used on the field sheets, and the question 

of inking or of engraving them left for office decision. (See "Depression contours," p. 296.)

Ditches, arrayos, etc. Where ditch contouring is congested and 

would be illegible to another person the expedients described below 

will aid the office inker in reading the copy. Where contour crossings 

can not be readily identified, each crossing should be designated at 

the end of a right line drawn to an open place within the map. Where 

the ditch is narrow and the side contour lines, when plotted to scale, 

touch the drainage line representing the ditch, the contours may be 

slightly separated, but this exaggeration is not warranted unless it 

can be accomplished without encroaching upon other essential map 

features.

Cliffs. In the representation of cliffs a number of contours may 

be merged to form a wide, line or band. Within such a band of.

qSqi§° 28 H
252 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

contours an emphasized contour would obviously lose its identity, and 

in such cases enough contours, both heavy and light, should be numbered in the vicinity of the cliff to insure a correct reading of the contours for office inking. (See "Cliffs," p. 295.)

Use of Jiachures. The use of hachures should be confined to the 

representation of depressions, mine dumps (see p. 234), and levees 

and such other banks as can not be shown by the regular contour 

interval and yet constitute important topographic features, to be 

determined for each map.

TOPOGRAPHIC EXPRESSION

Uses of the term. The term "topographic expression," in general, 

refers to the appearance of the contouring that denotes at a glance 

the character or type of the country that has been mapped for 

example, as flat, mountainous, rolling, or strikingly eroded. The 

term as used by the Geological Survey, however, denotes the faithfulness with which a given scale, contour interval, or individual 

may represent the character of the country as shown on the map by 

means of the contouring. As between different scales, contour 

intervals, and individuals, on the one hand, and the numberless types 

and varieties of topography that are to be found in the country, on 

the other hand, the subject of topographic expression presents many 

phases.

The relation between the topographic character of a country and 

its adequate representation on a map is so close that experienced map 

readers and physiographers may be able to recognize from the map's 

characteristic expression in what part or parts of the country the 

map was made or may have been made.

Topographic expression by different persons. Although the field 

drafting of contour lines is controlled by the location of certain salient 

points, contour construction, sometimes called contour sketching, 

is an art that is developed only through training and experience; and 

the contouring of two engineers working alongside each other in 

country of the same type will differ, not so much in the position 

of the contour lines on the map, for that is an engineering problem, 

but in the topographic expression. The less control that is available the larger will be the purely sketching functions of the topographer and the larger will be the differences that may be expected 

between the contouring of different engineers; and the larger the scale 

of the field work the smaller will be the differences that may be expected 

between the contouring of two or more persons using identical control.

Party chiefs should watch closely the contour expression of different persons working in the same or adjoining quadrangles and should 

take such steps as may be necessary to reconcile the differences in 

style that are found; and topographers working alongside each other 

should compare maps for the same purpose.
TOPOGRAPHIC MAPPING 253

Examples qf differences. Differences in topographic expression may 

consist in the mapping of an excess of unessential detail or in the 

omission of essential detail that is within the scale of the mapping; 

in the exaggeration of small features that because of their striking 

character may appear larger than they really are; in the use of sharp 

or curved stream reentrants where the opposite should be used; in 

the sketching of conventional curves rather than the diversified 

curves that are normally found in nature; in the sketching of rounded 

forms, where in general the type calls for forms of more angular 

appearance, or the reverse; and in other minor mannerisms that 

occasionally appear, such as the inadvertent use by the engineer of 

certain typical shapes recently used by him elsewhere and not to 

be found in the new area under survey.

Topographic license. In order to put all possible expressiveness 

into each contour line and in order to bring out prominent and 

characteristic relief that otherwise might not be shown, the topographer is occasionally justified in slightly disregarding an elevation 

determined for no purpose other than contour control. To force a 

contour into rigid conformity with an instrumental elevation and 

location where other contours are only sketched may result in a 

stilted form of detail adjacent to a control point and an appearance 

of relative absence of detail at a distance from the control point. 

Where elevations at sharp summits or on broad flats are just under 

a certain contour elevation, it is permissible license to add or move a 

contour and thereby bring out a conspicuous form. The need for 

such license is greatest where the sketching is being done with a large 

contour interval combined with a small scale, and in such places 

elevations may be disregarded for as much as 10, 20, or even 30 

per cent of the contour interval, the amount depending upon the 

prominence of the topographic feature and the scale. Where the elevation of such a feature is important map information, figures of 

elevation should be added and the slight inconsistency between contour and elevation disregarded. As the scale of the map increases 

and as the contour interval becomes smaller, the need for such topographic license decreases, for then the contouring approaches an 

engineering accuracy and the individual contour lines approach true 

contours.

Alinement of contours, The turning points of reentrant contours 

that define steep drainage channels should, in general, be in alinement with one another, and the closer the spacing of the contours 

the more exact should be the alinement. To insure accurate alinement the penciling of all drainage lines is essential. (See "Drainage 

lines as contour control," p. 244.) The penciled alinernent of contours up reentrants, on ridges, and on side slopes should be so 

carefully and clearly drawn that the office inker will not be forced
254 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SUBVEY

to correct obvious errors that appear to be due to hasty or careless 

penciling.

Physiography an aid. Contour lines, unlike most other map features, are largely sketched rather than completely surveyed, and thus 

contour sketching is an art as well as an engineering problem. The 

art of contour sketching consists of a free-hand delineation on paper, 

to the scale of the map, of the surface relief as seen in perspective view, 

but controlled by locations on the paper corresponding to salient 

points on the ground. However numerous may be the locations 

controlling a given contour line, it is always possible, so long as the 

locations are at an appreciable distance from one another on the 

paper, to give the line different significant shades of meaning, each 

equally justified by the control. That contour line therefore is likely 

to be nearest to the truth that is drawn with the fullest comprehension 

of the character of the feature expressed. The most accurate geometric representation of a land form may appear "wooden" or lifeless on a map unless it is also given its true characteristic expression. 

It is therefore desirable that the topographer have a sufficient working knowledge of some of the physiographic processes that sculpture, 

the earth's surface, in order that he may understand the type of land 

form with which he is dealing and realize wherein its peculiar character 

resides. Not only will the expressiveness of the contouring be 

enhanced by physiographic knowledge, but the early recognition of 

the prevalent topographic type forms will enable the engineer to 

place his control to the best possible advantage and in general will 

enable him to complete the contouring with less control. The smaller 

the scale of the map the more helpful will such physiographic knowledge be. Large-scale maps, on the other hand, are less of a problem, 

as all features that are not insignificant in size can be adequately 

shown on them.

Topographic engineers are encouraged to study topographic forms 

and to acquire an understanding of the elements of geology as a necessary foundation for the study of so much of physiography as may 

help them in their contour construction. The following references 

are suggested: "Interpretation of topographic and geologic maps," 

by C. L. Dake and J. S. Brown; "Physiography," by R. D. Salisbury; 

"Physical geography," by W. M. Davis; "Topographic surveying," 

by H. M. Wilson, Chapter VI, "Topographic forms"; and special 

texts on the back of several topographic maps.

MAPPING ON AERIAL PHOTOGRAPHIC BASE

If suitable aerial photographs and initial horizontal giound control 

are available the culture, drainage, and woodland outlines can, in 

large part, be delineated and the resulting base map used as a field 

plane-table sheet upon which the details of culture, drainage, and
TOPOGRAPHIC MAPPING 255

woodland outlines can be completed and the contours constructed. 

The method of preparing the aerial photographic base is described in 

partF, "Map compilation from aerial photographs." The base thus 

prepared is reduced by photolithography to the scale of field work 

and printed in light blue on double-mounted drawing paper. Such 

a culture and drainage base is then used in connection with the usual 

initial vertical control, and the topographic map is completed, the 

further necessary field work being executed in conformity with the 

instructions for topographic mapping.

Each map feature shown in light blue, such as a road, house, or 

stream, should be penciled in as soon as identified and found to be 

correctly plotted, in order that the copy may clearly indicate to the 

office inker the distinction between these features that are to be inked 

and those, such as fence lines plotted for control use only, that are 

not to be inked. Faint blue lines that remain on the base field sheet 

and represent features that are not to be inked should therefore be 

erased or crossed out in pencil; otherwise they may be taken to 

represent cultural or drainage features and erroneously inked.

Inasmuch as aerial photographs of shore lines maj7" be taken at any 

stage of water ranging from high to low, the shore line thus represented 

may accordingly differ from the shore line that should be mapped, 

which on tidal coasts is the margin of mean high water and on inland 

rivers is that of the normal stage of the water. (See pp. 242, 243.) 

Th£ stage of water that is shown on the aerial photographic base 

should therefore be ascertained by observation on the ground supplemented by local inquiry. If coastal photographs have been taken at 

any stage below mean high tide or if inland photographs have been 

taken during a period of high or low water the photographed shore 

line should be corrected by instrumental observations and based upon 

local information so far as practicable. A photographed shore line 

can represent the desired shore line at all stages of the water only 

where steep banks or the scale of the mapping renders the differences

inappreciable.

SAND

Sand above the level represented by the plotted shore lines, where 

devoid of vegetation, should be represented by the sand symbol, with 

the limits of the sand area indicated in pencil.

MAPPING OF WOODLAND OUTLINES

The outlines of woodland areas as defined below should be mapped. 

The accuracy in the location of woodland outlines for maps to be 

published on a scale of 1: 62,500 will be based upon the location of 

the principal salient features only, the intermediate details between 

located points being sketched. In general, the location of the four
256 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

corners of a small quadrilateral tract and additional locations of the 

principal bends in the outline of a large tract will be sufficient.

Definition of woodland. Woodland to be mapped includes all timber, woods, or brush, "whether alone or mixed, of sufficient stand and 

height to impede ordinary travel or afford cover for small detachments 

of troops. Logged over or burned areas, if covered by second growth 

or brush, should be shown as woodland.

Woodland sheet. Although woodland outlines must not be inked 

on the final drawings of topographic maps the penciled woodland outlines may be added to the field sheet if this is found more convenient 

than laying a tracing over the field sheet each tune woodland outlines 

are plotted. In either event a woodland tracing should be made and 

kept current. This tracing should be complete as to the woodland 

outlines before leaving the field. It can be most conveniently made 

in two halves for a standard quadrangle. Where two or more engineers are engaged in mapping a given half of a quadrangle at the 

same time, each man should make his own tracing, but their common 

edges should be compared before field work is completed, and, if 

practicable, a combined woodland tracing should be made for the 

entire half quadrangle.

Woodland data from aerial photographs. If woodland outlines are 

shown on the aerial photographic base they should be checked in the 

field as the topographic mapping progresses, and a woodland sheet 

should be prepared by adding a green shading to the checked or corrected woodland areas as printed on an extra copy of the aerial base 

provided for the purpose.

ROAD CLASSIFICATION 

BOADS SHOWN IN BLACK

The first classification of roads determines those roads that are to 

be indicated on the base by solid double parallel lines and those that 

are to be shown by broken double parallel lines; and these classification symbols should be penciled on the original field sheets and will 

be later inked and engraved in black. (See "Roads," pp. 229-230, 

284.)

ROADS SHOWN IN RED

A further classification of roads will be indicated by means of a red 

overprint on all new standard topographic maps, and the topographer 

should make the necessary observations or local inquiries to obtain 

field data for this classification, which should be submitted on a tracing or other separate sheet (not combined with other information), 

marked at the top "Road classification."

The distinction between through and secondary routes shown by 

means of a red overprint on many published topographic maps for
TOPOGRAPHIC MAPPING 257

which the surveys were made from 1920 to 1926, inclusive, will be 

discontinued in all new surveys, and the road classification described 

below will become effective. The following instructions are based 

upon an agreement between the War Department and the Department of the Interior, approved September 8, 1926, and upon a report 

on road classification approved by the Board of Surveys and Maps 

December 14, 1926:

Full red lines. Full red lines should be used to indicate "hard, 

imperviously surfaced roads." A hard, impervious surface is defined 

as a road surface of the dustless order and includes such artificial 

surfaces as concrete, brick, and all bitumastic mixtures or insoluble 

surface treatments. A hard, impervious surface excludes such surfaces as water-bound macadam, gravel, top soil, sand, clay, and all 

graded or ungraded earth roads. Detached stretches of hard-surfaced 

road should be shown as detached, but a hard-surfaced road that is 

only temporarily in poor condition should in general be shown by a 

full red line.

Broken red lines. Broken red lines should be used to indicate 

"other main traveled roads," denned as those roads that are most 

traveled whether for purely local use or for through travel. The 

selection of these roads has no reference to character or condition 

of road surface. In sparsely settled regions a road may be difficult 

to travel, but if it is the only practicable route through a country of 

few roads it should be shown in broken red lines. In regions where 

poor roads abound the best among them usually carries certain 

local or through travel, and such roads should be similarly shown/

In regions of prevalent hard-surfaced roads the full red lines may 

cover so many of the main traveled roads that little if any representation by broken red lines will be needed. Where ambiguity might 

arise in the indication of short detached stretches of hard, impervious 

surface aud of other main traveled roads, the hard-surfaced stretches 

should be marked "hard" on the tracing.

Objectives and distances. On the margin of each quadrangle map 

should be indicated the names of the next main objective and the next 

immediate objective of each road shown in red, with the distances 

thereto in miles.

Date. On the lower margin of the road-classification tracing should 

be shown the month and the year of the road information.

EOAD AND HIGHWAY NAMES

Well-established names for roads and highways, including route 

numbers or other recognized designations, should be indicated on 

the name sheets and will be published so far as Geological Survey 

policy provides; but such data will not be overprinted in red and 

should be omitted from road-classification tracings.
258 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

r

MAPPING OF LAND-CLASSIFICATION DATA

GENERAL REQUIREMENTS

Each topographer engaged in mapping areas in the States of 

Minnesota, Nebraska, Kansas, Oklahoma, New Mexico, or States 

west of them or areas containing public lands, national forests, or 

national parks in the States east of them, must make the field observations and local inquiries necessary to enable him to submit to the 

conservation branch a land-classification tracing and written report 

containing such data as will indicate the possible uses of the lands 

which he maps.

Such reports will be based only upon facts personaUy observed by 

topographic engineers or their assistants or obtained by them through 

inquiry from known and reliable sources.

The general character of the information desired by the conservation branch will appear from the folio whig list of subjects on which 

it is required to report to the Director for his submission to the 

Secretary of the Interior: ' 

(a) Designations of (1) areas which are not susceptible of success- ' 

ful irrigation at a reasonable cost from any known source of water » 

supply and which can therefore be entered under the general provi- > 

sions of the enlarged-homestead act (as suitable for dry farming); 

(2) lands in certain arid States which do not have an available supply /' 

of water (either surface or ground) for domestic purposes such as to 

make continuous residence on the land possible.

(&) Recommendations as to withdrawals of lands for water power, 

reservoirs, and public watering places.

(c) Recommendations for the protection of mineral resources and 

for other public uses.

(d) Reports on the valuable power-site and reservoir possibilities 

involved in (1) applications for rights of way for railroads or for 

canals, ditches, reservoirs, etc., included in power and irrigation 

projects; (2) proposals for alienation of tracts of land in Indian 

reservations and in the public domain under any of the laws providing 

for such alienation; (3) designations by Congress for special alienation 

or use of whole Indian reservations and other areas.

The conservation branch should be notified of the presence of any _ 

deposits of coal, oil, gas, or phosphate, the topographer bearing in I 

mind that it is much better to report facts that may be already 

possessed by the Geological Survey than to fail to report facts that 

are not on file. The land-classification material thus submitted will ,' 

be filed with the other records for the area covered and with them ( 

will become the basis for recommendations to the Secretary. ^

For the purposes of the conservation branch it is essential that 

enough land corners be identified on the ground and located on the
TOPOGRAPHIC MAPPING 259

map to enable the best possible adjustment of the land-line net to 

be made. The land should finally be classified by the smallest legal 

subdivisions, and the immediate availability of the classification data 

reported depends on its definite application in terms of the land-office 

surveys to the land described.

LAND-CLASSIFICATION SHEET

A sheet must be prepared that will show the classification of the 

land in accordance with the general outline and symbols described 

below. The base for this sheet will be the topographic map of the 

area covered, but the classification should be inked on tracing cloth, 

on which all projection lines should be fully shown and numbered. 

When transmitted to the conservation branch it should be attached 

to a photolithograph or photograph of the topographic map on the 

same scale.

An accompanying written description should explain and amplify, 

where necessary, the information given on the classification sheet and 

should include all facts which can not be clearly shown graphically, 

including the character of each examination. The description 

should, so far as practicable, be arranged in the order followed in the 

list of symbols given below and should be arranged in paragraphs, 

with headings corresponding to those there given, including the index 

letters. This description should include a discussion of the usual 

money value of the different classes of land in the locality, so far as 

known. The description should be appropriately headed, and each 

page should be so designated that if separated from the others it 

could be quickly restored to place.

The outline and sets of symbols shown in Figures 9, 10, and 11 and 

described below should be used in preparing agricultural data for 

submission to the conservation branch. The system permits the 

overlapping of different classes of lands to be shown. For example, 

land bearing merchantable timber may be good summer grazing 

land, and these facts may be indicated by vertical lining and the 

letters "F t" in green and by vertical lining and the letters "G s" in 

yellow.

The boundaries between the four principal divisions as listed below 

should be inked in black. The boundaries between the subdivisions 

of a principal division should be inked in the color of that division.

1. Forest land (fig. 9; green ruling): 

F t Merchantable timber.

F s Small or stunted timber which may be used for posts, firewood, etc. 

F b Burnt areas. 

The kind of timber should always be described in the accompanying text,

and where possible its kind should be indicated on the classification

sheet.
260 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

GREEN

Fs

Ft

Fb

unappro

FIGXTRE 9. Pattern and symbols for designation of forest land

2. Arable land (fig. 10; red ruling): 

C Cultivated land:

C i With irrigation. 

C d Without irrigation. 

I Lands not cultivated but which may be irrigated:

I s Irrigable [directly from streams or springs. State

priated water rights if known; if unknown, so state. 

I r Irrigable from possible storage reservoirs. 

I w Irrigable from wells. Give geologic source if known, 

p Irrigable only by pumping from any of the preceding three

(add "p" to other letters; as, I s p).

Lands that may be cultivated without irrigation (dry farming). 

Swamps:

S e Easily or readily drainable. 

S d Drainablc with difficulty.

RED

D

S

Is

tap,

Cd

Sd

FIQUEE 10. Patterns and symbols for designation of arable land
TOPOGEAPHIC MAPPING 261

3. Grazing and natural hay land (fig. 11; yellow ruling):

H Lands with sufficient natural grass to cut for hay.

G Grazing lands not included under "H." Indicate on classification

sheet where practicable the character of the vegetation and the

duration of the range: 

G y Year long. 

G s Summer. 

G w Winter.

4. Barren or waste land (no pattern): 

B a Alkali flats. 

B r Rock wastes, escarpments. 

B s Sand wastes. 

B x Other barrens.

YELLOW

Gy

Gs

Gw

FIQDBE 11. Pattern and symbols for designation of grazing land

AGKICULTURAL WATER SUPPLY 

Wells:

Character:

® Flowing.

O Nonflowing. 

Description:

Dug or drilled.

Diameter and depth, indicated thus: 3"XI68'.

Yield, where well is pumped or where well flows. 

Quality of water:

m Mineralized.

du Suitable for domestic use.

st Stock use.

rr Railroad use. 

Ownership.

Springs and watering places: 

Location. 

Description.

Quality of water (as for wells). 

Uses (domestic, stock, etc.).

Ownership, public or private. If private, name of owner or occupant. 

Area of range controlled.
262 TOPOGEAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY 

REVISION OF TOPOGRAPHIC MAPS 

REVISION DEFINED

The topographic surveys of the Geological Survey are classified as 

new surveys, resurveys, or revision. Resurveys are made under the 

same specifications used for new surveys on the same scale. By 

revision is meant an examination of all or a certain part of a map, as 

its cultural features, in order to bring it up to date. A cultural revision will involve only so much new survey as may be needed in order 

to add new cultural features to the map and tie them in to the cultural features that are unchanged, and it will involve only so much 

change in the drainage and relief features as may be needed to fit 

them properly to the new or changed cultural features. Where the 

cultural revision is extensive, owing to a rapid growth or to a long 

interval of time since the original survey, correspondingly extensive 

changes in the drainage and relief features may be needed. In proportion as the revision of the culture, drainage, and relief of a quadrangle becomes more and more extensive, however, the revision 

partakes more and more of the nature of a resurvey. A revision is 

therefore seldom more extensive than a so-called "cultural revision." 

The choice between a cultural revision and a resurvey can be made 

only after a knowledge of local conditions has been obtained and 

combined with an appraisal of the character of the original survey.

CULTURAL REVISION SURVEY

Personnel and instrumental outfit. A revision party need seldom 

consist of more than one topographer in charge, assisted by one rodman. The instrumental outfit will be similar to that used by a 

topographic party of the same size. The methods employed should 

largely conform to those in current use for new surveys in similar 

country mapped on the same scale.

Use of control data. The control data that were used in the original survey are shown on the published map, with the exception of a 

few intermediate points that wore determined for control but not 

for publication. Horizontal positions that have been determined 

since the time of the original survey should be plotted on the revision 

field sheets, and where the plotted positions disagree with the published adjustment of the adjacent topography a readjustment of the 

topography should be made if the discrepancy is but local, but if the 

disagreement covers a considerable area the matter should be at once 

reported to the division chief.

If leveling has been done in the quadrangle since it was originally 

mapped, the newly determined elevations should be compared with 

the contouring, and such differences as are found should be noted for 

a field examination and the correction of the contours.
TOPOGRAPHIC MAPPING 263

Control stations to be published. All transit-traverse stations and 

level bench marks falling along or near the line of cultural revision 

should be systematically looked for, and where they have been 

destroyed or moved the symbols should be crossed out on the field 

sheet and the change should be reported to the Washington office 

for the correction of office records; where they are found intact they 

should be indicated in pencil on the field sheet as clear copy for office 

inking and subsequent publication. All newly established transittraverse stations and level bench marks should likewise be shown 

in their correct relation with the topography. Newly established 

triangulation stations should also be shown, provided the adjacent 

topography can be properly tied in to them.

Scope of cultural revision. The features to be included in a cultural revision are those listed under "Mapping of cultural features" 

(pp. 229-242).

Examination of cultural features. The field work should consist in 

traveling over each road or other route of travel within the quadrangle and comparing each cultural feature with its corresponding 

representation on the map. Where new or changed features are 

found they should be surveyed and tied into the features that are 

not changed or to the horizontal control or some form of expansion 

from the control. It is imperative that the topographer know his 

true position in the quadrangle at all times, and for this purpose 

plane-table set-ups, traverses, or plane-table stations must be made 

wherever they may be needed.

The comparison between ground features and the corresponding 

map features must be thorough and complete and should include an 

examination of the direction, length, and angle of bend of each 

stretch of road, trail, railroad, or other line feature; a check of each 

house or other building; and a lookout for all other cultural features. 

A definite plan should be adopted in order that no part of the culture 

shall be overlooked in the examination. All existing houses and 

other small cultural features, including control stations and bench 

marks, should be clearly indicated by firm penciling over the faint 

color representation of the features or shown in their plotted positions 

where they are new features. Features that have been destroyed or 

abandoned shoulid be so indicated on the "take out" sheet (see below) 

and the symbols also crossed out on the field sheet.

Boundary lines. Each boundary shown on the map should be 

verified, and an inquiry should be made for new or changed boundaries and for the names of the subdivisions affected. The boundaries 

of cities or other places that have been incorporated since the first 

survey should be added.

Names. Each name on the map should be as thoroughly verified 

as the names for a new survey; names of new places and features
264 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

should be added; names that have fallen into disuse should be 

dropped but replaced if other names are found in current use. Where 

a post office has been discontinued owing to the introduction of 

rural free delivery, the name of the former post office should be 

retained if it represents a well-established locality. In short, every 

effort should be made to bring all names up to date. Each name 

should be recorded as soon as obtained, and this record may be made 

on the revision sheet, on a tracing, or on a copy of the published 

map.

"Take out" copy. Where a map feature has been abandoned or 

destroyed, as a road or a house, the corresponding copy on the copper 

plates must be smoothed out and "tapped up" to a flat surface. 

Engraver's copy for such "take outs" should be recorded as the 

revision field work progresses and may be conveniently indicated 

on the field sheets by penciled crosses or by wavy penciled lines 

placed on the features that are to be removed from the plates; but 

lest there be confusion in the final copy such "take outs" must be 

transferred to a clean published print of the map and later inked. 

The sheet so used should be marked at the top "Take out sheet."

Woodland. No revision of woodland outlines will be made unless 

instructions are issued authorizing such work. Inasmuch as a cultural revision is confined largely to rapid travel over routes of communication, such as roads, and inasmuch as woodland representation 

can not be revised but must be remapped, a resurvey of the woodland areas is seldom attempted during a revision of culture, for the 

reason that it requires much more traverse and map work than for 

revision of the culture alone.

Road classification. The roads should be first classified according 

to the instructions given under "Roads" (p. 229). Where it is found 

necessary to change from a full to a broken line or the reverse, such 

changes should be indicated on the "take out" sheet by inking the 

road in full or broken lines where such changes are needed.

The roads should be further classified as defined under "Road 

classification" (p. 256), and this classification should be placed upon 

a separate engraved copy of the map and not combined with any other 

data and should be marked "Road classification."

CULTURAL REVISION BY AERIAL PHOTOGRAPHY

Scope of revision. The cultural features of a topographic map 

may be revised by the use of aerial photographs, a procedure that 

promises increasing usefulness as the photographs and the methods 

of using them are further improved. The drainage features of the 

map may also be thus revised where revision is found to be necessary 

or desirable. A field examination may or may not be needed, as 

explained below.
TOPOGEAPHIC MAPPING 265

Good base necessary. The use of aerial photographs in topographic 

map revision should be confined to maps for which the original 

surveys were well controlled and the topographic details properly 

adjusted. If the map that needs to be revised has been insufficiently 

controlled or incorrectly adjusted the data that are obtained by 

aerial photographs can not be successfully used until the base map 

has been readjusted, and such a readjustment can not be made until 

further control has been supplied, involving field work. Inasmuch 

as such a procedure is not generally warranted, the revision of such 

a map can best be effected by means of a complete resurvey.

Type of photographs. Maps of cities and towns and of other areas 

that are closely built should be revised through the use of photographs taken with single-lens rather than multiple-lens cameras, 

because the single-lens vertical photographs show clearly the width 

of streets and the plan of buildings on each side of them, whereas 

the wing-print parts of the multiple-lens photographs represent 

exposures taken at an angle and show objects in such increased perspective that high buildings and even ordinary dwellings obscure 

streets and render the ground plan of buildings indefinite. Multiplelens photographs are suitable, however, for the revision of maps of 

sparsely settled areas.

Office use ojphotographs. The revision corrections that are obtained 

by an office compilation of the data found on aerial photographs 

should be drafted on an enlarged (field scale) photolithograph of 

the map printed in light blue on drawing paper. It may be advisable 

to use transfers from the engraved plates (on the same scale or 

enlarged) and print from stone in three distinctive and weakly 

photographic colors. The additions and corrections to the map can 

then be inked in the standard strong colors, such as will yield photographs showing only the revised data.

In the process of compilation each aerial photograph is used as a 

separate source of data, either by photographing the aerial print 

to the scale of the map and tracing the map features desired, or by 

using the original aerial photograph directly and taking off the 

features desired by means of proportional dividers. If the map that 

is to be revised is well controlled and adjusted, a careful comparison 

of the aerial photographs and map will determine the existence of 

new features and the need for possible correction of the old.

Field examination. When the office revision of the culture and 

drainage has been completed there may be need for a field examination in order to revise the contouring slightly to fit the new culture 

or drainage. The need for a field examination will depend upon 

the accuracy of the base, the nature of the topography revised, and 

the extent of the revision. Features obscured in the photographs 

by heavy timber may also need a field examination.
TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

The better the control and adjustment on which the map was 

based the less will be the need for a field examination. If a cultural 

feature is added to the map on or near a line of previous control 

the necessary changes in the contouring will be small and may 

generally be made from a close examination of the photograph, but 

if a cultural feature is added to the map in a place that falls between 

control lines that were not near together the need for a field examination will be increased.

A careful comparison of the photographs with the contouring 

adjacent to the revision copy will show that in certain types of 

country the necessary changes in the contours can be made from 

the photographs alone, but where there are numerous and rapidly 

changing land forms the need for a readjustment of the contours 

will be greatest, and in general a field examination is more likely 

to be necessary. In country of certain types the relief expression 

would be but little changed, if at all, by a field examination, and 

here the chief advantage gained would be in the determination of 

the actual elevations along the newly added features, a determination that has not yet been attempted by the Geological Survey 

from aerial photographs alone.

If the revision results in extensive corrections throughout the 

quadrangle or in complete changes within smaller areas the need 

for a field examination will be increased. Inasmuch as a large part 

of the expense of a field examination may be incurred in connection 

with preparation and in travel to and from the field, it is obvious 

that where it is found necessary to make a field examination the 

fullest advantage should be taken of the opportunity to visit all 

localities where contour changes may be needed. Such a field visit 

would also permit the examination at the locality of any doubtful 

adjustment or place where the interpretation of the aerial photographs was uncertain.

RIVER SURVEYS

SPECIAL EIVER SURVEYS

Special river surveys involving the delineation of alinement, 

water-surface contours, and adjacent topography and the construction of a corresponding profile ar° executed for all important streams 

that may be designated by the conservation branch of the Geological 

Survey.

Special supplemental instructions are prepared by the conservation 

branch for each locality of special river survey. If a representative 

of that branch accompanies the topographic field party, the topographic engineer will be relieved from the necessity of collecting the 

information outlined on pages 270-271 under "Written reports."
TOPOGRAPHIC MAPPING 267

Special river surveys should be executed on the scale of 1: 31,680 

(2 inches to 1 mile), except as provided for in connection with regular 

topographic mapping.

RIVER SURVEYS IN REGULAR TOPOGRAPHIC MAPPING

In connection with or as a part of all regular topographic mapping 

on field scales of 1: 96,000 or 1: 48,000, river surveys of ah1 important 

streams should be made on a uniform field and office scale of 1:48,000. 

For this purpose important streams may, in general, be defined as 

those that have a low-water flow of at least 10 cubic feet per second 

and also a product of at least 2,500 for faU in feet per mile multiplied by the low-water flow in cubic feet per second. On a scale 

of 1:48,000 the requirements as to detail that it is possible or 

desirable to show are considerably less than on larger scales.

Where regular field work is executed on a scale of 1:31,680 or 

1:24,000 the river surveys and profiles should be made on the 

same scale.

Where the regular field work is on a scale of 1:48,000 the principal 

additional work involved in making river surveys will be the location 

of 5-foot water-surface contour crossings and the determination of 

the elevation of the head and foot of falls, dams, and rapids and the 

elevation of the junction with tributary streams. Where the regular 

field work is on a scale of 1:31,680 or 1:24,000, no additional 

contouring will be necessary if the contour interval for the quadrangle 

is 5 feet.

In connection with field work executed on the 1:192,000 scale, 

only written reports as to important streams will be required. Reports 

should be based on such general observations and local inquiries as 

can be made without materially delaying the regular field work.

TOPOGRAPHY

The following instructions apply to both special river surveys and 

to river surveys made in connection with regular topographic mapping.

The field traverse sheets when carefully inked should serve as 

final copy for assembly on the plan sheets and for data from which 

corresponding profiles may be made on separate sheets.

Contour intervals on water surface. The contour interval on water 

surfaces should be 5 feet, and care must be taken to furnish clear 

penciled copy for office inking. In addition, the elevations at the 

head and foot of all falls, rapids, and dams and at the mouths of 

principal tributaries must be determined. Where the stream slope 

is so steep that a 5-foot water-surface contour interval can not be 

readily shown, the interval should be increased to 20 feet; beyond 

58515° 28 18
268 TOPOGEAPHIG INSTRUCTIONS OF GEOLOGICAL SURVEY

this the interval may be increased to 100 feet, but only where demanded 

by legibility.

Contour interval on land. The contour interval on land along 

river stretches should be 20 feet, but wherever a 20-foot office interpolation can be accurately made between the 100-foot contours the 

20-foot contours should be omitted and only 100-foot (heavy) 

contours drawn.

Tributaries. The topography of each tributary or side channel 

should be shown up to the limiting contour. In addition, the larger 

tributaries should be shown with topography for about a' quarter 

of a mile and then be sketched as far beyond as possible; for this 

purpose one or more additional set-ups may be taken if practicable.

Topography to be shown. The land features, including all culture 

usually found along streams but excluding large valleys or cities, 

must be accurately and completely surveyed by additional set-ups, 

intersections, or side traverses. The work should be done in such 

a manner that the data can later be incorporated in topographic 

maps when such areas are regularly mapped.

In the absence of special definite instructions the topography as 

outlined above should be mapped to an elevation of 200 feet above 

the stream and may be sketched for another 100 feet or more if such 

higher sketching can be done without additional set-ups. Mapped 

topography should be indicated by full lines, but where uncontrolled 

topography is sketched it should be drawn in dashed lines, to be 

clearly distinguishable.

To facilitate use of the field sheets by office engineers penciled 

figures of elevation must be placed wherever they will be legible, 

and numerous penciled contour numbers should be placed on intermediate as well as on emphasized contours.

Gaging stations, dams, etc. All gaging stations must be located, 

and the elevation of the zero of the gage given. The ownership, 

whether United States Geological Survey, Weather Bureau, Army 

Engineers, or private, must be stated.

The location of all dams, power houses, canals, flumes, penstocks, 

and points of diversion should be shown, with elevations above and 

below all dams and power houses.

Rapids should be indicated by means of the conventional sign, 

which, however, should not obscure contour crossings or other important data.

Long azimuth lines should be drawn on each separate traverse 

sheet.

Land lines. In sectionized country it is important that the land 

net be placed upon the sheets with an accuracy suitable for 40-acre 

references. Inasmuch as the width of a river survey is narrow at 

best, the search for all existing corners that may be found within the
TOPOGRAPHIC MAPPING 269

belt of the survey should be systematic and diligent. (See field 

instructions, p. 239.)

Party chiefs must procure reproductions of Land Office plats, which 

preferably should be photographs furnished on office requisition. 

They should also ascertain if any such plats are under suspension by 

the General Land Office and procure copies of the notes of all such 

retracements or exterior notes of townships not sectionized as fall 

within the limits of the river survey. General inquiry should also be 

made whenever practicable at the local United States land offices. 

Existing maps or plats showing corners previously found, such as 

those issued by the Forest Service or by railroad, power, irrigation, 

and other companies, should be systematically looked for and procured whenever possible. Inquiry should be made through deputy 

mineral surveyors, county surveyors, and local engineers as to the 

existence and location of known corners or ties.

Vertical control. In order that river surveys may be referred to 

sea-level datum the starting point of the line should wherever possible be tied to the nearest Geological Survey or other adjusted level 

bench mark before the survey begins; the elevations should also be 

tied to all other bench marks encountered in the course of the work. 

Owing to the difficulty of rerunning a line of river traverse extreme 

care should be taken both in the observations and in the notes, in 

order that errors in elevation may be avoided.

Horizontal control. As liver surveys are based upon a plane-table 

traverse line that is subject to no horizontal control, every effort 

should be made to reduce the errors of observation and plotting to 

a minimum, and to this end each stadia reading for distance should be 

twice read and each plotted distance checked.

KESERVOIR AND DAM SITES

The relations between possible reservoir sites and possible dam 

sites should be frequently observed as the work progresses in order 

that the survey of these two counterparts may illustrate to the fullest 

the natural storage possibilities. In considering the practicability 

of a reservoir site the character of the improvements and industries 

and the amount, kind, and distribution of the timber within the site 

should be noted and the value of the land to be submerged should be 

estimated.

The contours within reservoir sites should be accurately determined 

on a 20-foot interval up to the height of the possible dam. Ten-foot 

intermediate contours should be surveyed, drawn in close-dashed 

lines, and numbered wherever an office interpolation if erroneous 

would seriously affect an estimate of storage that is, wherever an 

irregular spacing of 10-foot contours extends over a considerable 

area.
270 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

Special large-scale surveys should be made of dam sites favorably 

located in regard to reservoir sites whose existence has been previously ascertained by survey, with 5 or 10 foot contours up to the 

height of the practicable dam or storage. The scale for dam-site 

surveys will be indicated by the conservation branch but in general 

will be from 100 to 500 feet to 1 inch. The depth of water at the dam 

site and the character of bottom and abutments should be noted 

wherever possible. The elevation of the water surface should be 

shown for each dam-site survey.

WRITTEN REPORTS

Signed written reports on river surveys, accompanied by photographs when practicable, should be submitted in general conformity 

with the following instructions, except that map references should 

be made either to the plan sheets or to an advance sheet of the quadrangle map. Many desirable facts pertaining to small streams can 

receive all necessary attention in the written report.

Stream flow. An approximate estimate of stream flow should be 

obtained a short distance below the mouth of each major tributary. 

The date of observation and the stage of the water should be noted. 

Measurements should be made, if possible, at a straight and uniform 

stretch of water about 200 feet long, free from rapids and cross currents. The velocity of the current in linear feet per second should 

be obtained by timing floats (chips) over a measured (stadia) course 

and using an average of two or more floatings made in or near midstream and nearer shore. The mean cross section in square feet 

may be assumed to be the mean of the cross sections at the two ends 

of the stretch. The individual cross sections are obtained separately 

by multiplying the local width (stadia or intersect) by the corresponding average estimated depth. The desired stream flow (discharge) in second-feet is obtained by multiplying the velocity in 

linear feet per second by the mean cross section. Example: Course 

200 feet; floats average 100 seconds in transit; upper and lower 

cross sections are 300 and 400 square feet, respectively; 2 X 350 = 700 

second-feet of stream flow.

Estimated flow of all important tributaries should be obtained in 

the same manner.

As the minimum, low-water flow denotes the maximum availability 

of the stream without recourse to storage, and as the high-water flow 

in large measure gives its availability for storage, all reliable information bearing on these points that it is practicable to obtain should 

be sought, and all information regarding the range of water stages, 

including data as to past floods or extreme low water, with dates, 

should be recorded.
TOPOGRAPHIC MAPPING 271

Water power. All dams or other existing natural sites for waterpower development should be located and described. If any present 

development exists, the ownership, character, abutments, possibility 

of increasing height, and condition of stream bed should be recorded.

The plan and profile sheets of all dam and reservoir sites determined 

by the river survey should be supplemented by all obtainable pertinent facts. Any favorable stretches of stream that might be of value 

for developing power should be noted. The essentials are a diversiondam site (intake), a site for a waterway alongside (canal or conduit), 

and a combined site for a relatively short pressure pipe line and for 

a power plant on the shore. Favorable sites for diversion of water 

for irrigation should be noted.

Information should be collected by observation and by local inquiry 

as to (1) power development, including location of existing or proposed power plants, points of diversion, location and capacity of 

conduit, amount of head available, location of power house, point 

of return of water to stream, installation and rating of turbines and 

generators, location, equipment, and ownership of power-transmission 

lines; (2) reservoirs, including location, height of dam, capacity, use, 

and ownership; (3) irrigation works, including canals and ditches, 

points of diversion, capacity, location, and ownership; (4) municipal 

water-supply systems, including location of pipes, source of water, 

etc.

Character of adjacent land. The belt of topography mapped should 

be classified as to kind, amount, and distribution of timber; extent 

of cultivated areas; existence of grazing or natural hay lands and 

duration of range; and extent of barren or A\raste lands.

ENDING FIELD SEASON

Work turned over to another. If unfinished field work is left for a 

successor to complete he should be provided with a list of the field 

sheets and other important field data that are turned over, also a 

memorandum of the condition in which the work is left, with copies of 

the original field instructions, including supplemental instructions 

that may have been issued. He should have a clear understanding as 

to where there may be need for additional inquiry regarding names or 

other data for example, the status of power lines, road classification, 

and city boundaries.

Completing field work. In order to insure against omission of field 

data the information sheet, name sheet, road-classification sheet, 

and woodland sheet should be checked over for completeness before 

making plans to leave the field. The plane-table sheets should be 

looked over for completeness and legibility.

Shipment of map material. In general, all field sheets completed 

before the end of the field season should be shipped to the office
272 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

rather than retained in the field; tracings, however, should be made of 

map borders needed for further field joining. All map material 

should be shipped by express or registered mail to the chief topographic engineer at Washington or, if so instructed, to the division 

chief in charge of a field office. All original and duplicate record 

books such as level and bench-mark books should be forwarded by 

registered mail on different days. A letter of transmittal covering 

each shipment of instruments, maps, or records, and a list of all 

items should be sent under separate cover. If any maps or map 

material is carried to Washington in personal baggage, it should be 

delivered immediately on its arrival at the office to the section of 

inspection and editing for recording.

Monthly field reports. See "Reports of field parties" (p. 19, part 

A). Reports should be complete so far as the data asked for are 

concerned or so far as they apply to the work in progress, and, in 

general, they should be confined to the data for which columns and 

spaces are provided. Promptness in the submission of reports is 

necessary because of the routine described under "Monthly office 

report routine" (p. 277).

OFFICE WORK 

SCOPE OF OFFICE WORK ON TOPOGRAPHIC MAPS

The office work in connection with topographic mapping consists 

in preparing the field sheets as copy for reproduction and in the reproduction of the maps. The preparation of the copy and the proof 

reading of reproduction is done in the topographic branch, but the 

reproduction of the maps is done in the engraving division of the 

Geological Survey. The office work of triangulation, transit traverse, 

leveling, and map compilation from aerial photographs is described in 

parts B, C, D, and F of the "Topographic instructions." In general, 

the sequence of the office work in topographic mapping is as outlined 

below.

Assembly. The field sheets representing the completed topographic mapping should be assembled into as few final sheets as 

practicable, preferably into two half sheets representing the north 

and south halves of the quadrangle. The two half or other sheets 

should be cut at their common sheet borders and by transfer of 

topography where necessary made complete copy when fitted together. 

Where final topographic mapping has been done on separate field 

sheets other than on the principal north or south half sheets, such 

separate field sheets should be stripped and pasted in position on the 

principal half sheets on which they fall. (See "Transferring," p. 282, 

and "Pasting," p. 283.) The field sheets should be assembled and 

completed in pencil before the inking begins, if this is practicable,
TOPOGRAPHIC MAPPING 273

inasmuch as the inking of the map can then go forward without the 

delays incident to joining the interior edges that may be on several 

separate field sheets.

Adjustment. The results of separate traverse surveys that may 

not have been adjusted in the field should be completely adjusted into 

position on the final field sheets before these sheets are assembled 

or inked. (See "Adjustment of traverse lines," p. 212.)

Inking. When the penciling and adjustment and preferably also 

the assembling of the final field sheets is complete they should be 

inked. (See "Inking of topographic field sheets," p. 277.)

Lettering. When the inking of the map has been completed it 

should be lettered. (See "Lettering of topographic field sheets," 

p. 304.)

Checking? When the topographic map has been completely inked 

and lettered and before it is reproduced in any form the inking and 

lettering should be checked by someone other than the one or more 

engaged in the inking. (See " Checking of inked field sheets," p. 310.)

Inspection. Prior to the submission of final map drawings for 

advance-sheet photolithography they should be passed upon by the 

section of inspection and editing to insure general conformity with 

standard practices. (See "Inspection of topographic maps," p. 313.)

Advance sheets. Completed topographic map drawings are first 

reproduced by photolithography and issued as "advance sheets subject to correction." (See "Advance sheets," p. 317.) Advance sheets 

are intended to serve the immediate needs of engineers and others 

pending the publication of the engraved map, and they also serve 

as a basis for corrections, which are invited from any competent 

source.

Control examination. Each topographic map should be examined 

in the section of inspection and editing for the correctness of its 

representation of the primary control features of the map. (See 

"Control examination," p. 319.) The control examination should be 

made before the map is edited for engraving or before it is photolithographed if the map is to be reproduced by photolithography 

alone. The control examination is usually made after the advance 

sheets have been issued but may be made before.

Editing. Each topographic map that is to be regularly published 

by the Geological Survey, whether by engraving or by photolithography, must be edited prior to its submission for final reproduction. 

(See "Editing of topographic maps," p. 320.) The map editing consists in a critical review of the map for its general coordination and 

conformity with Geological Survey instructions and policies and in

3 The term "proof reading" has long been used in the topographic branch both in its ordinary sense, 

meaning the reading of proof, and in reference to the checking of manuscript maps preliminary to the 

inspection and advance-sheet photolithography by others than those who have done the work. For this 

special sense the term "checking" will be used hereafter.
274 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

the preparation of special instructions for its engraving or other 

reproduction.

Engraving. Most topographic maps of the Geological Survey are 

reproduced by engraving on copper, from which transfers are made 

to the printing stone or metal. (See "Engraving of topographic 

maps," p. 336.) The engraving is done in the engraving division of 

the Geological Survey.

Proof reading of engraved maps. Proofs from the separate copper 

plates and combined stone proofs from the final printing plates for 

each topographic map that is reproduced by engraving are read by 

the section of inspection and editing.

Reprints of topographic maps. When the map-room stocks of topographic maps become nearly exhausted reprints are requested by the 

division of distribution. The section of inspection and editing prepares the reprint copy. (See "Reprints of topographic maps," 

p. 340.)

Monthly office reports. See "Office reports" (p. 19, part A). Inking should be reported in terms of square miles inked and not in 

percentage of area. The column headed "Sq. mi. mapped" should 

agree with the total area reported as mapped. Inasmuch as a report 

on the number of square miles inked each month is intended to 

indicate approximate progress only, the figures need be given only 

to about the nearest 5 per cent, which for a 15' quadrangle would 

be to the nearest 10 square miles. As the inking approaches completion the accuracy of reporting should increase, and for this purpose 

the uninked area can be readily measured.

Where culture and drainage only have been inked such inking 

should be converted into an approximate equivalent expressed in 

square miles, in order that the inking report may give an index of 

progress. For example, if the total culture on the mapped area is 

roughly estimated to represent 30 per cent, the drainage 10 per cent, 

and the contours 60 per cent of the time needed to ink the sheet, and 

if half the culture has been inked but no drainage or contours, then 

one-half of 30 per cent, or 15 per cent, of the total area mapped 

should be reported as having been inked, and this for a quadrangle 

covering 240 square miles would represent an equivalent of 36 

square miles inked, which may be reported in round numbers as 

40 square miles. A statement showing total areas inked to date, 

listed by States, quadrangles, and months, may be obtained on 

request from the section of inspection and editing, where the data 

are filed in a book kept for the purpose.

MISCELLANEOUS OFFICE WORK

Field sheets to section of inspection and editing. All field sheets and 

field map material reaching the office from the field must be at once 

delivered to the section of inspection and editing, where they will be
TOPOGRAPHIC MAPPING 275

inventoried, filed under the name of the quadrangle or project, and 

made promptly available for issue for office work. Each separate 

original field sheet, traverse sheet, tracing, file of notes or plats, 

miscellaneous map, or other field map material will be listed in ink 

on the front cover of the jacket for the quadrangle or project. The 

list should be dated and headed "Received from the field." Subsequent receipts of maps or map material from the field or elsewhere 

should also be listed and dated. Withdrawals of field material should 

be charged out on the right-hand side of the cover and should be 

dated.

Jacket. The jacket, indorsed with the list of maps and material 

received from the field, should remain in the custodian's room in 

the section of inspection and editing, where it should be available 

for reference until the map is ready for approval and transmission 

for advance-sheet photolithography. From the time the map is 

made available for editing, by j acket indorsement'' On editing docket'' 

(see p. 321), until the map is finally engraved and printed, the map and 

its necessary accompanying sheets must be transmitted in the jacket. 

Each transmission should be suitably indorsed on the jacket and 

dated, the jacket thus providing a complete record of the progress 

of the map through all its stages, beginning with the receipt of the 

original material from the field and ending with the final publication 

of the :z:ip.

Progress book, Held mapping. A progress book showing the areas 

mapped to date throughout the United States is filed in the office of 

the chief topographic engineer and should be kept current by the 

section of inspection and editing. The progress book consists of a 

series of sectional maps of the United States printed on a uniform 

scale of 1:500,000, on which the names and quadrangle limits of 

published maps and the reserved names and quadrangle limits for 

future work are indicated. The maps that have been published in 

final form should be shown by a line underscored below the name of 

the quadrangle. The areas covered by topographic mapping during 

successive fiscal years should be distinguished by flat tints of distinctive colors, and the areas covered by new mapping should be 

entered in the progress book at the middle of each month from data 

supplied on the monthly field reports.

Authority for quadrangle names. The published and reserved names 

as shown in the progress book of field mapping are the only authorized quadrangle names to be used in connection with the standard 

topographic mapping of regular quadrangle areas, whether used for 

planning field work, for making estimates, or for field or office cost 

keeping or reports.

If a named quadrangle, whatever its size, is to be subdivided into 

four quarters which have not been or for reasons of expediency are
276 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

not to be provisionally named, the four quarters should be designated 

Nos. 1, 2, 3, and 4, the numbering progressing in a counter-clockwise 

direction. For example, the four 15' quadrangles within the Riverside 30' quadrangle would be designated "Riverside No. 1," "Riverside No. 2," "Riverside No. 3," and "Riverside No. 4" for the northeast, northwest, southwest, and southeast quarters, respectively.

Where a reserved quadrangle name, after the field survey, is found 

to be inappropriate or incorrect or can be replaced by a more suitable 

name the change can be authorized only by a special letter signed 

by the chief topographic engineer. (See "Changes in names," p.304.) 

Changes in quadrangle names should be promptly indicated in the 

progress book of field mapping and in all other current office and field 

records.

Progress book, inspection and editing. A progress -book should be 

kept in the section of inspection and editing showing in condensed 

tabular form the office progress of each topographic map and project from the receipt of the field sheets to the final publication of the 

map. The names of quadrangles and projects should be entered in 

the book in the order in which they are received from the field or 

elsewhere, and the finding list should be an alphabetic index that is 

kept current by including each new topographic map that is received 

for office work. Entries in the book should be made on the day the 

information becomes effective.

The purpose of this book is to afford ready reference to office progress on any topographic map and to supply a means of locating the 

map itself when needed. The list also serves as a check against undue 

delay in the inking or other completion of the office work on maps 

and as a guide in the preparation of the annual engraving docket.

Annual summary ojfield work. An annual summary of topographic 

field work, including control, for the fiscal year should be prepared in 

the section of inspection and editing. The data listed should be such 

as are needed for the annual report of the director, the monthly report 

of the chief topographic engineer to the director, and such monthly 

reports to cooperating officials as are currently required. The summary should be kept by States and separate cooperative State or 

other appropriations. The data should be added to the summary by 

months and directly from the monthly field reports as soon as received. 

Quadrangles and projects should be indicated as "completed" when 

so reported from the field.

