USGS DIGITAL CARTOGRAPHIC DATA STANDARDS 

USGS Circular 895-A: Overview and USGS Activities 

B: Digital Elevation Models 

C: Digital Line Graphs from 1:24,000-Scale Maps 

D: Digital Line Graphs from 1:2,000,000-Scale Maps 

E: Land Use and Land Cover Digital Data 

F: Geographic Names Information System 

G: Digital Line Graph Attribute Coding Standards 

Questions regarding availability and ordering of US GeoData (all 

types of digital cartographic and geographic data produced and 

distributed by the u.s. Geological survey) should be addressed to: 

User Services Section 

National Cartographic Information Center 

u.s. Geological Survey 

507 National Center 

Reston, Virginia 22092 

Technical questions and comments should be addressed to: 

Chief, National Mapping Division 

u.s. Geological survey 

516 National Center 

Reston, Virginia 22092 

Any use of trade names and trademarks in this publication is for 

identification purposes only and does not constitute endorsement by the 

u.s. Geological Survey. 
DIGITAL LINE GRAPHS FROM 1:2,000,000-SCALE MAPS 

By Michael A. Domaratz, Cheryl A. Hallam, Warren E. Schmidt, 

and Hugh w. Calkins 

USGS Digital cartographic Data Standards 

Edited by Robert B. McEwen, Richard E. Witmer, and Benjamin s. Ramey 

Geological Survey Circular 895-D 

1983 
United States Department of the Interior 

JAMES G. WATT, Secretary 

Geological Survey 

Dallas l. Peck, Director 

Library of Congress Cataloging in Publication Data 

Main entry under title: 

TJSGS digital cartographic data standards. Digital 

line graphs from 1:2,000,000-scale maps. 

(u.s. Geological Survey circular ; 895-D) 

Bibliography: p. 

Supt. of Docs. no.: I 19.4/2:895-D 

1. Map scales. 2. Digital mapping--Standards. 

I. Geological Survey (U.S.) II. Title: U.S.G.S. 

digital cartographic data standards. Digital line 

graphs from 1:2,000,000-scale maps. III. Series. 

GA118.U73 1983 526 83-600189 

Free on application to Distribution Branch, Text Products Section, 

U.S. Geological Survey, 604 South Pickett Street, Alexandria, VA 22304 
FOREWORD 

In recent years, the disciplines of cartography and geography have undergone a rapid and striking reorientation as the 

techniques for digital collection and manipulation of data have 

evolved from fledgling laboratory procedures into dominant and 

driving forces that now pervade the disciplines. Digital techniques have provided a variety of new and powerful capabilities 

to collect, manipulate, analyze, and display spatial data. 

However, this evolution also has introduced a number of new and 

complex problems. One of the most pressing problems, and one 

which is receiving particular attention at present, is the issue 

of digital cartographic data standards. 

The u.s. Geological Survey (USGS) has been actively 

developing digital cartographic and geographic techniques for 

over a decade and has taken significant steps to develop and 

define in-house standards governing the various types of 

digital cartographic data that are being collected and archived 

in a national digital cartographic data base. The in-house 

standards are expressed in the form of specifications documents 

that were prepared to govern collection of the data and in the 

form of user guides that were prepared for distribution with 

the data. 

In an effort to fulfill lead agency requirements ~or 

promulgation of Federal standards in the earth sciences, the 

documents have been assembled with explanatory text into this 

USGS Circular consisting of separately bound chapters. This 

Circular describes some of the pertinent issues relating to 

digital cartographic data standards, documents the digital 

cartographic data standards currently in use within the USGS 

National Mapping Division, and details USGS efforts to define 

national digital cartographic data standards. 

Chapter A is an overview in which the major issues involved 

in developing digital cartographic data standards are discussed 

and the activities of the USGS related to digital cartographic 

data production and standards development are described in 

detail. Succeeding chapters comprise the pertinent documents 

that establish USGS in-house standards for the various types of 

digital cartographic data currently produced by the National 

Mapping Division--that is, digital elevation data, digital 

planimetric data, digital land use and land cover data, and 

digital geographic names data. 