The total area in square miles reported for each completed quadrangle should be checked with the figure given in the standard tables, 

and in case of a difference the tabular figure should be used. Large 

differences should be subject to correspondence or review when the 

map involved reaches the office.
TOPOGRAPHIC MAPPING 277

Monthly office report routine. Promptness in the submission of 

reports is necessary because of the following monthly office routine: 

(a.) Check up to insure a 30-day report from each employee; (&) 

assignment of cost charges by division and section chiefs against 

each piece of work by each employee; (c) entry of field data in the 

annual summary of field work (see p. 276); (d) entry of field and office 

data in the monthly summary of completed quadrangles (or projects) 

and in the inking progress book; (e) compilation of data for the 

report of the chief topographic engineer to the director, rendered on 

the 8th of each month; (/) compilation of sheet and salary charges 

for submission to the section of accounts on the 10th of each month.

Annual report. The annual report of the work of the topographic 

branch (director's annual report) should be prepared in the section 

of inspection and editing. Chiefs of sections and others responsible 

for information needed in the annual report should forward such data 

to the chief of the section of inspection and editing as soon after July 1 

as practicable.

The chief of the section of inspection and editing should also prepare and forward to the editor of texts a summary for the work of 

the section of inspection and editing reported under "Work on 

publications."

INKING OF TOPOGRAPHIC FIELD SHEETS

GENERAL INSTRUCTIONS

Reference to Jield instructions. The inking of topographic maps 

should be done with as full an understanding of the instructions for 

field work as is essential for a proper interpretation of the penciled 

copy. Topographers inking their own field sheets will obviously have 

this knowledge, but an inker who is not himself responsible for the field 

mapping (either as author or as party chief) should familiarize himself 

with as much of the instructions for field work (see pp. 226-272) 

as may be necessary to interpret the penciled copy properly. For 

this purpose many cross references are given in the instructions that 

follow for the inking of the cultural, drainage, and relief features.

Character. In inking field sheets that are to serve as copy for the 

engraver the topographer or draftsman should first ascertain the scale 

of final publication and then do his inking in accordance with that 

scale. He should bear in mind that most manuscript maps are to be 

reduced and that due allowance must be made in the inking for the 

reduced size of the final map. He should also remember that all 

drawings are to be transferred to the copper plates by photographic 

processes and that it is important that all lines, whatever their color, 

shall be so inked as to photograph with distinctness. The topographer should execute his inking with neatness and exactness, so that
278 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

there may be no doubt as to the placing and meaning of the symbols 

and lines, and he should aim to give the drafting such quality and 

clearness that it will enable the engraver to work with rapidity and 

certainty; but inasmuch as anything beyond that is superfluous, he 

should beware of wasting time and effort on artistic effects or excessive 

refinement.

Occasionally more detail is mapped than can be legibly engraved 

and printed either on the same scale or on a reduced scale. When 

areas of unusual congestion are reached in the course of inking the 

topographer or draftsman should seek instructions with a view 

toward possible generalization or even omission, in order that the 

engraver may have copy that can be readily understood and legibly 

reproduced. Where, however, there is unavoidable heavy culture, 

detailed contouring, or close register between any of the three colors 

used, no refinement either in the penciling or in the inking can be 

regarded as excessive. In congested places, therefore, no more lines 

should be inked than are absolutely necessary for the guidance of the 

engraver, and the copy should be left as open as the character of 

the topography will permit. If, however, the inker is unable to furnish the required clear copy in the congested place, he should seek 

advice before attempting the inking and thus assist rather than retard 

the completion of the legible copy the engraver must have.

Consultation with section of inspection and editing. Topographic 

engineers and others engaged in the office preparation of topographic 

maps for reproduction or other transmission are expected to consult 

freely with the members of the section of inspection and editing whenever any doubtful points arise and to follow their advice. Every 

effort should be made to have the map and all accompanying data in 

as complete and perfect shape as possible when submitted to the 

section of inspection and editing. Questions of a purely editorial 

nature, such as a matter needing correspondence or administrative 

decision, should be left for editorial attention, but data giving all the 

essential facts should accompany the map.

Certain maps twice inked. Cooperative agreements and other 

demands occasionally require that certain field surveys or parts 

thereof shall carry more detail than is to be reproduced save on 

advance-sheet photolithographs. For example, a city may be surveyed on a large scale, and the resulting map may be lithographed as 

an advance sheet on the same scale, and later the map may be 

redrawn on a smaller scale as copy for the usual engraved reproduction; or an area may be surveyed and the map lithographed for special use with a small contour interval and afterward engraved and 

published with a larger contour interval; or certain areas or strips 

may be surveyed on a larger scale than is usual in order to provide 

advance photolithographs of maps as, for example, for highway
TOPOGBAPHIC MAPPING 279

projects with provision for redrawing the maps on a reduced scale 

as copy for engraved reproduction. In these cases the field work 

should be executed in a detail commensurate with that called for 

by the special-purpose larger-scale survey, and the less detailed copy 

for final publication should be prepared by redrafting the same map 

after it has been reduced to the usual scale that is used as copy for 

engraving. For this redrawing it is customary to reduce the map by 

photolithography, print it in light blue on drawing paper, and redraw 

only such detail as is called for by the reduced scale of publication.

It is sometimes desirable to use a previously published map on a 

large scale as part copy for a new map on a smaller scale. In such 

cases the larger-scale published map should be reduced by photolithography to the scale of the new map, printed in light blue on 

drawing paper, and redrawn with its detail appropriately expressed 

for the smaller-scale reproduction. An example of the need for 

redrafting a published map is afforded by the survey of a 30' quadrangle, one quarter of which was mapped on a scale of 1 :4S,000, for 

publication on a scale of 1 :62,500, and it is found desirable to redraw 

the map on the reduced scale of 1 :96,000 (the field scale for the 

survey of the 30' quadrangle) in order that the greater amount of 

detailed expression used in the larger-scale survey may be generalized 

in redrafting and made to conform to the treatment used in the 

survey of the other parts of the 30' quadrangle.

Inks. The inks that are used must be the best obtainable to meet 

the office requirements. The important specifications are that the 

ink will permit a clear photolithographic reproduction, flow freely 

from the pen, and not spread or afterward smear as a result of any 

ordinary handling of the map. The following colors are issued: 

Black, a prepared waterproof liquid ink, in small bottles, to be used 

directly from the bottle; Prussian blue, burnt sienna, red, and 

Hooker's green paints, in small tubes, to be mixed in small bottles 

(furnished by the Geological Survey) in about the proportion of three 

parts of water to one part of the tube color, to which are added a few 

small glass beads to facilitate mixing when shaken.

Colors. The field sheets should be inked in the three standard 

colors used in printing the map black for the cultural features, 

blue for the drainage features, and brown for the relief features.

The use of red is reserved chiefly for the inking of certain data that 

are not to be engraved yet should be inked in order that they may 

become permanent office records and may appear upon the advance 

sheets. An exception is made for land lines, which will be inked in 

red (engraved in black) in order that the engraver may more readily 

distinguish them from road lines, projection lines, or other lines that 

may be on or near the section lines.
280

The use of green is reserved for exceptional needs, such as for 

showing a second projection which is based on another horizontal 

datum and for showing corrections where erasures on the original 

are not desirable.

Sequence of inking. Unless special reasons demand otherwise, 

the features on the map should be inked in the folJowing order: 

(1) Culture, (2) drainage, (3) elevations, (4) contouring, (5) lettering.

Precautions before inking maps. Where woodland outlines are 

carried in pencil on the final field sheets the field woodland tracings 

should be verified for completeness before the inking of the topog- 

* raphy obliterates the woodland copy. Where an elevation tracing 

has been made or is required (see "Elevation tracing," p. 241) the 

tracing should be compared with the final field sheets to insure that 

all necessary elevations have been traced before the inking and 

handling of the map render the faint pencil figures illegible. The 

final field sheets should also be carefully examined for names or 

road-classification data that may have been faintly lettered on them 

and inadvertently overlooked in making up the field name or roadclassification sheets.

Inking projection lines. In inking projections on topographic maps 

the penciled projection should be inked even though the paper has 

changed. The projection should not be corrected to agree with the 

tabular figures, nor should the quadrangle corners be connected by 

meridional straight lines in order to force a joining between the two 

half-sheet projections. If the projections do not join at the halfsheet line, the discrepancy, if appreciable, should be taken care of 

in the photolithography, if for an advance sheet, and by adjustment 

in small blocks, if for transfer to copper.

Over-edge inking. All over-edge topography should be inked that 

represents (a) an unmapped area (see "Adjoining unmapped areas, 

p. 227); (&) an area previously mapped on a smaller scale; (c) a 

correction to previous work that was mapped on the same scale 

(see "Joining previous work," p. 227); (d) an important correction 

to previous work on a larger scale. Over-edge topography on special 

large-scale military maps should not be inked unless inking is requested. 

The over-edge topography described under (a) and (6) should appear 

on the advance sheets, but that described under (c) and (d) will 

be wiped off the negatives and will not appear on the advance sheets.

Symbols. The symbols used on the topographic maps of the 

United States Geological Survey conform to the "Standard symbols" 

as adopted by the Federal Board of Surveys and Maps and prescribed for use by all map-making bureaus of the Government. 

(See pis. 18-23.) As many of the symbols in the standard set are 

not used at present by the Geological Survey, none should be used on 

manuscript sheets unless they have been approved for Geological
TOPOGKAPHIC MAPPING 281

Survey use. All topographic engineers are expected to be familiar 

with the symbols that are in current use by the Geological Survey.

SUGGESTIONS FOR INKING

The preparation of field sheets for reproduction differs somewhat 

from general drafting. Because of the relatively small scale upon 

which quadrangle maps are drawn their inking is essentially freehand drafting, and for this reason lettering pens of several degrees 

of fineness are employed almost exclusively.

Black irilc.. A waterproof black ink only is approved for regular 

use. Skilled draftsmen may draw better lines with a nonwaterproof 

black ink, especially on a poor surface, but the considerable handling 

to which the drawing is subjected before it is engraved or otherwise 

reproduced is so likely to smear the congested places in the inking 

that the use of a nonwaterproof black ink is not often approved for 

such use.

Pens. The use of a ruling (right line) pen for the drafting of straight 

lines is optional. Many draftsmen prefer to draw straight lines with 

a lettering pen. A ruling pen should be held nearly vertical and not 

on a slant, and just enough pressure should be exerted to keep the 

pen in contact with the paper. If the ink at the lower end of the 

pen dries slightly so that it will not flow, pinching the pen will often 

start the ink. A ruling pen should be kept sharp and clean, and its 

points should be ground to the same length. If ink will not flow 

freely from a lettering pen holding it in the blaze of a match for a 

second will burn off any oil that may have adhered to it from handling. 

All pens should be thoroughly cleaned before putting away.

Mixing water colors. Two methods of preparing water-color paints 

for use as inks may be used dissolving the paint with a wet brush and 

transferring it to the pen, or mixing a quantity of the paint in a bottle. 

The latter method is in more general use, and the mixture is prepared 

as described below: Squeeze the paint from the tube into a small 

wide-mouthed bottle in which four or five glass beads have been 

placed. Add 3 parts of warm water to 1 part of the paint and let it 

mix, shaking the bottle and the beads to facilitate the mixing. If the 

mixture is too thick it will not flow freely from the pen and if it is 

too thin, the drafted lines will lack depth of color. To obtain the best 

mixture, test it as follows: Dip a lettering pen deep in tr^e mixture and 

withdraw it. If the paint swells out in globular form it is too thick, 

and a few drops of water should be added; this should be repeated 

until the test shows the ink fairly flat on the pen. The bottle should 

be frequently shaken during the course of inking, in order to keep 

the paint in an evenly mixed suspension. A few drops of carbolic acid 

will prevent the mixture from souring in warm, weather.
282 TOPOGEAPHIC INSTEUCTIONS OF GEOLOGICAL SURVEY

Inking roads. Roads may be inked with a ruling pen but are best 

inked with a fine lettering pen, used against a small beveled triangle. 

A uniform width of road is dependent upon the skill of the inker, as 

the two sides of the road are inked separately. Curves may be shown 

as a succession of short tangents or inked freehand.

Inking railroads. Where sidings, spurs, and yard tracks are to be 

inked these tracks and the parallel main track or tracks opposite them 

should be inked first in fine lines, and then the main tracks on each 

end inked in slightly heavier lines. On the engraved plates the main 

track as well as the siding is cut in a fine line.

Inking drainage and contours. The drainage or contours should be 

inked toward the draftsman, the position of the map being shifted 

from time to time to make this possible, and all lines within convenient reach should be inked before the position is changed. To 

obtain the finest and sharpest lines for the intermediate contours a 

finer pen may be used than that used for the inking of the heavy 

contours. Contour figures should be made in a single-stroke style 

rather than shaded.

Erasures. In making an erasure a knife must not be used except 

to remove the ink that is on the surface of the paper. After this has 

been done the erasure should be completed with a fine sand and a 

plain rubber eraser, only light pressure being exerted and the surface 

afterward burnished with a smooth bone handle. If the paper has 

become soft and pulpy by erasures, an inking surface may be restored 

by brushing one or two coats of collodion over the area affected.

TRANSFERRING

Celluloid transfers. If a map section of considerable size heeds to 

be transferred to the main map and only slight adjustment is necessary, the work can often be advantageously done by means of a 

celluloid transfer. A celluloid transfer may be obtained on requisition 

and consists of a photolithographic reproduction of the map printed 

in a graphite ink on the under side of a sheet of transparent celluloid.

A celluloid transfer should be used within a few days, as the ink 

may dry, but if used at once the excess of graphite should be gently 

rubbed off until a trial transfer gives a sharp line. The celluloid transfer should be adjusted in place, printed side down, and burnished 

with a half round smooth piece of steel and moved as often as may be 

needed in the adjustment. Any graphite remaining can be easily 

erased after inking.

Transfer by tracing. A section of a map, such as a traverse line^ 

may be transferred to the main sheet by tracing on thin paper only 

the critical or salient parts and omitting lines or data that are close 

together, because these are more accurately added free-hand afterward; then slipping a piece of transfer paper, carbon, side down?
U. S. GEOLOGICAL SURVEY BULLETIN 788 PLATE 15

MISSOURI 

CIoARKSDALE QUADRANGLE

R.33 W. 135' R.32 W. 9A-°3O'.

x STATE OF MISSOURI ' 

BUREAU OF G-EOLOG-Y AND MINES 

H.A.BUEHLER, DIRECTOR AND STATE GEOLOGIST

4O 00 

T.6O N

^DEPARTMENT OF THE INTERIOR 

U. S. GE OLO GICAL SURVEY

R.34- W.I AO' I

T.59 N.

55

T.58 N. 

50'

1915000 

YARDS"

T.57 N. 

39'4-5'

A-O CO' 

T.6O N.

T.59 N.

55'

T.58 N. 50'

___ ...___ __,_ . 30° AC'

R.33 \(V. 35' R.3,2W. 9A-" 3D1 

Polyconic projection. North American datum. 

5000y;?rd grid based upon U.S.zone system,D.

Scale essoo

20000 Feet 

6 Kaloineters

Ccxrrbcrur interveQ. 2O feet.

Datum/ -is -metm s&m level

CLARKSDALE, MO.

Edition of 1925

4-5' R.34-W. AO' ||2I5000YAROS

Topography by J. B.LeavitT and F. L.Whaley 

Control by U.S.Geological Survey and 

U.S.Coast and Geodetic Survey 

Surveyed in 1923

DECLINATION, 1323

MARGINAL, LETTERING FOR TOPOGRAPHIC MAPS
U. S. GEOLOGICAL SURVEY BULLETIN 788 PLATE 16

PLAN AND PROFILE OF 

CLEARWATER RIVER, IDAHO SHEET A

DEPARTMENT OF THE INTERIOR 

U. S. GEOLOGICAL SURVEY

Subject to adjustment

DIAGRAM Of TOWNSHIP

(7 plan sheets, 7 profile sheets) 

Printed in 1926

Topography by R. W. Burchard 

Surveyed in 1924

APPROXIMATE MEAN 

DECLINATION, 1924

Scale 31,680

2Miles

4,000 2,000 8,OOOFeet

2 Kilometers

Contour interval on land 20 feet

Contour interval on river surface 5 feet

Datum is mean sea level

MARGINAL, LETTERING FOR RIVER-SURVEY SHEETS







TOPOGRAPHIC MAPPING 283

between the tracing and the map, and going over the traced lines 

again with a fine metal point or a hard pencil. Transfer paper may 

be made by blackening one side of thin tracing paper with a soft 

pencil and rubbing the blackened surface down to a smooth finish 

with blotting paper.

PASTING

Preparing a patch. A separate original section of a topographic 

map that needs no adjustment may be transferred to the main map 

by pasting it on as a patch in its true position. Indicate with a light 

pencil line the limits of the part that is to be pasted. The map section should then be separated from the linen filling of the doublemounted drawing paper. To do this lay the section of the map face 

down on a desk or other-hard clean surface and start the separation 

at one corner with the finger nail. As the peeling progresses follow 

up with a triangle weighted down by hand so that the face of the map 

will lie flat and be in contact with the desk or other surface at the point 

where the peeling is taking place. If this method is followed the map 

section will not be torn or buckled. When the map section has been 

peeled trim it along the pasting limits previously indicated by a pencil 

line and bevel the edge for a width of a quarter to half an inch. To 

bevel the edge place the patch face down on a cutting board, cut the 

bevel with a sharp knife and smooth it off with fine sandpaper. Do 

not cut along a projection line, and so far as practicable, avoid cutting along a road or land line.

Pasting the patch. Place the map section in position on the main 

map and indicate register marks so that it can be again placed in 

identically the same position. Rubber cement, thinned with pure 

benzine or refined benzol, may be used as the adhesive and has the 

advantage of slow drying and ease of removal at any later time if 

needed. Coat the area of the main map to which the patch is to be 

applied and the back of the patch with at least three paintings of the 

rubber cement and allow each coat to dry before another is added. 

Do not apply the patch until the last coat of cement is dry. To 

affix the patch place one set of register marks in position, holding the 

rest of the patch away from the map, while strips of paper are placed 

between it and the map in such a manner as to be removable after the 

other marks have been brought into register. When the patch is in a 

satisfactory position, withdraw the paper strips and burnish the patch 

into a good contact, paying particular attention to the edges. Superfluous cement can be rubbed off with the fingers or with a soft rubber 

eraser. If it is desired to remove the patch, start the peeling at one 

corner with a knife blade and gradually pry it loose. Before replacing the patch the old cement should be removed; then proceed as 

before.

58515° 28 19
284 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL, STJKVEY 

INKING OF CULTURAL FEATURES

Cultural features should be inked in black except as some other 

color is specified under the headings below. Cultural features that 

are added for sheet information only and are not to be engraved, or 

features for which the engraving may be in doubt, may be inked in 

red. For general instructions covering the inking of all map features 

see pages 277-283.

The field instructions for the mapping of cultural features (pp. 229- 

242) are to be regarded as supplemental information needed for the 

proper interpretation of the following instructions for the inking of cultural features, and for this reason frequent cross references are given.

Roads, country. Roads should be inked by solid double parallel 

lines or by dashed double parallel lines, according to the penciled 

copy furnished in compliance with instructions for field work. (See 

"Roads," p. 229.)

Roads are engraved to standard gages for each publication scale, 

unless the drafted copy calls for a wider gage for certain roads, such 

as highways or avenues of unusual width, or unless on large-scale maps 

special engraving instructions are given to cut all roads to widths as 

drawn. Roads should, therefore, with these exceptions, be inked of 

uniform width and with as fine lines as will remain firm and unbroken. 

As it is impracticable, however, especially on paper that has been 

rubbed in the field, to draft roads of the fineness and narrowness of 

engraved roads, even when these are enlarged to field scale, the topographer should ink the roads a little wider than the standard gage; 

a width of 75 feet (center measurement) when plotted on a scale of 

1 : 48,000 (approximately 0.02 inch) may be taken as a guide. If a 

narrower width is attempted the lines are likely to run together when 

reduced and transferred to the copper plates, and they may even run 

together on the drawing. A clear space in the middle of the road 

symbol is essential to furnish good road copy for the engraver.

In hiking the dashed double line road symbol care should be taken 

to maintain a uniform length of dashes, a uniform width between 

dashed lines, but not too close spacing between the successive pairs 

of dashes, and a uniform weight of individual lines, and the overlapping of either of the double dashed lines beyond the other should be 

avoided.

Where the middle of a road follows a projection line bordering an 

unmapped quadrangle, the road should be shown as entirely within or 

entirely without the mapped quadrangle so far as practicable. A 

space should be left between a house and the end of a road leading 

to it.

Streets, city. City streets should be inked only by the best draftsmen; and all street lines should be drawn fine and finished off neatly
TOPOGRAPHIC MAPPING 285

at the corners, a reading glass being used for this purpose where 

necessary. Any overrun of the inking into the open space inside the 

road symbol should be erased so as to leave clear copy. Cities and 

villages, where combined with contours and stream courses, present 

difficult copy for the engraver at best, and every endeavor should be 

made to keep the road lines fine and the copy as open as circumstances 

m'ay warrant.

Buildings in general. The houses on the manuscript sheet should 

be inked square and of uniform size and should be drafted by outlining 

an open inked square, with sharp corners, and afterward filling in. 

If houses are inked too small it becomes difficult to make them square, 

and unless they are inked square and sharp their identification as 

houses becomes uncertain even on the original drawing. The following approximate dimensions may be taken as standard for the inking 

of the conventional country-house symbol on the field scales specified : 

1 :96,000, 150 feet square; 1 :48,000, 75 feet; 1 : 31,680, 50 feet; 

1 : 24,000, 25 feet. These dimensions, however, should be increased 

or decreased in congested places, if the legibility is correspondingly 

improved. Large structures which, plotted to scale, exceed the size 

of the ordinary symbol should be shown with their individual plan 

outlines.

Use of blocks. If the buildings and blocks appear to have been 

penciled in conformity with the field instructions (see p. 231) they 

should be inked as penciled; but if they appear to be penciled closer 

together than the field specifications call for they should be inked in 

blocks.

Business and residence Nocks. Residence blocks (seep. 231) should 

be inked distinctly narrower than business blocks, but this distinction 

should be made in the inking only where it has been made in the field 

work and where the penciling or other copy is clear.

Churches and schoolhouses. The symbols for churches and schoolhouses are described under field instructions. (See p. 232.) The house 

part of either symbol should be inked the same size as called for under 

"Buildings in general" (p. 231). The flag may fly on either side of 

the pole, and in congested places the inked pole may be lengthened if 

the symbol is thereby made more legible.

Railroads. Before a railroad (see p. 232) is inked the penciled copy 

should be examined to determine its points of tangent and points of 

curve and then inked in such a way as to bring out a characteristic 

railroad alinement. The distinction between railroads of the steam 

type and electric trolley lines is given in the field instructions. For 

the former the cross ties are spaced twice as far apart as for the latter. 

Where the distinction is in doubt the wider spacing should be used, as 

the intermediate ties can easily be inserted if found necessary.
286 TOPOGEAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

In railroad yards, parallel spur tracks, etc., only as many tracks 

should be inked as can be legibly engraved on the publication scale, 

as too many tracks make difficult inking, illegible advance sheets, and 

impracticable engraving. Where switches and sidings are inked 

alongside single tracks both the main track and the side tracks 

should be inked in finer lines than the main track elsewhere; and 

these fine lines should be inked first and the extension of the main 

track inked afterward in a heavier line, to make clearer copy for 

engraving.

The penciled copy for railroads in juxtaposition should be checked 

before being followed.

Railroads and electric trolley lines that are within roadways should 

be shown only by the fine cross-tie lines at right angles to the road 

symbol, to the full width of the road as inked and with the spacing 

used in the corresponding regular symbols.

Tramways. Tramways should be inked in the broad-spaced railroad symbol. Aerial tramways should be inked in a broken line, and 

the name should be added where there is space.

Railroad crossings. In inking crossings of railroads and roads 

(see p. 232) a distinction should be made between a grade crossing and 

a crossing not on grade. Where the road passes under the railroad 

the road symbol should be broken and the railroad symbol continuous, 

and where the railroad passes under the road the railroad symbol 

should be broken and the road symbol continuous.

Railroad station buildings. A railroad-station symbol (see p. 232) 

should not be inked unless there is a building on the ground. The 

symbol for a railroad station should be carried across the track only 

where the location of the train stop would be otherwise uncertain. 

The railroad-station symbol should not be used in country regions 

where the presence of a crossroad or the position of the lettering 

sufficiently locates the tram, stop, and the use of the symbol should 

be confined chiefly to small towns and other places where the lettering can not be placed near the position of the train stop and where 

this position can not be inferred from the map.

Bridges. The bridge symbol (see p. 232) should be inked only 

where there is clear penciled copy or where definite information 

exists that there is a bridge of the importance specified in the field 

instructions. The symbol should be omitted in areas of heavy 

culture and wherever its presence would interfere with the legibility 

of the map on the publication scale. Ordinary railroad bridges and 

trestles should not be shown. Drawbridges on roads and railroads 

should be shown by a separate symbol. Bridge ends for viaducts 

should in general be omitted.

Ferries. Ferries (see p. 233) should be shown by the symbol, with 

the boat pointing upstream, or the word "FERRY," according to
TOPOGRAPHIC MAPPING 287

the available space on the map. The name of the ferry should be 

used in lieu of the word alone where the name is well recognized 

locally.

Fords. (See field instructions, p. 233.)

Trails. Poor pack trails and all foot trails should be inked in 

the dot symbol; good pack trails in the dashed-line symbol. Where 

the field penciled copy or classification is uncertain use the dashed 

symbol. (See p. 233.)

Steamboat routes. (See field instructions, p. 233.)

Canals and ditches. Canals and ditches should be inked in blue. 

(See p. 233.) Short ditches that have been penciled on the field sheets 

in the course of survey and have not been erased should not be inked 

if they appear to be laterals rather than main feeders. Abandoned 

canals should be inked if of the importance called for in the field 

instructions.

Canal locks. The symbol for canal locks should be inked only so 

far as it can be legibly engraved on the publication scale, and the 

upper and lower gates should be separately inked only where both 

gates can be legibly shown. If the penciled copy is not clear inquiry 

should be made before the inking is completed. (See p. 234.)

Aqueducts and pipe lines. (See field instructions, p. 234.)

Power-transmission lines. Power lines may be inked in black, 

but if they are in close contact with other cultural features they 

should be inked in red for clearer recognition. Power lines should 

not be inked in sections of heavy culture. (See p. 234.)

Tunnels. Railroad or road tunnels should be inked im black, 

aqueduct tunnels in blue. (See p. 234.)

Dams. The elevation of the top of a dam should be recorded. 

The dam should be inked to its mapped length only, and its ends 

should be represented at identical elevations as shown by the contouring. (See p. 234.)

Reservoirs. Artificial reservoirs surrounded by dams on all sides 

should not be inclosed by the dam symbol but should be outlined 

in blue like lakes or ponds; small reservoirs should be further emphasized by a blue wash. (See p. 234.)

Levees, cuts and fills, mine dumps. Levees, cuts and fills, and mine 

dumps should be inked in brown, and if more have been penciled 

than appear to be authorized by the field instructions (see p. 234) 

further instructions should be sought before inking those whose 

status is uncertain.

Depression contours. (See "Artificial depressions," p. 234.)

Wharves, piers, jetties, etc. Wh'arves, piers, docks, and similar 

structures should be inked in black, in outline only, as plotted to 

scale in the field. A narrow wharf or pier should, however, °be 

represented conventionally by a double line about the width of a
288 TOPOGKAPHIC INSTRUCTIONS OF GEOLOGICAL, SURVEY

narrow road. Jetties and breakwaters should be inked in single 

heavy black lines. (See p. 235.)

Lighthouses, etc. Lighthouses and lightships are to be shown by 

their respective symbols on all maps, whatever the scale.

Cemeteries. The outlines of cemeteries should be inked; the name, 

if well known, should be shown if there is space; otherwise a cross 

within the outline or the letters "GEM" alongside. Small private 

cemeteries should not be shown unless they constitute landmarks 

in a thinly settled country. (See p. 235.)

Mines and quarries. A careful distinction should be made between 

the inking of mine symbols in black if to be engraved and in red if 

intended for sheet information and advance lithographs only. (See 

p. 235.)

Oil and gas wells. The small circle inked in black, should be used 

to represent an oil or gas well. If the oil or gas field only is shown 

the outline should be inked by dashed lines in black. (See p. 235.)

Furnaces, smelters, and coke ovens. A furnace or smelter should be 

inked in black, like any other building. Only coke ovens that are 

to be engraved should be inked, in black. (See pp. 235-236.)

Civil boundaries. Civil boundaries (see p. 236) should be verified 

before inking as a precaution against gross errors in the interpretation of penciled field copy, as erasure of an erroneous inked boundary 

line usually involves erasure of adjacent topography also. Where 

civil boundaries of different classes coincide for a distance the symbol 

of the major subdivision should take precedence, but in particularly 

complicated regions, especially among minor subdivisions, it may 

sometimes be necessary for the sake of clearness to depart from this 

rule.

Where it is obvious that a civil boundary follows a stream or road 

for a short distance the boundary symbol may be omitted to avoid 

confusion. In some places, however, clearness may be increased by 

placing the boundary symbol immediately alongside of the stream 

or road in red.

For further detailed instructions, given separately by names of 

boundaries, see pages 322-328; for civil townships and other subdivisions see also page 237.

Boundary monuments. National, State, and national park boundary monuments, with designating numbers alongside, should be inked 

in black. Boundary monuments on other lines, with designating 

numbers if obtainable, should be inked in red. The open block indicating the monument should be oriented with the line it marks.

County subdivisions. If in do lib t whether to ink boundary lines 

showing subdivisions of the county, read carefully the field instructions (p. 237) and then look through the field material for comment 

from, the field engineers as to the local status of the lines. In those
TOPOGRAPHIC MAPPING 289

parts of the country or in those States where the Geological Survey 

has not in the past shown such subdivisions, each new map must be 

fully considered before a decision is reached, and under such conditions the inker should seek office advice.

Public-land lines. All public-land survey lines (see p. 238) should 

be inked in red so that they may not be mistaken for other cultural 

features; section lines should be inked in fine lines and township 

lines distinctly heavier. The adjustment of land lines should be 

checked by someone other than the compiler before they are inked; 

and the need for this examination increases with the proportion of 

the land net taken from the plats and notes alone rather than from 

the connection of found corners.

Only those township and section lines and parts thereof that have 

been surveyed and approved by the General Land Office, are not 

under suspension, and are indicated on the land plats by solid lines 

should be inked on Geological Survey topographic maps. The fractional distances for less than section lengths are usually found on 

the land plats, and such distances afford the means for plotting fractional land lines on maps. Land lines broken at water surfaces on 

account of shore meanders should in general be broken as shown on 

the plats. Meander lines should not be plotted or inked.

Found corners. Public-land corners that have been found in the 

course of field work and are clearly indicated as such on the field 

sheets should be inked in the symbol for found land corners. In 

hiking land lines adjacent to found land corners a short space should 

be left clear on all sides of the symbol so that it can be readily 

recognized.

Township and range numbers. Township and range numbers 

should be placed along the margin of the map opposite the middle 

of each township, the township numbers along the right and left and 

the range numbers along the upper and lower margins. If the numbering is irregular, however, the numbers should be placed within 

the townships. On large-scale maps that cover only two or three 

townships or fractions thereof the township and range numbers 

should be placed opposite the lines bounding the townships.

Numbers and names of base lines and principal meridians should be 

shown.

Section numbers. On the 1:62,500 scale and all larger scales sections within townships should be numbered.

United States location and mineral monuments. Each United 

States location and mineral monument (see p. 240) should be inked 

by a solid triangle and designated by letters and official number, 

preferably at the right of the symbol, as "USLM 2," "USMM 237."

Triangulation points and transit-traverse stations. Only those triangulation points and transit-traverse stations that have been used in
290 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

the course of topographic mapping (see p. 240) should be inked or 

shown on Geological Survey maps, and these stations should be 

inked by the triangle and dot symbol. No triangle should be inked 

until the identity of the station has been established and its plotting 

checked, and this check should precede the inking of any cultural 

features directly adjacent to the station.

The names of triangulation points and the numbers of transittraverse stations should not be added to the hiked maps prior to 

the control examination.

Level bench marks. For bench marks (see p. 240) all letters "BM," 

all crosses (permanent and supplementary), and all figures of elevation should be inked in black. The cross should be of the style 

used on engraved maps but with the lines of the cross inked fine 

and 0.2 inch in length, or longer if necessary for the better identification of its location. All bench-mark figures of elevation should 

be upright. All bench marks that have been plotted on the field 

sheets should be inked on the final sheets, except those in areas 

of heavy culture, but the figures for such supplementary bench 

marks as do not represent good engineering benches will be changed 

to red in the control examination.

Vertical-angle benchmarks. Vertical-angle bench marks (see p. 240) 

should be indicated in the same way as standard permanent bench 

marks, except that the letters "VA" will be added on the same 

line and in front of the letters "BM," if the bench mark is on or 

near a road or other route of travel and therefore liable to be mistaken for a standard permanent bench mark.

Control points adjacent to cultural features. In inking culture that 

is adjacent to control points (see p. 241) care should be taken to 

maintain the correct relative position of the control and the cultural 

features.

Useful elevations. All useful elevations as defined on page 241 

should be inked in black in slanting block figures. The elevations 

selected for engraving will be determined in the editing of the map 

and will be printed in black on the published maps. On maps that 

are to be reproduced by engraving no elevations should be inked in 

red. On maps that are to be reproduced by photolithography alone 

special instructions will govern individual cases, according to the 

arrangement of the copy.

Location crosses. Where the location of an important feature is 

not obvious from the position of the lettering designating it or where 

figures alone do not clearly indicate the location of a point whose 

elevation is given, a small location cross may be added in brown 

and may be engraved on the brown plate.
TOPOGKAPHIC MAPPING 291 

INKING OF DRAINAGE FEATURES

If a mixed blue ink is used for inking drainage features it must be 

thoroughly mixed and dark enough to insure strong photographic 

value.

Shore lines in general. Shore lines of all waters should be inked 

in a firm continuous blue line and not broken for wharves, piers, and 

similar structures that may be built out over the water; such structures should be inked in black. Sea and retaining walls that are 

but artificially constructed parts of the shore line should be inked in 

blue.

Tidal shore lines. (See field instructions, p. 242.)

Use oj Coast and Geodetic Survey charts. Before coast lines and 

the adjacent offshore features are inked the penciled copy should be 

compared with late large-scale Coast and Geodetic Survey charts 

(see p. 242), and wherever marked differences are found that are not 

fully explained in the field material or on the information tracing, 

further inquiry should be made of the author or other competent 

authority. Coastal features appearing only below the line of mean 

high water should be omitted from Geological Survey maps.

Under-water contours. Under-water contours should be added to 

the final drawings of coastal maps if the Coast and Geodetic Survey 

can supply the necessary data. They should be shown for offshore 

depths corresponding to the contour interval used on land and should 

be carried to the limits of the quadrangle or so far as data are available. Additional contours for depths of 5, 10, 20, and 30 feet should 

be shown where appropriate. Ink in blue.

Marshes in general. Marsh or swamp of any kind (see p. 242) should 

be inked by the symbol for marsh in. general; no distinction should be 

made between fresh, salt, or other marsh. The outlines of marsh 

areas should be inked by fine dashed blue lines, but the dashed lines 

should not be engraved save where they are needed to designate 

small and but slightly separated areas of marsh that otherwise 

would be collectively mistaken for large continuous areas or where 

they are needed to indicate small detached areas that have sharply 

defined limits but are not clearly outlined by the symbol alone and 

yet constitute prominent features or landmarks.

Submerged marsh. Areas of submerged marsh (see p. 242) should 

be indicated by inking grass tufts in blue (no horizontal lines) on the 

water surface.

Wooded marsh. Wooded marsh (see p. 243) should be inked in 

blue as marsh and the outline added to the woodland sheet.

River shore lines. The penciled copy for broad rivers (see p. 243) 

should be carefully examined before inking in order to ascertain 

whether the shore line shown represents the probable normal stage
292 TOPOGRAPHIC INSTRUCTIONS OP GEOLOGICAL SURVEY

of the water. If the appearance of the copy or an attached memorandum in any way indicates or suggests a mapping of the shore at 

some stage other than the normal, the inker should seek further 

office instructions before inking the shore line, islands, sand bars, etc. 

As the normal stage of inland waters is the accepted shore line on 

Geological Survey maps, no features that are exposed only below 

that stage of the water should be inked. Water-surface elevations 

should be inked wherever they can be legibly drafted.

River banks. (See field instructions, p. 243.)

Sand. The sand symbol (see p. 255) should be inked with brown 

dots of uniform size and spacing. Tidal sand that is exposed below 

the line of mean high tide or below the line of the normal stage of 

rivers and lakes should not be inked. The outline of sanded areas 

should not be inked but shown by a careful inking of the dots.

Natural lakes. If the appearance of the .penciled copy or an 

attached memorandum indicates that the shore line of a lake was 

mapped at a stage of the water above or below the normal stage, the 

inker should ask for instructions before inking the shore line. (See 

p. 243.) The shore line of a large lake whose surface is subject to 

periodic rise or fall should be that determined on the date of survey; 

and this date should be lettered on the water surface, with corresponding elevation. The elevation (normal stage) of all other lake 

or pond water surfaces should be inked wherever the figures are 

available and can be legibly shown.

Reservoirs. (See field instructions, p. 234.)

Artificial lakes. The elevation of an artificial lake (see p. 243) 

should be inked, if given, and should represent the stage of water 

mapped and as controlled by the dam.

Intermittent and dry lakes. Intermittent lakes and ponds, dry 

salt lakes, and alkali flats (see p. 245) should be inked by the symbol 

for intermittent lake or pond, a dashed outline with the surface 

indicated by hatching, in blue.

Islands. The instructions given above for inking tidal shore lines, 

river shore lines, and lake shore lines should be followed for island 

shore lines so far as they are pertinent.

Drainage classification. Before streams are inked the draftsman 

should look over the entire original and also the information sheets 

and adjoining maps in order that the classification as inked may represent the fullest information at hand. (See p. 244.)

Perennial streams. In general, all perennial streams (see p. 244) 

except very short stubs and insignificant rills should be inked on 

maps drawn for publication on a scale of 1:62,500. For maps on 

larger scales (1:31,680, 1:24,000, etc.) all perennial streams except 

the smallest rills may be inked, but rills also may be inked where, in
TOPOGRAPHIC MAPPING 293

the absence of contour lines defining their channels, they constitute 

features of topographic importance.

On maps drawn for publication on a scale of 1:125,000 the amount 

of perennial drainage to be inked should be only slightly less than 

that for a scale of 1:62,500, the omitted streams being the shorter 

forks or tributaries whose inking would give a stubby expression to 

the drainage. For a scale of 1:250,000 much less drainage should be 

inked than would be represented on a scale of 1:125,000.

Perennial streams should be inked with a solid blue line increasing 

in strength with the size of the stream but nowhere so broad as to 

be equivalent to double lines. Care should be taken not to draw 

streams to the edge of the map with a width that can not properly 

be continued on the next map. Stream lines should taper off toward 

the sources of the streams but should remain deep and strong in color 

to the head. If allowed to become faint the blue will not photograph.

Intermittent streams. On the penciled field sheets all intermittent 

stream courses (see p. 244) are outlined down to their minuter ramifications, as an aid in contour sketching, but. only the larger ones are 

to be inked and engraved. The general rule should be to ink no 

intermittent stream that will be less than three-quarters of an inch 

long on the scale of publication. In the more arid districts a smaller 

proportion of the intermittent drainage should be inked, and the minimum length should be increased to 2 inches or more, according to 

scale, as may seem appropriate to the degree of aridity.

It is to be borne in mind that drainage lines are delineated not 

merely because they indicate water features but because they constitute an important element in the conformation of the land surface 

and because they afford supplementary information of value in the 

interpretation of the relief. Whatever the degree of aridity, therefore, it is desirable to show a certain amount of intermittent drainage 

on the map for the sake of legibility. More especially is this true 

in delineating intricately sculptured areas, the topography of which 

in the absence of drainage lines appears chaotic and unintelligible at 

first glance.

Aggraded flats and valley floors devoid of well-defined stream 

channels or scars are not properly shown with drainage lines running 

through them.

Intermittent streams should not be inked up to or close to the 

divides, as the contours usually suffice to define the location of stream 

heads.

Double-lined streams. Only those streams should be double-lined 

whose actual width can thus be shown without exaggeration on the 

scale of publication. (See p. 244.)

Disappearing streams. Disappearing streams and streams starting 

from subterranean sources (see p. 245) should be inked to represent
294 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

the surface drainage only, and this will be classified as given under 

the rules for perennial and intermittent streams. On field sheets 

where the presence of disappearing or reappearing drainage is suggested by the representation of sink holes or other indication, the 

penciled copy should be carefully examined for possible drainage of 

this character.

Springs. Springs (see p. 245) should be hiked or not according to 

their importance as stated in field instructions. A walled-in spring 

should be shown like a well, by a blue circle, but a spring that is a 

source of a stream should be shown by a blue circle with the outlet 

stream as plotted.

Wells and water tanks. The symbol for a well or water tank is a 

small blue circle. (See p. 245.)

Glaciers. The outline of a glacier (see p. 245) should be inked in a 

dotted blue line and its surface contours in full blue lines.

Tinting of water bodies. Oceans, bays, lakes, ponds, and broad 

rivers should be tinted blue (blue tints will not photograph) on the 

manuscript sheets only in places where the copy for engraving would 

otherwise be ambiguous. If the tint is added after the shore line 

has been inked, the shore line should be reinked wherever the wash 

has destroyed or broken the line or so weakened its strength as to 

render it nonphotographic. As a further guide for the engraver, a 

deeper blue wash may be added immediately along the shores, islands, 

rocks, and other features. Bridges and other structures built over 

the water should not be thus outlined by a darker tint.

INKING OF RELIEF FEATURES

Relief features are to be inked in brown.

Strength of contour lines. Contour lines should be inked in firm 

smooth lines of even strength. For convenience in reading them 

every fifth or fourth contour should be accentuated (for contour 

intervals of 1, 5, 10, 20, 40, 50, 100 and 200 feet, every fifth; and 

for intervals of 25 and 250 feet, every fourth). The accentuation 

should consist in drawing the lines heavier, rather than in making them 

broken or dotted. The weight of the accentuated (heavy) contours 

should make them stand out from the intermediate contours but 

should not be so excessive as to cause them to dominate the relief. 

The intermediate (light) contours should be inked in fine lines.

Where the identity of a heavy contour is lost in a band of contours, 

as in the representation of a cliff, it may be advisable to place contour numbers on one or more adjacent light contours in order that 

the contouring may be more easily read.

Sequence of contour inking. The heavy contour lines should be inked 

first and should be finished over considerable areas before the light 

contours are inked, The heavy contours should be compared with
TOPOGRAPHIC MAPPING 295

adjoining bench-mark and other elevation figures as a check on their 

identification, and identification marks such as contour numbers in 

light pencil should be placed here and there upon them in order that 

the correct continuity of the heavy lines may be well established 

before light contours are inked. The heavy contours should not be 

dropped at any place save for contour numbers, but the light contours should be omitted on uniform steep slopes and in other places 

where their inking is not essential and would tend to confuse the 

copy rather than aid the engraver. Before the intermediate contours 

between any two successive heavy contours are inked, the penciling 

should be closely examined to insure that no contours have been 

dropped or duplicated.

Uniform steep slopes. Where the slope is both steep and uniform 

only the heavy contours need be inked, as the engraver can interpolate the light lines on the copper plate as readily as the topographer 

can ink them on his map, and the copy for the engraver is the clearer 

for their omission. Attempts to fill them in for the mere sake of 

enhancing the appearance of the manuscript sheet are not permissible.

Steep slopes that are not uniform. Where a slope is steep but not 

uniform the change in slope is more likely to occur on a light contour 

than on a heavy contour for example, with a 20-foot interval the 

chance of the slope changing at a light contour instead of at a heavy 

contour is as 5 to 1. Therefore, if the interpolation of the light contours on such slopes is left to the engraver, an erroneous banded 

effect will result on the engraved map where successive bands of light 

contours are uniformly spaced between heavy contours that are. 

themselves not evenly spaced.

Uniform gentle slopes. Where the slope is generally uniform but 

not steep ail light contours should be inked for the guidance of the 

engraver, especially where marked divergence or discordance exists 

among them. In general, the light contours should be indicated, 

at least by short lengths of lines, along every drainage line and every 

spur crest.

Cliffs. Extreme care must be taken in inking bluffs and cliffs on 

which not all the contours can be shown. The inked lines should 

be as sharp and smooth as they can be drafted, so as to reduce to a 

minimum the chance of their blurring in transfer to the copper. Inasmuch as very closely spaced lines on a drawing tend to run together where reduced in scale and transferred to copper, the inker 

should aim to leave the engraver's copy as open as possible, and 

this may be accomplished in part by omitting from the inking any 

four, three, two, or even single contours wherever two or more are 

closely spaced on the map. The contours that are omitted in the 

inking can be interpolated by the engraver, who can work more
296 TOPOGRAPHIC INSTKTJCTIONS OF GEOLOGICAL SURVEY

rapidly and with more assurance because the copy has thereby been 

rendered more legible.

Where cliffs are represented by bands of contours and are so numerous as to dominate the topography, as in the Grand Canyon of Arizona, it may be desirable to omit the usual emphasizing of contours 

and instead to add as many contour numbers as may be needed for 

identification. Such contour numbers may be most appropriately 

placed on the contours that otherwise would be heavy.

Depression contours. Contours inclosing depressions or sinks should 

be distinguished from hill contours either by rows of contour numbers 

indicating successive depths, instead of successive heights, or by 

hachures on the downhill side of each contour line. The depressions 

may be natural, such as occur in limestone regions, or artificial, such 

as are inclosed by railroad or road embankments. If the depression 

takes more than one contour, all should be hachured. In intricate 

areas it is often desirable to indicate the bottom elevation of the basin 

by figures, or, if space permits, to mark the elevation of some or all of 

the contours.

Depressions of large extent covering a considerable area on the map 

are intelligible without the aid of hachures provided they are liberally 

supplied with contour figures.

Contour figures. Figures of elevation on contours should be inked 

without shading. On heavy contours they should be placed with a 

special view to their effectiveness as an aid to the map reader. A 

sufficient number of them should be used to enable the reader to 

obtain a contour elevation with but slight examination. It is desirable, therefore, that they be placed in conspicuous positions and that 

they be distributed with some system. In general, contour figures 

are most effectively placed on or near the ends of spurs, tops of 

ridges, or bottoms of valleys and at pronounced changes in slope.

On features taking several tiers of heavy contours the figures may 

be placed in steplike series. Such series should follow the features on 

which they are placed in easy, gentle curves. On very steep slopes, 

where they would be too crowded, the figures should be omitted on 

alternate heavy contours. Each mountain group or separate map 

unit should have its own numbering system, so that there may be no 

need of referring to contour figures across valleys or canyons.

In regions of moderate or low relief the placing of the figures should 

be governed primarily by the disposition of the larger topographic 

subdivision. Each of these should have at least one complete set of 

figures. In areas of exceptionally intricate topography for instance, 

in areas pitted with solution sinks or traversed by high cliffs the 

figures on the heavy contours may not suffice to make the delineation 

intelligible, and it is proper to place figures on light contours wherever 

they will help to remove uncertainty. If need be, figures showing
TOPOGRAPHIC MAPPING 297

the elevation of several points may be introduced to supplement the 

contour figures.

Contour figures should not, as a rule, appear in close proximity to 

bench-mark and other elevation figures, which, on the other hand, 

should not be considered as taking the place of the contour figures.

Finally, care should be taken to select a position for contour figures that will accommodate the engraving on the reduced scale of 

publication.

Two contour intervals. Where two or more contour intervals have 

been used in a quadrangle (see p. 246) the inker should carefully examine the entire map to ascertain those parts of the quadrangle to which 

the different intervals apply. Before contour inking is begun full. 

instructions should be sought as to the proposed method of handling 

the contour inking.

Where it seems desirable to ink additional contours within certain 

areas, in order to bring out supplemental relief that has been mapped, 

such additional contours should be inked in dashed lines, in order that 

they may be distinguished from the contours of the regular system; 

and a footnote should be added directly under the contour-interval 

line reading " foot contours added in dashed lines."

Railroad contours. The penciled copy should be carefully examined 

and no excessive or improbable railroad grades, cuts, or fills inked 

unless the copy is clear and unmistakable. (See "Railroad grades," 

p. 250, and "Cuts and fills," below.)

Cuts and fills. Straight lines representing cuts and fills (see p. 251) 

should be ruled in, and the inked copy left as sharp and open as circumstances will allow. A slight separation of the lines may be 

warranted, but where this is not practicable a short stretch of perhaps 

0.1 inch or so of one or more lines that are closely spaced may be 

omitted in the inking and yet leave copy that will be understood by 

the engraver.

Use of hachures. The inking of hachures should be confined to the 

representation of depressions (p. 251), mine dumps (p. 234), and such 

other banks as are not shown by the contours and yet constitute 

conspicuous topographic features. (See "Use of hachures," p. 252.)

Contour disagreeing with elevation. An example of permissible topographic license (see p. 253) is the folio whig: A 1,300-foot contour 

(interval 20 feet) is penciled to represent a sharp summit whose elevation is given as 1,295 feet; both the 1,300-foot contour and the 

elevation may be inked. To omit the 1,300-foot contour would be to 

show the summit as flatter than it really is. Where such small differences appear to be fully justified, such topographic license may be 

taken, but the evidence must be clear that the differences are not the 

result of error; where error is suspected a question should be raised 

or the elevation omitted in the inking.
298 TOPOGEAPHIC INSTRUCTIONS OF GEOLOGICAL SUEVEY

Alinement of contours. The bends of contours in steep drainage 

channels and on steep ridges should, in general, be in line with one 

another, and in such places care should be taken in the inking to see 

that the contours are placed in the proper alinement. (See p. 253.) 

Careless or hasty penciling may throw contours out of line in steep 

places, and unless the pencil copy to the contrary is unmistakable, 

the inker may often be aided in properly aiming the contours by 

lightly penciling a drainage line or a ridge line on which to reconstruct 

the contour crossings.

Topographic expression by different authors. Where different parts 

of a quadrangle have been mapped by two or more persons, the contouring of the different authors should be carefully compared before 

it is inked in order that any minor differences in expression may be 

reconciled in the inking so far as that may be practicable. Attention 

should be called, however, to all material differences in topographic 

expression that are not plausibly explained by such differences as are 

to be expected where differing types of country are found in the same 

quadrangle.

INKING FEATURES BASED ON AERIAL PHOTOGRAPHS

If an aerial photographic base, such as is described on page 254, 

has been used in the field, the office inker should, in general, ink only 

those blue lines that have been penciled in on the final field sheet. 

A blue line that has not been verified by field penciling should be 

inked only where there is definite knowledge that the line represents 

a feature that is intended as a part of the map. Among the blue lines 

that should not be inked and may or may not have been erased or 

crossed out by the field engineer are fence lines added for additional 

control, woodland outlines, and lines of mistaken culture or drainage.

The copy for coastal shore lines and shores of large rivers should 

not be inked until the status of such shore lines has been determined 

either by explanations to be found in the field material or by administrative approval in the office. (See last paragraph under "Mapping 

on aerial photographic base," p. 255.)

RECTANGULAR GRID

Definition. A grid is a system of rectilinear lines forming squares of 

identical dimensions, which may vary according to the requirements. 

Grid lines may be drawn entirely across the face of the map or may 

be indicated by marginal registration marks only, as is the Geological 

Survey practice. Were the registration marks to be connected, in 

order to form a true grid, the lines would be drawn as straight lines. 

Each grid line has a numerical designation, and the notation adopted 

increases eastward and northward only. Distances east are termed
TOPOGRAPHIC MAPPING 299

x distances and distances north are termed y distances. An arbitrary 

point of origin or zero point is so placed that x and y distances are 

positive.

Where used. Each advance sheet and each published quadrangle 

map of the topographic atlas and most other topographic maps issued 

in quadrangle form should carry registration marks for a 5,000-yard 

rectangular grid, based on the United States zone system described 

below and in more detail in U. S. Coast and Geodetic Survey Special 

Publication 59. The registration marks should be plotted outside of 

and adjacent to the neat line of the map and inked in fine black lines 

a quarter of an inch long, with the x and y figures given for the registration marks nearest the southwest corner.

United States zone system. Inasmuch as it is not practicable to 

cover the entire area of the United States by a single grid system, 

based on one central meridian, the country has been divided into 

zones, designated A to G, each zone covering a range in longitude of 

8 degrees plus 1 degree for overlap, or 9 degrees. The middle meridians 

for the several zones are 73°, 81°, 89°, etc., and each of these meridians 

has an arbitrary x distance of 1,000,000 yards. The same table can 

therefore be used for each zone in the system, but the zone within 

which the map falls must be stated upon the map. An x distance, 

when the zone is known, gives then, in effect, a measure of longitude.

Plotting and checldng. The plotting and inking of the grid will be 

done in the section of inspection and editing and must be independently checked by a person other than the one engaged in the computation, plotting, or inking. The names of the plotter and checker 

of the grid and the names of the computer and checker of the figures 

representing grid distances on publication scale (see below) should 

be added to the impression of a rubber stamp provided for the 

purpose.

Publication distances. On each final drawing representing a map 

that is to be regularly published by the Geological Survey should be 

added in ink at the four corners of the projection thecc and y distances 

from each quadrangle corner to the nearest grid registration mark, 

expressed in inches and hundredths of an inch on the scale of publication. The directions in which the inked distances apply should be 

indicated by arrows, and the figures should be so placed that they 

can readily be brushed off the advance-sheet negatives.

Plotting grid on a projection. To put a 5,000-yard grid on a quadrangle map which is drawn on the poly conic projection, proceed as 

follows:

From United States Coast and Geodetic Survey Special Publication 59 take the x and y distances for each of the four corners of the 

quadrangle. These distances are given in yards for all 5' intersections 

of meridians and parallels in the United States.

58515° 28 20
300 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

To locate grid registration marks for the southwest corner of the 

quadrangle, subtract the x distance for that corner from the next 

higher 5,000 multiple and plot the difference east along the south 

projection line, then subtract the y distance from the next higher 

5,000 multiple and plot that difference north along the west projection line. To locate registration marks for the northwest corner of 

the quadrangle subtract the x distance from the next higher 5,000

79 30 41° 30'

2095000

 Yards

X = 1136 96S 

Y -2 122 637

X= 1137 491 

Y = 2092 272

2509*

- - 4-730

X-//59 79O 

Y = 2 J23O66

79 15' 

 14130'

X= / I6O 4O3 

Y-2092 70O

79 30 v.y /4-O ooo Yards 79 '^ 

FIGURE 12. Diagram showing registration marks for rectangular grid

multiple and plot that difference east along the north projection 

line; then plot south along the west projection line the difference 

between the y distance and the next lower 5,000 multiple. To 

locate registration marks for the southeast corner of the quadrangle 

subtract the y distance from the next higher 5,000 multiple and plot 

that difference north along the east projection line; then plot west 

along the south projection line the difference between the x distance
TOPOGKAPHIC MAPPING 301

and the next lower 5,000 multiple. To locate registration marks for 

the northeast corner plot west along the north projection line the 

difference between the x distance and the next lower 5,000 multiple; 

then plot south along the east projection line the difference between 

the y distance and the next lower 5,000 multiple.

Intermediate grid intersections can then be interpolated along the 

four ^ides of the map. If the projection is very much too large or 

very much too smaU a proportionate compensation should be considered in plotting the grid intersections.

Figure 12 gives the x and y distances in yards for the four corners 

of a 15' quadrangle, the distances in yards from each corner to the 

nearest grid registration mark, the complete x and y distances in 

yards from the point of origin for the grid lines nearest the southwest 

corner, and the interpolated grid lines.

INKING OF CULTURAL REVISION SHEETS

Field revision sheets. The field revision sheets are described under 

"Field sheets" (p. 179). So much of the new or changed culture, 

drainage, or relief as has been surveyed in the field should be inked in 

the three standard colors. (See "Inking of topographic field sheets," 

pp. 277 298.) Except as indicated below, the inking should be confined to the new or changed features, and the unchanged features will 

therefore, be left in the original faint photolithographic colors. The 

entire projection should be inked, however, and the sheets should be 

cut into halves or quarters, as may be most convenient, so that the 

separate parts when laid edge to edge will make a single continuous 

map. For this purpose small overhangs may need transfer to other 

parts before being cut away.

Where the cultural changes arc so numerous as to have warranted 

a complete or nearly complete resurvey of the topography of a small 

area it will in general be found advisable to ink the entire portion of 

the sheet representing that area.

Exception if cultural changes are extensive. If the cultural changes 

are so numerous and widespread that the correction of the black copper plate would cost more than the engraving of a new black plate the 

entire culture of the quadrangle should be inked. Therefore if cultural changes are extensive, instructions should be sought before the 

inking is completed.

Bench marks and other control. «AI1 existing control stations and 

bench marks, together with their established elevations, should be 

inked, whether they represent changes or not.

" Take out" sheet. The purpose of the "take out" sheet is to indicate all roads, trails, railroads, houses, names, and other features 

which no longer exist and for which the corresponding lines on the 

copper plates are to be taken out. The field copy of the engraved map
302 TOPOGRAPHIC INSTEUCTIONS OF GEOLOGICAL SURVEY

used as a "take out" sheet may, if in good condition, be used as engraver's copy; otherwise the "take outs'' should be transferred to a clean 

copy .of the published map. Careful preparation of the "take out" 

sheet is essential in order that the engraver may have a clear understanding of what is to be taken from the plates before beginning the 

engraving of the new or changed topography. Where solid areas have 

been inked on the revision sheets the corresponding areas should be 

marked for "take out."

Name sheet. In whatever form the name sheet is submitted (see 

"Names," p. 226), the copy must be complete and clear as to intent. 

Where a town or other named feature has been moved or changed in 

appearance the new lettering should be placed in the appropriate 

changed position.

Road classification. The roads that are to be changed from full 

double lines to dashed lines and the reverse (see "Road classification," 

p. 256) should be so inked on the "take out" sheet; and such changes 

in road classification should be fully explained in the margin.

A separate engraved copy marked "Road classification" will be 

prepared as copy for the red overprint, in accordance with the instructions given on page 309.

BORDER CORRECTIONS

Where it is impracticable to join the new work to the maps of 

quadrangles that have been published on the same scale upon which 

the new work is to be published, border corrections to the previous 

maps should be prepared. Such corrections should be submitted on 

tracing linen, on the scale of field work, and inked in the standard 

colors used for topographic maps. (See "Map borders," p. 227.)

Purpose. The primary purpose of border corrections is to make 

maps of adjoining areas match if the maps are published on the same 

scale. Corrections should therefore be confined to this single object 

and the correction copy threaded into the previous work within the 

smallest practicable space and with the fewest possible changes in the 

older work. Even though the field topographer may inadvertently 

carry his over-edge mapping farther than may be needed to assure a 

good joining of the two maps, only so much of such over-edge mapping 

should be used as correction copy as is absolutely necessary to accomplish this result; any further correction of the older plates would 

involve needless expenditure. .

Preparation. The penciling or inking of correction copy for border 

corrections should be confined to the exact amount of correction that 

is needed and should not be extended to include a tracing of any 

topography that does not itself need correction. As soon as each 

line of the correction, such as a road, stream, or a contour line,
TOPOGRAPHIC MAPPING 303

joins the corresponding line on the other map, the correction should 

stop, as any further inking for register is not necessary.

A complete correction copy should be prepared for each of the three 

copper plates involved, but each should be confined to changes that 

are called for on its respective plate. For example, if the location of 

a stream is unchanged but the spacing of contours on the stream is 

changed, the stream should not be inked, as no correction to the blue 

plate is here needed. *

Where the topography is readjusted into a new position, aU houses 

and other cultural features and especially all drainage lines should be 

added to the inked correction copy so far as a change in their position 

is involved in the readjustment in topography. Contour numbers 

should be freely added to all correction copy as an aid in the positive 

identification of contours in editing, engraving, and proof reading.

Joining work on different scales. Where the previous work is on a 

smaller scale than that on which the new work is to be published, 

corrections to the borders of the older map should be made only where 

the differences indicate considerable errors in the older work, such as a 

large difference in elevation or an erroneous connection of drainage, 

that should be corrected on the next reprint of the older map. Minor 

differences such as may be expected where large-scale work adjoins 

small-scale work do not require changes in the older plates.

Where the previous work represents surveys that were made many 

years ago and are probably to be replaced by revised surveys or by 

new surveys on a larger scale, no correction copy should be preparedQUADRANGLE NAMES

Provisional names. In order to provide for the designation of the 

names of quadrangles in connection with plans for field work and for 

cost keeping during the progress of field work, provisional names 

have been given to all quadrangles in the country. These names 

are recorded in an administrative-progress book in the office of the 

chief topographic engineer and are also alphabetically recorded in a 

typewritten list. Both lists are kept corrected to date as changes 

are authorized.

As it is not always practicable to select the most appropriate name 

for a quadrangle in advance of its mapping, or to know whether a 

name that has been selected represents a city or place that will fall 

wholly within a quadrangle, many changes in provisional names are 

made after quadrangles have been mapped.

Final names. As a rule each quadrangle is named after the 

principal city or place or the most prominent feature within its 

limits. If the name of the largest place or most prominent feature 

duplicates a name previously used to designate a quadrangle in an 

adjoining State or if confusion might result by giving to a new
304 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

quadrangle a name £hat has been used in another State, not adjacent, 

the name of the second largest place or of some well-known feature 

is selected.

Changes in names. If it is found advisable to change a provisional 

name the final name should be selected after the map has been 

lettered and before the advance-sheet photolithographs are made, 

when all names and features can be seen in relation to the quadrangle fes'% whole. Changes in quadrangle names are approved by 

the chief topographic engineer, and a letter of advice, or copy, is 

refe$e(l to all persons whose records are aifected by the change*

LETTERING OF TOPOGRAPHIC FIELD SHEETS

SUBMISSION FOR LETTERING

On the completion of the inking of manuscript topographic maps, 

prepared either for engraving or for photolithography, the final 

drawing, accompanied by a legible lettering diagram on tracing 

paper or cloth, should be submitted to the section of inspection and 

editing for lettering. The lettered sheet should afterward be returned 

to the person who inked or submitted it, that he may review the 

complete inking before referring the map for checking.

LETTERING OF THE MAP FEATURES

 Lettering on oversheet or on original. The lettering for the topographic map features is usually done on tracing linen registered over 

the original drawing of the map, a separate tracing usually being 

made for each large separate section of the original, as the north and 

south halves. The advantages derived from lettering a tracing 

rather than the map itself are as follows: (a) The copper-plate transfer on which the contours are cut is not obscured by the lettering; 

(6) the names and elevations can be redrafted in their edited positions and thus supply better engraving copy (see p. 334); (c) the 

advance-sheet names can be printed in a distinctive color from the 

base; and (d) the lettering can be done and corrected more economically on tracing linen than on the map itself. If the lettering is very 

light in amount or if the topography is very open, however, the lettering may be placed upon the original.

Style of lettering. The office drawings of field sheets that are to be 

reproduced in small advance-sheet editions by photolithography and 

are afterward to be engraved should be lettered by hand in slanting 

block and italic letters (upper and lower case). The execution of the 

lettering should be reasonably uniform and based on legibility for 

the engineer and clear copy for the engraver rather than a wasteful 

refinement of drafting.

Punctuation. Periods should be omitted on all lettering within the 

margin of the map.
TOPOGRAPHIC MAPPING 305

Position of lettering. The position of the l^nd lettering should 

follow the general rules given for engraved lettering on page 329, 

except that refinements in placing should not be attempted, and 

allowance should be made for an advance-sheet reproduction in one or 

two colors instead of the three colors used in printing engraved maps.

Section numbers, On maps to be reproduced on scales of 1: 62,500 

or larger the section numbers should be, included in the lettering. 

Each section number should, if practicable, be placed in thle center of 

the section or considerable part thereof shown on the map. . If the 

center of a section falls on a road or an area of considerable clel^il on 

the map, the section number should be moved slightly away from the 

center in order that it may be more legible. Section numbers should 

be inked in slanting block figures.

MARGINAL LETTERING

Much of the marginal lettering (pi. 15) is common to all or to many 

maps and is supplied in the form of pasters, which are printed from 

type, and such pasters should be used in lieu of hand lettering. In 

attaching these pasters to the map care should be exercised to avoid 

rubbing them and thereby decreasing the strength of the lines for 

reproduction by photolithography.

Projection figures. The latitude and longitude of each projection 

line drawn across the map should be inked at the margins and usually 

expressed hi degrees and minutes (or seconds) at the four corners and 

in minutes (or seconds) only on the four sides.

Federal (leading. At the upper left-hand corner of the projection 

should be placed the following heading, with the lower line centered 

on the upper:

DEPARTMENT OP THE INTERIOR 

TJ. S. GEOLOGICAL SURVEY

Quadrangle, State, and county names. At the upper right-hand 

corner of the projection should be placed the name of the State or 

States within which the area mapped lies, and below this the name of 

the quadrangle or area. If the entire area falls within a single county 

the name of that county, in parentheses, should appear below the 

name of the State and should be omitted from the face of the map.

Cooperative headings. In. cooperative surveys the name of the 

cooperating State, county, or other body, together with the names 

and titles of the officials representing it, should appear at the middle 

of the upper margin of the projection. The officials named should 

be those in office during the period of the survey.

Differing arrangements of headings are necessarily used in different parts of the country, owing to the diversity in State and county 

organizations. The heading selected should be the shortest consist-
306 TOPOGRAPHIC INSTRUCTIONS OP GEOLOGICAL SURVEY

ent with Geological Survey practice and with approval by the cooperating officials.

Scales. At the middle of the lower margin the scale, expressed in 

the form of a fraction, a bar scale in miles, a bar scale in feet, and a 

bar scale in kilometers, should appear in the order named. Lithographic prints of appropriate bar scales for the several field mapping 

scales are kept in stock and should be tested for length after being 

pasted in position.

Contour interval. Directly under the bar scales should be placed 

a statement of the contour interval for example, "Contour interval 

20 feet." Where two contour intervals are used both should be 

stated, and if practicable a statement of the contour on which the 

interval changes should be added for example, "Contour intervals 

5 and 25 feet, changing on the 400-foot contour."

Contour interval under water. Where under-water (offshore) contours are drawn a statement of the contour interval should be placed 

directly under the vertical datum line. If additional contours of 

smaller interval are shown for the lesser depths near shore, such contours should be listed for example, "Contour interval offshore 20 

feet, with the 10 and 30 foot contours added."

Datum. Directly under the statement of contour interval should 

be placed the statement, "Datum is mean sea level," but if the vertical datum differs from mean sea level, the amount by which it differs 

should be stated in a note placed in parentheses directly under the 

datum line for example, "Readjustment indicates that elevations 

on this map should be increased by 4 feet." The alternate expression, 

"Datum is 4 feet below mean sea level," is too ambiguous for public 

use and should not be used.

Division engineer. At the lower left-hand corner of the projection 

should appear the name of the division engineer within*-whose division 

and under whose general direction the topographic mapping was 

done. This item is added for advance-sheet and office information 

only and should not be engraved.

Topographic authorship. Directly under the name of the division 

engineer should appear a paragraph stating the topographic authorship, with the names arranged in the order of seniority. By authorship is meant the independent survey of an area for which an author 

is wholly responsible. Traverses that are afterward adjusted into 

others' work and thereby absorbed will not be considered independent 

work entitled to credit in this paragraph.

Author diagram. An author diagram should be added at the lower 

margin showing the respective areas mapped by the men listed as 

topographic authors. This diagram" is intended for advance-sheet 

and office information only and will not be engraved unless an out-
TOPOGRAPHIC MAPPING 307

side organization has been credited with topographic authorship. 

(See preceding paragraph.)

Control authorship. Beneath the list of topographic authors should 

appear the name or names of organizations executing either horizontal 

or vertical control which has been used in the construction of the 

topographic map for example, "Control by U. S. Geological Survey 

and U. S. Coast and Geodetic Survey."

Credit jor outside data. Credit should be given for any outside 

data used in the construction of the map, whether from Federal, 

State, or private sources. (See "Data from other surveys," pp. 

178, 344.) Such credit may apply to topography, control, underwater 

contours, shore lines, or other data.

Date oj survey. The date of survey should be given beneath the 

statement of credit. The date or dates used should represent only 

Geological Survey topographic mapping and not dates for control 

or for outside topographic data. Any outside topographic data 

should have been examined and corrected to the date of the new 

topography before being incorporated.

Projection used. At the lower right-hand corner of the projection 

should appear a statement of the projection used, as "Polyconic 

projection."

Horizontal datum. Beside the statement of projection should appear the words "North American datum," if the map is drawn on 

that datum; otherwise, if the amount of shift in the projection lines 

necessary to place the map on the North American datum is known, 

an explanatory note should be added for example, "To place on 

North American datum move projection lines 340 feet west and 700 

feet south."

Joining lines. If a map of an adjoining area has been published on 

a different horizontal datum and joining lines have been inked on the 

new map. an explanatory note should be added below the statement 

of horizontal datum for example, "To join Galatia map use dotted 

projection corners."

Grid and zone. Opposite the x and y grid lines nearest the southwest corner of the projection the x and y distances should be stated 

in yards. Directly beneath the statement of projection and datum 

should appear a note stating the size of the grid (if used) and the 

zone in which it faUs for example, "5,000-yard grid based upon 

U. S. zone system, F." (See pp. 298-301.)

Land lines and topography. If the land lines are anywhere omitted 

because the Land Office plats can not be reconciled to the topography, 

an explanatory note should be added in the lower right-hand corner 

for example, "Note: Land lines pertaining to Tps. 32, 33, 34, and 35 

N., R. 4 E., T. 36 N., R. 2 E., and parts of Tps. 34 and 35 N., R. 2 E., 

are omitted because land plats and topography can not be reconciled
308 TOPOGEAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

and no corners could be found," or, "Note: As the Land Office plats 

can not be reconciled to the topography, the land lines are omitted. 

The few isolated corners found are shown."

Shore line and height of tide. If under-water (offshore) contours 

are plotted on the map a note should be added in the lower righthand corner stating the shore line used and the height of the tide 

for example, "Shore line is the margin of mean high water 1.8 feet 

above mean low water at Glymont."

Names of adjoining quadrangles. The names of adjoining quadrangles should be added in parentheses in the middle outer margin on 

each common border between them. If the scale of the map of 

the adjoining area is different that scale should be indicated.

Township and range numbers. Township and range numbers in 

the form "T. 5 S., E,. 7 E.," should be lettered on the map margin 

opposite the center of each township or portion of a township.

Township diagram. A small township diagram, for which pasters 

are provided, giving the relative positions of sections within a complete township, should be placed on the south border of the original 

drawing provided there is ample room and it assists in the identificacation of section numbers on advance sheets. The diagram is not 

needed on maps where section numbers appear either on the original 

or on the lettering tracing, and it is not engraved.

Declination diagram. On the lower margin of each map the magnetic declination should be shown by a diagram (see pi. 15) as east 

or west and stated in degrees. A statement to the nearest half degree 

will usually be as close as the data warrant. One line of the diagram 

should be oriented and marked true north, and the other line should 

be placed in the direction corresponding approximately to magnetic 

north for the locality represented.

Filing name. On the lower right-hand margin of each map should 

be placed the name of the quadrangle and State, for convenience in 

filing.

Edition and reprint dates. In the lower right-hand margin should 

be indicated the date of publication and the nature of the edition. 

The first printing of the map should carry the expression, for example, 

"Edition of 1922"; a reprint, "Edition of 1922, reprinted 1926." 

If material changes, such as cultural revision or extensive corrections, 

have been made the map should be regarded as a new edition rather 

than a reprint, and only the date of the new printing should be 

stated for example, "Edition of 1928."

PREPABATION OF WOODLAND SHEETS

Submission. A woodland tracing should be prepared for each topographic map and should be submitted when the map is turned in for 

inspection and advance-sheet photolithography. (See "Mapping of
TOPOGRAPHIC MAPPING 309

woodland outlines," p. 255.) If the quadrangle contains no woodland 

of the type defined on page 256, a blank tracing with an inked quadrangle outline should be submitted, across the face of which should 

be inked the words "No woodland on quadrangle."

Preparation. Woodland sheets should be made on tracing linen, 

on the scale of the field work, and preferably in two half sheets for 

each quadrangle. The woodland copy must be made to register 

correctly over the final drawing of the map. The outer projection 

of the quadrangle should be fully traced, but only the intersections 

of all other projection lines appearing on the original. Where an 

mterior projection intersection falls within a wooded area the green 

shading should be erased at the intersection. The outlines of wooded 

areas should be inked in firm solid black lines and the woodland areas 

shaded in by green pencil. The green shading should be carefully 

done at its outer borders, inasmuch as the copy is reproduced photographically, and any overrun of green will photograph and thereby 

render the black lines illegible.

Checking. Each woodland sheet should be checked (see "Checking defined," p. 310) and the tracing- signed and dated on a stamped 

form provided for the purpose. The checking should usually be 

done by the same person who checks the final map. It should consist of an examination of the tracing for completeness of drafting 

and comparison with the original or other woodland data in the field 

material. All edges of woodland areas on maps of adjacent quadrangles should be compared for joining.

Approval. Woodland sheets, after checking, should be approved 

by the division chief, who should indicate his recommendation for 

printing. The sheets should be finally approved for printing or 

otherwise by the chief of the section of inspection and editing.

PREPABATION OF BOAD-GX-ASSIFICATION SHEETS

A road-classification tracing should be prepared for each standard 

topographic map and submitted when the final drawing of the map 

is turned in for inspection and advance sheet reproduction. It 

should be made on tracing linen to register over the final drawing, and 

the classification data should be inked in red. Each tracing should 

carry at the bottom a key consisting of a red line followed by the words 

"Hard, imperviously surfaced roads," and a dashed red line followed by the words "Other main traveled roads." The data presented should follow carefully the specifications outlined under "Road 

classification" (p. 256) and should not be combined with any other 

required information. The date of the last month on which the 

data were obtained in the field should also be stated.
310 TOPOGKAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY 

PREPARATION OF LAND-CLASSIFICATION SHEETS

The preparation of land-classification sheets is fully explained 

under "Mapping of land-classification data" (p. 258). Such sheets 

should be submitted to the section of inspection and editing for 

examination when the final maps are submitted for advance-sheet 

photolithography. After examination and approval by the chief 

of the section of inspection and editing he will forward the landclassification sheets to the chief topographic engineer for transmission to the chief of the conservation branch.

CHECKING OF INKED FIELD SHEETS

CHECKING OF TOPOGRAPHIC MAPS

Need. The need for an immediate checking up of the inked 

topographic map by a person other than the author or inker arises 

from the expectation that one who has worked continuously on the 

map for many days or weeks may, through inadvertence, misinterpret or omit certain essential data or processes or make errors. 

If two or more persons ink on the same map, a checking is needed 

in order to reconcile possible differences that may be found between 

the parts inked by the different persons, owing to varying interpretations of instructions. The checker should therefore not only be 

a qualified topographic engineer but one who has had no association 

with the map in hand and who is to that extent disinterested.

CJiecJcing defined.* The function of the checker is to examine the 

final drawing of the map and its field material, through all its features and from every point of view that can suggest itself to an 

experienced topographer, and as a result of this checking to call 

the attention of the author or inker to such details as appear to have 

been overlooked, misinterpreted, omitted, or erroneously shown. 

The checker, however, should be reasonably familiar with the functions of the inspector and of the editor, that he may not waste time 

in the consideration of purely editorial matters which are to receive 

due attention later. (See below and also pp. 313 and 320.)

The checking should include the examination of the inked field 

drawings, lettering tracings, and woodland sheets, also of any corrections that may be necessary to make the new map join maps of 

adjoining quadrangles that have been previously surveyed.

Avoidance of duplication. Each topographic map in its transmission from the field to the map editor goes through the following 

hands: (1) Field topographer as author; (2) office inker; (3) checker;

«See footnote 3, p. 273.
TOPOGRAPHIC MAPPING 311

(4) inspector; (5) control examiner; (6) map editor. Nos. 1 and 2 

may or may not be the same person; the others are different persons. 

Checking and the inspection and editing of topographic maps are 

based upon a procedure that allows only so much duplication of 

work as may be necessary to insure that no errors or omissions have 

been made; and to this end the duties involved in the several stages 

listed in this paragraph are set forth in some detail in the pages 

that follow.

Attention to checker's questions. Questions should be referred by 

the checker to the person in immediate charge of the office inking 

of the sheet; such questions as apply to parts of the sheet that have 

been mapped or inked by others who are then in the office should 

be referred to them for attention, unless in the judgment of the 

topographer or inker in immediate office charge of the sheet such 

further reference is deemed unneccessary, in which case he himself 

may reply to all questions raised by the checker.

Checker's questions that can not be answered by anyone in the 

office, for the reason that an absent author or inker alone has the 

needed information, should so far as practicable be referred by letter 

to the author or inker. Such references may be made before advancesheet lithography if the advance sheet is not thereby delayed, but 

inquiries are best handled by indicating the questions on an advance 

sheet of the map, that the absent author or inker may the better visualize the subject-matter. If all authors and inkers of a map are 

absent from the office the checker should himself make all possible 

corrections and refer by letter to an author or inker only those questions about which there is reasonable doubt as to procedure or lack of 

information.

Use of tracing paper. In general, the checker's notes and queries 

should be placed on tracing paper registered over the inked map; 

questions should not be indicated by drawing pencil lines across the 

face of the map, for black pencil lines are strongly photographic, and 

erasures will weaken other inked fines. The checker's oversheets 

should be destroyed after they have served their purpose, outstanding 

questions of importance, if any, having been transferred in some appropriate way, such as writing them on the margin of the original, 

where they remain for future action.

SCOPE OF CHECKING

In general, the scope of checking is covered by the printed form 

reproduced on page 312, and this form should serve as a guide; it 

should, however, be regarded as suggestive rather than complete.
312 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY 

EECORD OF CHECKING........ --_____.--.- ... .. ....___-.----

TOPOGRAPHER CHECKER SUBJECT OF EXAMINATION

1. MARGINAL LETTERING, coordinate figures, township and range figures, 

scale, declination, statements of authorship, projection and datum, 

author and inking diagrams, cooperative headings.

2. NAMES, of post offices, cities, towns and villages, civil divisions, railroads 

and railroad stations, streams, highways, mountains.

3. FIELD NAME SHEET, compare with lettered sheet.

4. PUBLIC-LAND LINES, found corners, section numbers, location or mineral 

monuments.

5. CIVIL BOUNDARIES, national, State, county, county subdivisions, city, 

park, cemetery. Boundary monuments.

6. RESERVATION names and boundaries, national forests, monuments and 

parks, Indian, land grants.

7. ROADS, houses, schoolhouses, churches; trails. Check final drawing 

against other field sheets.

8. RAILROADS, trolley lines, switches, power lines, pipe lines.

9. BRIDGES, ferries, fords, dams, tunnels.

10. CONTROL symbols, level, triangulation, traverse.

11. MINES, mine dumps, quarries, prospects, oil and gas wells.

12. STREAMS, double or single line, intermittent, canals and ditches.

13. LAKES, ponds, reservoirs, springs, wells.

14. MARSH in general.

15. CONTOURS, cliffs and cuts and fills, depressions, under-water contours.

16. FIGURES of elevation, contour figures.

17. BORDERS and names of adjoining maps.

18. OVERSHEETS, woodland, road classification, land classification.

Place check marks in columns above opposite each subject and date and sign below. 

............... -. - -_ - -.19.. -__.- . -.-.-_ . _ ,19-

(Topographer) (Checker)

SUGGESTIONS FOB CHECKING

Material. The field material turned over to the checker by the 

topographer in charge of the sheet should agree with that listed on 

the sheet jacket filed in the section of inspection and editing and 

there listed under the heading "Received from the field." Supplemental checking material may include State, post route, and Land 

Office maps, postal and railway guides, and other authorities if 

appropriate.

Traverse sheets. Data found on traverse sheets should be checked 

with the final map from a broad rather than from a literal point of 

view, for the reason that the topographer may have had occasion to 

improve the shape of a road or contour, replot a house, or erase some 

traverse feature that has not been considered appropriate for the map.

Control. The checker should obtain lists of the control data used 

on the quadrangle, preferably those used by the field topographer, 

and compare the map with them. He should not seek the latest 

adjusted values of level bench marks, as that will be done during the 

control examination hi the section of inspection and editing. Here 

the chief checking function is to see that all control is on the original 

prior to advance-sheet photolithography. The office names of triangulation points and the office numbers of transit-traverse stations 

should not be called for by the checker; they are added to the inked 

map after the control examination above referred to.
TOPOGRAPHIC MAPPING 313

Streams. The checker may properly call attention to apparent 

discrepancies in the amount of classification of drainage inked on a 

map, but resulting changes in the original drawing should, be made 

only after full consideration by the author-topographer or inker. 

The proper coordination of drainage as shown on topographic maps 

is complex at best and is among the matters considered in the inspection examination of the sheet.

Elevations and contours. All elevation figures should be compared 

with the contours; and all contour numbers should be compared with 

the elevations and with one another. Doubtful points of application 

of figures of elevation should be questioned. The checker should ask 

for the inking of more figures of elevation if those inked are not 

adequately distributed.

Names and lettering. The lettering tracing should be compared 

with the field name sheet; and post office, railroad, and station names 

should be verified. All names should be examined. Names should 

be requested for prominent unnamed features, especially schools, 

isolated localities, streams, and conspicuous mountains and lakes.

Woodland sJieets. Woodland tracings should be examined by 

placing them over the map and by looking for register and for completeness of outlines and green shading, also for accuracy of tracing if 

the woodland outlines are shown upon the original. The woodland 

borders at the edges of the tracing should be compared with any 

woodland sheets for adjacent quadrangles. Woodland tracings of 

published maps are permanently filed in the section of inspection and 

editing.

Signature. When the checker is satisfied that his notations have 

received proper attention he should affix his inked signature, with 

date, on the original drawing and on the woodland sheet within a 

stamped form provided for the purpose.

CHECKING OF CULTURAL REVISION MAPS

Inasmuch as no advance sheets are made to represent the results of 

cultural revision surveys, the cultural revision sheets are not checked. 

To avoid unnecessary duplication the sheets are so carefully scrutinized in the editorial and control examination that no prior checking 

by a topographer will in general be needed other than that by the 

author or inker.

INSPECTION OF TOPOGRAPHIC MAPS

SUBMISSION

On the completion of the checking of the topographic map and its 

return to the topographer who inked it, the topographer should submit the map and the lettering, woodland, land-classification, and
314 TOPOGEAPHIC INSTEUCTIONS OF GEOLOGICAL, SURVEY

road-classification tracings and adjoining border corrections, together 

with all field-map material, to the chief of the section of inspection 

and editing for inspection, advance-sheet photolithography, control 

examination, editing, and further transmission for engraving or 

otherwise as may be appropriate.

INSPECTION DEFINED

The term "inspection" as applied to an inked topographic map 

means an examination that is made immediately after the checking 

of the map and before the map is approved for advance-sheet reproduction. The inspection examination should assume that the checking-has been adequately done; if the appearance of the map suggests 

otherwise the inspector may return the map for additional checking. 

The inspection of the map should also be made with the functions 

of the map editor well in mind, in order that there may be no unnecessary duplication of examination. The time spent in the 

inspection of a map will differ with different maps, but a day should 

suffice for the average map; additional time will be required for maps 

that are found to need a closer inspection.

The inspection of topographic maps should be made primarily 

from the point of view of the field topographic engineer and thus 

should be assigned to one who has had such experience. The inspection should also be made from the point of view of one who has 

had an adequate office experience. These two qualifications, when 

combined with an experience that is acquired only through the 

examination of many maps representing all sections of the country, 

may reasonably be expected to result in an inspection that will 

quickly appraise an inked map as to its completeness and general 

coordination with other maps and as to its conformity with Geological 

Survey policies and standard practices.

NEED OF INSPECTION

Experienced topographic engineers working in a country to which 

they are accustomed will produce a map of known standards and 

one that will be expressed from known points of view, and such a 

map will need a minimum of inspection; likewise a checker of experience, when examining a map of an area located in a general 

section of country in which he has had personal training, will read 

the map with recognized efficiency. But the personnel of a large 

organization is perforce made up of men who have had varying 

lengths of service and corresponding experience, and as the numerous 

maps made by the topographic engineers of the Geological Survey 

represent the great variety in types of topography that is to be found 

over the country at large, differences in the interpretation of standard 

instructions are to be expected. It is a province of the inspector
TOPOGRAPHIC MAPPING 315

to examine all maps in a comparative sense and to call the attention 

of the proper division engineer to such modes, of treatment as seem 

to depart from the desired standards, differences in terrain duly 

considered. In requesting or suggesting major changes that appear 

desirable, the inspector should act through the division chief or his 

delegate; minor changes may be taken up directly with the topographic author or inker involved. There should be the fullest cooperation between the inspector and the engineer in charge of the 

division in which the area represented on the map under inspection 

falls.

The inspector's field of service does not, however, lie alone in the 

examination of completed maps; he should advise those engaged in 

the office preparation of the drafted copy at all appropriate times 

and in so far as opportunity permits. As the individual engineers 

are encouraged to consult freely with the members of the section of 

inspection and editing on matters pertaining to the office drafting 

of topographic maps, the inspector is expected to offer the fullest 

cooperation, to the end that many matters may be cleared up before 

the map reaches the inspection stage.

ATTENTION TO INSPECTOR'S QUESTIONS

In general the questions raised by the inspector should be referred 

to the division or section chief having administrative charge of the 

map under inspection; but minor questions should be referred to 

the topographer or inker in direct charge of the office work on the 

map.

The inspector should bear in mind that the author or inker of a 

map is the one most directly concerned when additions or changes 

are found to be desirable or necessary and that he should be fully 

advised when one of his maps needs further attention, that he may 

correct it and note the changes for future use. The inspector therefore should not himself make corrections to maps, except in cooperation with the author or in the author's absence from the office.

SCOPE OF MAP INSPECTION

In general, the scope of an inspection examination of a topographic 

map is covered in the preceding paragraphs, but certain features that 

in practice demand especial attention may be briefly set forth.

Appraisal of checking. The first duty of an inspector should be to 

appraise the previous examination by the assigned checker in order 

to be assured that the checker has covered the ground expected of 

him. To determine this point the inspector may make inquiry when 

appropriate and may ask for further checking if that is needed. 

58515° 28 21
316 TOPOGKAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

Drafting. The map should be examined with reference to the 

strength of the inked, lines as good copy for reproduction by photolithography; and if the inking shows congested places where a clear 

photolithograph could not be reasonably expected such steps should 

be taken as seem warranted.

Completeness of copy. The entire map should be rapidly inspected 

for completeness of copy, both within the margin and in the marginal 

lettering. All marginal notes, scales, names of adjoining quadrangles, 

etc., should be read for consistency and correct application to the map 

in hand.

Drainage. The classification of drainage and the amount of 

drainage that is inked will differ with different topographers or inkers, 

and as no complete rules can be written, these features as expressed 

on topographic maps will need further consideration by the inspector, 

who may request slight changes to reconcile the treatment with 

existing standards. To this end the drainage as shown on maps of 

surrounding areas should also be examined, and adjustment of such 

differences as may be found should be made so far as practicable from 

the data on hand.

Detail. As topographic expression is more quickly and more 

accurately read on an inked map than on the penciled field sheet, 

the inspection should include a comparison of the work of the different 

men who have contributed to the field authorship or office inking, and 

this comparison should be extended to the maps of surrounding areas 

that have been surveyed. Attention should then be called to such 

contrasts in expression or treatment as may have escaped previous 

notice but appear not fully justified by known types or standards.

Bench marks and useful elevations. Although the final examination 

of the control will be made later, after the advance sheets have been 

issued, the inspector should see that the "B M" letters and crosses 

and their elevation have been inked and that there has been a reasonable interpretation of the instructions for the inking of useful 

elevations.

Standard symbols. The drawing should be looked over for the 

possible misuse of a symbol to represent a topographic feature or the 

use of a standard symbol that has not been approved for Geological 

Survey maps.

Signature. When the inspector finds that the map is in complete 

form for photolithography and is assured that any comment has 

received due attention, either by way of changes in the map or by 

notation for further inquiry and attention, he should attach his inked 

and dated signature within the form that is stamped on each map for 

that purpose.
TOPOGRAPHIC MAPPING 317 

APPROVAL OF TOPOGRAPHIC MAP DRAWINGS

Approval by division engineer. On the completion of the final drawing of the topographic map the drawing should be approved by the 

division engineer in charge of the division in which the area mapped 

falls. The approval should be entered in ink and dated within the 

stamped form provided for the purpose. Such signatures will be 

regarded as authority for advance-sheet photolithography and also 

as approval for engraving, provided the map is carried on the current 

engraving docket approved by the chief topographic engineer and 

the director. The drawing as approved by the division engineer is 

understood to be subject to editorial review before engraving and 

therefore subject to such editorial amendment as may, in the judgment 

of the chief of the section of inspection and editing, be found desirable.

Approval by chief of section of inspection and editing. The original 

drawings of topographic maps should be finally approved by the chief 

of the section of inspection and editing. Such approval will be understood as indicating that the previous examinations have been adequately made, that the needs of the map and questions of expediency 

have been adequately considered, and that there is a full understanding with the division engineer concerned or with the chief topographic 

engineer as to the further handling of the map for such reproduction 

as has been or will be duly authorized.

Changes in map after approval. No changes in the original drawing 

of a topographic map can be made after the final approval of the 

drawing unless they are called for as a result of the editing or unless 

they have been approved by the chief of the section of inspection 

and editing and recorded. This rule is necessary because the editing 

of the map is partly done on an advance-sheet reproduction of the 

drawing made immediately after its approval, and any unrecorded 

changes in the original drawing will result in unrecorded differences 

between the advance sheet and the original and may cause confusion 

in the engraving.

Approval of woodland tracings. The woodland tracing should be 

checked and signed by the topographer assigned to check the map; 

it should be approved by the division engineer concerned; and it 

should be finally approved for printing or otherwise by the chief 

of the section of inspection and editing.

ADVANCE SHEETS

Transmission of maps for pJiotolitJiography. After approval, the 

final drawing of a topographic map should be transmitted by the 

chief of the section of inspection and editing to the chief engraver 

for advance-sheet photolithography. Before the advance-sheet 

edition is printed a proof is submitted to the section of inspection 

and editing and is read, corrected, and returned approved.
318 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

Purpose of advance sheets. The purpose of the advance-sheet 

edition is to afford an immediate reproduction of the completed 

topographic map for the temporary use of cooperating State officials, 

Government bureaus, engineers, geologists, and others and for 

Geological Survey office use, pending the publication of the engraved 

map. Advance sheets are marked "Advance sheet subject to correction," and comment is invited from anyone qualified to submit 

constructive criticism. Most advance sheets are issued with the 

topographic base printed in a dark chocolate-brown color and the 

lettering overprinted in black, in order that the names may be easily 

readable and also in order that the base may be transferred to the 

copper plates without a transfer of the names until they are needed.

Long side bar scale. A long bar scale of miles should be transferred 

to each printing plate before the advance sheets are printed, and for 

this purpose the engraving division will keep zinc plates on hand 

prepared from drawings made by the topographic branch.

Advance sheets to authors and others Jor comment. An advance 

sheet will be sent to each author named on the map, to the cooperating 

official directly interested, to the Forest Service if a national forest 

is shown on the map, and to any other appropriate person or office 

from whom thoughtful criticism is likely to be received. Each 

advance sheet sent out for criticism will be stamped: "This proof 

is for criticism. No later proof will be sent. Submit corrections 

promptly to chief topographic engineer, U. S. Geological Survey, 

Washington, D. C." Geological Survey authors receiving such an 

advance sheet are expected to examine the representation of the 

areas credited to them and to return the sheet promptly with their 

comment. Such corrections or suggestions as are made should be 

applied to the original drawing of the map in so far as they can be 

approved and expressed in correct form. The copies returned by 

the authors should then be filed in the sheet jacket for the editors' 

information when the map is prepared for engraving.

Comments and corrections for first editions of topographic maps are 

invited only on advance sheets of the maps, and no further proofs 

are sent out for criticism. (See "Plate changes after editing,"p. 322.)

Size of advance edition and reprints. Inasmuch as the advance 

sheets are distributed free and to professional map users only, the 

editions printed are small and should be restricted to the estimated 

number that may be needed to supply the mailing list and office 

files. The plates from which the advance sheets are printed are 

held until the map is engraved and are then cleaned off for further 

use; but in the meantime the advance sheets may be reprinted if 

the demand for additional copies justifies a reprint.

Mailing list Jor advance sheets. A mailing list for advance sheets 

is maintained in the section of inspection and editing. Names are 

placed on this list only after proper administrative approval.
TOPOGRAPHIC MAPPING 319

TRANSMISSION OF WOODLAND, LAND-CLASSIFICATION, AND 

ROAD-CLASSIFICATION TRACINGS

Woodland. Woodland tracings, after approval, should be permanently filed in the section of inspection and editing. Woodland 

copy that has been approved for printing should be forwarded to the 

engraving division for reproduction when the map to which it applies 

reaches the stage of first plate proofs. When the woodland color 

has been printed the woodland tracing will be returned for. filing.

Land classification. Land-classification tracings or sheets and written reports that have been prepared in conformity with instructions 

on pages 258-261 should be submitted to the section of inspection and 

editing for examination and approval. Each land-classification tracing, attached to a copy of the topographic map it represents, will be 

transmitted by the chief topographic engineer to the chief of the conservation branch.

Road classification. The road-classification tracing or sheet should 

be submitted to the section of inspection and editing at the tune the 

original maps and field material are submitted. The road-classification data will be filed for later consideration when the copy for the 

red overprint showing road classification is prepared, just prior to 

the printing of the map.

CONTROL EXAMINATION

The final drawings of all topographic maps should be examined in 

the section of inspection and editing for the completeness and accuracy of their control, both horizontal and vertical. This examination should in general be made after the advance sheets have been 

issued if the maps are to be engraved; if the maps are to be photolithographed only, the examination should of course be made before 

photolithography.

Need. Inasmuch as the proper plotting of the initial control for 

a proposed map is a fundamental preliminary to any topographic 

survey, its correct expression on the published map is of prime importance. Although the nature of the control examination is editorial, 

the task calls for a previous field experience. As the control for a 

map may have been run in part during the progress of the topographic mapping, as the control data that are supplied to the topographic engineers may be divided between several men working on 

the same or adjoining quadrangles, and as party personnels may 

change, experience has shown that a check-up for completeness is 

necessary. For example, one inker may inadvertently fail to ink 

control used by another; occasionally only preliminary field determinations were available for the elevation of bench marks but can 

now be replaced by adjusted figures; control that was of value in
320 TOPOGKAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

field mapping and that has been inked on the map may not be appropriate for engraving and publication; or control that has been reported destroyed may be inadvertently inked.

Scope. The control examination should consist of a thorough 

search in the records of the section of computing for all control data 

affecting the area under examination and the comparison of these 

data against the control as shown upon the original drawing submitted. So much of the control as is found appropriate for engraving and final publication should be left in black on the original, and 

such as is not to be published should be changed to red and not 

engraved.

The figures of elevation of supplementary bench marks that do 

not represent good engineering benches should be changed from black 

to red, and these bench marks will not be engraved.

Copy should be prepared for the appropriate credit for such outside control as may have been directly used in the topographic mapping. In general, control that has not been used in the topographic 

mapping should not be published on Geological Survey maps.

The decimation diagram should be checked by comparison with 

the records of the section of computing and by the isogonic chart 

issued by the Coast and Geodetic Survey.

Triangulation and traverse designations. The names of triangulation points should be lettered in hair-line black on the original opposite the triangle, unless the feature on which the point falls is itself 

sufficiently named on the map to serve as an identification of the 

triangulation point. Names thus shown in hair line will not be 

engraved. Transit-traverse stations should be further identified by 

hair-line black lettering giving the recorded number of the station 

for example, "T Tr 17."

EDITING OF TOPOGRAPHIC MAPS 

CHARACTER OF EDITING

Editing for engrramTW/. Topographic maps that are to be engraved 

should be edited before transmission for engraving. The engraver's 

copy should consist of an inked original or final drawing and lettering 

tracings, together with supplemental instructions written in red ink 

on an advance sheet or other photographic copy of the map.

The editorial examination should consist of a careful scrutiny and, 

if necessary, rearrangement of the original drawing and lettering 

tracings to insure general conformity with Geological Survey instructions and practice. Changes in the topographic base should not be 

made by the editor, but if such changes appear necessary he should 

question them on the editing work sheet (seep. 322), and the action 

then taken by the topographic engineer or inker in charge of the map
TOPOGRAPHIC MAPPING 321

or by his representative should be written alongside the written 

marginal question, where it should remain as a record for the editing 

files. It is a function of the editor to arrange for the proper placing 

and spelling of all names, marginal notes, and numerals according to 

existing practice or instructions but to question them only when a 

fact is uncertain.

Engraving docket. LAn engraving docket should be prepared in the 

section of inspection and editing early in each calendar year. This 

docket should list all new topographic maps authorized for engraving 

in the order in which they are to be taken up. The priority interests 

of the several States in which the mapped areas lie are first indicated 

by the topographic division engineers, and a resulting draft of the 

proposed docket should be submitted to the chief topographic engineer and to the chiefs of the other Geological Survey branches concerned. The final engraving docket is then approved by the director. Additional or special engraving out of the docket order can be 

authorized only on approval by the director.

Editing docket. A topographic map will not be taken up for 

editing unless it has been listed on an engraving docket or unless its 

engraving has been provided for by a separate letter and authorized 

by the director. The editing of topographic maps should be taken up 

in the order in which the maps are placed on the engraving docket, but 

only in so far as they have been put on an editing docket. To be 

available for editing the map must have been examined for control; 

the advance sheets must have been issued, if to be printed; and all 

outstanding questions of major importance must have been settled. 

The sheet jacket should then be indorsed "On editing docket," 

dated, and initialed by the chief of the section of inspection and editing; and the map in the jacket, together with the appropriate oversheets and other field material needed in the editing, forwarded to the 

editing rooms.

Editing questions. Questions raised in the editing should be 

referred with the map in the jacket to the topographic engineers or 

inkers engaged in the office preparation of the copy or in their absence 

to some designated representative, that they may answer queries, 

supply omissions, explain discrepancies or apparent errors, review 

the corrections and rearrangements made by the editor, and clear up 

questions of interpretation or of legibility of essential data that 

should be clear copy for the engraver. Editing questions should be 

written in pencil on the margin of the editing work sheet, within a 

green penciled reference mark, and replies should be written in pencil and should indicate clearly the action taken for example, "Yes; 

original changed."

Outstanding questions that are not answerable from office data 

should be placed on an advance-sheet copy of the map and sent to
322 TOPOGEAPHIC INSTRUCTIONS OF GEOLOGICAL, SURVEY

such author topographers as may be in the field or to other persons 

who may be considered competent to answer them, and they should 

receive prompt attention. Other outstanding queries should remain 

on the margin of the editing work sheet for further adjustment.

Plate changes after editing. Edited topographic maps approved 

for engraving constitute final copy for engraving, and the very minimum of changes will be made after the maps have been engraved on 

copper. Topographic engineers and administrative officials must 

therefore make in ample time all corrections that they wish incorporated in the final publication, and no corrections to plate or combined 

proofs should be made except under extraordinary circumstances 

where the corrections are imperative. No combined proofs should 

be sent to field men or to officials of other organizations for comment. 

Such corrections as they wish to make for subsequent editions can be 

filed on a published copy of the map.

SCOPE OP EDITING

The details of the topographic map editing that appear under the 

headings given below should not be regarded as complete but only as 

covering a large part of the scope of' editing. Map editors are 

expected to find them suggestive of other details which in many 

individual maps will also need consideration and attention.

Comparison with other maps.

Waterlining and tints.

Detailed examination of original.

Depression contours.

Punctuation.

Position of lettering.

Abbreviations.

Selection of elevations for engraving.

Position of bench-mark letters and

figures.

Position of elevation figures. 

Position of contour figures. 

Style of engraved lettering within the

map.

Style of engraved marginal lettering. 

Style of figures. 

Parts of quadrangles. 

Edited map to topographer. 

Letters of inquiry. 

New lettering tracings. 

Instruction sheet for engraver. 

Filing of editing notes.

Editing work sheet.

Scale and contour interval.

Marginal lettering and scales.

Adjoining borders.

Post offices.

Railroads and stations.

Locality names.

State boundaries.

County boundaries and names.

County subdivisions.

Incorporated places.

United States Geographic Board.

Land lines.

National forests.

National parks.

National monuments.

Indian reservations.

Private land grants.

Federal game and bird preserves.

State parks and reservations.

Military reservations.

Power transmission lines.

Editing work sheet. The editing work sheet consists of an advancesheet photolithograph (seep. 317) or a photographic copy of the original map or final drawing of the map that is to be engraved. If the 

engraving copy consists of several large-scale maps, as when four
TOPOGRAPHIC MAPPING 323

maps are to be reduced and combined into one 15' map, the editing 

work sheet should be a single dummy made up from the separates 

photographed to the scale of publication.