This compendium of relevant material is prepared to serve 

as a benchmark and to assist ongoing efforts to establish 

acceptable standards and conventions for both Federal agencies 

and the public. 

Dallas L. Peck 

Director, 

u.s. Geological survey 

Department of the Interior 

iii 

R. B. Southard 

Chief, 

National Mapping Division 

u.s. Geological Survey 
PREFACE 

This Circular is the result of the efforts of numerous individuals who have contributed to the research, development, and 

preparation of various digital cartographic and geographic standards for the National Mapping Division of the u.s. Geological 

Survey. The individuals named as chapter authors represent both 

the originators of the various concepts as well as the writers 

who expanded and clarified these ideas. Their contributions, 

either to the concepts or the writing, are of such magnitude as 

to warrant crediting as authors. 

Atef A. Elassal was largely responsible for the original 

data structures and computer file formats that are used for the 

digital line graphs and digital elevation models. The attribute 

coding scheme was first developed by members of the Digital 

Applications Team under the direction of Robert B. McEwen. The 

Geographic Names Information System was conceived and developed 

by Sam Stulberg and Roger L. Payne. The Geographic Information 

Retrieval and Analysis System was developed by Robin G. Fegeas, 

K. Eric Anderson, Stephen c. Guptill, Cheryl A. Hallam, and 

William B. Mitchell. The small-scale Digital Line Graph data 

structure and attribute coding scheme was developed by Warren E. 

Schmidt and Michael A. Domaratz. 

The Circular was compiled in part from various user guides 

and technical instructions of the National Mapping Division. 

These documents were originally prepared by several individuals; 

credit is acknowledged to G. Michael Callahan, A. Joan Szeide, 

William R. Allder, Vincent M. Caruso, Hugh w. Calkins, Donna 

Cedar-Southworth, and Cheryl A. Hallam. The compilation of the 

various guides, instructions, and other material into the 

Circular format was performed with major assistance by Clark H. 

Cramer, Eloise R. Byrd, and Cynthia L. Cunningham. 

We acknowledge these substantial contributions that have led 

to this publication. 

iv 
CONTENTS 

Page 

Foreword ••••••••••••••••••••••••••••••••••••••••••••••••••• iii 

Preface •••••••••••••••••••••••••••••••••••••••••••••••••••• iv 

Abstract ••••••••••••••••••••••••••••••••••••••••••••••••••• 1 

Introduction ••••••••••••••••••••••••••••••••••••••••••••••• 1 

Data content ••••••••••••••••••••••••••••••••••••••••••••••• 1 

Data format •••••••••••••••••••••••••••••••••••••••••••••••• 2 

Data categories •••••••••••••••••••••·••••••••••••••••••••••• 4 

Data records ••••••••••••••••••••••••••••••••••••••••••••••• 6 

Organization of records in the file •••••••••••••••••••••••• 10 

Feature codes •••••••••••••••••••••••••••••••••••••••••••••• 11 

Coordinate systems ••••••••••••••••••••••••••••••••••••••••• 13 

Projection information ••••••••••••••••••••••••••••••••••••• 13 

Appendix A. DLG feature codes ••••••••••••••••••••••••••••• 18 

B. DLG record formats •••••••••••••••••••••••••••• 28 

c. DLG parameter codes used for Albers conic 

D. 

E. 

F. 

G. 

Figure 1. 

equal-area projection ••••••••••••••••••••••• 

Graphics format for DLG data •••••••••••••••••• 

Data sources and currency ••••••••••••••••••••• 

DLG record layout ••••••••••••••••••••••••••••• 

Coordinate conversion ••••••••••••••••••••••••• 

ILLUSTRATIONS 

Multistate blocks used for digital line graphs 

36 

37 

38 

39 

40 

Page 

from 1:2,000,000-scale maps •••••••••••••••••• 3 

2. Map elements ••••••••••••••••••••••••••••••••••• 4 

3. Areas used to define map topology •••••••••••••• 5 

4A. Network-type category •••••••••••••••••••••••••• 5 

4B. Area-type category ••••••••••••••••••••••••••••• 5 

5. An example of digital line graph topology 

relating nodes to lines and lines to areas ••• 7 

6. Sample topology, Catron County, New Mexico ••••• 8 

7A. Pecos River, southeastern New Mexico ••••••••••• 12 

7B. Rivers and water bodies, New Mexico •••••••••••• 13 

7C. Rivers and water bodies, New Mexico •••••••••••• 13 

SA. Interstate highway segments west of Denver, 

8B. 

9. 

10. 

Colo. •••••••••••••••••••••••••••••••••••••••• 14 

Interstate highway segments with connectors 

west of Denver, Colo. •••••••••••••••••••••••• 

Feature code assignment •••••••••••••••••••••••• 

Location of origin of the reference 

14 

15 

coordinates •••••••••••••••••••••••••••••••••• 15 

v 
TABLES 

Page 

Table 1. Small-scale DLG data records for Catron County, 

N. Mex. •••••••••••••••••••••••••••••••••••••••• 9 

2. DLG feature codes for single-line perennial 

rivers and streams ••••••••••••••••••••••••••••• 11 

3. DLG feature codes for roads and trails data 

file ••••••••••••••••••••••••••••••••••••••••••• 11 

vi 
USGS Digital Cartographic Data Standards 

DIGITAL LINE GRAPHS FROM 1:2,000,000-SCALE MAPS 

By Michael A. Domaratz, Cheryl A. Hallam, Warren E. Schmidt, 

and Hugh w. Calkins 

Abstract 

The discipline of cartography is 

undergoing a number of profound changes 

that center on the emerging influence of 

digital manipulation and analysis of 

data for the preparation of cartographic 

materials and for use in geographic information systems. Operational requirements have led to the development by the 

USGS National Mapping Division of several 

documents that establish in-house digital 

cartographic standards. 

In an effort to fulfill lead agency 

requirements for promulgation of Federal 

standards in the earth sciences, the 

documents have been edited and assembled 

with explanatory text into a USGS 

Circular. This Circular describes some 

of the pertinent issues relative to 

digital cartographic data standards, 

documents the digital cartographic data 

standards currently in use within the 

USGS, and details the efforts of the USGS 

related to the definition of national 

digital cartographic data standards. It 

consists of several chapters: the first 

is a general overview, and each succeeding chapter is made up from documents 

that establish in-house standards for one 

of the various types of digital cartographic data currently produced. This 

chapter, 895-D, describes the digital 

line graphs which were digitized from the 

1:2,000,000-scale sectional maps {U.S. 

regions) of the National Atlas of the 

United States of America. They are 

produced and available in both a topologically structured format and a simpler 

format optimized for graphic display. 

INTRODUCTION 

u.s Geological Survey (USGS) digital 

cartographic data files may be grouped 

into three basic forms. The first of 

these, called a digital line graph (DLG), 

is the line map information in digital 

form. The data files include information 

on planimetric base categories such as 

transportation, hydrography, and boundaries. The second form, called a 

digital elevation model, consists of a 

sampled array of elevations for a number 

of ground positions that are at regularly 

spaced intervals. The third form, the 

Geographic Names Information System, is 

an automated data system that provides 

primary information for all known places, 

features, and areas in the United States 

identified by a proper name. 

This document describes only DLG 

files collected from the 1:2,000,000-

scale National Atlas sectional maps. 

The digital data are useful for the 

production of cartographic products such 

as plotting base maps and for various 

kinds of spatial analysis. A major use 

of these digital cartographic data is to 

combine them with other geographically 

referenced data and thus enable scientists to conduct automated analyses in 

support of various decisionmaking 

processes. 

DATA CONTENT 

The 1:2,000,000-scale map series of 

cartographic data files contain selected 

categories of cartographic data in 
digital (computer-compatible) form. The 

data files are derived from the sectional 

maps of the 1970 National Atlas of the 

United States of America. Selective updating of the sectional maps was done 

before the digitizing opera~ions. Appendix E lists the source materials used to 

revise the sectional maps. 