On the editing work sheet the editor should enter in black pencil 

all notes and queries relating to discrepancies or apparent errors found 

in the course of the editing but should indicate in red ink instructions 

to the engraver. Such notes, queries, and instructions should for 

the most part be written on the margin of the paper and connected 

by a line with the feature to which they relate. All boundary lines 

to be published should be legibly emphasized by colored pencil lines 

drawn on the work sheet along them, a separate color being used for 

each kind of boundary; and a key should be added in the southeast margin explaining the color distinctions thus used. Certain 

data and names that are not to be engraved are inked on the original in 

red (see "Colors," p. 279); other data or names that may be eliminated in the editing should be indicated on the work sheet by red lines 

drawn through them. The original drawing should not be changed 

save where changes in the marginal lettering are necessary. (See 

"Marginal lettering and scales," below.)

Scale and contour interval. The scale and contour interval for the 

engraved map must be clearly indicated. If the editing is done upon 

a sheet that has been photographed to a scale larger than that of publication, due allowance should be made for the reduced size of the 

engraved map in providing for lettering, numbers, etc., in close 

places.

If the contour interval for the engraved map differs from that on 

the engraver's copy, complete and adequate copy must be furnished 

to the engraver for both heavy and light contours on the new interval.

Marginal lettering and scales. All marginal lettering should be 

examined for its correctness and completeness of statement as applying to the map in hand, for any changes in wording that may be 

needed in order to comply with existing standards, and lastly for its 

best placing on the plates. The engraver should be instructed as to 

what names of adjoining quadrangles are to be engraved, the kind 

of bar scales to be used, and the datum upon which the map is drawn 

if other than North American datum. The author diagram should 

not be engraved unless an outside organization has been credited with 

topographic authorship. Where changes in marginal lettering are 

indicated in red on the instruction sheet for the engraver the corresponding changes should be made on the original and in the usual 

inked or pasted form, in order that there may be no misinterpretation of engraving copy. Erasures of features such as military number 

and diagram, advance-sheet label, and field bar scale and other routine changes that are well understood by the engraver and apply to 

all sheets need not be made on the original.
324 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

Adjoining borders. The edges of the maps of adjacent quadrangles 

on the same scale should be compared to see that for each line, 

contour, road, or boundary drawn to the exterior projection line on 

one map there is a corresponding line on the other, and that these 

lines meet. Edges should be compared in a general way with maps 

of adjoining quadrangles on different scales to detect discrepancies 

that are not explained by differences in scale. Names of features that 

are common to two or more maps should be compared. The new 

map should be made to join and agree with the one already engraved 

so far as possible, but if this can not be done a correction of the older 

map should be called for. (See p. 227.) The margins of the instruction sheet sent to the engraver should then be marked "Join to 

 ," "Join to ; see corrections herewith," or "Cut to 

projection," as appropriate.

Post offices. Post offices should be compared with the post-route 

map for general location, with the Postal Guide for spelling, and with 

the monthly supplement to the Postal Guide for latest information as 

to the establishment or discontinuance of offices. The names of post 

offices discontinued through rural delivery should be retained as 

locality names if appropriate.

Railroads and stations. Names of railroads and railroad stations 

should be compared with the Official Railway Guide. "Bullinger's 

Shippers' Guide" should be used to identify places having different 

names for the post office and the railroad station; and "Poor's Manual 

of Railroads" to trace out railroads that are no longer listed in the 

Official Railway Guide. Local railroad folders should be obtained if 

necessary. (See p. 232.)

The abbreviation "R R" should not be used, and the word "railroad" should be used only where it is a necessary part of a descriptive 

title or name for example, "Lumber Railroad" and "Central Railroad of Oregon." The term "division," signifying merely an operating unit, should not be used, but "branch" or "line" as appropriate 

may be used to identify the different lines of a road appearing on the 

same or adjoining maps.

In the selection of railroad names where large systems or lines are 

involved, judgment will be required, and inquiry will often be necessary to determine ownership, control, operation, or trackage rights. 

Where a road has lost much of its former identity as a separate road 

through absorption or lease by a larger and operating organization, 

the name of the larger organization should be used, but without the 

word "system" or "lines" for example, the road formerly known as 

the "Northern Central" is now better identified by the system name 

"Pennsylvania." Where, however, the affiliation does not include 

operation, the name of the operating road should be used for 

example, "Baltimore, Chesapeake and Atlantic" should be retained,
TOPOGRAPHIC MAPPING 325

although this road is affiliated with the Pennsylvania system. Where 

a road is operated not only by its own well-known organization but 

also as a part of a larger system that exercises part control, as in the 

running of through trains, both loca^ and system .names should be 

used for example, "Southern Pacific System (Galveston, Harrisburg and San Antonio)." Preference is to be given to the name of 

the railroad that owns a line rather than to that of one that has 

trackage rights only. For a line under joint ownership the name of 

the road operating the line should be used.

Locality names. In addition to towns and localities designated by 

their post-office or railroad-station names, all other well-known 

localities should be designated by local names established through 

recognized usage. Among such localities are country schools, crossroads, and isolated churches. If the name of a feature, as a bridge, 

is also a locality name, preference should be given to the locality 

designation by the use of roman type. If the name of a railroad 

station differs from the name of a corresponding post office, or if 

either differs from a more widely used local name, the name by which 

the place is better known should be used, followed underneath by 

the other name, with "P O" or "Sta" affixed as the case may be.

State boundaries. Bulletin 689 should be consulted as to State 

boundaries, and any doubtful application of the statutes should be 

fully investigated. (See field instructions, p. 236.)

Although the province of the topographic engineer is first to identify the boundary line on the ground and then plot it on his map, the 

the ground conditions are sometimes found to be uncertain in that 

lines may be indefinite or not marked, and if they lie in streams with 

shifting channels or banks they are difficult to determine; and the 

line may not have been accepted by those living on both sides of it 

or by the proper county or State authorities and may be in dispute 

or even in court. The location of a State boundary line should 

therefore be subject to careful review in the editing.

The following principles should be kept in mind: (a) A line 

marked on the ground and once accepted by competent authority is 

the real boundary regardless of a statute to the apparent contrary. 

(6) The description of a particular bank or point in a stream may be 

indefinite in wording or difficult of application, and past practices 

or rulings should be sought. *(c) Early Supreme Court decisions 

that a boundary moves with a gradually shifting channel or bank but 

does not follow sudden shifts or cut-offs have in general been followed 

in recent decisions, (d) If the statute defines a boundary line as 

that of some channel or other part of a river, the location of the river 

itself at the time the statute became effective should govern, unless 

there has been a gradual change in the position of the river, as just 

indicated. The generally accepted location of the rivers that form
326 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL, SURVEY

State boundaries at or near the time of the enactment of most of the 

statutes defining the boundaries may be found on the plats of the General Land Office that were prepared at about such times. Supreme 

Court rulings must govern if tjiey have been made, but few decisions 

that affect the details needed on Geological Survey maps have been 

handed down by the court, and it may also be necessary to differentiate between gradual and sudden changes in a river course.

County boundaries and names. County boundaries and names 

should be compared with post-route maps, and information as to 

newly created counties should be sought in the monthly supplement 

to the Postal Guide. Any further necessary data should be sought 

through letters of inquiry or by an examination of the State statutes, 

which are obtainable from the Library of Congress. (See p. 236.)

County subdivisions. The subdivisions of the county should be first 

verified, as to kind, by the authorized list of county subdivisions legal 

for each State (see p. 237), and then by the Census reports in which 

all such subdivisions are listed. As the subdivisions of the county 

in some States are omitted on Geological Survey topographic maps, 

the policy that has been adopted should be ascertained in each case 

of doubtful application.

Incorporated places. For incorporated places the list given in the 

Census reports on population should be consulted, and any absence 

of boundary lines should be questioned.

United States Geographic Board. The decisions of the United 

States Geographic Board must be used for the names and spellings 

of the features listed and described in its reports and bulletins. If, 

however, the present local usage appears to differ persistently from 

a board decision, a review by the board should be requested. If other 

recognized authorities differ with Geological Survey topographers as 

to names or spellings of features upon which the board has not yet 

acted, a decision by the board should be requested.

A card list of the decisions of the United States Geographic Board, 

arranged by States and counties, should be maintained in the section 

of inspection and editing. The list should be kept current and should 

be referred to when each new map is edited. Decisions applying to 

maps already printed should be placed in the correction files when 

the decisions are received from the board.

The following are some of the principles adopted by the United 

States Geographic Board:

(a) Names suggested by peculiarities of the topographic features designated, 

such as their form, vegetation, or animal life, are generally acceptable, but duplication of names, especially within one State, should be avoided. The names 

"Elk," "Beaver," "Cottonwood," and "Bald" are altogether too numerous.

(b) Names of living persons should be applied very rarely, and only those of 

great eminence should be thus honored. No personal names should be attached 

because of relationship, friendship, or personal interest.
TOPOGRAPHIC MAPPING 327

(c) Long and clumsily constructed names and names composed of two or more 

words should be avoided.!

(d) The possessive fornj of names should be avoided unless the object is owned 

by the person whose name it bears.

(e) The multiplication of names for different parts of the same feature, such 

as a river or mountain range, should be avoided. Only one name should be 

applied to a stream or mountain range throughout its length.

Such names as "East Fork" and " North Prong" for branches of a river should 

be avoided unless there is a special reason for their adoption. Independent names 

should be commonly selected.

Land lines. Land lines and township and range numbers should 

be verified by comparison with the State maps of the General Land 

Office; in case of apparent disagreement the township plats may be 

examined for confirmation, but discrepancies should be questioned. 

Section numbers should be omitted on scales of 1:125,000 and on 

smaller scales.

National jorests. The boundaries and names of national forests 

should be verified by the latest maps and lists issued by the Forest 

Service and by Presidential proclamations and Executive orders, and 

further verified if necessary through inquiry at the office of the 

Forest Service.

National parks. The latest annual report of the National Park 

Service should be consulted for lists, of national parks administered 

by the Department of the Interior and by the War Department. 

Boundaries of national parks should be verified by the descriptions 

given in the acts creating them, by any existing maps, and, when 

necessary, through inquiry at the offices of the National Park Service 

or the Chief of Engineers. The existence of national parks should 

be further verified by the General Land Office State maps.

National monuments. The latest annual report of the National 

Park Service and the check list, issued by the Forest Service should 

be consulted for lists of national monuments administered by the 

Departments of the Interior, Agriculture, and War. Boundaries of 

national monuments should be verified by proclamations describing 

them, by subsequent Executive orders, and by inquiry if necessary.

Indian reservations. Indian reservations should be verified by the 

State maps of the General Land Office and as to their boundaries by 

existing maps, by the descriptions given in the acts creating them, 

by reference to the township plats of the General Land Office, or 

through inquiry at the Office of Indian Affairs.

Private land grants. Private land grants and donation tracts should 

be checked first by the General Land Office State maps and then by 

the township plats.

Federal game and bird preserves. The United States Biological Survey check list of Federal game and bird refuges and the General Land 

Office State maps should be consulted for these preserves, and their
328 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

boundaries should be verified by proclamations describing them or 

Executive orders modifying them. The word "preserve," "reservation," "refuge," or "range" should be used-as appropriate.

State parks and reservations. Names and bcundaries of State parks 

and reservations should be verified by State publications and local 

information.

Military reservations. Military reservations should be verified by 

reference to the General Land Office State maps and other general 

maps and through inquiry of the Corps of Engineers, War Department. The "List of military posts and camps in the United States" 

in the back of the Official Railway Guide should also be consulted.

Power-transmission lines. Each topographic map upon which 

power-transmission lines have been, shown and which is to be engraved 

for regular publication should be referred to the chief hydraulic 

engineer for his approval of the lines and designations for publication. 

For this purpose a colored pencil line should be drawn alongside 

each power-transmission line on an advance-sheet copy of the map.

Comparison with other maps. The names and features on the 

topographic map that is being edited should be compared with the 

names and features as given by recognized authorities on general 

maps, in gazetteers, in reports of explorations, or in other available 

and appropriate reports. If discrepancies or unusual names or 

spellings are found, they should be questioned and if necessary letters 

of inquiry should be sent out. (See p. 334.) If it seems advisable 

cases should be prepared for consideration by the United States 

Geographic Board. (See p. 326.)

Water lining and tints. In general, water bodies are represented 

on engraved maps by water lining. Water lining should be engraved 

to continue with the trend of the natural shore line and not follow 

around artificial features. Water lining should be carried continuously through piers, wharves, or other artificial structures built 

over the water if the cultural feature is shown in solid black, but if 

the cultural feature is shown with an open outline, as for a large 

pier or wharf, the water lining should be broken at the feature.

On maps that carry under-water contours water lining can not be 

shown, and it is desirable, when practicable, to use a flat blue tint 

to represent the water surface. Whether the flat tint is used or not, 

however, interior water bodies should be water lined, and large 

rivers should be water lined as far as the vicinity of the under-water 

contours.

Detailed examination of original. The original drawing should be 

examined in detail in order to see that elevations agree with contours, 

that the right contours are accented, that depressions are properly 

hachured, that there is an equable distribution and clear delineation
TOPOGRAPHIC MAPPING 329

of elevations and contour numbers, and that all symbols are clearly 

drawn and in conformity with Geological Survey practice.

Depression contours. The engraving of hachures for the identification of depression contours (see p. 296) should be confined to small 

depressions and to such larger depressions or parts thereof as can not 

otherwise be readily recognized as depressions by the contour numbering alone. In general, the engraving of hachures may be omitted 

from depression contours that exceed 1 inch in length on the publication scale.

Punctuation. Periods are to be consistently omitted on all lettering 

within the margin of the map.

Position of lettering. Names should be placed as specified below 

if they are legible when so placed; otherwise they should be moved 

to a position where they will be legible. If no such position can be 

found and no authorized abbreviation exists and there is no suitable 

substitute, the name may be omitted, but a position must be found 

for the name of every important feature.

All names should be so placed that they will be readable from the 

bottom of the map. Names that are lettered parallel to a meridian 

should read from south to north.

Names of places, public institutions, ranches, mines, and other 

lesser cultural features should be placed horizontally and so far as 

practicable to the right of the features to which they refer.

Names of ponds, lakes, islands, swamps, and glaciers should be 

placed horizontally and to the right of the features named, unless 

the area of the feature is so large that the space will accommodate 

the name within its limits. Names of oceans, bays, coves, fiords, 

and straits should be placed across these features in broad curves.

Names of broad, water-lined streams should be placed within 

those features. Names of small shore features, such as points, 

should be so placed as not to touch the shore line and placed on the 

water side so far as practicable.

Names of railroads, highways, roads, trails, canals, and streams 

should be placed on the upper side of the feature wherever practicable 

and approximately in the middle third, but if the middle third does 

not cover the feature sufficiently to make the application of the name 

clear the same name should be shown in two or more places.

Names of narrow valleys, canyons, gorges, gulches, arroyos, and 

washes should follow the general trend of these features in easy 

curves and be placed preferably on the upper side. Where the limits 

of such features may be obscure the names should be so placed as 

to show the limits so far as practicable.
330 TOPOGBAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

Abbreviations. The following are authorized abbreviations:

Aux Mer_ ______ Auxiliary meridian.

Ave--______--_- Avenue.

BM.___________ Benchmark.

Bdy___________ Boundary.

Br_____________ Branch, bridge.

Bk__________ Brook.

Bu____________ Butte.

Can.__________ Canyon.

C____________ Cape.

Cem___________ Cemetery.

Ch____________ Church.

CGS.__________ Coast Guard station.

Cor____________ Corner.

Co_-___________ County.

Cr_____________ Creek.

Dist___________ District.

Div.___________ Division.

E____________ East.

El.____________ Electric, elevated.

Elev___________ Elevation.

Fy___________ Ferry.

Fd-_______ Ford.

F, For___.___ Forest. 

Ft.______ Fort.

G Mer_________ Guide meridian.

GL____________ Glacier.

Gl.____________ Gulch.

Gh________ Gulch (in Alaska).

Hbr__________ Harbor.

Hdqrs._________ Headquarters.

HW.________ High water.

Hy____________ Highway.

Hoi._______ Hollow.

H_____________ House.

I, Ind__________ Indian.

!______________ Island.

Is.____________ Islands.

June.__________ Junction.

L______________ Lake, or little.

Ldg __________ Landing.

Lt.___________ Light.

LH____________ Lighthouse.

LM____________ Location monument.

LW.__.________ Low water.

Mdw__________ Meadow.

Mer___________ Meridian.

Mid____.______ Middle.

Mi____________ Mile.

MP____________ Milepost.

Mil.___________ Military.

MM___________ Mineral monument.

Mon___________ Monument.

Mt____________ Mount.

Mtn___________ Mountain.

Mts____-._____ Mountains.

N, Nat, Natl _ National. 

N__________ North.

No_ ___________ Number.

Par.___________ Parallel.

Pk_____________ Peak.

Pen.___________ Peninsula.

Pt.__________ Point.

Pd___._______ Pond.

PO_____.______ Post office.

PH____________ Power house.

Prin Mer_______ Principal meridian.

RR____________ Railroad.

R____________ Range, river, run.

Res____________ Reservoir, reservation. 

Rd____________ Road.

Rk____________ Rock.

Sch__________ School.

Sec, Sees _______ Section, sections.

Sd_____________ Sound.

S_____________ South.

Spr____________ Spring.

Std Par_ _______ Standard parallel.

Sta____________ Station.

Str____________ Stream, strait.

St_____________ Street.

T__________ Township.

Val____._-.__ VaUey.

VA____________ Vertical angle.

WT____________ Water tank.

WW___________ Waterworks.

W____.__.___._ West, water.
TOPOGRAPHIC MAPPING 331

For abbreviations of State names see the Style Manual issued by 

the Government Printing Office, or the Geological Survey pamphlet 

"Suggestions to authors."

Selection of elevations for engraving. The editor should select 

elevations for engraving on a basis of a spacing of about 1 inch apart 

on the scale of publication. He should be guided by the field instructions for "useful elevations" (p. 241) and should exclude all elevations 

for which the point of application appears to be indefinite. Preference should be given so far as practicable to important crossroads 

and road intersections, points in the vicinity of schoolhouses, and 

prominent summits. The elevations selected for engraving should 

be added to the new lettering tracings.

Position oj bench-mark letters and figures. Where practicable the 

letters "BM" should be placed above and to the left of the cross 

indicating a bench mark, and the figures of elevation below and to 

the left. Otherwise the letters may be placed to the right, above the 

figures. Different arrangements may be controlled by circumstances. 

If the bench mark is in a town or city and the lettering and figures 

can not be legibly placed near the position for the bench mark, the 

letters "BM" and the figures of elevation should be arranged in one 

line and inclosed in parentheses and placed directly under the name 

of the place. Figures of elevation for a supplementary bench mark 

should be placed to the right of the cross and above rather than below.

Position of elevation figures. Of first importance in placing figures 

of elevation is the identification of the feature for which the elevation 

is given. Although a rule may apply where both identification and 

legibility are obtained, another position must be sought if either is 

uncertain; and unless a position can be found where both tests can 

be met the elevation figure should be omitted. Elevation figures in 

cities and areas of heavy culture should therefore be omitted unless 

the scale of the map permits their insertion.

Elevation figures for road corners and peaks that are named should 

be placed to the left of the feature; those for an unnamed road corner 

should be placed in the northeast corner, and those for an unnamed 

summit to the right. Figures showing water-surface elevation 

should be placed on the pond, lake, river, or other water feature 

shown.

Position of contour figures. The purpose of contour figures being 

to facilitate the reading of elevations as expressed by contour lines, 

they should be placed at or near such critical places on the contours 

as the tops of ridges, saddles, the bottoms of valleys, and noticeable 

changes in slope. On some long slopes they may be advantageously 

placed in rows but the rows should not become too prominent on 

the map. A contour figure should not be placed at the extreme end

58515° 28 22
332 TOPOGEAPHIC INSTBUCTIONS OF GEOLOGICAL, SUEVEY

of a contour adjacent to a road, stream, or other feature, and it is 

not necessary near a road corner or other feature of which the elevation is given. Additional contour figures should be placed in outstanding and conspicuous places and with such frequency as will 

enable a map user to read any contour without prolonged search for 

a reference contour figure. This readability may generally be obtained 

by placing numbers only on the heavy contours, but it will sometunes be advisable to place contour figures on light contours and on 

depression contours.

Style oj engraved lettering within the map. The final drawings and 

lettering tracings should be lettered mostly in slanting block 5 and 

italic. (See p. 304.) The styles of the corresponding engraved lettering are well understood by the engraver and need be specified by the 

editor only where a doubt might otherwise exist.

All place names and names of country post offices, railroad stations, 

country schoolhouses, churches, and ranches should be lettered in 

lower case roman. The size of the letters should be commensurate 

with the importance of the place. Large cities, State capitals, and 

county seats should be shown in roman capitals.

Names of civil divisions, such as States, counties, districts, civil 

townships, and land grants; and of reservations, such as national and 

State parks, forests, and game preserves, Indian and military reservations, should be lettered in roman capitals.

Names of routes of communication, such as railroads, highways ? 

trails, and canals; of public works, such as bridges, ferries, fords, locks, 

tunnels, dams, and wharves; of public institutions, such as lighthouses, 

lightships, life-saving stations, universities, State hospitals, asylums, 

and city parks and cemeteries; and of mining features, such as mines, 

quarries, prospects, furnaces, and smelters, should be lettered in 

small slanting block capitals.

Names of small hydrographic features, such as creeks, branches, 

brooks, runs, streams, pocosins, ponds, glaciers, coves, marshes, 

swamps, and bogs, should be lettered in stump; names of large hydrographic features, such as oceans, large bays, straits, rivers, and 

lakes, should be lettered in italic capitals. The choice between 

stump and italic capitals will depend upon the relative size of the 

feature.

Names of hypsographic features, such as summits, peaks, hills, 

knobs, gulches, canyons, gorges, draws, arroyos, washes, and islands; 

and of land features along coasts, shores, or rivers, such as points, 

capes, and bends, should be lettered in upright block. Only features

 The terms used here to describe styles of engraved lettering have long been in use by engravers. 

"Block" is the style generally known to printers as "gothic," and "stump" corresponds to "lower-case 

italic."
TOPOGRAPHIC MAPPING 333

of considerable extent or importance, such as plateaus, mountain 

groups, ranges, basins, and valleys, should be shown in capitals.

Style of engraved marginal lettering. The quadrangle, State, and 

county names at the northeast and southeast margins of the map, the 

department and Geological Survey heading at the northwest margin, 

and the State or other cooperative heading at the middle of the upper 

margin should be lettered in finished hair-line capitals (with spurs). 

(See pi. 15.)

The credit and date of survey at the southwest margin, the projection and horizontal datum, the projection figures, the grid note 

and distances, and the edition date should be lettered in lower case 

hair-line block.

The contour interval and the words on the bar scales should be 

lettered in lower case roman.

The names of adjoining quadrangles and the sea-level datum should 

be lettered in stump.

Township and range letters should be lettered in upright block 

capitals.

The lettering for the magnetic declination diagram should be in 

hair-line block capitals.

Style of figures. The styles of figures inked on the original or final 

drawing (see p. 304) conform only in general with the styles in which 

the corresponding figures are to be engraved, but as the engraved 

standards are well understood by the engraver they need be specified 

by the editor only in unusual or exceptional cases. The following are 

standard styles of figures for engraving:

On the black plate, elevations of bench marks, both permanent 

and supplementary, are engraved in upright block. Elevations other 

than bench marks, such as those at road corners and summits and 

on lakes, are engraved in slanting hair-line block. Section figures 

are engraved in upright hair-line block on standard-scale maps and 

in open block on large-scale maps. Numbers on boundary monuments are engraved in slanting block. Township and range figures 

are engraved in upright block. Projection and grid figures are engraved in upright hair-line block; two sizes are used for projection 

figures, those for degrees being larger than those for minutes. Figures 

that occur in marginal notes or as part of a name follow the style of 

the accompanying letters.

On the brown plate, contour numbers are engraved in small italic.

On the blue plate, under-water contour numbers are engraved in 

small italic. Contour numbers on glaciers are also engraved in 

small italic.

Parts of quadrangles. On a topographic map that is published in 

incomplete quadrangle form the blank part of the map should carry 

an appropriate legend descriptive of the conditions applying to the
334 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

blank area, as, for example, "Preliminary edition, unsurveyed area," 

for an area not mapped on any scale and "This area is shown on the 

map of the Dinuba quadrangle, surveyed in 1916, scale 1:125,000," 

for an area that has been surveyed but of which the published map 

is on a different scale, usually smaller.

Edited map to topographer. On the completion of the editing the 

jacket should be dated, indorsed "Edited," and initialed by the one 

editing, and then with inclosures (original, editing work sheet, etc.) 

referred back to the author topographers or inkers, that they may 

see the result of the editorial review and reply to any editing questions. 

(See "Editing questions," p. 321.)

Letters of inquiry. Essential information that is not obtainable 

from author topographers or from office data should be sought through 

letters of inquiry to postmasters, local civil officials, or other authorities, on forms provided for the purpose.

New lettering tracings. On the return of the edited map from the 

topographers, new lettering tracings should be made in order that 

the engraver may have lettering copy with the names in their edited 

positions. If the names have been inked on the original drawing the 

necessary changes will have been indicated in red ink on the editing 

work sheet. The figures of elevation that have been selected for 

engraving should be added to this lettering tracing.

Instruction sheet for engraver. If the lettering is on the original 

map the editing work sheet becomes the instruction sheet for the 

engraver, but if new lettering tracings have been made the remaining 

engraving instructions, with outstanding notes and questions, should 

be transferred to a clean advance-sheet copy on which will be indorsed 

"New tracings are copy for names." All boundaries should be 

emphasized by colored pencil on the instruction sheet, a different 

color being used for each kind of boundary shown on the map and a 

key to the colors used being added in the lower right corner. The 

instruction sheet should be made complete copy for marginal lettering, 

scales, and notes, and the original drawing should be changed to 

conform, in order that there may be no misinterpretation of copy. 

All necessary engraving instructions should be indicated in red ink, 

and all notations in pencil (other than boundary data) should be 

disregarded by the engraver, as they are editor's memoranda only.

Filing of editing notes. A file of "editing notes " arranged by names 

of maps should be maintained in which all correspondence or copies 

thereof pertaining directly to the editing of topographic maps should 

be assembled. In this file should be placed all appropriate memoranda 

affecting important matters under discussion or in dispute, so that 

such data may be readily accessible for use in the editing of adjoining 

qmadrangles, in the editing of reprints, or in correspondence.
TOPOGRAPHIC MAPPING 335 

APPROVAL AND TRANSMISSION FOR ENGRAVING

When the editing is complete and all outstanding questions affecting the engraving have been disposed of, the jacket, on which the 

entire contents should be listed, should be indorsed "Approved for 

engraving" and should be dated and signed by the chief of the 

section of inspection and editing, who is responsible for the submission 

of topographic maps to the engraving division as complete and 

adequate copy for engraving.

Maps edited and approved for engraving and previously authorized for engraving should be forwarded direct from the section of 

inspection and editing to the engraving division.

EDITING OF CULTURAL REVISION SHEETS 

CHARACTER OF EDITING

The editing of cultural revision sheets consists largely of an examination of the copy to insure its proper presentation to the engraver, 

that he may clearly understand where changes are to be made in the 

plates. In general, the character of the editing should follow the 

outline given under "Editing of topographic maps" (pp. 320-334), but 

with the thought always in mind that changes in the plates should be 

called for only where demanded by the cultural revision or made 

necessary through changed practices since the first or some other 

prior edition of the map.

ENGRAVING AND EDITING DOCKETS

Cultural revision sheets should be included in the annual engraving 

docket of topographic maps (see p. 321) and should be placed on the 

editing docket in the same way as new topographic maps (see p. 321).

SCOPE OF EDITING

Work sheet and instruction sheet. The editing work sheet should be 

an engraved copy of the latest print of the map, and on this sheet all 

editing notes and names should be placed in pencil. The final 

markings and instructions for the engraver should be indicated in red 

ink, on the map margin or on the face of the map as may be appropriate. The instruction sheet should be mounted before the final 

markings are added.

Engraving of'new Hack plate. If the corrections to the culture plate 

are numerous the unedited cultural revision copy should be referred 

to the engraving division to determine whether it is more feasible to 

make a new black plate than to correct the old one. If the old plate 

is to be corrected the correction copy should be confined to changes, 

but if a new black plate is to be made the editor should ask for an 

inked sheet showing all the culture, and when that is furnished the
336 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

"take out" sheet may be retired. The road-classification data for 

the red overprint should be filed for editing when the reprint nears 

publication.

Editing of cultural revision. The editing of cultural revision sheets 

should, in general, follow the outlines given under "Editing for 

reprints" (p. 341) and described more in detail under "Editing of 

topographic maps" (pp. 320-335). (See also field instructions for 

"Revision of topographic maps," pp. 262-264, and "Inkingof cultural 

revision sheets," p. 301.) The items that require especial attention are 

new names, changed positions of names due to new or changed cultural 

features, changes in reservation and other boundaries and names, 

features such as power lines and oil and gas wells that were not shown 

on the former edition of the map, and marginal notes. The entire 

culture of the map should be subject to editorial review..

If the black plate is to be corrected rather than reengraved, the 

revision editor should call for as few small or immaterial changes as 

practicable in the position or arrangement of names or notes that are 

already engraved. If, on the other hand, it is found expedient to 

reengrave a new black plate full advantage should be taken of the 

opportunity to recast the names, figures of elevation, and notes into 

the best possible positions.

ENGRAVING OF TOPOGRAPHIC MAPS

The topographic maps listed in the annual engraving docket (see 

p. 321) are engraved on copper in the engraving division of the Geological Survey. For each map three plates are engraved, one for each 

of the three principal colors of the printed map a culture plate for 

the features and names that are to be printed in black, a relief (contour) plate for the features that are to be printed in brown, and a 

drainage plate for features that are to be printed in blue. These 

plates are sometimes referred to as the black, brown, and blue plates, 

respectively. Transfers are afterward made from the three copper 

plates to three lithographic stones, from which the maps are printed. 

Features subject to frequent change, such as national-forest boundaries 

and forest names, are not engraved on copper but are added to the 

stone by separate transfers from type and by handwork.

Transmission jor engraving. When the editing of a topographic 

map is complete and all questions have been answered so far as is then 

practicable, the sheet jacket, on which is entered a list of the contents 

forwarded, should be indorsed "Approved for engraving"; this indorsement should also call attention to any special or unusual features of 

the engraving and should be signed by the chief of the section of 

inspection and editing, who should also initial subsequent indorsements covering the transmission of engraved proof and copy. All
TOPOGRAPHIC MAPPING 337

engraving copy and proofs thereof should be transmitted direct to the 

engraving division.

Engraving. A j^olyjcpnic j)rpjectipn is constructed on each of the 

three^cop_pej plates on the scale_of: Jihejnap publication. The original 

drawing of one map that is to be engraved is photographed to the 

publication scale, and from the glass negative a contact print is made 

on a, zinc plate, on which the map features are in the reverse positions 

to those on the original drawing. The map on zinc is transferred in 

turn to each of the three copper plates by means of wax impressions 

obtained on celluloid and burnished down on the copper plates, where 

the impressions are suitably fixed. Transfers to the copper plates are 

made in small sections at a time, usually by coordinate blocks, in 

order to distribute any small errors that may exist in the scale of the 

original map. The reproduction of the map that has thus been transferred to copper is reversed, and the engraver must do his work in 

that position.

The several map features are cut into the surface of the copper 

plates by the engraver, who uses the transferred lines as copy and 

gages the depth of the cut according to the width of the line desired 

on the printed map for example, a heavy contour is cut deeper than 

a light contour. On the culture plate only those features are cut that 

are to be printed in black, on the relief plate only those that are to be 

printed in brown, and on the drainage plate only those that are to be 

printed in blue.

PROOF READING

First plate proofs. On the completion of the engraving on the 

three copper plates "first plate proofs," in black, are pulled from each 

of the three plates, are inclosed in the jacket together with the original map and all engraving copy, and are referred from the engraving 

division to the section of inspection and editing for revision.

The proof reader should first familiarize himself with the editor's 

special instructions to the engraver and should examine the proofs 

with these in mind. Each plate proof should in turn be compared in 

detail with the original map, and all corrections noted should be 

marked on the plate proof by drawing a red inked line to the border 

of the proof and there indicating by word or symbol or by both the 

nature of the correction necessary. This detailed comparison should 

be made house for house, bend for bend, contour for contour (including spacing), stream for stream, feature for feature, and symbol for 

symbol. If apparent errors are found in the original drawing they 

should be called to the attention of the editor of the map. In order 

that there may be no omission or repetition of comparison between 

proof and original, the proof sheets should be suitably penciled over 

and checked as the proof reading progresses, but notations for the 

engraver's attention should be made in red ink. Questions arising
338. TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL STJEVEY

in the interpretation of the original copy or outstanding editing questions should be brought to the sheet margin in pencil and referred to 

the editor. Proof readers should date and initial the j acket and also 

each plate proof read. The j acket should be indorsed "Approved for 

correction and second plate proofs" and returned to the engraving 

division. If a part of the map edition is to be overprinted in green 

to represent woodland areas, the woodland copy should be forwarded 

to the engraving division at this time.

Second plate proofs. When the corrections called for on the first 

plate proofs have been made on the copper plates, a second set of 

proofs is pulled and referred for further revision. The second plate 

proofs are checked, usually by the reader of the first plate proofs, in 

order to see that all the corrections that were noted on the first set 

have been made.

At this stage the reader of the second plate proofs should mark in 

blue pencil on the proof of the culture (or black) plate such headings, 

names, boundaries, scales, and notes as have not been engraved and 

are to be added to the lithographic stones by a separate transfer.

All outstanding questions, including references to author topographers and outside letters of inquiry, should be cleared up at this 

time, as transfers will now be made from each of the three copper 

plates to the three stones from which the final map in colors is printed, 

and any further corrections must be made by hand to these stones 

and also to the copper plates for future use.

The reader of the second plate-proofs should initial and date the 

jacket and also each proof he reads.

Letter check. After the second plate proofs have been read another 

proof reader should make an independent check of all lettering and 

elevation figures and should also initial and date the jacket and the 

proofs so read. This duplication in proof reading is justified because 

the names and numbers on a map are the features best understood 

and therefore most used and because experience has shown that a 

letter check is necessary. On the completion of the.letter check the 

jacket should be indorsed "Approved for correction and combined 

proofs" and returned to the engraving division. If woodland is to 

be shown by an overprint in green the indorsement should also include 

the request, "Submit woodland proofs." If a road classification is 

to be overprinted in red the indorsement should include the request, 

"Submit two faint-blue prints of the culture mounted on zinc."

Third plate proofs. Third plate proofs are requested only when the 

copy is unusually intricate.

Separate stone proofs. Separate proofs from one or more of the 

printing stones may be requested, if the supplemental transfers to 

stone are unusually numerous or complex or if there are necessary 

corrections to the stones.
TOPOGKAPHIC MAPPING 339

Combined proofs. When the corrections called for in the reading 

of the second plate proofs and the letter check have been made on the 

three copper plates, transfers are made from each plate to three lithographic stones, and to these stones are also separately transferred from 

type impressions or from stock engravings such lettering, notes, 

scales, etc., as may not be engraved separately for each map. From 

these three stones, representing the culture, relief, and drainage 

features of the map, are printed combined proofs in the colors to be 

used on the published map (pi. 17). Combined proofs should be 

examined for completeness and especially for register and for all data 

added to stone after transfer from copper. The reader of the combined proof, who is preferably the reader of the first and second plate 

proofs, should initial and date the jacket and the proof. (For 

approval for printing see p. 340.)

Woodland proofs. A proof of the woodland overprint is submitted 

on a combined proof of the map and should be read for completeness 

of copy and register, the woodland tracing registered over the original 

drawing being used as copy. The woodland proof should be initialed 

and dated by the proof reader.

BO AD-CLASSIFICATION COPY

From the road-classification sheets and data submitted by field 

topographers or others, and after an examination of available reference 

road maps, the map editor should prepare one or more road classifications based on existing instructions; such classifications should 

be drafted in black on faint-blue prints of the culture on paper 

mounted on zinc as photolithographic copy for printing. The 

marginal lettering required should be printed from type and pasted 

on the mounted sheet in the form of labels. (See p. 309.)

SIZE OF EDITIONS AND SPECIAL PRINTS

The chief engraver submits a combined proof of each new topographic map to be printed to the chief of the division of distribution 

for indication (on the margin of the map) of the size of the edition 

desired. The chief of the division of distribution transmits it to 

the chief of the section of inspection and editing, who should indicate 

on the same proof the proportion of the edition to carry the woodland overprint, or, if no woodland edition is. to be printed, should 

so state.

The proportion of the edition to be overprinted in red with one or 

more road classifications should be determined by the chief of the 

section of inspection and editing and so indorsed on the proof above 

referred to.

A combined proof of each new topographic map is submitted by 

the chief of the section of inspection and editing to the chief geolo-
340

gist, for indication of the number and kind of special prints desired. 

This request is then inclosed in the jacket, for information of the 

engraving division when the map edition is run.

APPROVAL FOB PRINTING

When all final proofs, including the woodland proof, have been 

read and when the road-classification copy for a red overprint has 

been prepared and the sizes of the several editions determined, the 

jacket should be indorsed "Approved for correction and printing, 

with woodland and road classification" [second clause omitted if 

not appropriate], dated, and signed by. the chief of the section of 

inspection and editing.

The jacket, with inclosures, should then be transmitted direct 

to the engraving division for final correction, preparation of the 

printing plates, and printing.

REPRINTS OF TOPOGRAPHIC MAPS 

GENERAL FEATURES

Distinction between reprint and new edition. The topographic 

maps are reprinted from time to time as the map-room stocks become 

exhausted. A topographic map that is reprinted without change 

or is reprinted with a few changes that are of a routine nature only 

and do not involve extensive corrections is designated a "reprint"; 

but a reprinted map that is materially changed, with the addition 

of considerable new information, or is altered by means of extensive 

corrections is designated a "new edition."

The designations of the several editions and reprints should be 

stated at the lower right-hand corner of the sheet. "Edition of " 

should be used for the first edition of the map, the blank being 

filled by the year, but not the month, in which the map is printed. 

"Edition of " should also be used for a new edition of the map, 

the date being changed. "Edition of , reprinted " should 

be used for all reprints, the dates being those of the last previous 

edition and of the forthcoming reprint.

Correction files. A file of correction material for use in reprints 

should be maintained in the section of inspection and editing, and 

the corrections filed should, so far as practicable, be confined to those 

that can be approved 'at the tune of filing. The practice of filing 

a map correction that may be incomplete or of doubtful value or 

application and marking it "To be considered at time of reprint" 

should be avoided if possible; the correction should preferably be 

fully examined when it is received and when the facts are fresh in 

mind and at that time prepared for future reprint use and approved, 

or? if found unavailable, disapproved and discarded.
TOPOGRAPHIC MAPPING 341

Requirements for corrections. Corrections to topographic maps are 

received by the Geological Survey from many sources. To be acceptable a correction must be specific and complete in itself; it must be 

complete as to the need for a rearrangement or omission of adjacent 

features; it must contain sufficient data upon which copy can be 

prepared for the changes hi the copper plates; and it must be based 

upon authentic sources of information. In general, unless a correction is small or is of a simple nature, it can be satisfactorily prepared 

only by the employment in the field of means that are commensurate 

in accuracy with the methods used in the original survey for the map. 

With these requirements few outside engineers can comply, and 

therefore many corrections fail of approval.

Stock lists. Stock lists, serially numbered, are prepared periodically in the division of distribution and list the topographic maps 

and other topographic publications of which the supply is nearly out 

of stock. Each stock list also gives the size of the reprint edition 

needed to supply the expected demand for each map listed, as estimated from recent sales and determined by current Geological 

Survey policy. Such stock lists, after administrative approval, are 

referred to the section of inspection and editing for the preparation 

and editing of copy for reprint. Each stock list is accompanied by 

two copies of the map to be reprinted.

Reference to geologic branch. A carbon copy of each stock list 

together with one copy of each mar> listed on it, is referred by the 

chief of the section of inspection and editing to the chief geologist 

that he may indicate the kind and number of special prints desired 

when the edition of the reprint is run. A carbon copy of each stock 

list is also referred to the chief of the section of geologic maps for the 

preparation of a marginal note, if appropriate, to describe the geologic publications that treat of the quadrangle.

EDITING FOR REPRINTS

Character of editing. The editing for reprints should consist in an 

examination and appraisal of the corrections on file and in the preparation of engraver's copy for such of the corrections as have been or 

can be approved. The reprint editor should also carefully consider 

the advisability of the changes that are described below under separate headings and should raise all questions that Geological Survey 

policy may suggest for consideration and decision in respect to the 

map that is up for reprint.

Worlc and instruction sheets. The latest print of the map should be 

used as a work sheet upon which to assemble the changes that are 

contemplated for the new printing. The reprint instructions for 

the engraver should be written on the margin of a separate copy of the
342 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

same map, in red ink for plate changes and in colored pencil for stone 

work. Corrections and additions to the topography may be drawn 

on the instruction sheet or attached to it as separate copy. A filed 

correction that constitutes adequate copy for the engraver should be 

used rather than a copy made from it.

Borders. The names of adjoining quadrangles that have been 

surveyed since the last printing of the map should be added. Border 

corrections that are on file should be carefully examined, and where 

additional drafting is needed it should be requested. Border-correction copy must be complete for all the copper plates involved and 

must include the marking of the "take outs," as this is necessary 

information for the engraver. "Take outs" should be indicated on 

a printed copy of the map. Border corrections that are small or of a 

simple nature may be drafted on a printed map and inked in one or 

more distinctive colors, but large or intricate corrections must be 

inked in standard colors on a tracing. Border corrections may be 

made on the scale of publication or on the scale of field work but 

must be accurately registered over the nearest projection corners. 

(See "Border corrections," p. 302.)

Attention should be given to the horizontal datum and to the possible need for dotted projection corners to join maps of adjacent areas, 

with an accompanying explanatory note.

Filed corrections. Corrections, whether additions to the map or 

changes in features already shown, must subscribe to the requirements for corrections given on page 341. If the information given is 

complete but the drafting is deficient the correction should be referred 

for proper drafting. Inasmuch as the correction files contain some 

correction material the use of which can not be approved, for reasons 

of expediency, the reprint editor should seek administrative approval 

before considering the use of any correction material of doubtful 

value. The corrections themselves may be drawn on the printed 

map provided they can be made legible; otherwise the correction 

copy should be drawn on tracing cloth registered over the map. 

Corrections that are drawn on a printed map must be indicated in 

distinctive colors that are readily distinguishable from the lines of the 

map, but corrections that are shown on a tracing should be inked in 

the standard colors used for topographic map drawings.

Geographic Board decisions. The section of inspection and editing 

should maintain a State and county list of Geographic Board decisions, 

and each new decision that affects a name shown upon a published 

Geological Survey map should be entered in the correction files. 

Board decisions that have been made since the last previous printing 

of a map should be applied to the next reprint.

Reservation boundaries. Corrections should be made to show 

changes in boundary lines or names of national forests, national
TOPOGRAPHIC MAPPING 343

parks, national monuments, and Indian reservations. If such 

boundaries and names were not shown on the last printing of the map 

they should be added, and for that purpose the map should be referred 

for the needed plotting. All reservation boundaries and names 

should be thoroughly checked for each reprint.

Public-land lines. Land lines that have been surveyed by the 

General Land Office since the prior printing of the topographic map 

should not, as a rule, be added to reprints, for the reason that they 

can seldom be properly tied to the topography, and their adjustment 

may entail more office work than can be expediently provided for. 

Where an office adjustment is practicable, however, and where 

important joining with other work is involved a small amount of such 

additional engraving may be requested. If addition or change of a 

public-reservation boundary is involved it may be necessary to ad just 

a provisional land net on the map in pencil as a base upon which to 

construct the new boundary.

New or changed notes. The following marginal notes should be 

added to reprints provided they were not carried on the previous 

edition of the map: Poly conic projection; North American datum; 

statement of direction and amount off North American datum if not 

on North American; statement of the correction necessary to place 

the vertical datum on the latest adjustment to mean sea level; quadrangle and State name in lower right-hand corner; magnetic-declination diagram; long bar scale of miles on east margin of map; and any 

other note or legend needed to explain a new or changed condition on 

the map. (See "Marginal lettering," p. 305, for the positions of many 

of these items.)

Cooperative Tieadings. A cooperative heading that has been used 

on the first edition of a topographic map may be used for a reprint of 

the same map provided the identical cooperation is still in effect 

under the same officials. This condition, however, seldom exists, 

and as a consequence many forms of cooperative reprint headings 

are needed. The following arrangements of reprint headings should 

be used when the conditions specified exist at the time of reprint.

(a) If there is present cooperation with the original cooperating 

body but with different officials, use the original heading with the 

names and titles of officials omitted. If the designation of a public 

office, as governor or State engineer, should be retained in order to 

identify the former cooperation, the heading may be supplemented by 

such an expression as "Represented by the governor [or the State 

engineer]."

(6) If there is present cooperation with the same officials or their 

successors but under a reorganization, use the form "Represented by 

the ," supplying the name of the new body and omitting 

the names and titles of officials.
344 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

(c) If there is no present cooperation but the original cooperating 

body is still in existence, use the original heading with the names 

and titles of officials omitted, whether the same or successor officials 

are in office.

(d) If there is no present cooperation and the original cooperating 

body is not in existence, use the original heading with the names and 

titles of officials omitted.

(e) If there is no present cooperation and the original cooperating 

body has been reorganized under the same or successor officials, 

use the reorganization name in the form "Represented by the 

 ," but omit the names and titles of officials.

Outside credit. Credit for material additions to the topography 

derived from sources outside the Geological Survey should be given 

in a footnote, in the form, "Roads and trails added 1920 by National 

Park Service."

Woodland. In general, a woodland edition is printed only for the 

first edition of the map. Where the woodland copy fairly represents 

the conditions at the time of reprint, however, the woodland may be 

again overprinted. The reprint editor should ask for instructions 

in all appropriate cases.

Correspondence. If doubt exists as to the correctness or appropriateness of a reprint correction and if information can be obtained 

through correspondence, letters of inquiry should be sent out, forms 

provided for the purpose being used if practicable. Such inquiries, 

however, should be made far enough in advance to avoid unnecessarily delaying the reprint and should preferably be made when the 

correction is first received.

Approval of reprint copy. When the reprint manuscript is complete and in. proper form as copy for the correction of the copper 

plates and printing stones it should be approved and forwarded to 

the engraving division. The reprint copy for each map should be 

indorsed "Approved for correction" and dated. The indorsement 

should also request such plate, stone, or combined proofs as may be 

needed for the proof reading of the corrections before the map is 

printed and should list all special prints needed by other branches of 

the Geological Survey. When as many maps on a stock list as can 

be conveniently prepared at one time are ready for transmission, 

these, together with the stock-list letter appropriately indorsed, 

should be forwarded to the engraving division. Further transmissions of delayed reprint copy for maps on the same stock list sh uld 

be forwarded singly from time to time as the copy can be prepared.

Transmissions, approval of corrections, and final approval for 

printing should be made by the chief of the section of inspection and 

editing. Recommendations affecting a change in the size of a reprint
TOPOGRAPHIC MAPPING 345

edition or the cancellation of a reprint should be made through the 

chief topographic engineer.

Proofs and proof reading. Each proof that has been requested will, 

upon submission, be read and afterward returned to the engraving 

division with indorsements for further action. When all corrections 

have been made the reprint material should be indorsed "Approved 

for printing." Successive indorsements should be made in sequence 

on the margin of the engraved map that is used as the base correction 

copy.

PREPARATION OF RIVER SURVEY MAPS FOR 

PHOTOLITHOGRAPHY

REPRODUCTION

The plan sheets and profile sheets of the river surveys are not 

engraved on copper but reproduced by photolithography on the field 

scale, in one, two, or more colors. In general, a small edition of 

advance sheets is printed in black, and this edition is followed by 

such regular publication as may be decided upon for each project, 

in two or three colors as may be found expedient.

INKING OF FIELD SHEETS

The field plane-table sheets should be inked in standard colors; all 

the drainage and culture should be inked, but only so much of the 

contouring as can be clearly read on a reproduction by a single-color 

photolithograph.

Free-hand inking must be done in sharp, fine dark lines, suitable 

for clear reproduction by photolithography, and right linos may need 

to be twice lined if fine or in color. As it is the readability of the 

contours from the engineer's point of view that is desirable rather 

than their graphic expressiveness of relief, the inking of contours 

that closely parallel any shown drainage or culture should in general 

be avoided. Numerous contour figures should be added, and location crosses with figures of elevation should be inked for such exterior 

points as are instrumentally determined.

Water-surface crossings. Water-surface contour crossings must be 

drawn heavy and solid from shore to shore. Every fourth contour 

crossing, where the contour interval on land is 20 feet (or intermediate 

crossings if spaced far apart), must have its elevation placed at the 

outer end of a black right line drawn out clear of all topography.

All water-surface elevations should be inked on the outer edge of 

the topography, in red, for sheet record only; accompanying reference 

or direction lines should be inked in red but should be kept clear of 

all topography. Such data are not intended for final printing and 

should be brushed out on the negatives.
346 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL, SURVEY

Land lines. Land lines must be drawn solid, and township lines 

emphasized. Only such section and township lines should be inked 

as the Land Office plats or notes show have been run and have not 

since been suspended. Section numbers must be shown only where 

land has been sectionized; they should be drawn preferably at the 

centers of sections but should be offset from the center if necessary 

to gain legibility.

The entire land net should be checked against the land plats before 

the land lines are inked.

Rapids. Rapids should be hiked in the conventional symbol, but 

the inking should be so spaced that it will,not obscure the contour 

crossings or other important river data.

Other features. In the inking of other map features found on riversurvey sheets the inker should be guided by the instructions given 

for the inking of the corresponding features on topographic maps.

Mileage. Before the field sheets are cut and assembled into plan 

sheets, the mileage must be plotted by pivoting and swinging a scale 

of miles (drawn as a straight line on tracing paper) within the channel; 

it must not be stepped off with dividers. The same tracing should 

pick up the contour crossings for subsequent plotting on the profile 

sheets. The mileage should not be inked until after the field sheets 

are assembled into plan sheets.

Inking of intermediate contours. All intermediate contours should 

be omitted in the inking wherever they are closely spaced or where 

their facing between the heavy contours is even. This omission is 

required because closely spaced lines will run together in a photolithographic reproduction and because the needless cost of such inking 

should be avoided. An engineer values a contour map for its readability in terms of elevation rather than for its expressiveness of 

shaded relief.

SIZE OF SHEETS

Sheets showing river surveys are of uniform size (22 by 29 niches), 

with all plan or profile work kept within an 18 by 25 inch neat line, 

which should be drawn with margins of 2 inches on all sides. Marginal lettering should be kept within as short a vertical space as 

possible.

Double-mounted drawing paper, cross sectioned in light blue 

within an 18 by 25 inch neat line, is carried in stock and will be found 

convenient for use for plan or profile sheets. It is divided into fifths 

of an inch horizontally and quarters of an inch vertically, thus giving 

tenths of a mile on a scale of 2 inches to 1 mile (1:31,680) and convenient intervals for profile construction.
TOPOGRAPHIC MAPPING 347 

PLAN SHEETS

Assembly of field sheets. The field plane-table sheets must be 

peeled from the cloth (see p. 283) and by means of cutting and pasting 

assembled within the 18 by 25 inch neat-line limits of the plan sheets. 