The data are recorded in 

files or subfiles according 

category: 

• Political boundaries 

• Administrative boundaries 

• Roads and trails 

• Railroads 

• Streams 

• Water bodies 

separate 

fo major 

• Cultural features (airport~, Alaska 

pipeline) 

• Hypsography (Continental Divide only) 

Although coverage is nationwide, the 

data were digitized predominantly in 

multistate blocks (to m1n1m1ze edgejoin problems if a user has a need to 

aggregate the data). The total number of 

files is 21--15 for the conterminous 

United States, 5 for Alaska, and 1 for 

Hawaii. The grouping of the States is 

shown in figure 1. 

All data contained in the DLG data 

files are represented on maps as points, 

lines, and areas (fig. 2). 

• Points -- Features such as airfields. 

• Lines Features such as roads, 

railroads, and streams. 

• Areas -- Features such as national 

forests and water bodies. 

In digital form, these points, lines, 

and areas are represented as various 

kinds of •lines• as follows: 

• Point features -- Degenerate lines; 

lines with no length. 

• Line features Directly represented as lines. 

• Area features A line that describes the boundary of the feature. 

When these data are abstracted and 

represented as lines and are topologically encoded to retain the spatial 

relationships, a logical and consistent 

2 

data file is created for computer 

processing. 

DATA FORMAT 

Digital line graphs from 1:2,000,000-

scale maps are available in two formats: 

• A graphics format {suitable for preparing maps using the Geological 

survey Cartographic Automatic Mapping 

GS-CAM) software. 

• A topologically structured format 

(standard DLG format). 

Graphics Format Files -- A major use 

of the 1:2,000,000-scale DLG data will 

be automatic plotting of small-scale 

maps. To facilitate this process, the 

data are available in a special graphics 

format. This simplified format is designed especially for use with GS-CAM 

plotting package. GS-CAM, a modified 

version of the CIA's Cartographic Automatic Mapping computer mapping program, 

is available from the National Cartographic Information Center (NCIC). 

The graphics format files contain 

only line descriptions and are derived 

from the standard DLG data files. Such a 

graphic file contains only minimal descriptive information about each line, 

and the relationship between lines is unspecified. The graphics format files are 

organized by feature type. Within a 

given file, if a line has two attributes 

(for example, a boundary between a national forest and an Indian reservation), 

the line will appear twice in the file, 

once with a feature code indicating national forest and once with a feature 

code indicating Indian reservation. The 

format for the graphics format files is 

given in Appendix D. 

Topologically structured data 

files _...; Digital line graph is the term 

adopted by the USGS to describe line map 

data that are available in digital form. 

The DLG concept is based on graph theory, 

in which a diagram can be expressed as a 

set of nodes and links in a manner that 

shows logical relationships. Applied to 

a map, this concept is used to abstract 

the features shown on the map and to rep-. 

resent these features as various kinds of 
w 

, ... ~ 

~. ®e> 

.. "" 

INDEX MAP 

1 NORTHEASTERN STATES 

2 MIDDLE ATLANTIC STATES 

3 SOUTHEASTERN STATES 

4 FLORIDA 

5 SOUTHERN MISSISSIPPI VALLEY STATES 

6 CENTRAL MISSISSIPPI VALLEY STATES 

7 NORTHERN GREAT LAKES STATES 

8 SOUTHERN TEXAS 

9 SOUTHERN PLAINS STATES 

10 CENTRAL PLAINS STATES 

11 NORTHERN PLAINS STATES 

12 ARIZONA AND NEW MEXICO 

13 SOUTHERN CALIFORNIA 

14 CENTRAL PACIFIC STATES 

15 NORTHWESTERN STATES 

16 SOUTHEASTERN ALASKA 

17 CENTRAL ALASKA 

18 NORTHERN ALASKA 

19 SOUTHWESTERN ALASKA 

20 ALEUTIAN ISLANDS 

21 HAWAIIAN ISLANDS 

Figure 1.--Multistate blocks used for digital line graphs from 1:2,000,000-scale maps. 
Figure 2.--Map elements. 

lines. The abstraction of the map data 

according to the rules of graph theory is 

necessary to preserve the spatial relationships inherent in map data and to 

create a logical and consistent data file 

structure for computer processing. A 

digital data file of cartographic/geographic data that maintains the spatial 

relationships inherent in the map is 

called a topologically structured data 

file. 

A topologically structured data file 

has the spatial relationships inherent in 

the data explicitly coded. For example, 

a boundary is a line separating two 

areas. Generally, in a topologically 

structured data file, the boundary description contains references (termed 

pointers) to each area separated by the 

boundary, a description of each area, and 

pointers to all lines that make up the 

complete boundary of the area. 

It is necessary to define map features in this manner because the spatial 

relationships, obvious when a map is examined visually, are lost when the map is 

converted to digital form unless those 

relationships are explicitly encoded. 

Topological structuring is illustrated in figure 3. Specific DLG data 

file topology is defined by lines 1, 2, 

3, 4, and 5, which separate areas A and 

B. Each line description contains 

pointers to both areas A and B indicating 

that area A is on one side of the line 

and that area B is on the other side. 

Area A -in this example is an actual feature such as a national forest. Area B, 

4 

however, is the remainder of the map and 

carries a special code that indicates 

this fact. In this case, area B does 

not correspond to an actual feature but 

must be encoded to maintain the logic and 

consistency of the data file. In addition to recognizing all areas within the 

map, it is necessary to define the area 

outside a map sheet (area c, fig. 3) in 

order to encode the map boundary in a 

consistent manner. 

DATA CATEGORIES 

There are two types of categories in 

the 1:2,000,000-scale DLG data files: 

• Network categories, which include 

roads and trails, railroads, streams, 

cultural features, and hypsography. 

• Area categories, which include political boundaries, administrative 

boundaries, and water bodies. 

Network Categories For network 

categories, the topological coding 

recognizes only two areas--one within the 

map (background area) and one outside the 

map. All line descriptions in a network 

category, except the map border, are described as being within the background 

area of the map (fig. 4A). 

Area Categories -- Each real feature 

(for example, a national forest) is an 

area and is given a unique area identification number. In addition, any area 

within the map that is not part of a real 
area is assigned to one or more background areas, and the area outside of the 

map border is coded. Figure 4B represents these relationships. 

DATA RECORDS 

The map data in digital form contain 

three types of information: 

1. Topological codes define spatial relationships. 

2. x,y coordinate values define the 

location of the feature (seep. 13). 

3. Feature codes describe each point, 

line, or area or some characteristic 

of that point, line, or area (see 

p. 11). 

Topological Codes -- Spatial relationships are represented in three kinds 

of data records: 

1. Node records define locations that 

are needed for topological consistency, computer editing, and quality 

control. Nodes are used to define 

the starting and ending points of a 

line, the intersection of two or more 

lines, significant points on a line, 

or any arbitrary point. 

2. Area records define the actual area 

features on the map, the remainder 

of the map (background area), and 

the area outside of the map. 

3. Line records define the location of a 

line. The line represents either a 

linear feature on the map (for example, a road or a stream), a boundary of an area (for example, a lake 

or a county), or a point feature, 

which is a degenerate line (for example, an airfield). 

The line record contains the topological codes to relate nodes to lines 

and lines to areas (fig. 5). Data for 

point features are contained in the line 

record. The line--the primary structure 

of the files, carries the topology. The 

area and node records provide additional 

information. 

6 

A 

this: 

N 1 

(1) (2) 

typical node record 

-3326 -1074 0 

(3) (4) 

looks 

0 

( 5) 

like 

Node records contain the following 

information: 

(1) Type of record indicator (N for node 

record). 

(2) Internal sequential identification 

number. In this example, it is the 

first node record ( 1) in the overlay. 

(3) x,y coordinate values for the node. 