Before the field sheets are peeled, however, azimuth lines must be 

transferred to enough places on each field sheet to permit the placing 

of each patch in a correct azimuth on the plan sheet. The azimuth 

used should be that of true north.

The plan should be assembled hi as few and in as continuous 

stretches on the same sheet as is practicable, and these stretches 

should be condensed within the sheet so far as the necessary allowance 

for outlying section lines, lettering, and other markings will warrant. 

Space must be left for the key map on each sheet.

Immediately after the patches are pasted on the plan sheets the 

sheets should be placed flat under heavy weights and allowed to dry 

under pressure for one and preferably for two days.

Joining lines. When the field sheets have been cut and pasted, 

joining lines should be inked as right lines at both ends of the cut, 

and the two ends that join should be lettered identically A-A for 

the first cut, B-B for the second, etc. When the alphabet has been 

exhausted double letters should be used, as AA-AA, BB-BB.

Mileage. The plotting of all mileage (see p. 346) must be independently checked before it is inked, as an error afterward discovered 

necessitates moving all mileage marks that are beyond the one 

erroneously plotted. An error in the plan-sheet mileage would also 

correspondingly affect the profiles.

Distances along the river should be indicated in black by figures 

within small circles placed at the ends of right lines drawn clear of 

all topography from the center of the stream opposite each plotted 

mile of channel flow. The circles should be placed on the same 

side of the stream for as long stretches as is feasible, for greater 

convenience in rinding and reading, but this practice need not be 

followed if it would result in crowding and a better location for the 

circle can be found in a more open place. Preferably, the circles 

should be numbered upstream.

The uninked right lines that pass over the inked topography are 

drawn in on the glass negative later.

Boundary lines. The inking of county, national forest, and other 

boundary lines on plan sheets should be confined to the lines that 

fall within the zone of the survey and have been mapped in the field, 

and such boundary lines should not, in general, be extended beyond 

the inked topography, except for short distances for the purpose of 

keeping the necessary lettering away from the topography.

58515° 28 23
348 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

PROFILE SHEETS

Profile construction. Profiles should appear on separate sheets 

from the plans and should be drawn directly across the sheet, with 

the separate rows condensed as much as practicable. Their direction 

should be upstream as read from left to right, irrespective of easting 

or westing. Space must be left on each profile sheet for the key map.

For profiles uniform vertical scales should be used so far as possible, and profile angles in excess of 45° should be avoided. The 

profile should be constructed from the water-contour crossings, 

supplemented by elevations determined at the head and foot of falls 

and elsewhere. (See p. 267.) Profile lines should be drawn heavier 

than construction lines, and sharp angles should be slightly smoothed.

Before a profile is inked its construction must be carefully checked 

by a person who has not been engaged in its initial preparation.

Profiles of tributaries. Wherever the profile of a tributary is 

steeper than the profile of the main stream above the mouth of the 

tributary, the profile of the tributary should be constructed as a 

branch profile leaving the main-stream profile at the .junction point.

KEY MAP

A key map must be prepared for each set of river-survey maps. 

This map should be carefully generalized from the detailed plats 

and should be compiled in pencil on any convenient scale that is 

somewhat larger than that of publication. The compilation can in 

general be best made on tracing linen and must be afterward traced 

and inked as copy for photographic reproduction. The prints 

should be made on paper suitable for reproduction by photolithography, and one print should be pasted on each plan sheet and one 

on each profile sheet.

As the prime requisite of a key map is legibility, the county and 

national-forest boundary lines may in general be omitted from it, 

but a boundary line that crosses the line of survey at or nearly at 

right angles may be shown.

The limits of the river survey shown on each separate plan sheet 

should be indicated on the key map by a connected series of rectangular blocks, the end lines of which cross the river at these limits. 

Each block on the key map should be marked with the serial letter 

corresponding to that used on the plan sheet represented. (See 

below.)

The title "Key map of plan sheets" should be placed under the 

key map.

MARGINAL. LETTERING FOR ALL SHEETS

All sheets of the plan and profile set should carry identical headings 

and other captions except where the data shown necessitate changes, 

such as different scales, contour intervals, authorship, and serial
TOPOGRAPHIC MAPPING 349

sheet letters. The marginal lettering for plan and profile sheets 

should be printed from type impressions, and the printed labels 

should be pasted on the drawings in the positions that are indicated 

below. (See pi. 16.)

Title. The title used to describe river-survey maps should be 

identical for all sheets of the set, including both plan sheets and 

profile sheets, and should be printed in capitals and placed in the 

center of the margin above the upper neat line. The title should 

give the names of the main streams shown and include the names of 

the larger tributaries that have been surveyed, but if these tributaries 

are too numerous, too little known, or unnamed, they may be referred 

to by the phrase "and tributaries" or "and other tributaries." 

The title should include the name of the State or States through 

which the river runs and the names of the places at the ends of the 

survey.

Designation ~by serial letters. Each plan sheet and each profile 

sheet should be designated by a capital letter, as sheet A, sheet B, 

the first profile sheet being designated by the letter next following 

that used for the last plan sheet. The letter I should be used. 

This designation should be placed above the upper neat line and near 

the right-hand corner.

Federal heading. The heading "Department of the Interior" 

centered above "U. S. Geological Survey" should be placed above 

the upper neat line and near the left-hand corner.

Number oj sheets. Under the lower neat line and near the righthand corner should appear a statement in parentheses giving separately the number of plan and profile sheets for example, "6 plan 

sheets, 4 profile sheets."

Date $f printing. Below the statement giving the number of 

sheets should be given the date of the printing of the edition for 

example, "Printed in 1927."

MARGINAL LETTERING FOR PLAN SHEETS

In addition to the marginal lettering specified above all plan sheets 

should carry the marginal lettering described in the following paragraphs :

Authorship, date, and cooperation. Under the lower neat line and 

near the left-hand corner should be placed, in separate lines, the 

names of the topographers engaged in the mapping, the date of the 

survey, and the names of the organizations, if any, cooperating in 

the work. (See pi. 16.)

Scales. Under the center of the lower neat line the horizontal 

scale of the plan should be stated as a fraction, and directly beneath, 

on separate lines, should appear a bar scale of miles, a bar scale of 

feet, and a bar scale of kilometers.
350 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

Contour intervals. Under the bar scales the statement "Contour 

interval on land feet" should appear, and directly beneath it the 

statement "Contour interval on river surface feet."

Datum. Under the statement of contour interval should appear 

the statement "Datum is mean sea level" or the appropriate statement if the river survey is referred to a vertical datum that differs 

from sea level.

Horizontal adjustment. Inasmuch as river surveys are seldom 

horizontally controlled the plan sheets are generally subject to adjustment, and a statement to that effect should accordingly be placed 

under the lower neat line and a little to the left of the right-hand 

corner, unless the plan sheets are in true adjustment.

Declination. Under the lower neat line and to the right of the 

bar scales should appear a diagram showing the magnetic declination, 

with date.

MARGINAL LETTERING FOR PROFILE SHEETS

In addition to the marginal lettering for all sheets described on 

page 348, all profile sheets should carry the marginal lettering given 

below:

Horizontal scale. In general, the profile should be constructed on 

the same horizontal scale that has been used for the plans; and both 

fractional and bar scales should be placed on the profile sheets in the 

same positions as on the plan sheets.

Vertical scale. Under the bar scales should be placed a statement 

of the vertical scale on which the profile has been constructed, in the 

form "Vertical scale 1 inch ==40 feet." If more than one vertical 

scale is used on one profile sheet the separate parts of the profile that 

are drawn on differing vertical scales should be separated on the 

sheet by dividing lines, and within the borders of each divided section should be indicated its vertical scale.

Datum. Under the vertical scale should be placed the same statement of vertical datum used on the plan sheets.

No other marginal lettering. No statement of authorship, date of 

survey, or cooperation should be made on profile sheets.

HAND LETTERING

Plan sheets. Lettering in general should not be placed on or 

within the inked topography but kept in near-by open spaces, so far 

as such spaces can be found. The lettering should be kept near the 

pasted map strip to which it refers and not be extended near an 

adjoining strip. Emphasis should be given to the names of the surveyed streams.

On each pasted patch covering a separate stretch of the river 

should be lettered the stream name and in addition township and
TOPOGRAPHIC MAPPING 351

range numbers for identification. The joining letters at the ends of 

the patches should be inked in the sequence described on page 347.

Mileage and contour crossings should be inked as described for 

the penciling.

Profile sheets. On each separate stretch of continuous profile, 

either for the main stream or for a tributary, should be lettered the 

stream name, above and parallel with the slope of the profile.

The names of only the larger tributary streams should be lettered 

on the profile sheets, but the names of all bridges, dams, dam sites, 

towns, falls, and well-known rapids should be lettered and placed 

vertically over the corresponding points in the profile.

STYLE OF LETTERING

Marginal lettering. The styles of type that are in general use for 

the marginal lettering as designated in the engraving division type 

book (edition of January, 1926) are as follows:

Title, light copperplate gothic Nos. 5 and 6.

"Sheet A," etc., light copperplate gothic No. 7.

Federal heading, Celtic No. 1, 8 point.

Number of sheets, lining gothic No. 60, 10 point.

Date of printing, lining gothic No. 60, 8 point.

Authorship, etc., circular gothic No. 44, 10 point.

Contour interval and datum, circular gothic No. 44, 10 point.

"Subject to adjustment," lining gothic No. 60, 10 point.

Declination, lining gothic No. 416.

Title on key map, slope gothic No. 504.

Hand lettering. The style of hand lettering for plans and profiles 

should be as follows:

Stream names, slanting block, capitals or lower case as appropriate.

Place names and topographic features, upright block, capitals or lower case as 

appropriate.

Falls, rapids, eddies, dam sites, power plants, and ranger stations, slanting 

block capitals.

County names and land-line information, upright block capitals.

Railroads, roads, road designations, and bridges, slanting block capitals (smaller 

than falls, etc.).

Reservations, national forests, etc., slanting block capitals.

Ranch and cabin names, upright block lower case.

PBEPABATION OF DAM-SITE MAPS FOB PHOTOLITHOGBAPHY

REPRODUCTION

Large-scale dam-site maps are reproduced by photolithography on 

the field scale, in black only, in small editions for limited distribution; 

they are not included in the published series of plan sheets.
352 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY 

INKING OF FIELD SHEETS

Dam-site maps should be inked in the standard colors and in general under the instructions prescribed for river-survey maps. (See 

p. 345.) As the scale is large all intermediate contour lines should 

be inked.

Section corners located within the area covered by a dam-site survey should be designated by the symbol for a found land corner, but 

in general land lines should be omitted from dam-site drawings, 

inasmuch as the field work within the small area of the large-scale 

survey seldom supplies enough data for the proper plotting of land 

lines on that scale.

A line should be drawn across the map to represent the proposed 

location of the dam. This line should be inked in black between the 

same limiting contours on the two sides of .the stream at the site.

The elevation of the water surface at the proposed dam site should 

be inked.

DAM-SITE SHEETS

Assembly into sheets. Dam-site maps, after inking, should be 

assembled into sheets as described under "Assembly of field sheets" 

(p. 347), but space must be left between the separate dam-site maps 

for cross sections as described below. The sheets should be of the 

same size as those used for plan sheets. Dam-site maps should be 

pasted on the sheets in the same order in which the dam-site locations are found on the plan sheets, and they should be designated 

by the same mileage that is used on the plan sheets, expressed to the 

nearest tenth of a mile.

Cross sections. Cross sections should be constructed for each dam 

site that is designated by the conservation branch. The horizontal 

scale should be somewhat larger than that of the dam-site map, and 

the vertical scale should be such as will give a profile that is neither 

excessively steep nor too flat and may average 45°.

The line of the first cross section should be designated A-B, the 

letter A being placed on the left bank and the letter B on the right 

bank, looking downstream. The cross section should be drawn with 

the left-bank side shown on the left-hand side of the drawing and the 

right-bank side on the right-hand side. Succeeding cross sections 

should be designated C-D, E-F, etc., double letters (AA-BB, etc.) 

being used if necessary.

LETTERING

Marginal. The marginal lettering for dam-site sheets should 

accord with the instructions for marginal lettering for plan and 

profile sheets (see pp. 348-350) save for differences in scales, contour 

intervals, and other data.
TOPOGRAPHIC MAPPING 353

The title of the dam-site series should begin "Miscellaneous dam 

sites," and this phrase should be followed by a descriptive title, which 

may be identically the same as is used in the corresponding plan and 

profile set. The sheets of the series should be numbered instead of 

lettered, as sheet 1, sheet 2, and in the lower right margin, below 

the neat line, should be placed a statement of the number of the 

sheet in the set, as "Sheet 3 of 5 sheets." The statement "Subject 

to adjustment" should not be used.

The first line of the scale should read, for example, "Plan scale 

1:2400, or 1 inch = 200 feet." Directly under this statement should 

appear a bar scale of feet, and below the bar scale a statement of the 

cross-section scales for example, "Cross-section scale (horizontal 1 

inch = 100 feet; vertical 1 inch = 80 feet)." Next below should appear a statement of contour interval. The statement of datum 

should appear on the last line and should be identical with the one 

used on the corresponding plan and profile set.

If more than one horizontal or vertical scale or contour interval is 

employed on a single dam-site sheet, the maps and cross sections 

of the dam site or sites using such differing data should be separated 

On the sheet by bounding lines inked in black, within which should 

be given all necessary data that can not be given at the bottom of 

the sheet as applying to the sheet as a whole.

Hand. The dam-site plans should, in general, be lettered in the 

same way as the plan sheets of the plan and profile set. On the left 

and right-hand sides of the cross section should be lettered "Left 

bank" and "Right bank" respectively. Beneath the cross section 

should appear its designation for example, "Cross section C-D 

(3.4 m.)," the mileage being expressed to tenths. Above the cross 

section should appear the name of the dam site, if any for example, 

"Tully Rapids dam site." The name of the dam site and the 

mileage should also appear alongside the dam-site map.

INSPECTION AND EDITING OF RIVER-SURVEY MAPS

CHECKING

General character. The checking of river-survey maps should be 

based upon the instructions for the checking of topographic maps 

(p. 310) so far as they apply. Checkers of river-survey sheets should 

also be familiar with the instructions for river surveys (p. 266) and 

with the instructions for the preparation of river-survey maps for 

photolithography (p. 345) and the preparation of dam-site maps 

for photolithography (p. 351).

Plan sheets. If the mileage has been checked before inking it 

should need no further checking. All figures of elevation, whether 

land or water contour, bench mark, or useful elevation, should be
354 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

checked and compared with the contouring. The separately pasted 

patches of topography should be tested at their joining edges for 

azimuth and matching. The entire land net shown on the plan 

sheets should be checked. The entire drawing of each sheet should be 

examined for completeness. The river-survey sheets should be compared with maps representing any previous surveys inclosing, crossing, 

or adjacent to the new survey, and attention should be called to 

discrepancies that may affect the new river survey or any previous 

work on the same or any similar scale.

Profile sheets. If the profiles have been compared with the plansheet contour crossings and checked before they were inked they 

should need no further checking. The mileage figures and the profile elevation figures should be checked for sequence and correct 

application. The names of the river features that have been selected 

to appear on the profile sheets should agree in spelling, point of 

application, and mileage with the corresponding names on the plan 

sheets.

Key map. The key map, having been previously edited before 

photography, should need no further examination in the checking. 

(See "Editing," below.)

Checker's signature. The checker's signature and all further signatures should be placed upon sheet A of the series and should be 

understood as applying to the set as a whole.

INSPECTION

The inspection of river-survey maps should be based upon the 

instructions for the inspection of topographic maps (p. 313) so far as 

they apply, and also upon a familiarity with the instructions for 

river surveys and their office preparation for photolithography. The 

Inspection should also be made with reference to legibility and the 

use of the maps by engineers.

EDITING

Character of river surveys. The editing of river survey sheets (see 

pp. 266, 345) should in general be restricted to plan and profile sheets 

that are to be issued as sale publications. River-surveys sheets that 

are to be issued only as advance sheets in one color and sheets of 

miscellaneous reservoir and dam sites should be edited only under 

exceptional conditions.

Character of editing. River-survey plan and profile sheets should 

be edited for completeness of copy, spelling, agreement of names, 

and other features with those shown on other reliable maps, including Geological Survey maps if the area has been previously surveyed, correct sequence of mileage, and boundaries falling within the 

limits of the river survey. The key-map tracing should be edited
TOPOGRAPHIC MAPPING 355

before it is photographed for the several sheets, and the title for the 

series should be edited before it is printed. The names that are 

shown in common on the plan and profile sheets should be compared 

for agreement in point of application as well as in spelling. Features of a doubtful nature should be questioned.

EDITING OF STATE INDEX CIRCULARS

Character of index circulars. Index circulars are issued for each 

State or small group of States to show the progress of topographic 

and geologic mapping. The base map that is used is either a photolithographic reduction to a scale of 1:1,000,000 of the 1:500,000 

State map or a transfer from a United States base map. This base 

is printed in gray in order that the outlines and names of the quadrangles that have been surveyed and published may be legibly overprinted in red. The back of the circular carries a description of the 

character of topographic maps, geologic maps, and river surveys, 

descriptions of special maps that are either not indicated or not sufficiently indicated by the red overprint, lists of other publications 

covered by the several Geological Survey activities within the State, 

a list of libraries where these publications may probably be consulted, 

and. a list of authorized agents selling the maps of areas in their 

vicinity. Index circulars are frequently revised in order to show 

current progress in mapping and are issued free on application to the 

director.

Printing of index circulars. The base for an index circular may be 

printed from plates on hand, without correction, from old plates after 

correction, or from new plates. For the correction of old plates or for 

the making of new plates correction copy or a new base must be prepared. The red overprint may be printed from old plates after correction or from new plates made from new copy.

Stock lists. As the stocks of index circulars are exhausted they are 

reprinted and brought up to date under the authority of stock lists. 

(See p. 341.) Each separate index circular is placed upon a separate 

stock list.

Character of editing. The topographic editing of an index circular 

should be confined to the base map and the red overprint. So much 

of the red overprint as applies to geologic folios is edited by the editor 

of geologic maps and the text part of the circular is edited by the 

editor of texts. The topographic editor should appraise the base map 

that was used for the last edition of the circular, as to its present correctness of data, such as county lines; inquire as to the condition of 

the printing plates in case the old base is to be reprinted; consider 

the availability of any new base, whether a reduction from a new or 

revised State map or a transfer from a new United States map; consider the amount of addition or change to the old red overprint plates,
356 TOPOGBAPHIC INSTRUCTIONS OP GEOLOGICAL SURVEY

and inquire into their condition in case the corrections can readily 

be made on them, but otherwise prepare the copy for a new plate. 

The further editing should consist in preparing the appropriate copy 

and instructions for the engraving division for use in reprinting 

the circular.

When new bases become available consideration should also be 

given to the practicability of changing an index circular representing 

a group of States into separate index circulars for each State in the 

group.

If reductions to a scale of 1:1,000,000 of the State maps of the 

1:500,000 series are used as bases for index maps consideration should 

be given to the date of the latest revision or new compilation of the 

State map, and the advantages of such a base should be listed and 

instructions sought as to its possible use. Particular attention should 

be given to the accuracy of county lines and the showing of new 

counties as they are created, inasmuch as many mquiries are received 

concerning areas within a specified county.

Work sheet. The work sheet for the red overprint should be a copy 

of the latest index map, on which the names of newly printed maps 

and newly surveyed quadrangles should be indicated in pencil.

Preparation of reprint copy. Instructions should be prepared for 

the use of the engraving division stating specifically what base is to 

be used for the new edition of the index circular; and if a new or 

corrected base is required the proper copy should be specified or 

prepared. The quadrangle outlines for the red overprint copy should 

be drafted in solid black lines on a faint-blue photolithographic reproduction of the base that has been printed on mounted drawing or 

chart paper, on the scale of publication of the index map. Quadrangles that have been mapped to the State line only, whether in 

the State for which the index is being prepared or in an adjoining 

State, should be shown as mapped, with a solid black line along the 

State boundary. The names of quadrangles and the notes that are 

to be printed in red should be printed from type and pasted on the 

copy in proper positions. Information as to the progress of new surveys should be taken from the general progress book that is kept in 

the topographic branch, and this should be further verified by inquiry 

in order to provide for the plotting of all quadrangle maps which have 

been completed or whose completion can be safely estimated. Publication of a map should not be anticipated by more than three months 

unless approved by the division of distribution.

Approval and transmission. Copy for index circulars should be 

approved by the chief of the section of inspection and editing and 

by him forwarded to the engraving division for correction and printing. 

Combined proofs should be asked for, corrected, and returned with 

approval for the printing of the edition.
TOPOGRAPHIC MAPPING . 357 

EDITING OF ILLUSTRATIONS

Kind of illustrations edited. The reports of the Geological Survey 

on the many phases of geology, including mineral resources, water 

supply, conservation, and other subjects, carry many illustrations 

such as maps, charts, diagrams, and sections. These illustrations 

are of great variety, ranging from details on large scales to small maps 

covering large areas on small scales and including both general maps 

and conventional base maps; but whatever their kind, most of them 

are designed or adapted to serve the single purpose of the paper they 

illustrate. Most illustrations are prepared in the section of illustrations, although some are prepared in the separate branches. Proposed illustrations that are topographic or geographic in their nature 

are referred to the section of inspection and editing for examination 

and editorial approval before publication.

Need for topographic editing. Illustrations are edited from a topographer's viewpoint in order to make them as accurate, legible, and 

presentable as the character of their compilation and their purpose 

permit. Inasmuch as such illustrations are largely special-purpose 

maps they are not required to have the balance and finish of permanent maps, but they are required to withstand the tests of reasonable criticism.

Scope of editing. The editing of a map illustration should determine 

whether it is suitable for its purpose and of the best possible quality, 

limitations of time and cost considered; should assure its freedom 

from errors and important omissions; and should include an examination for legibility, both in execution and in the choice of symbols. 

Consideration should also be given to a comparison with other maps 

and publications covering the same area, both for accuracy and for 

cross reference. Geographic names should be edited for their propriety, spelling, placing, and comparative prominence. Projection 

and elevation figures, land-subdivision designations, scales, and other 

details should be verified. Topographic representation, even though 

sketched or approximate only, should be free from error or inconsistency of expression.

EDITING OF STATE MAPS

Character of State maps. The State maps to be edited (see p. 360) 

are those of the 1:500,000 series, new compilations and revised 

editions of which are issued from time to time. The State maps are 

published in one or two colors as conditions warrant; if two colors 

are used the drainage and drainage names are printed in blue. The 

manuscript maps that are to be edited are compiled on a scale of 

1:500,000 and are reproduced by photolithography on the same scale.

Character of editing. Inasmuch as the corrections called for by 

the editor will have to be made on the original drawing itself, for the
358 TOPOGRAPHIC INSTKUGTIOiNS OF GEOLOGICAL SURVEY

reason that this drawing is the camera copy for the reproduction of 

the map, the original drawing should be so carefully prepared that 

the editorial corrections will be largely in the nature of details and of 

such a character as can be readily made on the original drawing. 

There should therefore be a cooperative understanding between the 

cartographer and the editor to the end that the general plan of compilation may conform to the desired standards, leaving to the editor 

only a checking up of such details as may escape the cartographer, 

who is fully occupied for the time being with the task of compilation.

The editing should consist in an examination of the original drawing for completeness of representation, adequacy of the drafting for 

photolithographic reproduction, proper distribution of the features 

shown, and correct spelling of the names shown. The correct reduction and transfer of the map material that has been used should be 

assumed to have been properly done, unless a casual examination 

discloses otherwise. Data of a general nature, however, such as 

postal, railroad, and public-land line data and boundary lines, should 

be verified by the editor.

Editing marks and corrections. The editing notations shoiild be 

made in such a way as not to injure the original drawing and may in 

general be indicated in light pencil on the map margins. Where the 

copy is intricate or the changes appear to be numerous, however, a 

photostat copy of the original should be requested, and this copy may 

be made on any convenient scale.

Editing in detail. In verifying the data shown on the State map 

reference should be made to the instructions for the corresponding 

features on topographic maps (pp. 320-334). Many of these instructions may not apply to the State map in hand because of the absence 

of relief, smaller scale, or different form of publication, but in general 

they will serve as a useful guide. Features of especial importance to 

be examined are the names and boundaries of counties; national and 

State forests, parks, and reservations; place, stream, and railroad 

names; titles; and scales. The published maps of the Geological 

Survey should receive consideration as maps that have themselves 

been edited, but allowance should be made for changes subsequent to 

publication and for the more thorough examination that has been 

given to maps of a more recent date.

EDITING OF UNITED STATES MAPS

Character of United States maps. The character of the maps of the 

United States published by the Geological Survey is described in 

each of the State index circulars. The maps are published on several 

scales, ranging from 40 to 260 miles to 1 inch. As the scale decreases 

the character and amount of detail that can be legibly shown decrease 

correspondingly. United States maps are compiled and drawn on
TOPOGRAPHIC MAPPING 359

scales slightly larger than the scale of publication and are reproduced 

by engraving.

Character of editing. Editing notes can usually be most conveniently placed on a photostat reproduction of the original drawing. 

The editing, in general, should consist in a careful scrutiny of the 

entire hiap for completeness and consistency of representation and 

as adequate copy for the engraver; in an examination of the map for 

the proper distribution and selection of features and names to be 

shown; and in a review of all names for correctness of spelling and 

best arrangement. Legibility of the published map should be provided for, and where the data shown are found to be excessive for a 

clear reading of the printed map they should be reduced in amount.

Proof reading of engraved maps. The plate and combined proofs 

of engraved United States maps should be compared with the final 

manuscript map that was submitted for engraving under the same 

general plan that is followed in the reading of proofs of engraved 

topographic maps. (See p. 337.)

SUPPLEMENTARY DATA

GENERAL MAPS 

DEFINITION

General or geographic maps are maps that show the general rather 

than the detailed character of a region or large tract of country such 

as State and United States maps. General maps are usually published 

on small scales, usually represent large areas, and are more commonly 

published without any representation of relief other than that which 

may be inferred from the drainage. Some of the general maps 

issued by the Geological Survey, however, show relief by means of 

contour lines, shading, or bands of color. The several classes of 

general maps published are described below and also in the State 

index circulars. The general maps are compiled in the section of 

cartography.

INTERNATIONAL MAP OF THE WORLD

Character. By international agreement most countries are now 

engaged in compiling and publishing a sectional world map that is 

being issued on a uniform scale of 1:1,000,000, or approximately 1 

inch to 16 miles, each sheet covering 4 degrees of latitude and 6 

degrees of longitude. The maps follow standard international specifications, so that the people of each nation may read and understand 

the maps of all other nations, regardless of differences in language. 

The United States maps of this series are in course of preparation 

and publication by the Geological Survey, and of the 52 sheets that
360 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

will cover the entire United States four have been published; these 

are K 19 (Boston), K 18 (Hudson River), J 10 (San Francisco Bay), 

and 110 (Point Conception). An index map of the United States has 

been issued to show the location of the areas covered by these maps 

and those to be published, and also the mode of designation by letters 

and numbers.

Compilation. So much of the base map as has previously been 

compiled on a scale of 1:500,000 for the State map series (see "Map 

compilation," p. 362) and is needed for the international sheet in hand 

is reduced to a scale of 1:750,000 and printed in light blue on drawing 

paper to serve as a base for the compilation of the additional features 

represented on the international series, such as land contours, submerged contours, and highways. The copy for engraving is prepared 

in the section of cartography.

Projection. For the engraved plates of the sheets of the international map of the world the modified polyconic projection is used, 

to which the reduced maps of the 1:500,000 scale compilation on the 

Lambert conformal conic projection are readily fitted in the transfer to copper on a scale of f: 1,000,000.

Reproduction. The United States maps of this series are reproduced by engraving. Each map is printed in several colors and in 

the symbols determined by international agreement, which differ in 

some respects from the standard symbols adopted by the Federal 

Board of Surveys and Maps for Government use. Cities, railroads, 

State and county boundaries, and names are shown in black; 

streams in blue; highways in red; land contours (metric) in 

black; 6 and submerged contours (metric) in blue. The successive 

heights of the land surface are further emphasized by hypsometric 

tints ranging from green for the lowlands to pale buff for higher elevations, gradually deepening to a brick-red at snow line, above which 

the region of perpetual snow is indicated by the absence of color. 

For the water, beginning at the shore line, a pale-blue tint is employed 

to represent shallow water; a gradually deepening tone of blue for 

depths down to 6,000 meters; and the darkest blue for all greater 

depths.

STATE MAPS

Character. Maps of all the States except California (which is partly 

completed) have been published on a scale of 1:500,000, or approximately 1 inch to 8 miles. The features shown are cities and towns, 

railroads, State, county, and reservation boundaries, township lines 

of the public-land surveys, and streams, all with their appropriate 

nomenclature. The earlier issues were printed in black, but those

6 The original specifications provided for the printing of land contours (metric) in brown, but the color 

for this feature was later changed to black.
TOPOGBAPHIC MAPPING 361

more recently compiled are printed in two colors, the drainage in 

blue. The State maps are reproduced by photolithography. Their 

uniform scale affords opportunity for a direct comparison of size and 

for the combination of any number of them into a single map on the 

same scale or reduced by direct photolithography. In addition to 

their use as general maps, they are extensively used as bases on which 

to overprint in colors special information, such as geology, the location 

of oil, gas, and coal fields, power-transmission lines, and national 

forests.

Projection. In the earlier one-color editions the modified polyconic 

projection was used, but the present two-color maps are based on the 

Lambert conformal conic projection, in which the parallels are 

represented as arcs of concentric circles and the meridians as straight 

lines. The Lambert projection used for each State map is but a section of one covering the entire United States, so that each map if 

desired may be fitted exactly to the maps of adjoining States to form 

a huge map of the country. An added advantage resulting from the 

use of this projection for the State map series lies in the fact that the 

slight error in scale is the same in all directions and that the true 

shapes of the areas represented are retained. Tables for the construction of the Lambert projection are given in Coast and Geodetic 

Survey Special Publication 52. The construction of the projection 

is facilitated by the use of a plate recently devised in the section of 

cartography which obviates the use of beam compass and scale and 

provides for a mechanical construction of an accurate projection on 

the scale of 1:500,000 for any area in the United States.

Compilation. State maps are compiled on the scale of publication 

(1:500,000) and the same base after reduction to a scale of 1 :750,000 

is used for the compilation of the additional data needed for the international map of the world. The details of map compilation are 

described on pages 362-366. The compilation for the State maps is 

made in sections, a State or part of a State or international sheet being 

used as a unit, as may be most convenient, and the assembly of the 

separate parts being left to be accomplished in the transfer operations 

of photolithography. Preliminary State maps of Utah, Nevada, New 

Mexico, Oklahoma, and Louisiana have been prepared from State 

maps issued by the General Land Office and do not represent compilations for the international sheets.

UNITED STATES MAPS

Present series. Maps of the United States are published in several 

sizes, ranging from a large wall map in two sheets, on a scale of 

1 :2,500,000 (approximately 1 inch to 40 miles), measuring 49 by 76 

inches, down to a map on a scale of 1:16,000,000 (approximately 

1 inch to 290 miles), measuring 8% by 12 inches. The maps of this
362 TOPOGEAPHIO INSTEUOTIONS OF GEOLOGICAL SUBVEY

series were compiled on scales slightly larger "than the scale of publication and reproduced by engraving. The polyconic projection was 

used.

Proposed series. Under a plan recently adopted by the Federal 

Board of Surveys and Maps there will be prepared a new and interrelated series of general United States maps ranging from a large wall 

map measuring about 4 by 7 feet, to be published on a scale of 

1 :2,500,000 (approximately 1 inch to 40 miles) to a small outline 

map measuring about 4 by 7 inches, to be published on a scale of 

1 :27,000,000 (approximately 1 inch to 425 miles). Under this 

cooperative plan the Coast and Geodetic Survey was designated to 

make the projection and plot the coast lines for the wall map and the 

Geological Survey was designated to compile the interior data, 

execute the drafting, and publish this map as well as the rest of the 

series. The wall map has been compiled on a scale of 1 :2,000,000 for 

publication on a scale of 1 :2,500,000 and will be a basic source of 

data from which the features needed for the other maps of the series 

can be rapidly used by selection and reduction, each map in turn 

omitting features and details not suitable to its scale. The wall map 

will be prepared in several plates in order that it may be printed in 

several colors and also in order that separate printings may be made 

of selected features apart from others that are not desired.

The maps of the United States of this series will be based on the 

Albers projection, in which the meridians are straight lines and the 

parallels are concentric circles. This projection was selected because 

it presents a minimum error in scale combined with an equal-area 

representation in a degree not found in other projections.

MAP 'COMPILATION

Special maps for special and general purposes are prepared for other 

bureaus and departments and for cooperating States, and in their 

execution special methods of compilation are used as may be found 

necessary.

Definition. Map compilation involves the making of a new map 

based on all previous maps or existing map data that can be found 

representing any part of the region for which the compilation is to be 

made. Map compilation is distinctly office work and in general has 

to do with a small-scale map of a region of relatively large extent, as a 

State, in distinction from a map of a small area, as a quadrangle, 

which is surveyed in the field and on a relatively large scale.

Map compilation consists in the collection of the available map 

data for the proposed map, the selection of such of these data as are 

found to be most suitable for the purpose, the reduction of the selected 

map material to the scale of the proposed compilation, its adjust-
TOPOGKAPHIO MAPPING 363

ment and plotting on the base compilation sheet, and its inking and 

preparation for reproduction.

Collection and selection of data. The search for existing compilation 

data should be as thorough as circumstances warrant, because its 

object is to bring together all known data that can be used in the 

construction of the new map, and upon the completeness of the search 

depends much of the value of the compilation in so far as its representation of known facts is concerned. In the collection of available 

map data search should be made at those Federal bureaus that either 

make or are most likely to have collected maps in the region for which 

a map is to be compiled; the files of the map information office of the 

Federal Board of Surveys and Maps should be examined; inquiries 

should be addressed to appropriate State departments, such as State 

geological surveys and offices of State engineers, and to railroad 

companies, commercial firms, and individuals. As fast as authentic 

map compilation data are received they should be graphically outlined on an index map for ready reference.

Scale and projection. A map may be reproduced on the scale of 

compilation, or the drawing may be reduced in scale. If practicable, 

a compiled map should be drawn on a scale that is slightly larger 

than the scale of publication in order to derive certain advantages 

resulting from reduction. The series of State maps compiled by 

the Geological Survey on a scale of 1:500,000 are based primarily 

on the needs of the international map of the world, the sheets of 

which are engraved on the reduced scale of 1:1,000,000. The 

1:500,000 State maps are therefore in a sense by-products of the 

international series. The inking of so much of the 1:500,000 

compilations as are included in the State map series must conform 

to the drafting needs for reproduction on the same scale, whereas 

so much of the compilation as pertains only to the data that are 

reproduced by engraving for the international sheets on the reduced 

scale of 1:1,000,000, such as the contours and highways, may be 

inked with slightly less exactitude.

The different projections used by the Geological Survey in map 

compilation are described under "General maps" (p. 359). For 

other map compilations not listed above the projection used should 

be the one best suited to the map in hand, the selection being 

governed by the area to be represented, the scale of the map, and the 

purpose for which it is intended. The projection should be made 

to cover the entire area of the proposed compilation but should be 

drawn in small sections if so warranted by the convenience of office 

use.

Control. All maps that are to be used in a compilation must be 

reduced to the same horizontal datum, for which the North American 

58515° 28 24
364 TOPOGBAPHIC INSTRUCTIONS OF GEOLOGICAL SUEVEY

datum is standard. If the data used are fully controlled, as in the 

Geological Survey quadrangle maps and Coast and Geodetic Survey 

charts, no further control is needed. Such maps and charts should 

be corrected to the North American datum if necessary and when 

reduced to the scale of compilation may be transferred directly to 

the projection. Before compiling those parts of the map that are 

not covered by maps resulting from controlled surveys, all available 

triangulation and transit-traverse positions that fall within the area 

of the map should be plotted so far as they can be used in adjustments. To the primary control thus established data from railroad, 

river, and other instrumental surveys are tied in an effort to subdivide the map with lines of supplemental control and into small 

sectors, in order that the use of the additional data of a miscellaneous nature may require only local adjustment. For maps within 

the public-land States the entire network of township lines should 

be adjusted and plotted from the records of the General Land Office, 

and inasmuch as this compilation may be regarded as preliminary 

and subject to change before the final adjustment is determined, 

it is generally convenient to make it on tracing paper on which the 

projection and control have been traced and later to transfer it into 

position on the map.

Reduction. Before any map data (other than initial control) can 

be transferred to the map they must be reduced or, if necessary, 

enlarged to the scale of the compilation. The reduction may be 

effected by photography, but it is more practicable to use the pantograph, because with that instrument only the features desired 

need be included and the copy can be made on thin tracing paper, 

which facilitates the adjustment and transfer of the data to the map. 

If a pantograph is used a clearer impression can be obtained if carbon paper is placed over the tracing paper and a metal point is used 

in the pantograph instead of a pencil point. Carbon paper of 

different colors may be used to obtain any desired distinctions, such 

as blue for drainage lines. It will generally be more convenient to 

reduce large-scale township plats by sketching the data on blocks 

of sectionized townships that have been made on the scale of the 

compilation and printed on transparent paper, as data thus prepared 

can be readily transferred to the map.

Adjustment and transferring. The most authentic maps should be 

first incorporated in the compilation, as their plotting will afford 

further control to which maps that have been less completely controlled can be tied, and thus through a gradual building up process, 

often through repeated trial adjustments of the less reliable data, 

the final adjustment and compilation are accomplished. A map, 

even though well drafted, should be fully tested before it is used, 

and a map should not be discarded because it lacks in appearance
TOPOGRAPHIC MAPPING 365

only. Although the suitability of existing maps or map data can 

in general be determined by inspection, the ultimate determination 

may rest upon the possibility of fitting or reconciling them to other 

data covering the same or adjacent territory.

Although a large part of the generalization of features is accomplished in the pantographing, further elimination, especially in 

drainage, may be needed when the data are transferred. Features 

such as railroads do not need so much generalization, and boundary 

lines should be delineated as accurately as the scale will permit.

Inking. The process of reproduction determines the method of 

inking. If the map is to be engraved all the features are included 

in one drawing, but great refinement in the drafting is unnecessary. 

The photolithographic process requires excellent drafting, and if the 

map is to be printed in more than one color a separate drawing may 

be made for each of the colors used if desired. The most satisfactory 

method of doing this is to provide photolithographic copies of the 

pencil compilation, one for each color to be used, printed in nonphotographic blue on drawing paper or bristol board. Only the features 

that are to be printed in the same color are included in one drawing, and as the blue copies of the map are identical, perfect register 

should be assured when the reproductions of the several drawings 

are combined in the printed map. The drainage should be carefully 

generalized as it is inked, and as a rule streams less than 6 miles in 

length may be omitted in a compilation on a scale of 1:500,000. 

Main streams should be inked heavier than the small tributaries, 

and a distinction should be made between perennial and intermittent 

streams. State and county boundary lines should be drawn reasonably bold, but public-land lines, with the exception of base lines and 

principal meridians should be inconspicuous. Railroad tracks should 

be represented by firm lines, with very short lines for the cross ties, 

which should be spaced at intervals of not less than one-tenth of an 

inch.

Lettering. In planning the lettering for the map, a complete 

diagram in which provision is made for the position each name is to 

occupy should be prepared for the draftsman's use. The diagram 

may be made in pencil on a photograph or photolithograph of the 

compilation. The map should not be congested with names, and in 

the selection of a place to be named consideration should be given 

to its population, importance as a railroad or postal center, and commercial or historical importance. In thickly settled regions the 

names of many places of only local importance must be omitted for 

lack of space, but in sparsely settled areas the names of small settlements or even of ranch houses assume importance as reference points. 

Space may be economized, where necessary, by abbreviating railroad names and by using "R" or "Cr" for the words "River" and
366 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

"Creek." All place names should be lettered in a horizontal position, 

and the names of railroads and streams should follow their meanderings and be so placed as to read from the south edge of the map. 

The spellings approved by the United States Geographic Board 

must be followed, and the diagram should be carefully checked before 

the lettering is executed. . The lettering may be done either by hand, 

by means of pasting type impressions on the map, or by a combination of both. Single-stroke lettering is comparatively easy to do and 

reproduces well, and its use is recommended. If type impressions 

are used instead of hand lettering the names should be listed in 

systematic order for type setting and printed on light-weight gummed 

paper. In applying names printed from type they should be cut 

out without much margin and pasted on the map, care being taken 

to avoid as much as possible, covering up any of the features. It 

is more satisfactory to letter the stream, names by hand, and this 

should be done on the drainage drawing, in the event that the colors 

of the map are separated -in the drafting.

Checking. During the whole course of the compilation the map 

should be constantly verified, so that upon its completion it may be 

free from error. It should also, however, be subjected to a final 

exhaustive checking, and such errors as are then detected should be 

corrected before it is sent to the printer.

Compilation record. As the compilation progresses a record should 

be kept of the data that were used, and this record should be later 

transcribed to a printed copy of the map. Errors or omissions that 

may be detected from time to time should be noted on a file copy of 

the map, for correction in the next edition.

Reproduction. Compiled maps are generally reproduced by photolithography, although engraving is used for such maps as those of 

the United States and of the international world series. To assist 

the lithographer in retaining the scale of a map reproduced by photolithography a projection should be constructed on paper mounted on 

a metal plate to serve as a key sheet in assembling the map for transfer 

to the printing stone.

SHADED RELIEF MAPS

Relief may be represented on maps by means of contour lines, 

form lines, hachures, or shading. It may be expressed by shading 

alone, or the shading may supplement other means of expression, as 

contouring. If relief shading is artistically added to the contouring 

it will so tend to throw into the background the rigid details of 

contour construction and so emphasize the broader features of the 

map as to give to the map a relief expression that may be understood 

by laymen unfamiliar with contour lines. Shaded relief maps may 

also assist map users who, although versed in the theory of contours,
TOPOGRAPHIC MAPPING 367

can not in practice get a picture of a region from a glance at a contour 

map of it; and the trained map user may often see in the shaded map 

some general aspect of the terrain that he has failed to grasp in the 

exacting detail of the contouring. Finally, even the engineer or 

geologist may find hi relief shading, especially when a number of 

such maps are used in combination, a meaning to be recognized in no 

other way save through models. As relief shading is a generalized 

portrayal of the relief in a pictorial sense, data of insufficient accuracy 

for contouring may often be employed with pleasing and advantageous effect.

In the early years of the Geological Survey experimental work in 

relief shading was carried on with some success, two such maps being 

published about 1882 by the lithographic process, but owing to the 

prohibitive cost of reproduction at that time the plan was abandoned. 

In recent years the discovery of the cheaper and more effective 

photo-transfer process has afforded a means for economical publication and caused a revival of interest in relief shading, which has 

grown in popularity and developed to such an extent as to enlist the 

commendation of geographers throughout the world.

Although shaded relief maps are called picture maps, they in 

reality portray with remarkable fidelity all the bolder topographic 

features, both in precise location and physical character, the illusion 

of relief being obtained by a judicious manipulation on the drawing 

of lights and shades so as to produce an effect similar to that which 

would be obtained if a carefully sculptured relief model were obliquely 

illuminated by the sun around 4 o'clock in the afternoon of a day in 

late summer. In addition to the representation of the bolder forms 

of relief, relative differences in elevation of valleys, plateaus, and 

other lesser relief forms are shown by a system of delicately graded 

tints dark tints for the lowlands, grading upward to light tints for 

the highlands. This mode of representing high and low lands has 

been developed in the Geological Survey and differs from other forms 

of hypsographic expression. Shaded relief maps should not be confused with those in which the process of modeling in clay or other 

plastic material has been used.

The Geological Survey has published a general shaded relief map 

of the United States on a scale of 1 : 3,168,000, one of Alaska on a 

scale of 1 : 2,500,000, and shaded relief State maps of Ohio (1 : 380,- 

160), Arizona (1 :500,000), Kentucky (1 : 500,000), and Idaho 

(1 : 760,320) and has in preparation similar maps of Pennsylvania, 

New York, New England, West Virginia, New Mexico, Colorado, and 

Wyoming. Shaded relief editions of 12 recent topographic maps 

have also been published, in which the shading has been overprinted 

hi a light olive-drab over the contours; for these editions special 

printings of the topographic base are made in colors that harmonize
368 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

with the overprinted relief shading. The methods of relief shading 

are also used for illustrations that show in detail special types of 

physiographic phenomena and geologic structure.

In the compilation of a base map upon which to add relief shading 

for maps of areas for which no contour maps are available, all authorities bearing upon the probable relief are used, including interviews 

with those who have traveled through any of the unmapped regions. 

Thus, in the preparation of the manuscript for the shading of the wall 

map of the United States over 5,000 maps were used, and many 

persons who had personal knowledge of unsurveyed areas were 

interviewed.

UNITED STATES SYSTEM OF PUBLIC-LAND SURVEYS

The following discussion, based on the "United States manual of 

public-land surveys," to which the topographer is referred for more 

detailed information, is intended to give a general outline of the 

plan and practices of the public-land surveys.

TOWNSHIP UNITS

The unit of the system is the township, a tract 6 miles square, or 

nearly so, bounded on the east and west by true north-south lines, 

and on the south and north by east-west lines, and subdivided 

into 36 sections, each a mile square, or nearly so.

As true north-south lines (that is, meridians) converge northward 

to the pole, it is evident that the width of a township decreases 

slightly from south to north (41.9 links in latitude 30° N. to 86.5 links 

in latitude 50° N.),7 and that its shape is really trapezoidal and not 

square. It is evident also that as the meridian lines are extended 

northward townships will become progressively narrower and will 

be reduced in area. These complexities growing out of the inherent 

convergence of meridians on a spherical surface like that of the 

earth were not taken into account in framing the original law, the 

intent of which was apparently to provide for square units of uniform size; nor was any provision made for a system of control lines 

whereby the narrowing of the townships, on the one hand, and the 

inaccuracies in the surveying of the subordinate lines, on the other 

hand, might be kept within convenient limits. However, the first 

public-land surveys to be executed, notably the classic "Seven 

Ranges" in Ohio, demonstrated the need of remedying these defects, 

and as a result there has been evolved by successive legal steps a 

system of rectangular surveying which "harmonizes the incompatibilities of the requirements of law and practice" and has become 

the accepted standard for the entire country.

i All public-land measurements are expressed in chains and links. A chain of 100 links is equivalent 

to 66 feet common measure, and 80 chains equal 1 mile.
TOPOGRAPHIC MAPPING 369 

PRINCIPAL MERIDIANS AND BASE LINES

All surveys in a given area are referred to two primary lines, a 

principal meridian and a base line, passing through an initial point; 

the one is a true north-south line and the other a true east-west line 

that is, a parallel of latitude. These two lines constitute the axes 

of the system, and the township units are numbered with reference 

to them in consecutive tiers to the north and to the south, beginning at the base line, and in consecutive ranges to the east and to 

the west, beginning at the principal meridian. Any township, 

accordingly, may be designated by tier and range number, as T. 

14 N., E. 7 W. fourth principal meridian, or T. 10 N., R. 28 E. 

Mount Diablo principal meridian. The principal meridian must be 

added to each designation to give complete identification; there are 

about 30 separate systems in the United States, each with a separate 

set of axes and a separate system of numbers. The number or 

name of the principal meridian serves to distinguish these from one 

another.

STANDARD PARALLELS AND GUIDE MERIDIANS

From the principal meridian, commonly at intervals of 24 miles, 

auxiliary base lines called standard parallels, or correction lines, are 

extended east and west. They are numbered each way from the 

base line for example, first standard parallel north, third standard 

parallel south.

From the base line, usually at intervals of 24 miles, auxiliary 

meridians called guide meridians are run due north. They are 

numbered each way from the principal meridian for example, first 

guide meridian east, second guide meridian west. As they converge 

appreciably in a distance of 24 miles (the exact amount depending 

on the latitude), they are not continued beyond the first standard 

parallel north but end at closing corners on that line and start afresh 

from standard corners a full 24 miles apart. It will therefore be seen 

that standard parallels have two sets of corners, one set referring to 

lines north of the parallel and the other being established by township and section lines from the south, closing on the parallel. The 

process is repeated at the second and each succeeding standard parallel 

Each guide meridian thus runs due north from parallel to parallel, 

and on each of the parallels is an offset to correct for convergence.

South of the base line guide meridians are run not south but north, 

so that the blocks inclosed between them and the parallels are essentially similar to those north of the base line. In case conditions require 

that a guide meridian be run south it must be begun at a properly 

computed and established closing corner.

The standard distance of 24 miles between parallels and meridians 

is not always strictly adhered to. Thus, in many parts of the far
370 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

West there are five tiers of townships (30 miles) between parallels and 

six, seven, or more ranges between guide meridians. In some places 

these irregularities in the spacing of the standard lines necessitate 

the introduction of intermediate meridians and parallels. These are 

designatedbylocalnam.es.

The offsets of the meridians on the parallels and their closing distances are of special importance in the plotting of guide meridians 

and standard parallels, and these data the topographer should not fail 

to procure from the General Land Office.

The meridional convergence increases proportionately to the distance from the principal meridian. Therefore the offset of the second 

guide meridian is double that of the first guide meridian (between the 

same parallels); that of the third guide meridian is three times as 

great; and so on in proportion (the intervals being assumed to be 

regular). Again, the convergence increases slightly northward with 

the latitude. Thus the offset of a first guide meridian in latitude 50° 

is more than double what it would be in latitude 30°. Of course the 

actual offsets depart somewhat from the theoretical offsets because of 

inaccuracies in surveying, and this makes it all the more imperative 

that they be noted on the plats.

It is to be remembered that all errors of closure in distance are 

thrown in the last mile and are not distributed over the entire length 

of the line. The spacing of the corners along the line is thus not 

affected by the amount of the closure.

Whenever practicable the survey of township exteriors within a 

'block bounded by standard lines begins with the southwest township 

and continues northward until the entire west range is completed; 

thence it goes from south to north through the next range east, etc. 

The mode of procedure is first to run the east boundary of a township 

due north a full 6 miles; then to run its north boundary on a random 

or trial line from east to west, correcting back on a true line after the 

"falling" north or south of the northwest township corner has been 

ascertained. The closure in distance, however, is thrown in the last 

half mile at the west end of the line that is, between the last quartersection corner and the township corner. The purpose of this is to 

throw the meridional convergence and all irregularities arising from 

inaccurate surveying toward the west boundary of the township. 

The last quarter-section corner accordingly lies not midway in the 

last mile but always an even 40 chains from the mile corner east of it, 

whatever the distance between it and the township corner may be.