In this example, x=-3326 and y= 

-1074. In DLG files, x and y coordinate values can be negative because the origin of the internal 

file coordinate system is in the 

middle of the map. 

(4) Indicator specifying the number of 

feature codes that describe the node 

(in this example, 0). 

(5) Indicator specifying the length of 

the text string (that is, number of 

characters) used to describe the 

node (in this example, 0). 

For the 1:2,000,000-scale DLG's, the 

values of (4) and (5) will always be O, 

an indication that neither feature codes 

nor text has been encoded. 

A typical area record looks like 

this: 

A 3 

(1)(2) 

-1250 1087 1 

(3) (4) 

90 104 

Area records contain the 

information: 

0 

(5) 

following 

(1) Type of record indicator (A for 

area rE;!cord). 

(2) Internal sequential identification 

number. In this example, it is the 

third area record in the overlay 

(3). 

(3) x,y coordinate values of a reference 

point. In this example, x=-1250 and 
Q; 

'E 

~ 

g. Area B 

:E 

line Number~ 

2 5 

Area A 

3 

4 

AreaC 

Figure 3.--Areas used to define map topology. 

Area A 

Figure 4A.--Network-type category. All area within the map is defined as a 

single background area, designated in this example as Area B. 

Background Area F 

Area A 

Figure 4B.--Area-type category. Each area (real and background) 

within the map is assigned a unique identifier. 

5 
Node 1 

Area 1 

(lt!lt Area for Lrne A) 

lmphP.d Direction c! line A __. 

{Rrflhl ArP:t for Lu1e A) 

Aren2 

Figure 5.--An example of digital line graph topology relating 

nodes to lines and lines to areas. 

y=l087. (This reference point is not 

required to fall within the area 

that it represents). 

(4) Indicator specifying the number of 

feature codes that describe the 

area; in this example, 1. 

(5) Indicator specifying the length of 

text string used to describe the 

area (for 1:2,000,000-scale DLG's, 

always 0.) 

When the indicator specifying the 

number of feature codes that describe the 

area is other than 0, the feature codes 

will follow in a separate record. In 

this example, 90 104, the feature code, 

indicates a national forest. 

A typical line record looks like 

this: 

L 14 24 21 12 11 2 2 0 

(1)(2) (3) (4) (5) (6) (7)(8)(9) 

1672 -2808 1584 -2656 

290 6091 290 6087 

7 

Line records contain the following 

information: 

(1) Type of record indicator (L for line 

record). 

(2) Internal sequential identification 

number (in this example, 14). 

(3) Internal sequential identification 

number of the starting node of the 

line (in this example, 24). 

(4) Internal sequential identification 

number for the ending node of the 

line (in this example, 21). 

(5) Internal sequential identification 

number of the area to the left of 

the line (in this example, 12). 

( 6) Internal sequential identification 

number of the area to the right of 

the line (in this example, 11). 

( 7) The number of x ,y coordinate pairs 

that describe the line (in this 

example, 2). 

(8) The number of feature codes that 

describe the line (in this example, 

2). 
( 9) The length of text string that 

describes the line (for 1:2,000,000-

scale DLG's, always 0.) 

Since the value for (7) is 2 we know 

that, immediately following the line 

record description will be the actual 

x,y coordinate values that describe the 

line (in this case 1672 -2808, and 1584 

-2656). 

Since the value in (8) (number of 

feature codes) is greater than 0 (in this 

case, 2), these codes will be listed 

following the coordinate data (in this 

example, 290 6091 and 290 6087). 

The x,y coordinate values, feature 

codes, and text strings are in separate 

logical records. 

8 

Ol 

·~ 

-~ ::!: 

~ <( z 

Node 44 Line 76 

Area 30 

0 

co 

Cll 

c: 

::::i 

A line record representing a point 

feature (a degenerate line) can be identified by comparing the starting and 

ending nodes, which in all cases will 

have the same value and will have exactly 

two coordinate pairs. 

The complete description of any given 

feature can be obtained by examining all 

node, area, and line records that describe the feature. For example, figure 

6 shows Catron County, New Mexico, and 

its nodes, areas, and lines. Table 1 

lists the data records that completely 

describe Catron County. 