In getting data for platting township exteriors, therefore, special 

note should be made of the closing distances at the west ends of the 

latitudinal township boundaries. The accuracy of the surveys may
TOPOGRAPHIC MAPPING 371

be gaged from a comparison of the actual with the theoretical closing 

distances as indicated below:

Theoretical closing distances at different latitudes

30°

35°

40°

45°

60°

Closing distance

Chains

79.58

79.49

79.39

79.27

79.14

Feet

5,252

5,246

5,240

5,232

5,223

In the northermost tier of townships in a block it is further necessary to take note of the closing distances of the range lines on the 

standard parallel. Theoretically these distances should be an even 

80 chains, but inaccuracies in the azimuth of the standard lines on 

the one hand and of the township lines on the other hand usually 

cause discrepancies. It frequently happens that the length of chain 

used for the one set of lines differs appreciably from that used for the 

other, and the closure errors may then amount to several chains 

Such discrepancies should be marked on the plats.

SECTION LINES

Each township is divided by section lines into 36 sections, which 

are numbered consecutively, commencing with No. 1 at the northeast corner of the township and proceeding west to No. 6, thence 

east to No. 12, thence west to No. 18, and so on, alternately east 

and west, to No. 36 in the southeast corner. In all fractional 

townships the sections bear the same numbers they would have if 

the township were full.

As townships are trapezoidal and not square, they do not contain 

a full 36 square miles each but fall short of that amount by a number of acres. It being undesirable to distribute this shortage among 

all the 36 sections, the law provides that it shall be thrown into 

the westernmost range of sections, and that the other sections shall 

be laid out so as to contain a full 640 acres each, as near as may be. 

Accordingly, the longitudinal lines between sections are run not 

due north but parallel to the east boundary of the township. Each 

bears slightly west of north, according to the latitude of the township and its distance from the east boundary. The latitudinal section lines are run parallel to the south boundary of the township 

that is, as a rule they run practically east and west.

The subdividing of all normal townships begins with the southeast section. Its west boundary is run N. 0° 1' W. a full 80 chains; 

its north boundary is then run east on a random or trial line, a quar-
372 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

ter-section corner being temporarily placed at 40 chains. The "falling" north or south from the appropriate corner on the township 

boundary having been measured, the quarter-section corner is then 

shifted proportionately and set exactly midway between the section 

corners. In many of the older contracts these rules were not faithfully carried out, and in consequence little dependence is to be 

placed on the position of the quarter-section corners on the latitudinal section lines. The west boundary of the next section north 

is then run out, and then its north boundary as before, and so on 

through the entire east range of sections. The other ranges are 

taken up consecutively from east to west, each being surveyed from 

south to north. The range lines of the northernmost tier differ from 

the others hi that they are connected with the corners along the 

township boundary and consequently are not always parallel to the 

east boundary nor measure an even 80 chains in length. Theoretically they should do so, but in practice the inaccuracies in the surveying of the township exteriors, on the one hand, and of the section 

lines, on the other hand, cause discrepancies. Accordingly, these 

lines are run first on a random or trial line parallel to the east boundary and then corrected back according to their falling. In order 

to confine the irregularities in acreage to the northernmost tier of 

lots, the excess or deficiency in measurement is thrown north of the 

quarter-section corner, which is consequently set not midway but 

an even 40 chains from the south end of the line.

In the west range of sections, again, the latitudinal lines are 

connected to corners along the west township boundary. Each is 

therefore run first on a random parallel to the south boundary of 

the section and then corrected back according to its falling. Here 

again, in order to confine the irregularities in acreage to the westernmost range of lots, the error (which normally is a deficiency equal 

to the meridional convergence) is thrown west of the quarter-section 

corner, which is consequently set not midway but an even 40 chains 

from the east end of the line.

MEANDERS

Where any lines cross rivers the right-angle width of which is 3 

chains or more, lakes, bayous, and deep ponds having an area of 25 

acres or more, meander corners are established on each bank, and 

from these are run meanders (corresponding to traverse lines) along 

the banks, to close on other meander corners. Similarly, water 

bodies having an area of 25 acres or more, lying within sections, are 

surrounded by a meander tied to the two nearest section or quartersection corners. Islands are located by triangulation from meanders 

on the shore, an auxiliary meander corner being established on each 

one of them.
TOPOGRAPHIC MAPPING 373

Meanders are run for the sole purpose of providing a definite 

boundary for the land areas in the lots abutting on water bodies, 

so that the acreage of such fractional lots may be computed with 

accuracy. There is consequently no object in publishing meanders 

on the topographic maps, and they are to be omitted. At the same 

time, distances to meander corners and notes or plats of meander 

lines are often of great value in the construction of the maps hi the 

field, and such data should therefore be procured.

Care should be taken in drafting the field sheets to discontinue 

land lines at such river banks and lake shores as have been meandered. They should not be represented as crossing the water body 

unless the lines were actually so run.

BLAZING LINES

Trees on a line have two chops or notches cut on the side facing 

the line. Other trees standing within 50 links of the line, on either 

side of it, may be blazed on two sides diagonally or quartering toward 

the line, the blazes approaching nearer each other the farther the 

tree stands from the line.

Random lines are not blazed.

MARKING CORNERS

Classes. Land-survey corners are divided into the fourteen following classes, each of which has a distinctive set of marks and is 

marked in accordance with difinite rules:

Standard township corners. 

Closing township corners. 

Corners common to four townships. 

Corners common to two townships only. 

Corners referring to one township only. 

Standard section corners. 

Closing section corners. 

Corners common to four sections. 

Corners common to two sections only. 

Corners referring to one section only. 

Quarter-section corners. 

Standard quarter-section corners. 

Meander corners.

Corners on reservation or other boundaries not conforming to regular 

system.

Each of these fourteen classes of corners may be constructed as 

the character of the country and the availability of the materials 

permit, in eight different ways as follows:

Stone, with pits and mounds of earth. 

Stone, with mound of stone. 

Stone, with bearing trees.
374

Post, with pits and mounds of earth. 

Post, with bearing trees. 

Mound of earth, with deposit and stake pit. 

Tree corner, with pits and mound of earth. 

Tree corner, with bearing trees.

No less than 112 different combinations may be met in the field. 

There is, however, no need of describing each combination separately; the marks follow a definite simple system and in a measure 

are self-explanatory.

Notches and grooves. Stones and posts on all township and section 

corners (except those on standard parallels) are set diagonally to the 

lines that is, with an edge on each line. On the edges are cut 

notches, the number of which indicates the number of miles to the 

near^t township corner in the direction of the edge. Thus, the 

first mile corner on a range line between two townships has one 

notch on the south edge and five notches on the north edge; and the 

second mile corner has two notches on the south edge and four notches 

on the north edge. On a latitudinal township boundary the first 

mile corner west of the township corner has one notch on the east edge 

and five notches on the west edge; and the second corner west has 

two notches on the east edge and four notches on the west edge. A 

corner common to four townships has six notches on each of its four 

edges.

Section corners within a township are notched on their south and 

east edges only. The number of notches on them therefore indicates the distance in miles to the south and east township exteriors, 

respectively. Thus, the corner between sees. 25, 26, 35, and 36 has 

one notch on its south edge and one notch on its east edge; the corner 

between sees. 10, 11, 14, and 15 has four notches on its south edge 

and two notches on its east edge; the corner between sees. 5, 6, 7, 

and 8 has five notches on both its south and east edges.

Stones and posts on standard parallels are set square with the 

lines that is, with a flat face on each line. Their faces are grooved, 

the number of grooves on any face indicating the number of miles to 

the nearest township corner in the direction of the face. Accordingly, 

standard township corners have six grooves on their north, east, and 

west faces; closing township corners have six grooves on their south, 

east, and west faces. Standard section corners are grovoed only on 

their east and west faces with respect to the standard township corners. Closing section corners are similarly marked with respect to 

the closing township corners.

Tree corners are notched to correspond with the notches or grooves 

which stones or posts would bear in the same situation.

Additional marks. Standard corners of all kinds are marked "s c" 

on the north face; closing corners, "c c" on the south face. If posts 

or trees are used the township and range numbers also are indicated
TOPOGRAPHIC MAPPING 375

on the appropriate sides of standard and closing township corners, 

and the township, range, and section numbers on the appropriate 

sides of standard and closing section corners.

Posts at ordinary township corners have each township and range 

marked on the appropriate face; tree corners bear the same marks 

on large blazes.

Posts at section corners are similarly marked with the numbers 

of the surrounding sections and, in addition, with the number of 

the township and range on the northwest and northeast faces, 

respectively.

Quarter-section corners are marked "%s" on their north face if on 

a latitudinal line, on their west face if on a meridional line. If stones 

are used the "s" is omitted.

Pits and mounds. In open country where the soil is soft enough to 

permit digging square pits are dug about each corner, and the earth 

taken from them is heaped up into a conical mound. At corners 

common to four townships the mound is placed immediately south 

of the monument; at corners common to four sections, west of the 

monument; at standard corners, north of the monument; at closing 

corners, south of the monument; and at quarter-section corners, 

north or west of the monument, according as the line is latitudinal 

or meridional.

The pits are placed on each line about all corners except section 

corners; at these the pits are placed diagonally, one in each section.

Where neither stone nor wood is available for suitable corner 

monuments a marked stone, charred stake, or quart of charcoal is 

deposited 1 foot below the surface of the ground and the mound 

placed above it.

Where the ground is stony and does not permit the digging of pits, 

a pyramid of stones is built in lieu of a mound.

Bearing trees. Bearing trees, each with a large blaze facing the 

corner monument, are used wherever the required number of trees 

within proper distance is available. They are disposed and marked 

as follows:

At township corners, one in each surveyed township, marked with 

township, range, and section number, followed by the letters "B T" 

(bearing tree). At section corners, one in each section, marked with 

township, range, and section number. At standard corners of all 

kinds, two trees, one in each section north of the parallel; at closing 

corners, two trees, one in each section south of the parallel. At 

quarter-section corners, two trees, one in each section.

Witness corners. When the true point for any corner falls in a 

place where its destruction by natural or other causes would be certain, a witness corner is established in a secure position on a surveyed 

line, if possible, within 20 chains of the corner point thus witnessed.
376 TOPOGKAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

A witness corner bears the same marks that would be placed on the 

corner for which it is a witness with the addition of the letters "w c" 

conspicuously displayed above the markings. Its bearing trees, 

similarly, are marked "w c."

ADJUSTMENT OF PUBLIC-LAND LINES

To adjust the lines of the public-land surveys to the control of a 

topographic map it is necessary to understand the manner in which 

those lines were run. (See preceding section.) This adjustment 

offers a direct parallel to the relocation of lost land corners of the 

public-land surveys in the field. For purposes of adjustment the 

land corners located by the control are the only known corners, and 

all other corners, to be located by adjustment, must be considered 

lost corners. The approved methods for the relocation of lost corners 

of the public-land surveys have been developed to conform to court 

decisions as to what constitutes the most reasonable location for such 

corners. Apparently the topographer can do no better than to follow 

the rules for the relocation of lost corners in his adjustment of the 

lines of the public-land surveys to his field sheet.

On principal meridians, guide meridians, base lines, standard parallels, and township and range lines, the lost corner should be restored 

in line between the nearest known corners on the same line and at 

distances from them proportional to those shown in the field notes and 

on the plats of the original survey. This rule assumes that the original line was a straight line. Frequently it is not, but in most places 

the variations from a straight line are first in one direction and then 

in the other, approximating a straight line so closely as to be difficult 

to show otherwise on the scale of a topographic map. In the absence 

of definite knowledge to the contrary, it is best to assume that the 

original line was straight.

Lost township corners that are common to four townships should 

be restored at distances from the nearest known corners, north, south, 

east, and west, proportional to those shown in the field notes and on 

the plats of the original survey. This rule also applies to the relocation of lost ulterior section corners. Lost township corners that are 

common to only two townships should be restored in line between the 

nearest known corners on the same line and at distances from them 

proportional to those shown in the field notes and on the plats of the 

original survey.

Lost quarter-section corners should be restored in line between section corners that stand on the same line at distances between them 

proportional to those recorded in field notes of the original survey. 

Quarter corners for which such distances are not given on the plats 

are midway between and on line with adjacent section corners.
TOPOGRAPHIC MAPPING 377

Distances along township and section lines that are not given on. 

the land plats are an even 80 chains. The distance is given for the 

last quarter of the last mile to the west and to the north in each township, as any discrepancy is thrown into this quarter, other fractions 

of the mile being 40 and 20 chains unless otherwise shown.

The rules given above will not apply rigidly and inflexibly to all 

cases. The best judgment of the topographer should always be applied to find out or decide not where the corner or line ought to have 

been but where it actually was. In exercising such judgment the 

topographer may have to wait until he can supplement his control 

with traverse lines before he can adjust the land net with accurate 

results.

In applying the above rules to the adjustment of the land net to 

his field sheet, the topographer should first sum the distances as given 

by the plats along the township exteriors across his sheet from control point to control point, both in a north-south and an east-west 

direction. The same distances between control points should be 

carefully scaled from the field sheet. In summing the distances 

from the plats it is best to take the distances as given on the north 

side of the east-west lines and on the west side of the north-south 

lines, as there will be fewer fractional distances and the sum will be 

the same as if distances given on the other sides of the lines had been 

taken. Any discrepancies between the summed and the scaled distance for any line should be distributed proportionally to distances 

given by the plats, and the east-west and north-south location of 

each township corner should be marked on the field sheet by a short 

line at right angles to the direction in which the line is measured. 

The intersection of these short lines or dashes, drawn at right angles 

to each other, gives the adjusted location of the township corner. 

In the absence of definite information to the contrary, it is most 

reasonable to assume that straight lines connecting the corners with 

adjoining corners of the same line and with control locations on 

township exteriors will give the adjusted location of the township 

exteriors. After the exteriors have been drawn the section corners 

on the north side of the east-west lines and on the west side of the 

north-south lines should be plotted, the same proportional correction 

to the distances shown on the plats being made as was applied for 

the same line in the location of the township corners. Corners on 

the opposite sides of the same lines should be plotted next, the offset 

distances shown on the plats being used and the same proportional 

corrections being applied if the distances are large enough to warrant it.

The corners along the township exteriors located by adjustment 

can now be used as found corners for the adjustment of the interior 

section corners of the several townships. This work should be done 

in the same manner as the location of the township corners. Dis-
378 TOPOGRAPHIC INSTKUCTIONS OF GEOLOGICAL SURVEY

tances along section lines across the township both in a north-south 

and an east-west direction should be summed from the plats and 

scaled from the field sheet. Any discrepancy between the two should 

be distributed to the sections in proportion to their distances as 

shown on the plat, and a north-south and an east-west location should 

be marked for each section corner by a short line at right angles to 

the direction in which the measurements were made. The intersection of these short lines gives the adjusted location of the section 

corners. Lines joining such points in the same lines give the adjusted locations of the section lines.

By the method of adjustment above set forth errors in the original 

surveys due to the use of a chain that was too long or too short are 

taken care of, and bends in the section lines at section corners are 

faithfully reproduced on the field sheet. Gross errors or fraudulent 

work in the original surveys can not be taken care of by any method 

of adjustment. They are, by the method here prescribed, confined 

to the township in which they occur.

In localities where the public-land surveys are known to be poor 

or where discrepancies between the plotted and the scaled distances 

are so large as to indicate a weakness in the land surveys, it is best 

to wait until the control can be supplemented by stadia traverse or 

by other means before attempting to adjust the land net to the field 

sheet. This precaution is equally desirable if the marginal control 

is weak or the topographer has to depend on railroad control.

When the township and section lines are well adjusted, the quarter 

and the sixteenth section lines can be drawn on the field sheet as an 

aid to the topographer in future work.
F. MAP COMPILATION FROM AERIAL PHOTOGRAPHS

By T. P. PENDLETON

INTRODUCTION

The value of photographs for map construction was appreciated 

immediately after the invention of the camera, and many methods 

of utilizing photographs made from ground stations for this purpose have been perfected, but until some time after the development 

of the airplane no attempt was made to use aerial photographs in 

this way. No effort is made to describe here any of these older 

instruments or processes, nor methods of compilation other than 

those used by the Geological Survey.

As considerable experimentation on the design of instruments 

and the development of a compilation process that will utilize 

advantageously aerial photographs for mapping has been carried 

on, it seems advisable to describe the instruments and methods now 

in use by the Geological Survey, recognizing the fact that they may 

soon be supplanted by newer and better ones.

INSTRUMENTS

SINGLE-LENS CAMERA

The single-lens camera most commonly used is shown in Plate 24 

in a dummy installation and is often called the " K" type, the 

several models being denoted by numbers as "K-3." This camera 

is entirely automatic and is so designed that the interval between 

exposures may be varied from 4 seconds to over 1 minute. It is 

equipped with an anastigmat lens having a maximum stop opening 

of f/4.5 and a focal length of 12 inches. The shutter is of the 

"between the lens" type and gives exposures of 1/50, 1/100, and 

1/150 second. Photographs 18 by 24 centimeters are made on roll 

film about 75 feet in length, sufficient for about 120 exposures. The 

camera is motor driven, power being provided by a storage battery, 

and may be loaded during flight, as the magazine with the exposed 

film may be removed and another containing unexposed film quickly 

substituted.

58515° 28 25 379
380 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEt

The intervalometer controlling the intervals between exposures 

having been set to give the desired overlap of photographs, the 

motor will trip the shutter, count the exposure, remove the pressure 

of the film-pressure plate, wind an unexposed portion of the film 

into position, replace the film-pressure plate so that the film is held 

in close contact with the glass focal-plane plate, and set the shutter 

ready for the next exposure. The camera is suspended in gimbals 

that allow it to be rotated about its vertical axis and to be leveled 

in the focal plane. A horizontal position of the focal plane is indicated by a circular level attached to the camera.

RECORDING CONE

\

The latest model of the single-lens camera is the K-8 type. This 

camera is in certain minor details simply an improvement on earlier 

models, but the recording cone used with it is unlike anything that 

has been introduced heretofore.

The purpose of this recording cone is to register photographically 

on the negative, at the moment of exposure, all pertinent data concerning it and thus provide positive identification for each photograph. This is accomplished by photographing on the edge of the 

negative a watch face, a circular spot level, an altimeter, a mechanical counter, and a card on which any data concerning the flight 

may be written. This device is set in a door in the side of the lens 

cone and functions just after the camera exposure has been made 

and before the film is wound forward. The photograph of the recording device is easily read, although it occupies a space but 10 by 

38 millimeters, and as it appears along one edge of the print it 

does not interfere with the usefulness of the print in the least.

MULTIPLE-LENS CAMERA

Multiple-lens cameras of the type so extensively employed at present in the photographic mapping of this country have many advantages due to the large area photographed at each exposure. These 

advantages are so great that they more than offset the slight indistinctness often encountered at the outer edges of the photographs. 

This lack of definition does not result from lack of perfection in the 

construction of the camera, but is caused by the distance and angle 

at which the objects in this portion of the field are viewed and l?y 

the transformation that these oblique views must undergo in preparing them for use in mapping. During the last few years there has 

been a remarkable improvement in the quality of photographs of 

this type and it is not too much to expect that this improvement will 

continue until they are entirely satisfactory.
MAP COMPILATION FROM AERIAL PHOTOGRAPHS 381

The multiple-lens cameras are constructed with either three or four 

lenses each. The four-lens or T-2 camera is an improvement on the 

tri-lens or T-l and will probably soon supersede it on account of the 

increased ease and accuracy of map compilation that it makes 

possible.

The four-lens camera consists of four sections, two of which are 

film magazines containing the rolls of film and two contain the lenses 

and dark chambers of the camera proper. This instrument can be 

considered a tri-lens camera to which has been fitted an additional, 

detachable lens unit.

The object in designing the multiple-lens camera was to include a 

larger field of view at right angles to the direction of flight of the 

airplane than is given by any photographic lens of large lightgathering power. This was accomplished by fixing the central lens 

with its axis in the vertical position while the axes of the other two 

lenses were in the same plane but at an angle of 35° to the left and 

right. The combined field of view in the plane of the lens axes is 

115°, which leaves a liberal margin of overlap of fields for matching 

the photographic prints. This overlap can be most clearly visualized 

by considering the two oblique lenses as located in the same position 

as the central lens, as shown in Figure 13, an assumption which is 

permissible, as the actual separation is only a few inches. The maximum angular field of view and the amount of overlap differ slightly 

in different cameras, owing to the small differences that exist in the 

focal lengths of the lenses selected for each camera.

Front and rear views of the T-2 camera are shown in Plate 25. 

In the front view the line of division of the upper and lower portions 

of the camera can be easily distinguished. The base contains three 

lenses, dark chambers, and focal-plane surfaces. The three lenses 

and their corresponding focal planes are distinguished by the letters 

A, B, and C. The compartment for the fourth lens is accordingly 

called the D compartment. The A, C, and D focal planes make an 

angle of 35° with the focal plane of the B compartment. A view of 

the focal planes is shown in Plate 26. A. The center (B) compartment contains two level vials, so placed that an image of the 

bubbles will photograph on the negative when the exposure is made. 

The four index marks that appear at the edges of each focal plane 

play a very important part in the use of the photographs. The intersection of the lines defined by these indexes is the " principal point" 

of the negative and marks the intersection of the optical axis of 

the lens with the focal plane.

Rollers are provided at each end and between the focal planes to 

reduce the friction encountered in winding the film into position. 

The lenses have a focal length of about 7.5 inches for the A, C, and
382

D chambers and are matched at the factory to about 0.10 millimeter 

in order to insure equality of focal lengths. This agreement of the 

focal lengths of the oblique lenses renders the transformation of the 

negatives a relatively simple matter. The B compartment is 

equipped with a lens having a focal length of about 6.5 inches, as this 

shorter focal length permits the construction of a much smaller 

camera than would otherwise be possible. The lenses have a maxiFIGURB 13. Lateral field of view of T-l camera

mum stop opening of f/4.5 and are mounted in "between the lens " 

shutters. The arrangement of the lenses and the shutter-release 

mechanism are shown in Plate 26, B. As it is essential that the 

four lenses be exposed at the same instant, provision is made whereby 

the shutters of the oblique lenses can be synchronized with the shutter 

of the central lens.

The upper or magazine section of the camera can be detached 

from the base by loosening four clamp screws, two of which are
U. S. GEOLOGICAL SURVEY 

A SIN(iLE-LKNS CAMERA 

Photograph used by permission of Fairchild Aerial Cam
TJ. S. GEOLOGICAL SURVEY BULLETIN 788 PLATE 25

Ji

T-2 CAMERA 

A, Rear view; 13, front view
IT. S. GEOLOGICAL SURVEY BULLETIN 788 PLATE 20

B

T-2 CAMERA 

A, Focal planes and dark chambers; B, arrangement of lensi
D. S. GEOLOGICAL SURVEY 

THE FIXED T-2 TKAiMSFOHMINU P
MAP COMPILATION PROM AERIAL, PHOTOGRAPHS 383

shown in Plate 25, B. The two film-carrying spools are so mounted 

that they are on the vertical axis of the camera, with the take-up 

spool above the full spool. The film must be wound onto the empty 

spool by the hand crank shown in the illustration, as this camera is 

not of the automatic type. The film is guided in its journey from 

one spool to the other by several guide rollers in the magazines in 

addition to those in the base. The proper amount of film to be 

wound forward between exposures is indicated by one revolution of 

the dial shown above the hand crank in Plate 25, B. The. film is 

held in the focal plane by three spring pressure plates which are 

provided with stops that prevent the pinching of the film between 

the focal planes and the pressure plates. The plate back of the B 

compartment is removable to facilitate the loading of the camera 

in the dark room. Two handholes with light-tight covers are provided on the sides of the magazine section for the same reason. The 

top of the camera is fitted with two level vials to aid the observer in 

keeping the camera in an upright position at each exposure and 

with an exposure counter and stop watch for recording the number 

and indicating the instant of each exposure. These devices are 

actuated by cams and gears on the shaft of the shutter-release 

mechanism.

The D unit of the T-2 camera is attached to the base of the camera 

on the side opposite the hand crank, with its optical axis at an angle 

of 35° with that of the B chamber. This arrangement places the 

focal plane of this unit-at the same angle with the B plane as is 

made by the A and C planes and furnishes a photograph of the 

region back of the airplane. It is equipped with a lens identical in all 

respects with the A and C lenses, but has an independent film chamber and two film spools. The relation of this unit to the rest of the 

camera is shown in Plates 25, A, and 26, B. The shutter is synchronized with and actuated by the same mechanism as the B shutter, and the film is wound into position by the hand crank of the 

camera by an arrangement of bevel gears and a universal-joint shaft, 

also shown in Plate 25, A.

This camera uses hypersensitized panchromatic film in a roll 6 

inches wide by 380 feet long, which is sufficient for 190 tri-lens 

exposures, and a shorter roll of the same width for the D unit. As 

this film is sensitive to light of all colors, it is necessary to load 

the camera in total darkness, and as its keeping quality is not good 

it should not be ordered until needed for use. It is kept under 

refrigeration at other times.

Color screens are used with this film to eliminate certain undesirable light rays and thus increase the ability of the film to record 

the details desired. These screens are in the form of thin gelatin
384 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL, SURVEY

sheets and are inserted back of the front element of the lens. 

Several grades are available for use to compensate various atmospheric conditions.

The camera is provided with a suspension mechanism designed 

to reduce vibration and to make possible the leveling and orientation of the camera to obtain the most advantageous position for 

aerial mapping. This is accomplished by hanging the camera in a 

gimbal mount, which is equipped with rollers traveling on p, circular track, and providing the entire apparatus with brackets and 

shock-absorbing cushions by which it may be attached to the iuselage 

of the airplane. These adjustments are necessary, for it is essential 

that the camera be placed in a predetermined position with respect 

to ground objects, with the axis of the B lens in an approximately 

vertical position. The azimuthal adjustment is important, as it is 

generally necessary to rotate the camera a few degrees in order to 

compensate for any wind effect on the airplane or to improve the 

angles of intersection, so that a more strongly adjusted map may 

be produced.

TRANSFORMER

The three oblique photographs made by a T-2 camera can not 

readily be used in topographic mapping until they have been reprojected into the plane of the B photograph. A special apparatus, 

which is both a camera and a printer but is usually called a transformer, shown in Plate 27, is used for this purpose. The spools on 

which the negative film is carried are shown on the end adjacent 

to the light source, and on the opposite end of the transformer is 

the suction back used to hold the photographic paper in the image 

plane of the lens. A motor and vacuum pump provide the necessary suction. The lens used in this transformer is of the wideangle type, with a maximum stop opening of f/18 and a focal 

length of about 7.5 inches. It is set in the interior of the transformer in a partition that divides the negative from the image end. 

The angles made by the negative and image planes in this transformer are unusual but are fixed by the focal length of the lenses 

used in the aerial camera and in the transformer and by the 

dihedral angle between the oblique and horizontal focal planes in 

the aerial camera. On account of this complex relation it is necessary to construct a transformer for use with each multiple-lens 

camera.

STEREOSCOPE

The interpretation of aerial photographs is much easier when 

overlapping prints are examined through a stereoscope, for this 

instrument has the peculiar property of causing the photographic
MAP COMPILATION FROM AERIAL PHOTOGRAPHS 385

image to be seen in three dimensions. The third dimension, that of 

relief, is so strongly emphasized that differences of elevation as small 

as 50 feet can ordinarily be detected without magnification of the 

image, and with a special magnifying stereoscope very small differences can be seen and measured. The unusually strong stereoscopic 

effect obtained when aerial photographs are viewed through a 

stereoscope is due to the fact that the distance between the eyes 

(the " eye base ") is increased in effect from a few inches to several 

thousand feet, as the observer sees the photographs as the terrain 

would appear to one whose eyes were separated by the distance 

between the exposure points of the two photographs. The magnification of the image by suitable lenses will increase this effect.

Stereoscopes of many different types are constructed, some being 

intended for use with glass negatives and transmitted light and others 

for use with photographic prints and reflected light. The highpowered instruments usually have very small fields; those of low 

power have larger fields. The Geological Survey has several stereoscopes using low magnifications, but by far the most useful is a 

simple mirror stereoscope of the Pellin type, which is not equipped 

with lenses for the magnification of the image. The Pellin stereoscope has four mirrors adjustably mounted on a bar and suitable 

standard in such a manner that by looking downward into two small 

mirrors the photographs can be seen by reflection in two larger mirrors. It has a large field of view, and the size of the image reaching 

either eye can be easily and quickly varied a small amount by a simple 

adjustment of the mirrors. The large field permits a better interpretation of the relief than can be obtained if only a small area appears 

in the field, and the variable magnification is helpful in the examination of those T-2 photographs that can not be viewed stereoscopically 

in the outer parts owing to differences in scale introduced by rolling 

of the airplane. Two such prints can often be brought to the same 

scale and a satisfactory stereoscopic view obtained by sliding the 

large reflecting mirrors along the bar on which they are mounted 

until a position is found that permits the merging of the two images.

Several forms of stereoscopic instruments have been designed for 

the purpose of making very exact measurements from aerial photographs that enable the topographer to complete the mapping of an 

area without field work other than the usual control surveys. This 

interesting phase of the subject of photogrammetery has not yet been 

undertaken by the Geological Survey.

PHOTOGRAPHIC OPTICS

An elementary knowledge of the formation of an image by lenses 

is essential to a thorough understanding of photographs used in 

mapping, and this applies to photographs taken in the air or from
386 TOPOGEAPHIO INSTEITCTIONS OF GEOLOGICAL SURVEY

the ground. A short study of this subject will also explain the 

underlying principle of the stadia and of all other devices in which 

angular or linear measurements of an image in the plane of the 

reticle are made. Neither the use of the panoramic mapping camera 

nor the theory of the transformer can be clearly understood without a knowledge of this principle.

OPTICAL DEFI3STITIONS AND FORMULAS

The optical axis of a lens is the path of a ray that will pass 

through the lens without deflection. In a well-centered lens the 

axis passes through the centers of curvature of the different lens 

surfaces.

If rays from a very distant object (such as the sun) are allowed 

to pass through a lens, the image will be formed in a plane called 

the secondary focal plane, or image plane. The primary focal plane 

can be found by reversing the lens and allowing the image to form 

on the opposite side of the lens. The intersections of the axis with 

these focal planes are the focal points of the lens and will be referred 

to as the principal points.

The two nodal planes are perpendicular to the axis and pass 

through the nodal points of the lens, which are designated the nodal 

point of incidence and the nodal point of emergence. One of the 

most interesting properties of the nodal points is that a ray entering 

the lens from any direction toward the nodal point of incidence will 

leave the lens parallel to its original direction but as if it had come 

from the nodal point of emergence. The location of these points can 

be found graphically by extending the incident and refracted ray to 

intersection with the optical axis, as shown in Figure 14, in which 

the nodal points of incidence and emergence for a double convex 

lens are designated by the letters N and N'', respectively. A study of 

this figure will show that regardless of the direction from which 

the ray approaches the nodal point of incidence it can be considered 

as leaving the lens from the other nodal point and parallel to its 

original direction. This property is utilized in measuring the focal 

length of a lens and in the construction of panoramic cameras, for it 

can be seen that a lens can be rotated about an axis passing through 

the nodal point of emergence without causing a movement of the 

image on a screen. The nodal points may fall outside as well as 

inside the lens, their separation and position being fixed by the type 

of lens under consideration.

The object and image planes are also perpendicular to the lens 

axis and as their names suggest are the planes in which are found 

the object and its image. These planes are conjugate and have a
MAP COMPILATION FROM AERIAL PHOTOGRAPHS 387

fixed relation to each other that must be known in order to determine 

the scale of the image.

The equivalent focal length of a lens is the distance from the nodal 

plane to the image plane. The back focus is the distance between the 

rear surface of the lens and the image plane.

The focal length of a lens and the position of its nodal points 

can be readily determined on an optical bench and should always 

be known for all lenses used in mapping cameras. With a knowledge of these constants it is possible to determine the position and 

size of an image, either graphically or by computation. The graphic 

solution commonly used is as follows: A ray from A (fig. 15) parallel to the axis can be considered as passing through the lens as

FIGURE 14. Nodal points of a double convex lens

far as the nodal plane of emergence and there being refracted so 

that it passes in a straight line through the rear focal point. Another ray from A can be considered to travel straight through the 

front focal point as far as the nodal plane of incidence and from this 

point be parallel to the axis of the lens. The intersection of these 

two rays (a) is the location of the image of point A. In a similar 

manner the location of the image of point B can be found. The 

path of the actual rays through the lens is quite unlike this, 

although the location of the image is accurately given by this graphic 

method.

The primary and secondary focal points are shown in the same 

figure at F and F', respectively; the distances from these points 

to the object and image planes are denoted by SB and x' and the 

focal length is /. The distances os+f and a?' + / are designated p 

and p', respectively. "With this notation it is evident that

size of object (AB) ^p j^ j 

size of image (a&) / p' /

(1)
388 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

By equating the last terms and simplifying the expression it can 

be reduced to the easily remembered relation

P

1 = 1 P'-J

It is also possible to derive from the figures the relations

image size_j/ 

object size" p'

A/ A/

A/A/

N N = PLANE OP INCIDENCE 

N'N' = PLANE OF EMERGENCE.

FIGURE 15. Conjugate focal planes

(2)

(3)

(4)

. 

_ 

. . 

__ 

 . 

_ 

 x.,__  ..._  .. . 

_ _ »|« ^ i^. __ 

. _ g f - . _ 

As the scale of a map or aerial photograph is expressed as the 

ratio of size of drawing to size of original, equation 3 can be rewritten as

1 _ image size _ p'_ 

r "object size" p '

(5)

where - denotes the scale. 

r

The expression scse'=f2 is easily derived from equation 1 and is 

the condition that must be fulfilled in order to obtain a sharply 

focused image.

SCALE OF AN AERIAL PHOTOGRAPH

Equation 5 shows that the scale of an aerial photograph can be 

found from the ratio of distances to image ana object planes when 

the measurements are made from the lens or from the ratio of the
MAP COMPILATION FROM AERIAL PHOTOGRAPHS 389

length of a line measured on a photograph to the length of the 

corresponding line on the ground. The ideal condition of a horizontal plate and a horizontal ground surface must be assumed.

It is evident that under the conditions in which aerial photographs are made the distance from the camera lens to the object 

plane is the altitude (H) of the camera and corresponds to the distance p in equation 5 and Figure 15. The substitution of widely 

separated values of H (or p) in equation 5 will show that for all 

altitudes at which aerial mapping is done p' is practically equal to 

/, the focal length. This equation may therefore be written

showing that the scale can be determined by dividing the focal 

length of the lens by the altitude of the camera. It is impossible 

to obtain very accurate determinations of the scale of aerial photographs by this method, however, as the only available knowledge 

of the altitude is that given by the altimeter (barometer) carried 

.in the airplane. The method is readily used for approximate determinations if the camera has 12-inch lenses, for it follows that the 

scale is then the reciprocal of the altitude in feet. The most accurate 

results are obtained by scaling distances on the photographs and 

comparing them with the corresponding distances) measured on 

the ground or scaled from an accurate map.

A photograph is a perspective representation of the objects appearing in it, and consequently has no uniform scale throughout 

unless the objects photographed are all in one plane that is parallel 

to the focal plane of the camera. This condition is so difficult of 

accomplishment in an aerial photograph that it is never fulfilled 

exactly, although good photographic flying over level areas will 

furnish aerial photographs that are nearly uniform throughout in 

the matter of scale. Uniformity of scale can not be obtained if 

differences of elevation exist within the area photographed, or if 

the camera axis is inclined, however slightly, to the vertical, and 

consequently the scale quoted for an aerial photograph must be 

considered only an approximation. It is evident that the top of 

a plateau or mesa will photograph to a larger scale than the valley land at its base, and for the same reason all photographs of 

any but very level land can not have a given scale throughout.

This variation in scale and other displacements that exist in 

the aerial photographs make it impossible to enlarge or reduce 

them successfully to any desired scale.
390 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY 

SOME DISTORTIONS OF A PHOTOGRAPHIC IMAGE

Two types of aerial photographs are employed for mapping, differing only in the position of the camera axis at the moment of exposure. Photographs made with the axis within a few degrees of the 

vertical are called " verticals; " all others are called " obliques." As 

the condition of exact verticality of the lens axis is difficult to fulfill, 

the term " verticals " is now used to designate photographs that are 

made with the lens axis in an approximately vertical position. Photographs obtained while every effort is being made by the pilot and 

observer to maintain the camera axis truly vertical are the so-called 

" verticals "; those made with the axis intentionally inclined are the 

" obliques."

A truly vertical photograph of a horizontal ground surface that 

is, a photograph taken when the photographic plate is exactly horizontal is a reduced copy of the original and is, in a sense, a map, 

as it is a reduced horizontal projection of the original. If the camera 

axis is not exactly vertical or the terrain photographed is not horizontal this condition is not fulfilled, and a photographic image is 

obtained that shows the ground features in improper relation. Fortunately these displacements follow definite mathematical and geometrical rules and can be corrected if the factors causing the displacements are known.

If angles between points on a photographic plate are measured 

at its center it can be proved that they equal the corresponding horizontal angles that would be measured by a transit, providing that 

the photographic plate was horizontal and vertically above the 

transit station when the photograph was made. If A, B, (7, Figure 

16, represent three points on a horizontal ground surface subtending 

the angles ANB and BNC at the point TV, which is vertically below 

the aerial camera and is therefore called the nadir point, and &,&,<?, 

represent the corresponding images of these points on the horizontal 

plate, it is evident that the angles appb and bppc on the plate will 

equal the angles ANB and BNC on the ground. This equality of 

corresponding angles also exists whatever may be the elevation of 

points A, B, and (7, for although the points may be displaced on the 

plate by their position above or below the datum plane, these displacements are radial and do not affect the size of the subtended 

angles. That this is true can be seen by reference to Figure 17. In 

this figure, A is the high point, A' its projected position in the datum 

plane, ppN a vertical line passing through the lens and perpendicular to both the photographic plate and the datum plane; a' 

is the image of point A' and a the image of point A. The figure 

shows that the difference of elevation A A' causes the image point to
U. 8. GEOLOGICAL SUBVEY

17.000 1

/6000-

fSDOO

BULLETIN 788 PLATE 28

9000

Ij a0o0

GPOO

SffOO

3POO

2POO

1.000

Formula 8 -^

The correction is minus for objects above 

and plus for objects below the datum.

Sca/e h 

Distance of object above Tor below datum (feet)

DISPLACEMENT CHART
MAP COMPILATION FROM AERIAL PHOTOGRAPHS 391

be displaced on the plate from a,' to a, and as A is vertically above 

A', the triangles AOA' and aOa' are in a vertical plane which is 

perpendicular to the plate and which contains the line ppN. This 

being so, a and of must be on a radial line passing through the plate 

center pp, and thus the displacement due to the difference of elevaPhotographic plate

Nadir point (N)

FIGDBE 16. Relation of angles on photographic plate to corresponding angles on the

ground

tion can not affect the value of angles measured at the center of the 

photograph. The amount of image displacement due to the elevation of an object can be easily found from Figure 17. Let the angle 

AA"A'=a, which is identical in value with the angle ppaO, as they 

are alternate angles. The altitude of the camera lens is E, and its
392 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

focal length, ppO, is /. The following equations are easily derived 

from this figure:

,,_^LJ'sin (90°-cQ _________ (8)

sin a

The substitution of the value of A' A" given by equation 8 in 

equation 7 gives

, j[AA' sin (90°-a)] aa Esina (9)

a a' pp

FIGURE 17. Displacement of photographic image due to relief

The value of a. can be computed, for the abscissa app can be 

measured on the plate, and the focal length of the camera, /, will 

be known.

The amount of image displacement to expect can also be found by 

the chart shown as Plate 28. Its use will be apparent by reference 

to the key given on the chart itself.

Any inclination of the camera axis will distort the angles on the 

plate and render them useless for all purposes that demand exactitude in this regard. The angles are sufficiently accurate for smallscale mapping, however, if the tilt of the camera is not more than is 

ordinarily encountered in good photographic flying. A skilled 

pilot may be expected to keep his airplane within 3° of the horizontal,
MAP COMPILATION FROM AERIAL PHOTOGRAPHS 393

and as long as this angle is not exceeded no difficulty due to erroneous 

values of the central angles will be encountered in the use of the 

photographs. The effect of a tilt at right angles to the direction of 

flight is shown in Figure 18, in which the tilt is assumed as the large 

amount of 10° in order to render the effect more apparent. The 

lower portion on this figure shows in vertical section that when the

A'.

Horizontal

rrf _ --, I I ^---^

___^ - 

p/ate

FIGOBB 18. Displacement of photographic image due to tilt

camera axis is tilted images on one side of the plate are enlarged 

while those on the other side are correspondingly reduced. The 

effect of this distortion of the image is more forcibly indicated by the 

horizontal projection in the upper portion of the figure. The shape 

of the ground figure is correctly represented by AA'C'C', in which 

the side C'C is equal to A A'. The inclination of the camera dis-
394

torts the figure, however, and aa'c'c results, in which the side ao! is 

shorter than the side c'c, obviously an incorrect representation. The 

figure also shows that the tilt of the axis causes the principal point 

of the plate to move from PP to ppf and therefore distorts all 

angles measured from this point. This change in the value of the 

angles can be seen when the dotted lines radiating from pp' are 

compared with the corresponding solid lines from the point PP. 

Fortunately, very small tilts do not affect these angles so much that 

their usefulness for small-scale mapping is entirely lost, and consequently any point near the principal point of the photograph may 

be selected as the station point for the photograph. Further inspection of the figure will show that a line across the photograph midway 

between PP and pp' perpendicular to the direction of tilt is the 

only line on the inclined photograph that has the same scale as the 

horizontal photograph. This line, shown in the figure as SS, is of 

very great importance in the transformation of the oblique A, C, and 

D photographs of the T-2 camera, for as it is already at the desired 

scale the problem becomes one of reducing and enlarging the rest 

of the photograph where needed while holding this line unchanged. 

On account of this peculiarity the line is often called the " line of 

equal scale," or simply the "scale line," and its distance from the 

principal point is the distance PP-/S.

CONTROL. FOR MAPS COMPILED FROM AERIAL 

PHOTOGRAPHS

The succesful compilation of maps from aerial photographs is 

largely dependent on the qharacter of the traverse or triangujation 

upon which it is based. Both types of control can be used successfully.

Transit traverse for the control of aerial photographs does not 

differ greatly from that used in the past for the control of topographic maps, the principal differences being in the character of 

the points and the location of the lines. Road corners or intersections, streams or railway crossings, fence lines beaten out by cattle 

or defined by a growth of brush, sharp angles in wood lines, or lone 

evergreen trees standing entirely isolated are all easily recoverable 

on the photographs. Buildings are in the doubtful class, as they are 

not positively identifiable, especially when standing in a group. 

Many points commonly used in the past are useless in controlling 

photographs. Among these are gates, nails in tree roots, and iron 

posts or tablets set in rock. Where tablets or iron posts are located 

near road corners or other points that are easily distinguished on 

the photographs, these points should be used as reference for the 

permanent points. Nothing is superior to a road intersection in 

sectionized country.
395

Single-lens photographs can usually be°well controlled by a transittraverse line around and across the center of the quadrangle, but 

for multiple-lens photographs the best control is obtained only when 

points are so located that they will be found on the center and on 

each oblique print both at the beginning and end of each flight, and 

this combination is often not attained when the traverse line is run 

before the photographs are made. When the flying has been done 

well in advance of the time the field work will start it is advisable 

to make a sketch, based on the photographs, showing the most 

advantageous location of the traverse lines for the guidance of the 

control party. This may necessitate placing the line 1 or 2 miles 

inside or outside of the edge of the quadrangle, depending on the 

location of the photographs, but it will insure a more easily and more 

accurately controlled map than would otherwise be obtained.

The control of a quadrangle by graphic plane-table triangulation 

has certain advantages to the map compiler working with T-l or 

T-2 photographs and probably is more accurate than control by 

transit traverse. This greater accuracy is due to the fact that by 

triangulation numerous points can be located within the quadrangle 

and used as checks on the compilation and thus prevent the accumulation of errors of position. The plane-table triangulation must be 

carefully done, for the control sheet must be able to stand enlargement to a scale of about 1: 20,000, the scale at which the photographic 

compilation is usually made. It is advisable, particularly in wet or 

humid climates, to have the control sheets mounted on zinc before 

the projection is made, as that assures a sheet free from paper 

distortion.

Flags in trees, water tanks, church steeples and similar points 

can not be recovered positively in small-scale photographs and 

should be located by reference to something that can be identified. 

Sharp-topped hills or peaks can often be distinguished on the photographs with a stereoscope and successfully used. An accurate sketch 

of the fences, roads, and woodland around a located point is more 

valuable in identifying the point than any discription can be.

PHOTOGRAPHING A QUADRANGLE

REQUIREMENTS FOR FLYING .

The successful flying over a quadrangle for the purpose of mapping calls for rare skill on the part of the pilot and a thorough 

knowledge of the use and care of the camera on the part of the 

observer, with fine teamwork between the two. For this work a 

pilot must have not only ability to fry .his airplane but knowledge of 

the undesirable effect that certain movements of the airplane have 

58515° 28 26
396 TOPOGEAPHIC INSTRUCTIONS OF GEOLOGICAL. SURVEY

upon the photographs and the proper procedure to take to avoid 

them. There is nothing more discouraging to one who must compile 

the base maps from aerial photographs than the receipt of a shipment of photographs that immediately display the pilot's unf amiliarity with photographic flying or his carelessness. Inability to keep 

the airplane on an even keel, "banking" on the slight changes in 

direction that are made in attempting to keep on a predetermined 

course, and continuous changes in altitude are all very clearly 

indicated on the photographs and with an exactness far beyond that 

of any indicating instruments that may be carried in the airplane. 

The speed and accuracy with which a base map may be compiled 

being largely influenced by these factors, it is essential that the 

pilot should clearly realize their effect and fly his airplane in such 

a manner that it will be minimized. An exact knowledge of his 

position at all times and ability to recognize landmarks and fly by 

them can be acquired by practice and are essential to the 

photographic pilot.

In sectionized country photographic flying is best done in the 

north or south direction. This is specially important for work done 

with the single-lens camera, as the photographs can be worked up 

with greater ease and more valuable comparisons can be made with 

section-line measurements than is possible when the flights are directed east or west. For flights along stream valleys, where only the 

course of the stream is to be mapped, or for flights over country that 

has not been sectionized, courses can be chosen that are most convenient to the pilot, and with regard to the layout of control, existing or 

proposed, although in flying along a stream the changes in direction 

should be made with as little banking of the plane as possible.

The question of the correct exposure to be given to an aerial photograph is fixed not so much by the lighting of the subject as it is by 

the exposure necessary to " stop " the movement of the image on the 

film. A photographic airplane flying at 80 miles an hour is moving 

at a rate of 117 feet a second. When flying at 12,000 feet with a 

camera having a 12-inch lens the image of a given point on the 

ground will move a distance of about 0.12 inch on the plate in 1 

second. To make a sharp picture it is essential that the shutter 

exposure be short enough to prevent any blurring of the image 

on account of this movement, and it has been found that -j-^j- of 

a second will easily accomplish this end and will ordinarily prevent 

any indistinctness due to vibrations that are transmitted to the camera 

through its shock-absorbing suspension. In order that the aerial 

photographic work may be carried on at any time during reasonably 

clear weather, hypersensitized panchromatic film is used, and the
MAP COMPILATION PEOM AERIAL PHOTOGRAPHS 397

' cameras are equipped with lenses having maximum stop openings of 

f/4.5 and light filters of various degrees of absorption. American 

aerial cameras are commonly equipped with "between the lens" 

shutters, for these, although not so efficient as the focal-plane shutters, 

do not cause distortion of the image by their method of operation. 

This disadvantage of the focal-plane shutter is more theoretical than 

real for small-scale mapping, however, for the flying is done at so 

great an altitude that the movement of the image is slow and the 

resulting distortion consequently very small.

To compute the altitude at which he should fly in order that the 

photographs may be made at a predetermined scale, it is essential 

that the pilot should know the general elevation of the country 

over which the work will be done and the exact focal length of the 

camera lens. The fact that a camera has, for example, a 12-inch or 

a 6-inch lens is not sufficient to fix more than approximately the 

altitude at which the photography should be undertaken. The 

exact value of the focal length of every camera lens used for mapping should be obtainable by the pilot or observer from the records 

of his office. The altitude at which the flying should be done in 

order to obtain the desired scale can be determined by the relation

f Altitude =^

in which / is the focal length in feet and r the scale expressed as a 

fraction.

In hilly country it is impossible to have the photographs at a 

constant scale throughout, but by selecting the mean elevation of the 

country as a datum plane for determining the scale, the variations 

in this respect will be at a minimum.

After the altitude at which the flying should be done has been 

determined it is the pilot's duty to find and maintain this altitude 

while the photographs are being made. The accuracy of the altimeter 

will determine how nearly the desired altitude can be approached, 

and its readiness in responding quickly to small changes of altitude 

will determine how closely the altitude can be maintained. Although every change in level of the airplane is indicated in the 

photographs as a change in scale, this difficulty is probably the least 

troublesome of all with which the map compiler must contend and 

apparently is the feature in which photographic pilots approach 

nearest to perfection. The small-scale changes that are always to 

be expected in aerial photographs do not increase the difficulty of 

compilation or introduce errors of any kind in the resulting map 

when T-l or T-2 photographs are used, for all compilation with these
398 TOPOGRAPHIC INSTRUCTION'S OP GEOLOGICAL SURVEY

photographs is based on the radial-line method, which is independent 

of the scale of the prints. Differences in scale on single-lens photographs, however, seriously affect the compilation, as there is no 

economical way of reducing them to a common datum. It is possible 

to eliminate such differences from single-lens photographs having a 

scale of 1:10,000, or less, by using the intersection method, providing that large end and side overlaps were obtained by the pilot 

and that numerous well-determined control points exist upon which 

to base the compilation. But this is very expensive, and for several 

other reasons this method can not economically be used with singlelens photographs in small-scale map compilation. The area covered 

by a single-lens photograph is relatively small (see table on p. 399), 

and consequently it is necessary to space the control points closely 

in order to get at least three points on each photograph at the beginning of each flight. Where this distribution of points is available and the overlaps are sufficiently large the graphic control net 

can be extended with accuracy for several miles, and this distance 

would be greatly increased if it were possible to work from the 

negatives and have the advantage of using the proper stereoscopic 

instruments. For the sake of accuracy and ease of compilation it is 

well to have another line of control across the center of the area to 

be mapped that will serve as a check on the accuracy of the graphic 

control and as a basis for a new start. On a 15-minute quadrangle 

this will call for three lines of control across the area with computed 

points at intervals of not more than half a mile and preferably 

closer. Another serious difficulty is that of the time demanded to 

work up a satisfactory strong control net with the large number of 

photographs that must be handled. Still another lies in the skill 

needed to maintain accurate orientation of the prints with the short 

lines available. This difficulty arises from the fact that the longest 

line that can be used for orientation is equal to the semidiagonal of 

the photographic print. This distance is about 5 inches, whereas the 

centers of adjacent photographs will ordinarily be separated by 3 

inches. This gives a ratio of 5 to 3, which is too low to give the 

accuracy that can be obtained from tri-lens photographs having a 

ratio of 5 to 1.
MAP COMPILATION FROM AERIAL PHOTOGRAPHS 399 

Areas covered by aerial-mapping cameras

Single-lens camera, 18 by 24 centimeter (7 by 9 

inches net), 12-inch focus

Altitude 

(feet)

9,000

9,250

9,500

9,750

10,000

10,250

10,500

10,750

11,000

11,250

11,500

11,750

12,000

12,250

12,500

12,750

13,000

13,250

13,500

13,750

14,000

14,250

14,500

14,750

15,000

15,250

15,500

15,750

16,000

16,250

16,500

16,750

17,000

17,250

17,500

17,750

18,000

Scale

1: 9,000

1: 9,250

1: 9,500

1: 9,750

1:10,000

1:10,250

1:10,500

1:10,750

1:11,000

1:11,250

1:11,500

1:11,750

1:12,000

1:12,250

1:12,500

1:12,750

1:13,000

1:13,250

1:13,500

1:13,750

1:14,000

1:14,250

1:14,500

1:14,750

1:15,000

1:15,250

1:15,500

1:15,750

1:16,000

1:16,250

1:16,500

1:16,750

1:17,000

1:17,250

1:17,500

1:17,750

1:18,000

Major 

axis 

(miles)

1.278

1.314

1.349

1.385

1.420

1.456

1.491

1.527

1.562

1.598

1.633

1.669

1.705

1.740

1.776

1.811

1.847

1.882

1.918

1.953

1.989

2.024

2.060

2.095

2.131

2.166

2.202

2.237

2.273

2.308

2.344

2.379

2.415

2.450

2.486

2.521

2.557

Minor 

axis 

(miles)

0.994

1.022

1.049

1.077

1.105

1.132

1.160

1.188

1.215

1.243

1.270

1.298

1.326

1.353

1.381

1.409

1.436

1.464

1.491

1.519

1.547

1.574

1.602

1.630

1.657

1.685

1.712

1.740

1.768

1.795

1.823

1.850

1.878

1.906

1.933

1.961

1.989

Area 

(square 

miles)

1.270

1.343

1.415

1.492

1.569

1.648

1.730

1.814

1.898

1.986

2.074

2.166

2.261

2.354

2.453

2.552

2.652

2.755

2.860

2.967

3.077

3.186

3.300

3.415

3.531

3.650

3.770

3.892

4.019

4.143

4.273

4.401

4.535

4.670

4.805

4.944

5.086

Three-lens camera (T-l), 6.4-inch focus

Altitude 

(feet)

7,000

7,250

7,500

7,750

8,000

8,250

8,500

8,750

9,000

9,250

9,500

9,750

10,000

10,250

10,500

10,750

11,000

11,250

11,500

11,750

12,000

12,250

12,500

12,750

13,000

13,250

13,500

13, 750

14,000

14,250

14,500

14,750

15,000

15,250

15,500

15,750

16,000

Scale

1:13,125

1:13,594

1:14,062

1:14,531

1:15,000

1:15,469

1:15,937

1:16,406

1:16,875

1:17,344

1:17,812

1:18,281

1:18,750

1:19,219

1:19,687

1:20,156

1:20,625

1:21,094

1:21,562

1:22,031

1:22,500

1:22,969

1:23,437

1:23,906

1:24,375

1:24,844

1:25,312

1:25,781

1:26,250

1:26,719

1:27,187

1:27,656 '

1:28,125

1:28,594

1:29,062

1:29,531

1:30,000

Major 

axis 

(miles)

3.977

4.119

4.261

4.403

4.545

4.688

4.829

4.972

5.114

5.256

5.398

5.540

5.682

5.824

5.966

6.108

6.250

6.392

6.534

6.676

6.818

6.960

7.102

7.244

7.386

7.528

7.670

7.812

7.955

8.097

8.239

8.381 8.523

8.665

8.807

8.949

9.091

Minor 

axis 

flmiles)

1.139

1.180

1.221

1.261

1.302

1.343

1.383

1.424

1.465

1.506

1.546

1.587

1.628

1.668

1.709

1.750

1.790

1.831

1.872

1.912

1.953

1.994

2.034

2.075

2.116

2.157

2.197

2.238

2.279

2.319

2.360

2.401

2.441

2.482

2.523

2.563

2.604

Area 

(square 

miles)

5.41

5.80

6.21

6.63

7.06

7.51

7.97

8.45

8.94

9.44

9.96

10.49

11.06

11. 59 .

12.16

12.75

13.35

13.97

14.59

15.23

15. 89 .

16.56

17.24

17.94

18.65

19.37

20.11

20.86

21.63

22.41

23.20

24.00

24.83

25.66

26.51

27.37

28.25

CHOICE OF SCALES

The scale that should be chosen depends largely on the use for 

which the photographs are intended. The single-lens type of photograph is usually needed in regions where there is a great concentration of culture, as in cities, and where there is need for extreme 

sharpness of image. It has been found that a scale of 1:12,000 is 

sufficiently large to show all the detail that can be included on the 

map, and on this scale it is possible to cover a sufficient area at 

each exposure without flying at extreme altitudes. The multiplelens photographs allow a great variation of scale owing to the short 

focal length of the lens used with this type of camera. Scales as 

small as 1:31,680 cart be obtained with this camera without requiring the pilot to fly at extraordinary heights. A scale as small as 

this is advantageous, inasmuch as with it the quadrangle is covered 

by fewer photographs and less ground control is needed. Experience 

has indicated, however, that larger scales will serve the topographer's 

need better, as it is difficult to distinguish buildings and other small
400 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL, SURVEY

objects on a scale of 1:31,680. A scale of 1:20,000 or slightly 

smaller seems very satisfactory for the compilation of maps for 

publication on a scale of 1:62,500, as all necessary detail can be distinguished easily on the photographs, and a 15-minute quadrangle 

can still be covered by three flights of the airplane. With this 

scale, the sheet on which the base map is drafted is small enough 

to be easily handled, but that is hardly true with a scale much 

larger.

OVERLAPS AND " CRABBING " OF PHOTOGRAPHS

A large overlap of the photographs in the direction of flight is 

absolutely essential to map compilation by the radial-line method, for 

every point must appear on at least three consecutive prints of a 

flight in order to make this method operative. This can be accomplished only by so timing the exposure that the overlap shall; never 

be less than about 60 per cent. An overlap of less than 50 per cent is 

equivalent to a shutter failure so far as the compilation is concerned, 

for it halts the progress of the work just as effectively as a missing 

photograph. A lateral overlap is also necessary, in order that adjacent flights may completely cover the area to be photographed, without leaving a strip of unphotographed country between them. This 

lateral overlap should preferably be about 30 per cent, which effectively ties the two flights together and strengthens the entire net of 

graphic control. Smaller overlaps than this have the disadvantage 

of giving weak ties between the flights and should therefore be 

avoided. The size of the angles of intersection between flights can 

be somewhat increased by rotating the camera in its mount so that it 

makes an angle of 10° to 15° with the direction of flight. This procedure is particularly valuable with the T-1 type of photograph but 

is not so necessary with the T-2 type. Rotation, or " crabbing " of 

the camera, as it is sometimes called, should not be allowed to exceed 

15°, however, as a greater angle renders it extremely difficult to control the photographs by the usual method of running transit control 

lines.

LABORATORY WORK

The development and fixing of the exposed negatives need not be 

considered here, as the process does not differ greatly from the usual 

method of developing panchromatic film or plates and has no bearing on the work of the topographer. The fact that the film is 

in rolls ranging in length from 100 to 380 feet makes it necessary 

to develop the film by the tank method and is probably the most 

unusual feature of this work.
 MAP. COMPILATION FROM AERIAL, PHOTOGRAPHS 401 

NUMBERING THE NEGATIVES

The films must be numbered in order to identify the prints and 

to show the order in which the exposures were made. If the job 

is a large one in which several rolls of film were used the rolls may 

be numbered separately, and then the consecutive exposures, beginning 

with 1 for each roll, but consecutive numbering throughout a job 

is much simpler and more satisfactory to the map compiler. The 

film from multiple-lens cameras m'ust be numbered in triplicate or 

quadruplicate, as the A, B, C, and D prints of each exposure must 

carry the same number. The numbering is done on the margin 

of the film in a space provided for that purpose adjacent to the 

shadowgraph showing the camera number. The figures should be 

put in with black India ink in order that the numbers may print 

sharply. The single-lens photographs can be numbered in any 

corner, although it is helpful to have the number always appear 

in either the northeast or the northwest corner, as this indicates the 

north direction on the print and is thus a great time saver.

TRANSFORMATION OF OBLIQUE NEGATIVES

The transformation of the oblique A, C, and D negatives and the 

contact printing of the B negatives is the next step in the preparation 

of the photographs and is another photographic process in which 

the topographer is only indirectly interested. The transformation 

has been so greatly simplified that it is now not much more difficult 

than contact printing. The careful registration of the negatives 

with certain index marks in the camera is the only step calling for 

special care, but this must not be slighted if the A, C, and D prints 

are to match the B prints properly. Even a slight inaccuracy in the 

adjustment of a negative in the holder will so distort the print that 

it will be useless for intersection work.

INDEX MAPS OF AERIAL FLIGHTS

After transforming the negatives the pilot and photographer must 

prepare an index sketch, or map, on which is shown the approximate 

location of each strip flown, the direction of flight, and the numbers 

of the prints at the beginning and end of each strip. This is most 

easily done by making the index on the best map available, but if 

no map exists a sketch of the quadrangle should be made and the 

area covered by each flight indicated. This sketch should give also 

the date and hour of the flight, ag these data are sometimes needed 

in the compilation.
402 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

OFFICE PROCEDURE

The unmounted prints and the index map are then sent to the 

compiling office, where they are mounted and indexed preparatory to 

the map compilation. The mounting can not be undertaken without 

a knowledge of the correct alinement and the proper separation of 

the A, B, C, and D prints. The position that the prints must have 

in relation to each other when mounted varies slightly for different 

cameras but is a fixed relation for any one camera. A drawing showing the proper position of the four indexes of each photograph is 

prepared and used as a copy in the preparation of lithographic 

prints on heavy paper. The prints are trimmed and " dry mounted " 

on these sheets, with each axis of the individual photographs superimposed on the corresponding axial line on the mount. Oblique 

prints that have been correctly transformed and mounted will make 

a perfect joining with the image on the B print, and "the axes of all 

will fall in the proper positions on the mount. The failure of the 

assembled composite print to meet these conditions indicates faulty 

transformation and can be corrected only by a retransformation. As 

the successful use of multiple-lens photographs depends largely on 

their mounting, it is important that great care be given to this part of 

the work.

The assembled composite multiple-lens photographs or the singlelens prints, as the case may be, are numbered consecutively and then 

filed until they are needed for map compilation. The numbers are 

entered on cards, which are filed by quadrangles or projects and 

which contain all pertinent information regarding the aerial photographs and the map compilation to be based on them.

COMPILATION OF MAPS FROM AERIAL PHOTOGRAPHS

Aerial photographs can be assembled for use in compiling a map 

in various ways. Experience acquired during several years indicates 

that it is necessary to select that method of compilation which will 

give the most accurate determination of positions for each individual 

area. The conditions that largely control this selection are the type 

of photograph and the relief of the area to be mapped. The lack 

of horizontality of the photographic film at the moment of exposure 

affects the usefulness of the photographs severely, but as this condition reflects the skill of the pilot and the flying conditions at the 

time it can not be accurately determined in advance by the map 

compiler. However, when the photographs are known to be badly 

distorted by tilt this fact should be kept in mind in selecting the 

method of compilation. The methods commonly used by the Geological Survey in compiling maps from aerial photographs are referred
U. B. GEOLOGICAL SURVEY

73" 52'30"

BULLETIN 788 PLATE 29 

73° 47'30"

73° 47'30"
MAP COMPILATION PROM AERIAL PHOTOGRAPHS 403

to as the straight-line method, the section-line method, and the radialline method. For some uses a picture is more valuable than a map, 

and a mosaic should be constructed.

STRAIGHT-LINE METHOD

The straight-line method can be most advantageously used to 

assemble aerial photographs of the single-lens type having large 

overlaps, in which the distortion of the images due to tilt of the 

camera or to relief of the terrain is a minimum. To utilize this 

'method it is well to regard the photographs extending from one 

known control point to another control point as portions of a traverse 

line. The evenness and regularity with which the photographic work 

was accomplished and the amount of ground relief will then determine whether it is best to use a single straight line throughout for 

orientation, or to break the flight up into several smaller sections. 

For a country of small surface relief it will generally be possible to 

utilize a single straight line for orientation of the photographs.

The principal point of each photograph should be located approximately by drawing its two diagonals, after which the photographs 

should be laid out in regular order on a large table and fitted together as accurately as possible by photographic images alone. A 

straight edge is then placed on the assembled photographic strip and 

so adjusted that its edge will pass as closely as possible to the principal point of each of the photographs, the fact being kept in mind 

that a well-selected line should have an equal number of principal 

points at equal distances to each side. The line indicated by the 

straight edge should be transferred to the end photograph that is 

uppermost in the strip of photographs, by carefully drawing a fine 

sharp line along the straight edge. This line is drawn on only one 

photograph. The photographs are then taken up from the drafting 

table in order to extend the straight line onto each photograph in 

turn. On the straight line drawn on the first photograph and in the 

region overlapped by the second photograph two points as far apart 

as possible are selected. These points should be very sharply defined, in order that they can be positively identified on the second 

photograph. Through these two points so identified on the second 

photograph a fine sharp line is drawn and produced to each side of 

the photograph. This process is repeated with the second and third 

photographs, and so on until such a line has been drawn on each photograph in the strip. There now appears on each photograph a line 

that is identical in azimuth with the lines on all the other photographs. A straight line is then drawn on any large sheet of paper 

as a guide, and the first photograph is placed over it, so oriented that 

the line on the photograph will coincide with the line on the paper.
404 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

This photograph should be held in place in any convenient manner, 

and the second photograph should be similarly adjusted over the 

guide line and slipped along with the same orientation, until any 

point on or near this line is exactly above the same point on the first 

photograph. The process is repeated with the third and succeeding 

photographs. These photographs are then as accurately joined as is 

possible by this method and should be permanently fastened together 

in this position.

It is often impossible to utilize a single straight line from beginning to end of a flight on account of the disposition of the photographs. If the airplane was badly " crabbed " with respect to the 

line of flight on account of adverse winds, or if the line of flight 

was irregular, it will be found impossible to select a single straight 

line that will not depart a considerable distance from the line of 

principal points. In this event a line should be selected that will 

fulfill the desired condition for as large a number of adjacent photographs as possible, and one or more additional straight lines 

should be similarly selected for the remainder of the strip. Usually 

two lines will be sufficient to control a strip of the length ordinarily 

occurring between fixed control points.

In any event the entire strip of photographs extending between 

fixed control points should be laid out and fitted together by photographic images as described above for orientation by a single 

straight line. The directions of the two or more guide lines can then 

be determined from inspection of the principal points of the photographs, and the one or more photographs on which an intersection of the guide lines should be located can be selected. The guide 

lines should then be transferred to the one or more photographs on 

which bends in the composite guide line occur, making the intersections or bends at the principal points of the photographs. Working 

in both directions from the photograph on which the first bend 

occurs the guide lines should be transferred to each photograph in 

turn as described above for a single guide line. If more than two 

guide lines are necessary, the transfer of the second guide line should 

be duplicated, working forward from the first bend and backward 

from the second, and the best possible adjustment should be made in 

the final orientation. The angles between adjacent guide lines are obtained from the photographs on which the bends occur. The first 

angle should be reproduced on the guide sheet and the courses carefully extended. The photographs are then oriented and adjusted 

as described above for a single guide line except that the work is 

started at the first bend and carried in both directions. If more 

than two guide lines are used, the adjustment of the photographs 

along the second course should be carried to the second bend. If
MAP COMPILATION FROM AERIAL PHOTOGRAPHS 405

there is an appreciable difference between the projected guide line 

and the one originally drawn at the second bend the photographs 

should be readjusted, beginning at the second bend and working 

backward until the 'discrepancy disappears. In any event the adjustment of the third course should be commenced at the second bend 

and carried forward from the original position and direction of 

the plotted guide line.

The best location of the control points with respect to the guide 

line and the centers of the photographs will be obtained by intersecting the control points from the principal points of the photographs on which they appear. These intersections are made on the 

sheet on which the guide line is drawn. Location of the control 

points by this method is particularly important if these points fall 

near the edges of the photographs.

The data desired from this strip mosaic, as it is commonly called, 

can then be reduced to the scale of the map either by pantograph or 

by photography, the amount of reduction being determined by comparing the map distance between the control points with the distance 

indicated on the photographs. If the reduction is made photographically, it will be necessary to trace in ink the data desired before 

reduction. This process gives a narrow strip map showing an area 

extending between known control points on a scale that very closely 

approximates the scale of the map that is to be drawn. This strip map 

is very much like a road traverse by a topographer who has extended 

his sketching out to a distance of three-quarters of a mile to each 

side of his plane-table stations, except that no contours are shown. 

A number of such interlocking strip maps should be considered, 

in adjusting them to the base map, as so many traverse lines, and 

they will require the same consideration in adjustment that is given 

to plane-table traverse. It will be found, however, that the photographic strip maps will have very small discrepancies in scale, 

probably not over 50 or 100 feet, and they can easily be adjusted 

to true distances.

In many areas known control points may not be available for 

determining the mean scale of the photographs, or for fixing the 

strip in proper position on the "compilation sheet. The proper procedure under such conditions can be determined only after a careful 

study of the material and data available. In general, the photographic strips on which two or more control points occur should 

be adjusted first. The photographic strips without control will then 

be dependent on these adjusted strips for position and scale. If the 

photographs reveal any straight lines, such as roads, railroads, or 

section or fence lines, passing from one adjusted strip to another, 

these should be carefully noted, as they are of very great help to
406 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

the map compiler in fixing the scale and orientation of all the map 

detail in their vicinity. The intervening strips are compiled by the 

usual straight-line method, definite points that exist on both the 

controlled and the uncontrolled strips being used as a basis for 

determining the scale for the new strip. A single strip can be 

added on each side of an adjusted strip in this way, and these 

in turn will serve to adjust other strips. All the skill and judgment possessed by the compiler will be called into use to obtain even 

a reasonably good adjustment under such conditions, and if the 

distance between adjusted strips is more than 3 or 4 miles the 

positions shown on the resultant map will not be of great accuracy. 

If the area has been covered by the section lines of the public-land 

system the problem is simple, as explained below.

The straight-line method will fail absolutely or will result in 

a poor orientation of the photographs if a large overlap between 

successive photographs is not obtained throughout the flight. The 

distances measured along the strip map in the direction of flight 

will be fairly accurate if the country being mapped is flat, but they 

will not be uniform in scale throughout if it has considerable relief.

SECTION-LINE METHOD

The section-line method will give excellent results with photographs 

of either the single-lens or multiple-lens type, if it is possible to reconstruct accurately the net of section lines from the notes of the 

original survey, and if these lines or their corners can be identified 

on the photographs. Roads or fences known to be On section lines 

offer the best means of identification on the photographs. If the 

section lines are not marked on the ground so as to show on the 

photographs, it will be necessary in advance of the flying to mark 

the section corners by large white markers, such as white cloth 

banners or whitewash crosses on the ground or white banners in trees.

With a line of transit traverse extending around the quadrangle 

and another across the center in an east-west direction it is possible 

to reconstruct the land net with the accuracy demanded by the usual 

field-map scales, even if the surveyor's chain used in the original 

survey was not true in length. In this case a correction is obtained 

for the particular chain used by the surveyor, by comparing true distances between transit-traverse points with corresponding distances 

as measured with the chain. For this comparison it is permissible 

to use scaled distances between carefully plotted transit-traverse 

points, so that it is possible to make numerous determinations of 

this correction, both in north-south and in east-west directions. The 

photographs can then be adjusted to the net of section lines, because 

known points are available at each section and quarter-section cor-
MAP COMPILATION FROM AERIAL PHOTOGRAPHS 407

ner, and the desired data can be reduced by the pantograph or by 

photography and transferred to this net. This method should always be used wherever it is possible to obtain a good adjustment 

of the public-land net.

It may be found impossible to reconcile the distances given by the 

photographs with those of the adjusted land lines. This indicates 

that the adjustment is at fault, either locally or as a whole. It is 

often possible to obtain a better adjustment by disregarding the notes 

of the original survey and reconstructing the net wholly from data 

taken from the photographs. This method is slow and should be 

undertaken only when absolutely necessary, for it calls for a very 

close analysis of all the data available to the map compiler. The 

errors that were bound to creep into the notes of old surveys, because 

the azimuths of the lines were determined by magnetic compass, are 

often clearly indicated in aerial photographs by slight bends in the 

lines that the surveyor intended to be straight. These slight deviations in azimuth can be detected and measured on the photographs 

with a fair degree of accuracy.

In order to reconstruct the net of section lines from the photographs, it is advisable to lay down the meridional lines first. These 

lines are more likely to be straight than east-west lines, and they have 

the great advantage that they can be traced between transit-traverse 

points on a single set of north-south overlapping photographs. The 

overlap is very valuable in detecting bends in the section line that is 

being traced. Should a section line be followed in this way and 

found to be straight, it can be drawn on the map with confidence, for 

it is manifestly impossible for a topographer working on a field scale 

of 1:48,000 to detect deviations that the map compiler, can not find 

on photographs having a scale of 1:12,000. The section corners can 

be tentatively plotted along such lines by applying the accepted correction to the chained distances as given in the field notes of the 

original survey. The photographs should then be carefully examined in order to find any east-west lines that are straight between 

transit-traverse stations. These are more difficult to find than northsouth lines, for in general they are bent, many of them are offset 

on the range lines, and they are difficult to handle because it is 

necessary to use photographs from many different flights, between 

which there is not usually a large overlap.

A well-constructed index map is a great help in this work, as it 

will show the photographs that are adjacent in a lateral direction 

and enable the map compiler to follow rapidly the section line that 

he is investigating. As the later overlap is usually very small 

it is of no help in detecting bends in a line. Fortunately, such 

bends are generally found at section or quarter-section corners, 

and a test with a straightedge will determine whether the line is
408 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

straight through such points. Such east-west lines a§ are found 

by this test to be straight throughout are then added to the map, 

and their intersections with the straight north-south lines previously 

placed on the map are carefully marked as the most probable locations of these corners. If such located corners do not agree in 

position with those obtained by applying a correction to the chained 

distances, the latter should be abandoned. The north-south lines 

in which bends occur can now be handled more easily. Such lines 

should be reconstructed on tracing paper to the map scale, the 

angular value of the bends being obtained from the photographs. 

These lines when transferred to the map sheet will give other welllocated section corners at points where intersections are obtained 

with lines previously fixed in position. The remaining corners can 

usually be located by the corrected chained distances, such locations 

always being checked by the photographs.

When other methods fail to give satisfactory location of corners 

on east-west lines, they may be fairly well located by data obtained 

from the photographs, if the line is controlled at both ends by 

transit-traverse points. This can be done by reconstructing the line 

on tracing paper and adjusting it between the transit-traverse points 

on the map. To obtain the most probable azimuth for each section 

of the east-west line a tracing is made of the north-south lines that 

have previously been fixed in position on the map, and to this as a 

base the east-west lines from the photographs are added, the mean 

azimuth of each section being used as the best value. These northsouth lines are numbered in order from west to east. The mean 

bearing of each east-west line should be used, for it will be found 

that the azimuths of such lines, 1 mile in length, are not always 

the same when determined from each end. These mean bearings 

can be determined graphically, as follows: Place the tracing of the 

north-south section lines so that the line passing through the fixed 

control point on the west side is superimposed on the corresponding 

line ~ on the photograph. Copy the east-west line desired and mark 

the point where it cuts the north-south section line No. 2. Adjust 

the tracing in such a manner that line No. 2 is superimposed on its 

image on the next photograph to the east, and the same east-west 

line passes through the primary point on line No. 1. Mark the 

point where line- No. 2 is cut by this east-west line. If this point 

differs from the position obtained previously, use a point midway 

between them as the true position for this corner. Continue the 

location of corners across the entire sheet in this manner, until the 

transit-traverse point on the east side has been located. The section line shown on the tracing can then be transferred to the map.

The adjustment of the details that make up the body of a map 

compiled from single-lens photographs is not difficult if the lines
MAP COMPILATION PBOM AERIAL PHOTOGRAPHS 409

representing the public-land system have been accurately adjusted. 

If the amount of detail to be taken from the photographs is not large, 

it will probably be best to pantograph the strip mosaics on tracing 

paper and adjust them to the section lines as plotted on the final 

map sheet. It has been found that better copy is obtained from the 

pantograph if a steel stylus is substituted for the usual pencil reproducing point. This stylus should have a thin conical point, 

slightly ro'unded on the end so that it will not tear the carbon paper 

over which it will work. The tracing paper on which the reproduction is to be made is fastened to the drawing table in such manner 

that it is possible to slide a sheet of carbon paper beneath it. The 

carbon surface should be upward, so that the movement of the steel 

point over the tracing paper will cause the drawing to be reproduced 

on its lower surface. The particular advantage of this method of 

operation is that an extremely fine, even line is obtained and that 

by using carbon paper of different colors, the drainage, culture, and 

woodland features can be shown separately, thus making the drawing more legible. Added advantages are that the steel point rarely 

needs sharpening and the drawing may be transferred to the map 

sheet readily by rubbing with a burnisher.

It will generally be found that all s'uch pantographed detail 

will require some adjustment to fit the control scheme, owing to 

the fact that any photograph may not have a constant scale throughout, as has been explained elsewhere in this chapter. This variation 

in scale is due to inclination of the photographic plate at the moment 

of exposure and will generally be exhibited as a contraction in size 

of image on one side of the line of flight and an enlargement on the 

other side.

In mapping areas of great detail it may be advisable to ink on 

the face of the photograph the detail that is to be shown on the 

map, using a waterproof black ink. The photographic jmage can 

then be bleached out, leaving only the inked lines on a white surface. This line drawing can then be reduced photographically to 

the desired map scale and adjusted to the correct position on the 

map. '

EADIAL-LINE METHOD

The radial-line method of compiling a map from aerial photographs is practically restricted to the multiple-lens type of photograph, because the lines available for orientation on single-lens 

photographs are not sufficiently long to give the best resiilts. This 

objection to the use of single-lens photographs largely disappears 

when the map scale is very large or when great difficulty is encountered in joining the prints by image points owing to displace-
410 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

ments caused by the relief of the terrain or tilting of the aerial 

camera.

On account of the extremely large angle of view utilized in the 

multiple-lens camera, slight tilts of the airplane or small differences 

of elevation of the ground surface have very pronounced effects on 

the photographic image near the outer limits of the angle of view. 

With ordinary good flying by the pilot, and only small differences 

of elevation on the ground surface, these effects do not greatly increase the difficulty of utilizing the photographs for small-scale 

maps. The comparatively large displacements at the edges of the 

multiple-lens photographs are very valuable in indicating the 

amount of the displacement due to tilt that exists near the center of 

the photograph. In the ordinary single-lens photographs the angle 

of view is so small that it may be impossible to determine whether 

the photograph is undistorted or not, for the distortions, if present, 

are not readily apparent to the eye. In using the multiple-lens photographs, however, it can be safely assumed that if known parallel 

lines or right angles near the edge of the field of view are shown as 

such in the photograph, then the image near the center must be free 

from distortion caused by tilting of the airplane, and will have a 

constant scale throughout.

The principle utilized in the radial-line method of compiling a 

map from tri-lens photographs is that if from any unknown point 

the two angles to three instrumentally determined points are observed, then it is possible to compute the location of the unknown 

point and the azimuth of any or all three of the unknown lines. 

This is the three-point problem, familiar to all triangulators. If 

the two observed angles are carefully plotted on tracing paper,, it is 

possible to shift the tracing until the three radial lines pass through 

the three corresponding known points, as plotted to scale on the 

drawing. The unknown station, which is represented by the point 

from which the radial lines diverge, is then located correctly with 

regard to the known stations. This graphic method of solving the 

three-point problem is known to all topographers and is commonly 

called the tracing-paper solution. It has the advantage that all 

the known points visible to the topographer can be utilized in solving the problem.

The best determinations of position and orientation are obtained 

by this method if the angles are large and the distances to known 

points are comparatively great. The tri-lens or four-lens type of 

photograph is superior to the single-lens type both in size of angle 

and in length of line available for orientation, and for this reason the 

single-lens type will not be considered in describing this method.

Multiple-lens photographs that will enable the map compiler to 

distinguish houses and other fine detail with reasonable certainty
MAP COMPILATION FROM AERIAL, PHOTOGRAPHS 411

should have a scale of 1:20,000 or slightly larger. Compiling the 

map to approximately the mean scale of the photographs has the 

advantage that many of the data desired can be transferred directly 

from the photographs to the map with only slight adjustments in 

position. However, a map of a 15-minute quadrangle on a scale of 

1:20,000 is large and hard to handle, and, if practicable, it should 

be compiled in quarter-sheet sections that is, in T^-minute sheets. 

The disposition of the control points over the area plays an important part in determining the size of the sections to be compiled as 

separate units.

The greatest speed in compilation will be attained in this type 

of work by compiling these units on tracing cloth or celluloid sheets. 

After determining an appropriate scale for the photographs covering 

a quadrangle, a polyconic projection should be made to that scale 

on celluloid or tracing cloth and the primary control plotted thereon. 

Each control point should then be carefully located and marked on 

the photographs by a small dot of red ink. To insure accurate positions and orientation of the photographs in a strip it is essential 

that one of these control points be located well to the outer edge of 

each A and C picture and a third point close to the center of the 

line of flight. This set of three control points must appear on two 

overlapping photographs. Careful inspection of the photographs 

should be made to determine where this condition is best fulfilled, 

and the compilation should be started at that point, for its accuracy 

is largely dependent on the correct disposition of these startingpoints. On the first photograph draw a short radial line in black 

ink or Chinese white through each control point from either the 

principal or the nadir point of that photograph. The principal 

point may be defined as the intersection of the optical axis of the 

camera lens with the plane of the photographic negative, and the 

nadir point as the representation on the negative of the ground 

point vertically below the camera at the moment of exposure. As 

the separation of the principal and nadir points on any photograph 

is due to the inclination of the camera that existed when the photograph was made, it follows that these points will coincide whenever 

the exposure is made with the lens axis in the vertical position.

In addition to the lines through each control point draw other 

short radial lines through other definite points that it is desired to 

locate carefully. These tertiary points, if they may be so termed, 

should be well distributed over the photograph, always including 

some to each side and along the forward edge. One tertiary point 

should always be chosen as close as possible to the radial line drawn 

in the direction of the center of the next photograph. If possible, 

identify on the first photograph the nadir point of the second photo58515° 28 27
412 TOPOGRAPHIC INSTRUCTIONS OF GEOLOGICAL, SURVEY

graph and draw a radial line through this point. With these radial 

lines drawn in "ink on the photograph it is ready for use. Place the 

tracing cloth on which the control points have been plotted over this 

photograph and shift it until each plotted point falls on the corresponding radial line on the photograph. The photograph is then in 

correct orientation, and the nadir point or the principal point, as the 

case may be, is correctly located. Mark the position of the nadir 

point on the tracing with the number of the photograph for identification. From the point representing the nadir point trace the 

radial lines to the tertiary points previously selected on the photograph and to the point representing the nadir point on the next 

photograph. This photograph may then be removed from under the 

tracing. Prepare the second photograph by drawing short radial 

lines from the nadir point or principal point to the control points 

previously identified on the first photograph and to all tertiary 

points that are to be located, including all the tertiary points that 

coincide with those selected on the first photograph and any new 

ones on the forward edge of the second photograph. Draw also a 

radial line to the point representing the nadir point of the third 

photograph if it can be identified. The second photograph can then 

be placed under the tracing and oriented by causing the plotted 

control points ta fall on the corresponding radial lines, as was done 

for the first photograph. This adjustment should be carefully inspected to see that the radial line traced from the nadir point of the 

first photograph to the point representing the nadir point of the second photograph actually falls over the nadir point of the second 

photograph. If this condition is satisfied, the photograph is probably well oriented, and its nadir point can be marked and numbered 

on the tracing. The radial lines to the tertiary points should then be 

carefully copied on the tracing. It will be found that the radials to 

a tertiary point drawn from the nadir points of the first and second 

photographs will intersect, but at a point that probably does not 

coincide with the image of the point on either photograph. This 

intersection, however, should be the true position of the point, regardless of any distortions existing in the photographs, if the angles of 

intersection are not too acute and the nadir points of the photographs 

are exactly known.

The third photograph is handled in the same manner as the first 

and second with the exception that the three original control points 

will not appear on it. Points located by good intersections must 

be used for orientation of this and succeeding photographs, until a 

photograph made where the flight again crossed a control line is 

reached. Points on this control line are then intersected on the 

tracing in the same manner as other tertiary points, and this operation is a check on the accuracy of the position carried forward by
MAP COMPILATIOISr FROM AERIAL, PHOTOGRAPHS 413

the photographs. The closure of this line on fixed points near the 

line of flight will probably indicate a small error in distance and 

a very small one in azimuth. If this error is very small it can 

be neglected in view of the large reduction to which the drawing 

is subjected before reaching the topographer, but if it is too'large 

to be neglected the work should be repeated until the closure is 

satisfactory. The intersected points falling in the outer portions 

of the wing pictures may be expected to be out of position laterally, 

owing to the acuteness of the angles of intersection. They serve 

to orient the photographs, however, and the location of each is 

strong in the general direction of the radial lines, but their preliminary positions must be used with care in the final compilation.

In flying over a quadrangle to obtain multiple-lens photographs 

for use in mapping, the pilot will often either purposely or accidentally overlap one flight a considerable amount on another. 

This overlap is of great help to the map compiler, as it strengthens; 

his work by eliminating the most acute intersections near the outer 

ends of the photographs, and moreover, it gives him many common 

ties between the two flights which will necessarily bind them together more rigidly than if the two flights overlapped but a small 

amount. Probably the strongest combination is obtained by overlapping the flights more than 50 per cent. This will result in a 

series of photographs showing on their outer wings about half of 

the area photographed on the central part of each photograph in 

the adjacent flights. Points along the center of a photographic 

flight are more accurately located than points shown elsewhere on 

the photographs, and if they appear on the wing pictures of the 

adjacent flight they can be used as points of control for that flight.

To make the best use of this method it will be necessary to build up 

the tertiary control net from the two or more overlapping flights 

simultaneously, assembling three pictures made in the first flight, 

then three in the second, three in the third, and so on as far as the 

large overlap extends. Intersections from other photographs in these 

flights can be built up gradually in the same manner, using a few 

photographs from each flight at a time. To work most rapidly by 

this method and to insure the use of the same points in the overlapping region, it is well to select and mark the points that will be used 

before undertaking the work of intersection. If difficulty is experienced in identifying the points readily, they may be numbered. The 

nadir point is more accurately located than other points of a photograph; consequently it should be identified on the wing pictures of 

the adjacent flights, if possible, and used as a fixed point in the 

control net.

The accuracy of acute intersections such as occur on the wing 

prints or tri-lens photographs is greatly increased when four-lens
414

photographs are used, for these acutely intersecting lines may be 

strengthened by an additional line from the D photograph of the 

adjacent flight, provided that a normal lateral overlap of flights 

has been attained. This strengthens the entire compilation so much 

that rotation of the camera in its mounting in order to increase the 

angle of intersection on the wings, the usual practice with a tri-lens 

camera, is unnecessary.

. If the scale of the projection has been carefully chosen to .fit that 

of the photographs, it will be found that the tertiary intersected 

points that correspond to points near the center of the photographs 

agree very closely, but that those toward the outer edges will diverge. 

In flat, country this discrepancy will be due to tilt of the airplane at 

the moment of exposure and will generally be exhibited as a reduction in scale on one side of the line of flight and a corresponding 

enlargement on the other side; in mountainous country it will be due 

to a combination of the displacements caused by tilt and by the relief 

of the terrain. The effect of this combination of two distortions of 

the image may be puzzling at times, for it is possible for the tilt to 

neutralize the effect of the relief on one side of the line of flight while 

increasing it on the other side. These two distortions occur in all 

aerial photographs, and their relations are so involved that they can 

be separated only by reprojecting the negative and eliminating the 

effect of the tilt. This procedure requires a knowledge of the elevation of ground points and special equipment for measuring the coordinates of these points on the negatives, and at present it is not 

practicable for small-scale mapping.

It is good practice to select road corners or bends in roads as tertiary points for intersection, as they serve the double purpose of 

controlling the map and building up the road net at the same time. 

If the road corners have been or can be located on the tracing by 

intersection, it will be an easy matter to build up the entire road net 

by simple inspection of the photographs if the roads are straight lines 

or by adjusting the intersected points over corresponding points on 

the photograph and tracing the roads directly if they are irregular.

After the roads have been satisfactorily located on the tracing it 

is well to introduce many of the more important fence lines. These 

also will serve a double purpose, for in addition to being helpful to 

the topographer in the field they break the area of the map into small 

units that are of great assistance in transferring details from the 

photographs to the base tracing. As many fence lines should be 

added as will be needed to limit the size of the inclosed parcels to 

2 or 3 square inches on the map. Near the outer edges of the photographs these parcels may well be smaller, as the distortions are 

larger in this region and there is consequently more need for ad-
MAP COMPILATION FROM AERIAL PHOTOGRAPHS 415

justment of the details. In sectionized country the correct positions 

of the fence lines are easily obtained, as each fence can generally be 

located by drawing a single radial line to the point where the fence 

intersects a road. As the road has previously been located, a single 

line cutting it at a good angle gives the true intersection. In the 

Eastern States, where property lines are irregular, it is difficult to 

locate the fences correctly, as the relief introduces apparent bends 

into them that are hard to distinguish from the real bends. Theoretically it is possible to locate these fences correctly by intersecting 

points along them at close intervals, but as the fence lines are not 

shown on the published map the result is not worth the time involved. Many fences are shown on the photographic base map, as 

they furnish some information concerning the country away from 

the roads, but it should be recognized that they are not located with 

the same care as roads. For this reason the topographer should not 

infer that his stadia traverse is in error should he fail to close on a 

fence line by a small amount. In wooded country that is being 

surveyed by means of a tape and aneroid barometer it is probably 

advisable to accept these fence lines as they are shown, for it is 

known that no very large errors of position exist in them.

When the area has thus been broken up into small parcels, the 

road and fence lines should be inked on the tracing in fairly heavy 

black lines. It is advisable to use only a single line for a road, as 

better positions can be obtained for houses adjacent to the road by 

so doing. The tracing should then be adjusted over the photographs and the details traced wherever the parcels have the same 

size and shape on both tracing and photograph. If the discrepancy 

between the tracing and photograph is small the detail on the photograph can be adjusted to an approximate position without difficulty. If the photograph is badly distorted it may be necessary to 

determine additional points on the tracing by intersection, thus 

further breaking up the area into parcels small enough to adjust 

with reasonable accuracy. As all portions of the area appear on 

at least two photographs it will often be found that an area badly 

distorted on one photograph is well represented on the adjoining 

photograph. In taking detail from the photographs the map compiler will find that he can distinguish and show with reasonable 

certainty houses, large buildings, minor roads and trails of sufficient 

importance to aid the topographer, railways, cemeteries, bridges, 

overhead and below-grade crossings, fences, and crop boundaries, 

grant lines, section lines and other civil boundaries, woodland areas, 

streams and water bodies, such as lakes, ponds, marshes, and small 

depressions holding water only during the rainy season. Familiarity with aerial photographs enables the compiler to distinguish
416 TOPOGRAPHIC INSTEUCTIONS OF GEOLOGICAL SUEVEY

usually between houses, barns, and schoolhouses, and in certain 

areas topographic features, such as cut banks and depressions, may 

be identified.

After all such detail has been traced it should be inked in black, 

using bold lines throughout. No time should be devoted to neat 

drafting, as this compilation is intended only as a guide to the 

topographer, and accuracy of position is the prime consideration. 

The photographic reduction to which this inked copy will be subjected before it reaches the topographer will sharpen it up, and 

if made too fine some of the detail might disappear in the process 

of reduction. It is generally advisable to give the exact outline 

of woodland areas and to indicate by means of the letter W or 

by the customary zigzag line that the area is wooded. Where details have been shown but not positively identified, an interrogation 

mark should be added to draw the topographer's attention to tie 

fact that they may need correction. Features that are discernible 

but not identifiable should be outlined and questioned in the same 

manner.

The position of the center of each photograph and its number 

should be marked, on the tracing in blue ink, which will preserve 

it on the original but will not reproduce on the field sheet. The 

points of control should be inked in black and marked in a distinctive manner so that the topographer can recognize them. The 

name of the quadrangle should be inked along the north edge 

of the drawing, and the quadrangle name, the file numbers of the 

photographs used, the scale of the projection, and the draftsman's 

name should be placed in the margin below the southwest corner.

The drawing is then ready for reproduction, and as it is on a 

medium greatly subject to uneven expansion and contraction, the 

usual graphic reduction scale should not be used, but the meridional 

distance desired in the reduced map should be given to the photographer. In this way the reduced drawing will be to the desired 

scale along the meridians but will probably be off scale a small 

amount in the east-west direction, on account of uneven expansion or 

contraction of the tracing cloth. This will not affect the accuracy 

of the field work and can be eliminated in reproducing the map 

for publication.

Photolithographic prints in nonphotographic blue are made on 

double-mounted paper, and additional prints in black are made on 

map paper. The black-line prints are made as office records and 

for the convenience of the topographer, as they are more legible 

than the blue-line prints. They provide a base on which may be 

shown information collected but not placed on the field sheet. Plate 

29 shows one of these sheets as it goes to the topographer.
MAP COMPILATION FROM AERIAL PHOTOGRAPHS 417 

MOSAICS

For the interpretation of certain features of the terrain photographs are so much more valuable than maps that it may be 

advisable at times to assemble the photographs as a composite 

picture, rather than use them for map construction. Such composite pictures are called mosaics. They may be either controlled or 

uncontrolled.

Controlled mosaics may be used in map construction under some 

conditions, but their usefulness is generally restricted to the commercial field to meet demands for local detail in city planning, laying out power lines, and other projects of similar nature. For this 

reason their construction is described only briefly.

The fact that a mosaic will not be accurate in scale should not 

be overlooked. The type of topography, the character of the flying 

accomplished by the pilot, and the skill of the mosaic builder all 

have their effect on the scale of the compilation.

For uses in which accurate scale is not important and the relative 

position of local details alone is needed an uncontrolled mosaic may 

be used to advantage. In a mosaic of this type the photographs used 

in the compilations are tied together only by their images, and consequently any displacement cf the image existing in the photographs, 

due either to tilt or to relief, will have its disturbing effect on relative 

positions and scale. The best mosaics of this type will be obtained 

where the terrain has but slight relief. Multiple-lens photographs 

are not satisfactory for mosaic construction, as even slight tilts 

distort the images on the wing pictures severely.

An uncontrolled mosaic may be built around a single photograph 

as a nucleus or it may be built laterally from a single flight accepted 

as a base flight. In building around a single photograph the prints 

are fitted together as accurately as possible by matching images, and 

when satisfactory junctions have been obtained they should be pasted 

down on compo board or some other firm mounting surface. In 

pasting the prints to the mounting board overlapping should be 

kept at a minimum, as it will increase the thickness of the mosaic 

in such portions and consequently increase the difficulty of obtaining an even illumination over the surface when it is copied photographically. Evenness of illumination is greatly improved by beveling the overlapping edges. Prints that do not match in scale the 

one that has been already fixed to the mounting board can be enlarged 

or reduced to fit. Such changes in the prints should be avoided if 

possible, however, for they can easily be the cause of much trouble 

if the photographs are distorted and not merely off scale. Any correction applied to a print that is off scale but not distorted will 

affect the entire print equally; but if an enlargement should be
418 TOPOGKAPHIC INSTRUCTIONS OF GEOLOGICAL SURVEY

applied to a tilted photograph to make its contracted edge join 

another print, it will be found that the enlarged edge of the tilted 

photograph has been still further enlarged and the error on that side 

increased. In regions where the relief is sufficient to distort the 

images- appreciably the photographs should be taken with very large 

overlaps and only the middle portions used in making the mosaic. 

This procedure reduces the effect of the distortion but does not eliminate it, and some difficulty is bound to occur in matching the prints. 

Moreover, the areas that stand above the accepted datum plane .are 

bound to have a larger scale than the rest, and nothing that can be 

done to the prints will alter that fact.

A mosaic compiled around a single photograph, as just described, 

will have as a scale the scale of the nucleus photograph if the matching was well done. Some other scale can be obtained in copying if 

the distance between two positively indentifiable points on the mosaic 

is known, or it can be obtained in the original mosaic by photographing the nucleus print to the desired scale, and reducing or 

enlarging all other prints sufficiently to match it.

More accurate determinations of position can be obtained in an 

uncontrolled mosaic by building laterally from the photographs of a 

single flight laid down by the straight-line method of orienting 

prints, already described. This procedure gives a more rigid " backbone " upon which to adjust the prints than a single print used as a 

nucleus.

Controlled mosaics are more accurate in scale and position than 

uncontrolled mosaics but are more difficult to construct. Well-run 

transit lines furnish satisfactory control when points visible on 

the aerial photographs have been located by the traverseman, and 

records of local engineering offices can often furnish data of value 

for this purpose. Triangulation is probably the least satisfactory 

of all forms of control for mosaic construction, as the stations are 

usually few and very difficult to identify on the photographs. An 

approximate form of control can be obtained by enlargement of 

an existing map, although this method has the great disadvantage 

that any error in the map will be magnified in bringing it up to the 

scale of the mosaic.

If transit traverse is used to furnish control with the usual northsouth direction of flying, it will generally be possible to find a 

control point at each end of a flight. The straight-line method 

makes possible good orientation of the photographs between these 

points, and by plotting the centers of the photographs in correct 

position with regard to the straight line the photographs are prevented from getting far out of position. The photographs of each 

flight that permits it should be tied down in the same manner. 

Advantage should be taken of any straight lines appearing on the
MAP COMPILATION FROM AERIAL PHOTOGRAPHS 419

strips laid down fitted to control by extending them as far as they 

appear on the photographs and holding the mosaic to them. Where 

control points are isolated the problem is more difficult, for it is 

necessary to build up straight-line control between each isolated 

point and the fixed strips already laid down. If the straight-line 

method is not used for this purpose, difficulty will always be experienced in obtaining the correct orientation and position for the photograph on which the isolated control point falls. The photographs 

of the mosaic that are not on lines connecting control points must 

be added by matching prints as in the uncontrolled mosaic.

The mosaic may be used in its original form or may be reproduced by photography in single sheets or in sections depending on 

its size and upon available photographic equipment. The reproduction can be made to any convenient scale.

INDEX

A Page

Abbreviations, list of_____.-__-. . 330-331

Accuracy in mapping, adjustment factor in.181-182

consistency in._________-- 184-185

control factor in.._._________-.- 181

date of survey affecting_...____-_ 186

detail and generalization affecting-. 183-184

errors and omissions affecting____. 185-186

feature-identification test for_____. 182-183

observation and plotting factors in___ 182

standards for__..-._____-.. .. 181-186

Addresses, changes of._..__.._...-.-_ 21

Adjustment, as factor in map accuracy.... 181-182

of instruments, instructions for........ 193-195

of plane-table traverse, completing work

in. ____._.___.._-_-.. ...-_.... 273

graphic method of __________ 212-214 

of public-land lines, method of_____ 376-378 

of tooography, use of celluloid transfers

in.............. .............. 282

use of tracing paper in__. ____ 282-283

reciprocal vertical angle method of___ 200

Administration, field and camp, rules for__ 10-17

Administrative office work, personnel for_. 7

Advance sheets, comment from authors and

others on.___ _____. 318

instructions for__ _________ 273,317-318

mailing list for__ ___ .._____ 318

purpose of._________.______ 318

size of edition and reprints of. ______ 318

transmission of maps for...________ 317

Aerial photographic base, inking on_ _ __ 298

mapping on.._____________ 254-255,256

topographic use of.___________ 196, 272

Aerial photographs, control for...______ 96

cultural revision by means of_____ 264-266

types used in______________ 265

differences in scale of... ________ 389

finding of scale of_____________ 388-389

index sketch of..._____________ 401

map compiled from.._ ___..__ _ 402

mounting and indexing of. ____ 402

numbering negatives of. _____ 401

overlapping required.._________ 400,413

transformation of oblique negatives of... 401

Albers projection. See Projections.

Alidade, Burkland, plate showing______ 178

Burkland, with Baldwin solar chart, use

of .......................... 224-225

new style telescopic, adjustment of side

level for..___ .___ 194 

sight, use of.._______________ 197 

stadia wires for.._______..____. 197,211 

telescopic, adjustments of . 194,199 

plate showing..._______.___ 194 

use Of--..___.___ 194-195,196,210-211 

See also Plane-table triangulation, 

Resection, and Three-point 

method, 

use of ruler of...___________ 194

Page

Altitude for photographic mapping, determining and maintenance of __ 397" 

Aneroid barometer, care of.__________ 218- 

construction of__...____... ____ 215 

elevation differences by..___._____ 216 

elevations direct by...__________ 217' 

field of use of. __....................... 214

plate showing.-..._____________ 194- 

reading of.-..______________- 218 

scale relations of-..____..______ 215 

tests for__- . 215-216

use of..._____.__..... 206, 211, 212, 216-219

useof'Tycos" type of.______.__ 217-218 

weather effect on..__.________ 218-219 

Angles, deflection, method of reading 100-101. 

deflection, computation of________ 112 

horizontal, micrometer measurement of.. 57,

62, 210

reading and recording of_ ... 62- 4 

tabulation of_._______ ... 66' 

vertical. See Vertical angles. 

Annual reports. See Reports. 

Annual summary of field 'work, preparation

of. ----- - 276

Appropriation acts, 1889-1927 ._ ________ 1-4 

Approval of topographic maps and drawings,

changes after.__________ 317,322 

instructions for..._______...... 313,316,

317, 335,336,338, 340, 344-345,354

Aqueducts, inking of...______ ... 287

mapping of----...--._____.__... 234

Areas covered by aerial-mapping cameras,

table showing...._______ 399

Assembly of field sheets, procedure in...... 272-273,

283,347,352

See also Transferring and Pasting.

Assistants, field, employment of________ 10

Authorization for topographic work__---... 1

Authorship, control, marginal credit for ... 307,320

topographic, marginal credit for___... 227,

228,306, 323, 344,349

use of diagram for________ 227,306-307,323 

Automobiles, abandonment of.__ ------ 1&

accidents with________.____ 18-19 

care of._......______________ 18

maintenance-cost record of...._____ 18

private, travel in_______________ 19

purchase of _ __ _____________ 17

State laws concerning____________ 17-18

storage of. ____._ 18

supplies for..._________.. 17,18

tags for______________ _ 17,18

Axis, optical, direction of_____ ._____ 386-

Azimuth, computation of. ___________ 67-69

observations for, making and recording of. 64-65

onPolaris-.____________ 64,101-105

on the Sun. ____._________ 105-110-

Azimuth marks, establishment of __-..--__ 95

421
422 INDEX

Baggage, personal, containers for-- 17 

Baldwin solar chart, description of - 219 

instructions for use of...- 219-^25 

orientation by.. . 223-225 

plate showing-- - 218 

.Banks, river, inking of_ - 292 

river, mapping of. - 243 

Barometer. See Aneroid barometer. 

.Base, aerial photographic. See Aerial photographic base.

Beads, glass, use of..__ 281 

.Beaman stadia arc, plate showing. 194 

use of ._____-.___________ 207-210 

See also Stadia traverse.

.Bench marks, construction of.._ 94-95,120-121

level, description of .- 125-126

distribution and locating of. 119

establishing of, after level line is run.. 121

in cultural revision, addition of.... 262-263

inking of- .-___~ 290,301,331 

mapping of. 240 

not found, reporting of_ 241 

on Federal buildings__ .120 

painted....... .__________ 121-122

plate showing... . 52 

setting of ________... 120-121 

stamping of._.___________. 122-123 

supplementary, placing of...__ 123 

traverse marks should be on suitable

sites for__'_____________ 96

tying new level lines to________ 118

vertical-angle, inking of___ _.... 290

mapping of_______________ 240-241

.Bills, payment of. . 21

Biological Survey, use of data from.____ 178,327

Bird preserves, Federal, data for. .__ 327

Birdseye, C. H., preface by ..________ v

.Blocks, business and residence, inking of__ 285

business and residence, mapping of.. . 231

house, inking of___ ._....____... 285

mapping of-. _........___ . 231

.Board of Surveys and Maps, reference to.... 178,

280, 360,362 

.Border corrections, preparation and inking

Of.. . ___ 302-303^324,341,342 

purpose of.________________. 178,302 

See also Map borders.

Boundaries, civil, inking of__ 288,325-326,327-328 

civil, legal status of.___'.......... 236,325-526

mapping of....... 95,236,325-326

monuments on, inking of._.____-... 288 

mapping of.. . . 95,237 

surveys of, National, State, park, forest,

etc..-.... __.___...... 178

See also Counties and States.

Breakwaters, inking of.____________ 287-288 

mapping of......__..___ _____ 235

Breed and Hosmer, reference to._______ 204

.Bridges, inking of-._______________ 286

mapping of-_________________ 232-233

Bubbles, setting of...___________ 54,91,191

B uildings, in general, inking of. _______ 285

in general, mapping of___________ 231

Bumstead projection plate, plate showing.. 178

use of _____...-.________ 167,175-176

Bureau of Reclamation, use of data from__ 178

Bureau of Soils, use of data from....___._ 178

Burkland alidade. See Alidade. Page 

Business and residence blocks. See Blocks.

Camera, multiple-lens, assembling of aerial

photographs taken with. ___ 406-416 

multiple-lens, description of-_ _-__. 380-384 

field of view of.____.______ 381 

plates showing..____________ 382 

scales obtainable with.. _______ 399 

single-lens, assembling of aerial photographs taken with._______ 403-409 

description of-______._____ 379-380 

plate showing. _____________ 382 

where advantageous__ ______ 399 

tilt of --_.... 392-394

tri-lens, disuse of..____________ 381

Camp administration, rules for_______.. 14-17

Canals and locks, inking of____ _____. 287

mapping of.________________ 233-234

Cartography, section of, work on general

maps by..___________ 359-366 

Celluloid transfers, use of____________ 282 

Cemeteries, inking of._____________ 288 

mapping of.__________________ 235 

Census reports, use of data from.. 179,237-238, 326 

Checking, cultural - revision sheets, instructions for..---------.___ __. 313

river survey maps, instructions for...., 353-354

topographic map, attention to questions

raised in.______________ 311 

avoidance of duplication in.____ 310-311 

definition of_____________ 273,310 

instructions for__________ 273,310-313 

need for.- ________________ 310 

printed form for.____..__.. 311-312 

suggestions for____._..__... 312-313 

use of term to replace the term "proof

reading".._____________ 273 

woodland sheet, instructions for___ __ 313 

Chief topographic engineer, annual report to

director, preparation of.. ____ 277

approval of annual engraving docket by. 321

approval of quadrangle names by_. __ 304

monthly report to director, preparation of 277

submission of map comment to__ __ 318

Churches, inking of...____.._______ 285

mapping of._________________ 232

City boundaries, incorporated lists for__ 179,326

Civil boundaries. See Boundaries:

Cliffs, contouring of.-___________.. 251-252

inking of__________________ 295-296

Closures, leveling, correction of discrepancies

in....__._._________.. 127-128

traverses__..-.-___ ._______ 115 

Coast and Geodetic Survey, field use of charts

of __.______.______ 242

office use of charts of___________ 291

use of data from________ 163,166,167-170,

178, 204-205, 242, 291, 299, 320,361, 362

Coast Guard stations. See Life-saving

stations.

Coke ovens, inking of..__ 288

mapping of-_________ - 236

Collimation, alidade adjustment for. 194

Color screens, use of..____ 383-384

Colors, standard, use of . 165,

279-280, 281, 284,291, 294

water, mixing of .379,281
INDEX 423

Page

Compass, box, adjustment of. 195 

box, plate showing___._._____ . 194

use of._-__________-- 196,197, 205-206 

Compensation for injuries, right to... 11 

Compilation. See Map compilation. 

Computers, suggestions to.-__.------.. 86-87

Contouring, by different persons, comparisons

between_______..._.__ 252, 253 

by different persons, inking of__ _. _ 298 

depressions in, inking of______ 287, 296, 297 

mapping of.___________ 234,251,252 

distances from which done____... 249 

expression in, examples of differences in.. 252-

253 

inking differences in....._ . 298

in form lines, field use of_..__.____ 249

methods of, from radial rods.. . ... 247

from station______________ 247-248

from traverse lines.____._ _- 246-247

in general____. __________ 248-254

physiographic aid in_____ _ __ __ 254

railroad grades in_____________ 250-251

skeleton outlines used in..._._.._. 248

special field features of____._._. 250-252

topographic expression in. _____ 252-254,298

two intervals in, inking of--...____ 297,306

mapping of._______________ 246

varying steep slopes, inking of______ 295

mapping of_______________ 250

Contour interval, marginal statement of__ 306,

323,350

relation of, to scale...____._____ 165 

standard sizes of..____________ 165 

Contour lines, advantages of_________ 164 

alinement in, inking of...________ 298 

mapping of._______________ 253 

definition of..__.______.__ 164-165,254 

disagreeing with elevation, license in_ 253, 297 

drafting of, in ink . 277-278, 280, 294-295 

in pencil________________ 249-250 

emphasizing of, in ink___________ 294 

in pencil____..__________ 250 

engraved figures on, position of____ 331-332 

style of __________________ 333 

hand figures on, inking of___ 296-297,331-332 

under-water, inking of__________ 291,306 

Control, authorship of, marginal credit for... 307 

checking and inspection of..__...__ 312,316 

culturea djacent to, plotting of____ 241,290 

examination of, on topographic maps, instructions for________ 273,319-320 

need of._________________ 319 

scope of...._______________ 320

 factor of, in map accuracy________ 181 

for photographic mapping, twotypes of. 394-395 

horizontal, plotting of..... 177-17S, 182, 241, 290

use Of..... 177-178,180,181,195-196, 240-241,

262-263, 269,290,301,312,319-320,350 

inking of. See Inking, of cultural features.

need for and amount of__ _______ 47-48

of maps, methods of obtaining____ 47-48,89

'requisition for data for.._________ 177

vertical, distribution of______.'__ 118-119

use Of . 177,180,181,195-196,200,240-241,

262-263, 269,290,301, 312, 316, 319-320

Conventional signs. See Standard symbols.

PageConvergence of meridians, computation of.. 112 

latitude and scale-plotting limits of. 176-177 

neat lines of..--_____ 177 

Cooperation, with other branches and bureaus_______________ 27,29-30 

with States, benefits of-..__... 30-31,34 

division of expense in 31 

enactments by States to provide for. 32-34 

funds expended in_ . ^ 36 

methods of Federal Survey to govern, 31 

must be requested by State. 32; 

States that have taken part in. . 30,35 

Cooperative headings, arrangement of, for

new maps------..--------------- 305

arrangement of, for reprints... 343-344 

Corps of Engineers, United States Army, use

of data from___________ 178,328

Corrections, topographic map, file of__.. 340,342

topographic map, requirements for..-. 341,342

Cost, record of.__________-... 22

Counties, boundaries of, inking of...._.. 288,326

boundaries of, mapping of.-....- ... 236, 326

subdivisions of, inking of..___-...-- 288,326 

mapping of...._____________. 237

policy in showing___________ 237 

State lists of.__....______ 237-238,326

"Crabbing" of aerial photographs, limit of.. 400- 

Credit, authorship, marginal statements

for... . 306,307

outside data, instructions for...____ 307,344

Cross wires, adjustment of___________ 58-59

mounting of.....______ 54-55,91-92,192,193

See also Stadia wires.

Crosses, location, inking of..._________ 290

Cultural features, definition of________ 229

inking of....________________ 284-290

list of ... ...._.___ . 229

mapping of._________________ 229-242 

See also particular features. 

Cultural revision. See Revision, of topographic maps.

Cuts and fills, contouring of.._________ 251 

inking of. ___________________ 287 

mapping of __________________ 234

D unit of multiple-lens camera, attachment

and mechanism oL.. _______ 383

Dams, inking of . _______________ 287

mapping of._._.....__________ 234

Dam-site maps, cross sections for.._____ 352

inking of _ . _____ .. _________ 351-353

lettering of..________________ 352-353

surveys for..____________..._. 269-270

See also River-survey maps and River

surveys.

Date, of printing. __ ____ .. . 308,349 

of survey, and features mapped, policy

regarding_____________ 186 

marginal statement of.____ 227,307,349 

Datum, horizontal, joining lines for differences in.___________ 228,307,342 

horizontal, marginal statements of__ 228, 

269, 306,307,319,323,350

North American, reference to___ 307,323, 343

use of_____ . 48

vertical, statements of ____ 269,306,319,350
424 INDEX

Page

Declination, magnetic, determination of_ 199,320

magnetic, marginal diagram of _ 308

readings for______________ 110

.Deficiency appropriations... 4

JDepressions, artificial, inking of_... . 287

artificial, mapping of.---------_____. 234

contours showing, engraving of______ 329 

inking of..- ......__. ... 287,296

mapping of___.--_.-------.---__ 251

Detail and generalization, definition of. 183-184

inspection of. ___--__-.- 316

relation of, to map accuracy.--.- ... 183-184

to map expression....---,-.--.-. 181,

183-184, 252-253, 274, 278,298,316 

Displacement chart, plate showing.. _.. 390 

Distances, computation of....- 82-83

ground measurements of_ 205,207,210,211-212 

map measurements of._------ i 200

stadia measurements of, limits of.... 207

Ditches, arroyos, etc., contouring of. 251 

inking of. ___________-__ _.. 287 

mapping of._.___-...- 233 

Division Engineer, approval of map drawings by______ _ __ 317 

designation of engraving priority by_. 321 

field reports to______ .. 229 

inspection reports to__ . ... 314-315 

letters of instruction from __..._ 165-166 

marginal use of name of___________ 308 

recommendation regarding contour interval to._______________ 245-246 

report on border joining to..._____ 227-228 

report on need for revision readjustment

to-.. .. ..___...__.__ 262 

Dockets. See Editing and Engraving. 

Docks, inking of______.___.._-___ 287-288 

mapping of._____.._----_-----__ 235

Drainage, contour control afforded by lines

Of............______ 245,247,248,253

field classification of.____________ 244 

office classification of...__________ 292 

See also Streams.

Drainage features, definition of.._______ 242 

inking of....________________ 291-294

list of.--....... ___...__...... 242

mapping of__________-___-__ 242-245 

See also particular features. 

Drawbridges. See Bridges.

Dumps, mine, inking of.____________ 287 

mine, mapping of. .....__________ 234

E

^Editing, cultural revision, instructions

for-....______________ 335-336

illustrations for reports, scope of- ____. 357 

index circular. See Index circulars, 

reprint, instructions for_-.__..__ 341-345 

river survey map, instructions for.-... 354-355 

State map, instructions for......__.. 357-358

topographic map, approval of, and transmission for engraving_______ 335 

character of._________ 273-274, 320-322 

dockets for..._____________ 321,335 

engraving instructions of ..... 334

filing of notes of...__________ 334 

instructions for ____ ___ 273-274, 320-335 

letters of inquiry needed in ___.. 334,344

Page

Editing, topographic map, list of details of. _ 322 

topograpic map, plate changes after __ 322 

questions raised in...,_______ 321-322 

scope of..-.______________ 322-334 

work sheet for.____._______ 322-323 

United States map, instructions for__ 358-359 

Edition and reprint dates, marginal statement of......___________ 308

Editions, map, sizes of--....._________ 339

Electric railroads. See Railroads. 

Elevations, determinations of. See Control, 

Plane-table traverse, Plane-table 

triangulation, and Vertical angles, 

field tracings of, required._______ 241-242 

figures for, engraved positions of_____ 331 

selection of, for engraving_______ 331 

painted marks for...__________ 121-122 

useful..........................____ 123-124

descriptions of.____________ 125-126 

inking of figures for_________ 290,316 

mapping of.______________ 241 

Employment of temporary assistants, rules

for.............................. 10

Ending field season, reminders for.. 271-272,274-275 

Ending office season, reminders for_____ 179 

Engraving, copy needed for, character of__ 189

190,277-278

docket for, preparation of________ 321,335 

International map of the world, specifications for_______________ 360 

legibility of reproduction by_______ 189. 

topographic map, authority for.____ 321,335 

process of._____________ 274,336,337 

proof reading of_________ 274,337-339 

transmission for.._..._..___ 336-337 

Entertainment of visitors, caution on. ____ 17 

Entrance to the topographic branch, method

of... _ .- 8

Erasures, method of making____ ____ 282 

Errors in mapping, causes of_____.__ 185-186 

Exposure for photographic mapping, length of 396 

Express shipments, field to office, forwarding

of.. __....___._.._. 271-272

F,

Federal buildings, bench marks on ...__ 120

Ferries, inking of _________________ 286 

mapping of_________________ 233

Field instructions, sundry__________ 228-229

Field party, personnel of..._____.____ 9,166

Field reports. See Reports.

Field sheets and material, filing of.__ 179,274-275

Field and camp administration, rules for__ 10-17 

reports required on.__.__....__. 19-20

Field of view of multiple-lens camera, width

of. . -- 381

Figures, bench-mark, hand style of 290 

bench-mark, position of.. 331 

contour, position of_____ 331-332 

elevation, position of....... 331

engraved, position of.---... 331

selection of..______ . . 331

style of.________ . 333

hand, style of..._...._._______ 290,333

section number, style of---. .--. 305

Filing, field sheets and material .... 179,274-275
INDEX 425

Page 

Piling, map material received from the field,

jacket list of..................... 275

Fills, mapping of._____.._._____. 234 

Film for aerial mapping, development of__. 400

kind used ____._____-____ 383,396

winding of________________ __ 383 

Flying for making aerial photographs, requirements for.__-----_-_ 395-397 

Foot traverse, adjustment of________ 212-214

use of.____________________ 212 

Fords, inking of..________________ 2S7

mapping of---.-...------------ ... 233

Forest fires, putting out or reporting_____ 26 

Forest Service, use of data from______ 178,327 

Found land corners. See Public-land corners. 

Furnaces, inking of.____________.. 288

mapping of-__________._-__ 235 

Q

Game preserves, Federal, data for.--__._.. 327

Generalization. See Detail and generalization.

General Land Office, deseription of publicland surveys by.._______ 368,376 

use of data from..:____________ 178, 

179,180, 238, 239, 269,289,327, 343, 361, 368-376 

See also Public-land lines and Public-land

surveys.

General maps, definition of..________ 359 

work of section of cartography on___ 359 

See also International map of the world, 

Map compilation, Shaded relief 

maps, State maps, and United 

States maps.

Geodetic coordinates, computation of.__... 83-85 

Geographic Board, United States, decisions

of.... .- . _- 326,342 

United States, functions of.... 226,326-327, 328 

Geographic maps. See General maps. 

Geologic branch, special prints for__ 339-340,341 

Glaciers, inking of__________._____ 294 

mapping of..________________ 245 

Grid. See Rectangular grid. 

Ground elevations, marking of.... ...__ 124

H 

Hachures, inking of.. . ......_. 297

use of - --. 234, 251, 252, 297

Heliotroping, outfit for. _ ___ 53

Highway surveys, use of, as transit-traverse

lines -. .. 97

Horizontal control. See Control.

Horizontal datum, joining lines for differences

in.- 307

Houses, blocks of, mapping of . ___. _. 231 

inking of......--.. 285

mapping of.... - . 231

See also Blocks and Buildings.

Hydrographic Office, Navy, use of data from. 178

I

Identification, of field sheets, data for..__ 228 

of topographic features, tests for..._. 182-183 

Elustrations, topographic editing of .. 357 

Image, photographic, determination of position and size of.-._..__.... 387-388 

Image displacement, correction of,. 390-394 

chart for.........____..__..... 390

Incorporated places, use of census lists of.. 179,326 

Index circulars, State, character of .-____ 355 

State, editing of..____________ 355-356 

preparation of reprint copy of____ 356 

printing of...--...___________ 355 

See also Progress book. 

Indian Office. See Office of Indian Affairs. 

Indian reservations, boundaries, inking, mapping, and maps of._. 178, 236, 288,327 

Information tracing, data to be shown on__ 228 

Injuries, compensation for.._____.__ 11-12 

Ink, nonwaterproof black, restricted use of 281 

red, use of- .. 235, 279,287, 288, 289, 345 

specifications for....__..______ 279

Inking, acquaintance with field instructions

needed for___________._ 277 

adjustments necessary preliminary to__ 212-

214, 272

assembling necessary preliminary to__ 272 

character of___.___________ 277-278 

colors used in____._____.._".. 279-280 

consultation with section of inspection and

editing in.....__....______ 278

erasure of ______________ 282

field, authority necessary for.....____ 229

general instructions for__. _______ 190, 

273,277-282,284-298,301-302, 345-353 

legibility of..._____.___.______ 190 

of certain maps twice, need for_____ 278-279 

of contours. See Contour lines and Contouring.

of cultural features, instructions for__ 284-290 

of drainage features, instructions for.._ 291 

of map features, sequence of.. -_. 280,294-295 

of overedge topography, instructions for. 280 

of relief features, instructions for. _ _ 294-298 

of river survey maps. See River-survey

maps, 

precautions before beginning....____ 280

standard symbols used in...___ 280-281,316 

plates showing--...__________ 282 

suggestions for ...___________ 281-282 

Inspection, questions raised by, attention to.._._------_._____ 315

river survey map, instructions for.__ 354 

submission of maps for. _._____ 313 

topographic map, definition of ....__ 314

instructions for_________ 273,313-316 

need of- _______________ 314-315 

scope of-..-_____________ 315-316 

See also Checking and Editing. 

Inspection and editing, section of, consultation with_____________ 278 

Instructions, field, letter of___________ 165 

Instruments, adjustment of._. ______ 56-60, 

90-93,137-140,193-195

care of- _____ 54-56,128-130,191-193 

cleaning of ______........ 192

minor repairs of._ ___ . 130 

packing and shipping of_... ... 55-56,193 

protection of_____._ 193 

requisitions for . 42-45 

topographic mapping, descriptions of.. 196-197 

plates showing.....__... 178,194

See also particular instruments. 

Insurance, field, association for 10-11 

Interest of employees in lands or mines prohibited. .... 27
426 INDEX

Page Intermittent streams. See Streams.

International map of the world, character of.. 359 

compilatio'n of....____.._______ 360 

projection for___ __ .... __. 360 

reproduction of..__.__ __ __ 360 

See also General maps.

Interval. See Contour interval.. __. 165

Islands, inking of-_. ___._______ 292 

mapping of.... . . 243-244

J

Jetties, inking of.________.___.__ 287-288 

mapping of..-. _ 235 

Johnson tripod. See Tripods.

Lakes, intermittent and dry, inking of.. 292

intermittent and dry, mapping of 245

natural and artificial, inking of.. 292

mapping of-..------ 243

Lambert projection. See Projections. 

Land classification, mapping of data for... 258-261 

sheets for, office preparation of 310 

transmission of... 319 

Land corners. See Public-land corners. 

Land grants. See Public-land lines. 

Land lines. See Public-land lines. 

Land Office. See General Land Office. 

Landowner, permission of, for setting a bench

mark____._-..._ 120 

Land-survey corners, locating of_ 96

See also Public-land corners. 

Latitude and longitude of traverse stations,

computation of_.-_... 114-115

Latitude and longitude scale, plate showing. 178

use of.. 178

See also Scales.

Latitudes and departures, computation of . 113-114 

Least-square adjustment.. . . 71-78 

Leave of absence, request for. 21 

Legibility in mapping, general statement regarding -. 188

reproduction and, relation between . 189,

277-278 

standards for... 188-191,278

Lenses, photographic, back focus of 387 

photographic, focal length and arrangement of___.___-______ 381-382 

equivalent focal length of. 387 

Lettering, engraved, position of --- 329 

engraved, style of-_-___..__ 332-333 

general instructions for____.._ 273,304-308, 

329, 332-333, 334, 348-351, 352-353, 365-366 

hand, instructions for . -- 304-305, 

350-351, 353, 365-366

position of___._____ 305,329,365-366

Style Of 304,351,353,365-366

marginal, instructions for 305-308,

348-350,352-353

plates showing _ . 282 

on oversheet or on original, choice of . 304 

punctuation omitted from. .. 304,329 

submission for......___..__------ 273,304

Letters of inquiry, occasions for 334,344

Levees, inking of. . 287

mapping of...__ .. 234

PageLevel, care of __.________ 128-129,137-140 

circular, adjustment for_________. 194 

plumbing, use and care of.________ 133 

prism, adjustment of.._________ 146-149 

care of. ___.________ 149-150 

length of sights with__________ 146 

striding, adjustment for._________ 194 

Level bench marks. See Bench marks and

Control. 

Level circuits, computation and adjustment

Of 155-160

Level lines, location of__.._______ 119 

tying of, to established bench marks.__ 118 

Leveling, first order or precise, limits of error

in............. .............. 130

first-order or precise, running and adjustment of. ______.__ 155,156 

grades of work in. ________'__ 130-131 

instruments used in, plate showing...... 128

marks for, plate showing._________ 52 

second-order, character, accuracy, and

procedure of ________ 151-152,156 

limits of error in___________ 130-131 

purpose of ______________ 150-151 

recording of notes and descriptions

in... ..._................ 152-154

third-order, adjustment of. ______ 156-160 

limits of eiror in________ 130-131,142 

with prism level and yard rods, onewire method of observation 

in._ 145-146

personnel and supplies for.. __ 142 

recording of notes in ___ __. 143-146 

three-wire method of observation

in.. . 142-145 

with wye level and target rod, adjustment and care of instruments 

in- 137-140

causes of error in______..... 137

length of sights in___------- 132-133

marking of turning points 

in.. .-.--.._ ...._ 133-134,150

measurement of distances in _.. 133 

personnel and supplies f or -. __ 131 

reading of target rod in.. ____ 132 

recording of notes in______ 134-136 

See also Control.

Leveling rod, plate showing..______.. 128

testing and care of__________ 129-130,133

Levelman, responsibility of...____ 117,128-130

Life-saving stations, mapping of.._....... 235

Lighthouses, inking of_______-__ 288 

mapping of...-------------- 235

Location and mineral monuments, inking of. 289 

mapping of._------ . 240

Location crosses, inking of.--.- 290 

Locks, canal. See Canals and locks.

M 

Magazine section of multiple-lens camera,

mechanism and attachment of, 382-383 

Magnetic declination. See Declination. 

Map borders, extension of, into unmapped

areas...._ 227

field instructions on...---. -------- 227-228

horizontal daturas of 228
INDEX 427

Page

Map borders, joining of, preliminary office

preparation for....._..__.... 178

joining of, to previous work_..__... 227-228 

office instructions on______ 302-303,324,342 

See also Border corrections.

Map compilation, collection of data for..__ 363 

control for__________________ 363-364 

definition of.._________.____ 362-363 

inking and lettering of________ _ 365-366 

instructions for______________ 362-366 

reduction, adjustment, and transferring

of........... -.. 364-365

reproduction of____......____._. 366

selection of scale and projection for. .._ 363 

See also General maps.

Map information office, use of files of.____ 178 

Mapping, data from other surveys for..... 178-179

of cultural features. See Cultural features, 

of drainage features. See Drainage features.

of relief features. See Relief features. 

on aerial photographic base. See Aerial

photographic base.

standard scales used in, list and distribution of.................. 161-162,165

topographic, control for________ 195-196 

control for. See also Control, 

funds expended for..________ 36 

instruments used in..______ 196-197

See also Instruments, 

methods used in__________ 195-205

See also Plane-table traverse. 

Maps, compilation of, from aerial photographs, choice of method.-__ 402-403 

compilation of, from aerial photographs,

radial-line method_______ 409-416

from aerial photographs, sample of.. 402

section-line method_______ 406-409

straight-line method______ 403-406

control of, for aerial photographs____ 47-48,

89,394-395 

See also Control.

uses of_____________________ 28-29 

Marginal lettering. See Lettering. 

Marks, for transit-traverse lines, material

and sites for.-..___-...._. 94-96

reference, establishing of_ _______ 95,121

Marsh, fresh and salt, no distinction between. 242

in general, inking of. -___________ 291

mapping of__..___________ 242

submerged, inking of...__________ 291

mapping of __.. _______ ___ 242

wooded, inking of...___________ 291

mapping of_____.._....__... 243

Methods, topographic. See Mapping, topographic.

Micrometer eyepiece, use of..________ 210 

Micrometer theodolite, adjustment of____ 57-58 

plate showing.._.____________ 52 

Military information, collection of____.-.. 5,6 

Military reservations, boundaries, inking,

mapping, and maps of. 178,236,288,328 

Millionth-scale map of the world. See International map of the world. 

Mine dumps, inking of...._________ 287

mapping of __________________ 234 

Mineral monuments. See Location and 

mineral monuments.

58515° 28 28

Page

Mines and quarries, inking of. 288 

mapping of._______-- 235 

Mining maps, special scale, symbols for.. 235 

Mississippi River Commission, use of data

from.--.---.-....---_______ 178

Monthly reports. See Reports.

Monuments, boundary, inking of.... ____ 288

boundary, mapping of... ..__ 237 

location and mineral, inking of..... ___ 289

mapping of.-_..-.-...---------_...- 240

See also Boundaries. 

Mosaics, aerial photographic, construction

and value of_____- _. __ 417-419

N

Names, authority for.. ... _.... 226,326-327,328

field oversheets for..------- __ 226

Geographic Board's function in. ..... 226,

326-327, 328

list of features to be shown by___ 226-227, 325 

marginal, to be added to name tracing 227 

new, procedure regarding.... __.. 226,326-327

quadrangle. See Quadrangles. 

See also Lettering. 

National forests, boundaries, inking, mapping,

and maps of--..._-.. 178,236,288,327 

National monuments, boundaries, inking,

mapping, and maps of........ _ 178,

236, 288, 327 

National parks, boundaries, inking, mapping,

and maps of...---_-- 178,236,288,327 

National Park Service, use of data from. 178,327, 344 

Neatness, legibility through_. .. 191 

North American datum. See Datum. 

Notes, leveling, method ofkeeping._...._. 134-136,

143-146

theodolite readings__ . 62-63

transit traverse, method ofkeeping-.. 110-111

Notes and records, making and forwarding of. 124-

125 

Notes and notebooks, use of. ______ 200,209,216

O

Oblique photographs, definition of. . _____ 390 

Office of Indian Affairs, use of data from. __ 178 

Office reports. See Reports.

Office season, reminders at end of-.-._ _. _ 179 

Office work, on topographic maps, miscellaneous procedure in....____ 274-277 

summary of routine procedure in. ___ 272-274 

See also Cultural features, Drainage features, Inking, Relief features, and 

other particular 'headings.

Omissions in mapping, causes of... ____ 185-186

Optics, photographic, need for knowledge of 385-386

Organization, office and field-..._...___ 7-9

Orientation, Baldwin solar chart method of. 219-225

compass use in. ______________ 197,205

process of... ... 196-197,199, 202, 202-205

use of alidade ruler in... __________ 194

See also Plane-table triangulation.

Orthometric correction, formula for finding. 155-156

Outside data, map credit for__ __ ____ 307,344

Overedge topography, inking of..______ 280

mapping of ...._.____ 206, 227

Oversheets, separation of data on______ 228
428 INDEX

Packing and shipping, instructions for. _ ... 193

Pasting, attaching the patch in __. ...... 238

preparing a patch for.--'...___ . ... 283

Peeling mounted paper, method of _____: '.. 283

Peg method, test and adjustment of levels

by____. __ -__ _ 140-141,146-149

Penciling, field, legibility of........ 190,230,249-250

grades of pencils to be used in-..-.. . '. . 249

Pens, drafting and right line, use of... 281

Perennial streams. See Streams.

Personnel, classification of ___ _ 7-8 

field-party._..I..._____-.'..... .:.- 1'66

Photographic base, aerial. See Aerial photographic base and Aerial photographs.

Photography, development of, in map con-

 struction - -- -- ---- J- 379

 aerial. See Aerial photography. 

Physiography, contouring aid from ... 254 

Piers, mkingof........ ' - -- - 287-288

mapping of .^. ...I- - 235

Pipe lines, water and oil, inking of__- --. 287 

water and oil, mapping.of-----.-:.- 234

Plane, image, situation of ---.. . 386

object, situation'of..__ ._. _ 1 386

Plane-table, boards for,-sizes of--___ 197,211

description and use of-.^_ .. I_..'. 196-197

paper used on..______ .___ 166,198,206

.inetal mounts for, use of__.____ 198

use of celluloid for------_ _.__. ; 206

.plate showing.__________ __ _____ 194

rods and tripods used with; plates sho'w-

.ing.._______'. -....___ 194

types of.__________-....i_< 197

See also Alidade and Instruments. 

Plane-table traverse, adjustment of.... 212-214, 273

general .methods of_____I __ _ 205-206 

instructions for ___.-___--.-__'.. 205-214 

showing closures in.___-.....___'_. 206

See also Foot traverse, Stadia traverse, 

Tape traverse* and Wheel traverse. 

Plane-table triangulation, Bessel's method,

reference to___.______.._ 204 

choice of stations for_____________ 199 

control of aerial photographs by... _ _ . 395 

definition of--,_-----___...L____ 197

instructions for..'___-..__ _'_._ 197T205 

intersected points, stations at__'.....'.. 201

notes for____________________ 200 

preparation for..___.__ __.___ 198 

projection for.--i..-.-_. 162-164; 166-176,198 

plotting of points on___:____ 177-178 

resection, location by.________... 201-202

 signals for..._____....____i...... 199

 ' station work of.___________ 197,199,200

' ' suggestions for..__________.____ 200 

three-point method, location by___'_202-205 

tracing-paper solution, location by.___ 205 

transfer or further use of_..... ........... 198

Planes, focal, situation of_.'....;_'____.....'. 386

Plotting. See Control and Scales.

Points, nodal, situation and properties of.. 386-387 

principal, on focal planes, situation of.. 381,386

Polyconic projection. See Projections.

Post-route maps, use of-___..... 179,180,324,326

Posts,.concrete, making and setting of..l 94-95,121

Page

Power-transmission lines, inking of. _____ 287 

mapping of.._------__________ 234

reference to chief hydraulic engineer for

approval_______...____. 328 

Preface____------__...__..._' _.-...... V

preserves. See Bird preserves. -and Game 

 - . preserves. ...

Press, information to..-----...- ..'__ -_ 28

,-Progress book, field mapping, description of. 275

inspection, and editing, description'of__ 276

Projections, AlberSj use of -..^ _ ____':.... 362

: construction of,-,,_.__-_ 166-177,198, 363

, Bumstead plate for, plate showing_ . 178

useof. .... T - ..-,-.. 175-176

Coast and Geodetic Survey method. 167-170

Geological-Survey, me thod ^.___ 170-175

convergence of meridians in. -__..... 176-177

figures for, inking of..--.........;..^._ .._ 305

form and lines for, plate showing part of.. 282 

Lambert, use of___.'._.________ 360-361 

lines representing, inking of- ___ ... 280 

marginal statement regarding__,__- 307 

nature and kinds of__.-----.____.'__ 162-164

plotting horizontal control on__.,.... 177-178

polycQnic.advantagesandlimitationsof- 163-164 

construction of. ___________ 163-164 

modified form of, use of_".......... 360-361

use of._..___....,__'--. 163,167,170,175

rectangular grid on....!._..____ _ i 298-301

Promotions, basis of....___________ 8

Proof reading, of engraved maps, instructions

for ....-... ...,. 274,337-339,359

of field sheets. See Checking. 

Property, abandonment of....___;___ 14

certificate of users.of ,______ ..+.... 20

lOSS Of.--.-._________...______ 1-..;......... 14

private, entry on..__: .______i __ 28 

purchase, care, and storage of.__ 12-14,16,18 

requisitions for...______.,__.. 16,36-45 

.return of__'..._____±.....^.____ 14 

transfer or sale of-________.1___ 14 

Prospects, mineral, inking and mapping of.. 235 

Protection of field sheets____. ___ 198-199,228 

Public, relations toL__.____ ____,;_ 27-28 

Public-land corners, inking of-_____- __,. ' 289 

obtaining preliminary data for..____ 179 

search for -.___ __ _ - __...^ 239, 268-269 

Public-land lines, adjustment of__ 239,376-378 

inking of-..-.____....;.... ... 289,346,352 

mapping of.____ ___ ___ 238,239,268-269 

new, addition to reprints of i____;___ 343 

, obtaining preliminary data for_:____ 179 

. plats disagreeing with topography, marginal note for..---.---..-... 239,307-308 

use of oyersheet tracing for. _______ 239 

Public-land surveys, meander lines of.._ 372-373 

outline.of plan and practices of... _ 368-376 

'.principal meridians and,base lines of 1. 369 

section and township corner markings of. 373- 

 ".. .376 

section lines of -___ .__._i___ 371-372 

standard parallels and guide meridians .. of...:--.-. -_----- _.. 369-370

table of latitudinal closing distances of_ 371

; township exteriors of. ______.__'_.. 370-371

township units of _ - -.______ 368

See also General Land Office.

Publications, classes of..........______ 8
INDEX 429

Page 

Q

Quadrangles, names for, authority for..-.. 275-276,

303-304

names for, final selection of. _______ - 303

letters for changes in__ . 304

provisional designation of..._____ 303

nature of.._.._-...-____....__ 161

partly mapped, explanatory note for_ 333-334

Quadripods, triangulation, construction of..- 51-52

Quarries, inking of.______..______ 288

mapping of._____________._.. 235

R

Railroads, contouring cuts and fills on___ . 251 

crossings of, inking of___........__ 286

.mapping of,__________..._ 232 

curve and tangent, alinement of.____. 232 

grades and. contour crossings on, table of- 251 

inking of _ . ... .282, 285-286, 324-325 

mapping of.___________ 206,232,250-251 

plane-table traverses of. __________ 206 

station buildings on, inking of.-.l-__. 286 

mapping of.,...--_ __.____:... ',232 

traversing oL:_____-......... . ..... * 206,232

valuation, surveys, of, use' of alinement

maps of,.,..____,.,-_-,__ 179 

Range rod, plate showing,___'..__'_ 91 

Rations, lists of__.,________'___,. 15-16 

Reciprocal angles.. See Vertical angles. : Recording cone, description of.___^....... 380

Records, field,.care of_____ ___'.... 20-21

Rectangular grid, definition of____'..^.^... 298 

plotting of, by whom_1. _.__ ____ .299 

instructions for_____ .. _ 299^301 

map-corner distances for.._ __'_ . 299 

United States zone systehrof __ ___.- 299 

use.of________J__._____------ .299

'' zone for, marginal statement of j....... 307

Red .ink, use of.__.....- 235, 279, 287, 288, 289,345

Reference marks_________........... 51,121

Relief features, inking of__:..; ___ 294-298 

mapping of...__ ...-- .. 245-255 

' See also Contouring, Contour lines, and

particular features.

Relief maps. See Shaded relief maps. . 

Repairs. See Instruments. 

Reports, annual, chief topographic engineer

.to director, preparation of..._. 277 

annual, of section of inspection and editing to editor of texts ---.-- 277 

monthly, of chief topographic engineer to 

director...-----__ ..... 277

field, submission of...__ 19-20,229,272

office, submission of.._ 19,274,277

Reprints, distinction from new editions. '.- 340

' topographic map, correction files for.... 340

editing for.... 341-345

See also Editing.. ; 

general features of-. ...:...-.. 340-341 

procedure in._____1 274,340-345 

reference of, to geologic branch 341 

stock lists for 341

Reproduction, advance sheets by photolithography,- transmission and 

proofreading_.__ 317 

engraving propess of,.___ 336,337 

topographic map, plate showing part of., 282 

See also Engraving.

Page

Resection, plane-table location by _ 201-202 

Reservoirs, inking of.--------- .. 287, 292

mappingof__.__.___. ------ 234

Responsibility of leveknan...__ 117,128-130 

Revision, resurveys, and new surveys, differences between__________. 262 

topographic map, aerial photographic,

. . methods of.-_____-I..__. 264-266 

cultural, field work of________ 262-264 

... inking of..___________ 301-302 

definition of._____________ 262 

field work of 262-266

inking of........ ... _ 301-302

'office preparation for...______ 179-180

road classification for..____... 264,302

woodland outlines for..._______ '264

River banks, inking of...____ ..___ 292

mapping of.____._____...____ 243

River-survey maps, checking of...____ 3-53-354:

editing of.--...._- . .._ 354-355

: InMng.of--________-____.__ 345-353

.dam-site maps.of.-- -... .'... 351-353

field .sheets of.___...____ 345-346,352

inspection .of__.--..-___ _._._ :354

key map for.____________...... 348,354

.lettering for. ... _______.. 348-351,352-353

.plan sheets of__________.__ .347,.353-354

plotting mileage .on ___ ___, 346,347

. profile sheets of__.__.___ '__ 348,354.

reproduction of._.._____.___ 345,351.

 size of published sheets of_ _______ 346 

See also Dam-site maps and River surveys. . . ' River surveys, control for.. .. ..__. ,269 

field work pfr ._. T ......,_: .__ 266-271

in regular mapping, description'of..._ _ ,267 

land lines in,,...,_.. ___...._. 268-269

 reservoir and dam sites on__.._;.. _ 269 

special, description of__._.__ _,. ' 266. 

topography in..,.. , ,-- 267-269 

written reports of,, .__.. ___ 270 

.See also. Dam-site maps and River-sur- '

 ' vey maps. ' . . . ;

Road classification,, editing of printing copy

..for.. _ ... _: 339,

mapping of___________-__ ,'. 256-257

revision copy for,. .. 264

tracings of, office preparation of , 309

transmission of..._.=. 319

Roads, field penciling of .: - ,, 230 

good and poor motor, definition of__ 229-^230 

inking of._ I___.. 282,284-285 

mapping of,_____.__..__...._ 229-230 

public and private, definition of. _ . 230 

revision of classification of '.... ..V V. 264

Rock cairns, construction of ..I 51

Rod, level. See Level rod.

range. See Range rod. 

stadia. See Stadia rod. 

yard. See Yard rod.

Rope, braided, plate showing . . 194 

braided, traverse use of.___ ..... 197

Rubber cement, use of...____ 283

Rural-delivery maps, field use of. 179

' S

Sand, inking of... .. .__ 292 

mapping of. 255
430 INDEX

Page

Scales, bar, on map margins, kinds of.__ 306,

323, 349,350,353

choice of, for photographic mapping... 399-400

latitude and longitude, plate showing.. 178

use of.............___.............. 178

metal plotting, projection use of, by

Coast and Geodetic Survey ... 170

plotting, plate showing. ___ . . 178

use of.._________________ 196,206

relation of, to contour intervals 165

standard map, list and distribution of- 161-162

Schoolhouses, inking of._.__ 285

mapping of.__ ..............--------- 232

Section numbers, inking of. . _ . . 289,305 

Service, daily reports of.------ 19-20

Shaded relief maps, description of_----- 366-368

published and in preparation 367 

section of, work by._______ .. 366-368 

Shore lines, aerial photographs showing, correction of...____... -.-. 255 

in general, inking of._ 291 

island, inking of._________ ---. '292 

mapping of______.. 243 

river, inking of.._._________... 291-292 

mapping of._____________ 243

tidal, inking of..______________ 291

mapping of.._______. -... 242

Shutter for aerial camera, kind preferred.._ 397

Slope, method of using tape on________ 98

Smelters, inking of___ _.. __ 288

mapping of___-__.______.___ 235

Solar chart. See Baldwin solar chart.

Speed in mapping, advance planning for..... 187

cooperati ve effort effecting. _ ______ 187 

diligence needed for._._... __ 188 

efficient methods effecting____ ___. 186 

experience effecting.....___.__.__ 187

standards for____...____ __ 186-188 

Spherical excess, computation of___....__ 70-71

Springs, inking of__ .__.___________ 294 

mapping of.. . ____ _... 245 

Stadia arc, Beaman, use of__-...__...- 207-210 

Stadia distances, substitution of, for tape-line

measures..... . __ 100

Stadia rod, description of...____-.--.__ 197 

plates showing___ ...... .._ 91,194

Stadia traverse, Anderson and Johnson

tables for, use of____ _____ 207 

elevations by _ 207 

instructions for._______.......... 207-210

instruments used in____________ 210-211 

use of stadia arc in___________ 207-210 

See also Alidade and Plane-table traverse. 

Stadia wires, collimation part of adjustment 

for...... . .... ... 194

intercept for__._____________ 197,211 

mounting of._.______________ 192,193 

Stamping of bench marks____ .. 122-123 

Standards for field work, accuracy factor

in... ........................ 181-186

legibility factor in____________ 188-191 

speed factor in______________ 186-188 

Standards of micrometer theodolite, adjustment of__.__--------___ 56-57

Standard symbols, Geological Survey use

of.,-..- - _____.... 280-281

misuse of.._____________ .-.. 316 

plates showing__.. __ 282

Page

State officials, relations to.___________ 27

States, boundaries of, inking of____ 288,325-326

boundaries of, legal status of______ 325-326

mapping of.... ............. 236,325-326

monuments on____________ 237,288 

See also Boundaries.

cooperation by_______________ 7

maps of, character of________ 357,360-361

compilation of_____________ 361

editing of. . . ___. 357-358

projections for.____________ 360,361

parks and reservations of, data for ____ 328

Stationery, requisitions for,__________ 36-42

Stations, centering of signals over....____ 52

reduction to center..__ ________ 66-67

unoccupied, adjusting lines to...____ 82

Steamboat routes, inking of__________ 287

mapping of__________________ 233

Stereoscopes, types and uses of...__.... 384-385

Stock, pasturing of..______________ 16-17

rations for_________________... 16

Stock lists, routine use of____________ 341

See also Reprints.

Storage of property, rules for______ 12-14,16,18

Streams, contour control afforded by..___ 244

disappearing, inking of..________ 293-294

mapping of __ ___________ 245

double-lined, inking of.__________ 293

mapping of_________.._____ 242

intermittent, inking of.__________ 293

mapping of________________ 244

perennial, inking of.___________ 292-293

' mapping of ________________ 244

photographic mapping of ...__ 396

See also Drainage.

Streets, city, inking of.____________ 284-285

city. See also Blocks.

Striding level, adjustment of.________ 56 

Strip mosaic, production of.________ 403-405 

Submerged contours, inking of ___ 291,306 

Subsistence, rules for...... __ 15

Summits, elevations of-... .._ 123 

Suspension mechanism for camera, features

of.., .......................... 384

Symbols. See Standard symbols.

T

Tangent screw, care in use of. ..... 207

Tangents, data for plotting .... __. _____ 101

Tanks. See Wells.

Tape, "breaking" of, on slopes_ ____ 98

linen. See Rope.

testing of ___________________ 98-99 

Tape men, duties of._______ ____ 97-98 

Tape traverse, adjustment of. ... 212

use of.____________._.__.. 211-212 

Taping, causes of errors in__ 99-100 

Target rod, reading of--- 132 

Telescopic alidade. See Alidade. 

Temperature, effect of changes on steel tape. 99

record of.____ 100 

Temple Act to provide for greater progress.. 4 

Theodolite, micrometer, adjustment of 56-59

transit, adjustment of...- - 59-60,92-93 

Three-point method, plane-table locations

by............. v ... - 202-205

Tidal shore lines. See Shore lines.
INDEX 431

Page

Tilt of camera, effect of ___________ 392-394 

limitof . ___ 392-393

Tint, flat blue, use of....___..._____ 294,328

Topographic authorship. See Authorship. 

Topographic branch of the Geological Survey,

organization of.._______.. 7-8

Topographic expression. See Contouring.

Topographic maps, approval for printing of. 340

definition of._.__________.__ 161

features shown on....________ 164

reproduction of, plate showing...-......-. 282

sizes of editions of.____________.. 339 

standards for field work of making__ 181-191 

See also Checking, Control, Editing, 

Engraving, Inking, Inspection, 

Projections, Reproduction, Reprints, and Revision.

Towers, observing, construction of.. 52 

Township and range numbers, inking of_ 289,308 

Township diagram, marginal use of....._.. 308

Trails, inking of...............________ 287

mapping of_---____.____..__.. 233

Tramways, inking of...______.___.. 286

mapping of.____ .. 232

Transferring, celluloid method of. ______ 282

tracing method of.._-... .. 282-283

Transformer, construction of._ . 384

plate showing. _______-__ ... 382

Transit traverse, accuracy required in. ... 96-97

computing of azimuth for .. 101,112-113

apparatus used in, plate showing- ... 90

computations for..__....__ 112-116

control of aerial photographs by... 394-395 

detection of errors in____ ______ 115-116 

field record to be made.... . _ 110-112

highway surveys may be substituted for.. 97 

location of line of.. _ 93-94 

marks for, plate showing...__ ... 52 

method of observing and recording_. 100-112 

methods of field work.._____.__. 97-100 

supplies for...--_..__..__ ... 90 

Transit-traverse lines, additional points on.- 95 

adjustment of closures on____..__.. 115 

marking of._________________ 94-96 

Transit-traverse stations, culture adjacent to,

mapping of-__________. 241 

inking of.....-.. ........ ... 289-290,320

mapping of... -..... 240

Transmission lines. See Power-transmission

lines.

Travel, authorization for__ __ .. 9 

Traverse. See Foot traverse, Plane-table 

traverse, Stadia traverse, Tape 

traverse, Transit traverse, and 

Wheel traverse.

Triangles, tabulation of 69-70 

Triangulation, amount of control required

for...... _-.- . . - 48-49

computation of results of.. --...__.. 66-87 

figures composed of triangles used in_.. 49-50 

least-square adjustment of 71-82 

making of field record in.. 61-62 

marks for, plate showing.... 52

observing in, method of...^ 60-61 

preparation for........ 60

Page

Triangulation, observing in, time for 60 

observing tower and signals for, plate

showing. . 52

outfit for._._____-___ -- 53-54

secondary points for, importance of. 50

stations for, consent of owner to establish. 50

marking of....___ ... 50-51

selection of.._______ . 49 

signals on....._____------__ 51

Triangulation, plane-table. See Plane-table

triangulation.

Triangulation plot, making and use of__ 64 

Triangulation points, culture adjacent to,

mapping of..... .. ... 241

inking of... .._ . 289-290,320 

mapping of-_______ .... . 240

Tripods, plane-table, plates showing _ 194

plane-table, types of.___________ 197

triangulation, construction of.. __..'. 51-52

Trunk lines, for leveling, running of..__ 150-151

for transit traverse, accuracy required in. 112

Tunnels, inking of__________.___ 287

mapping of. ......._ ... _ 234

Turning points, marking of_______ 133-134,150 

Typhoid fever, prevention of_______.. 12

U

Under-water contours, inking of_ . 291

United States maps, character of..._____ 358

compiling of________________ 361-362

editing of... .... _______ 358-359

present series of.-...___________ 361

projections for________________ 362

proposed series of___...________ 362

Useful elevations. See Elevations.

Vernier, adjustable, use of.-.-.-.____- 194-195 

effect of tangent screw on reading of.-... 207 

Vernier transit, plate showing....____... 91 

Vernier transit-theodolite, plate showing.. _ 52 

Vertical angles, bench marks based on. See

Bench marks, 

plane-table traverse elevations by means

of-.----. -_ . .. 196,207 

reading of....__ ... _- 200,207 

reciprocal use of..__________ 200,240-241 

station elevations by means of______ 200 

See also Vernier. 

Vertical control. See Control. 

Vertical photographs, correction of displacements in....__________ 390-394 

definition of._________________ 390 

Viaducts. See Bridges.

Visitors to camp, entertainment of______ 17 

Vouchers, rules for......___ . 22-26

W

War Department, special mapping for___ 5-7 

Watch, regulation of----...________ 110 

Water colors, mixing of.__._________ 281 

Water surfaces, elevations of, to be dated__ 124 

Weighting of observations _ .... 78-82 

Wells, oil and gas, inking of.________ 288
432 INDEX

Page

Wells, oil and gas, mapping bL."_iLi...i..';..^ ' 235

Wells and water tanks,, inking'of L'-.-J.-^. J" 294

. mapping.of..._..-- --- _ .. - - Li'..'.'.:.____ 245

Wharves, inking.of_..-. _-_ _ _ ._ .. _ _ .. _ _ ._:.'_.:_ 287-288

mapping'of...'J:'.L.-'-::---'-__'.ji..iJi'.j.-"- 235

 Wheel traverse; distances'by.-.-L^it.L.'-Ji:..'' 211

Wilson, .Herbert M., reference to:_'_... 204,254

Wires, cross, mounting.of _-^_L-:i--'-'-^i.. 192

Woodland,.definition ot^^..:^.^...J...il^.'... 256

outlines'of, field sheets of __...i -L-.^J '256

mapping of.__..J.!.!..: l.i__ 255-256

Page

Woodland, outlines of, reprinting of _.._ ' 344

tracings of, checking and approval of.. 309,317

.->' ' office preparation of .-........'...... 308-309

submission of___..._....____ 308

. transmission and filing of....'_.. . ' 319

 ' See also Land classification. ; 

Yard rod, graduation of...______._ .'... ' 142

' plate-showing..........._______j. 128

: ' testing and care of. 1.'.....__'_..!.'.... . 146

o