Catron County is fully described in 

the data file by 13 entries: 6 nodes, 1 

area, and 6 lines. The six node records 

contain only the x,y coordinate values 

Area12 

Node 52 

Area9 

Area 10 

Catron County 

O Graphic 0.0 

co Reference ~ Point in ::::i Node 45 Area Record 

v Ol 

"" Line 87 ~ ::::i Node 53 

Area 29 

Node 115 Line 86 

Node 56 Area 6 

Area7 

Figure 6.--sample topology, Catron County, New Mexico. 

8 
Table 1.--small-scale DLG data records for Catron County, New Mexico 

[N, node; A, area; L, line] 

N 

N 

N 

N 

N 

N 

44 -86 948 

45 -90 -831 

52 2297 947 

53 2361 -1484 

56 1840 -2085 

115 -91 -2102 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

A 10 428 -934 2 0 

91 35 92 3 

L 76 44 52 12 10 4 1 0 

L 

L 

L 

L 

L 

-86 948 1155 938 1565 940 2297 947 

290 6009 

79 115 45 29 10 3 1 

-91 -2102 -91 -1770 -90 -831 

290 6005 

80 45 44 30 10 3 1 

-90 -831 -86 8 -86 948 

290 6005 

85 53 52 10 9 4 1 

2361 -1484 2329 -706 2319 252 2297 947 

290 6009 

86 115 56 10 7 3 1 

-91 2102 195 -2091 1840 -2085 

290 6009 

87 56 53 10 6 4 1 

1840.-2085 1842 -1482 2285 -1484 2361 -1484 

290 6009 

9 

0 

0 

0 

0 

0 
for each node and are used for editing 

and quality control. The area record 

contains the identifying information: 

the internal sequential identification 

number (10), the x,y coordinates of a 

graphic reference point ( 428 -934), and 

an indicator specifying th~ number of 

feature codes in the following record 

( 2). The feature codes appear in the 

next logical record. The major codes 91 

and 92 indicate that the following minor 

codes are the State and county Federal 

Information Processing Standards (FIPS) 

codes. The minor codes 35 and 3 are the 

State and county FIPS codes for New 

Mexico and Catron County, respectively. 

The boundary of the county is made up of 

six lines. Following each line record 

are the x,y coordinate and feature code 

records. The feature codes 290 6009 and 

290 6005 identify the lines as county 

and State boundary lines, respectively. 

ORGANIZATION OF RECORDS IN THE FILE 

The DLG data files contain nine 

record types, shown in the right column. 

1. Header records 

Type A (one record) 

Type B (one record) 

Type C (one record) 

2. Data records 

Node records 

Node description (D.l) 

Feature codes (F) 

Text string (G) 

Area records 

Area description (D.l) 

Feature codes (F) 

Text string (G) 

Line records 

Line description (D.2) 

x,y coordinates (E) 

Feature codes (F) 

Text string (G) 

3. Accuracy estimate 

Type H (one record) 

10 

Record Contents 

Type 

A Header record containing DLG identification information 

B Header record containing projection information and registration 

points 

c Header record identifying data 

categories contained in this DLG 

and indicating the number of nodes, 

areas, and lines in each category 

D.l A node or an area record 

D.2 A line record 

E Record containing x,y coordinate 

string 

F Record containing the feature codes 

G Record containing the text string 

H Record containing accuracy 

estimates 

(Records G and H do not 

exist for any DLG file) 

The relationships between these 

record types is shown diagrammatically 

in Appendix F. The actual sequence of 

records in the data file is as follows: 

Repeated 

for each 

node within 

a category 

Repeated Repeated 

for each for each 

area within data 

a category category 

Repeated 

for each 

line within 

a category 
FEATURE CODES 

In the DLG data files, feature codes 

are used to identify each feature (such 

as a road or stream) and to provide 

additional information about the feature. 

The feature code consists of two 

parts: a three-digit major code and a 

four-digit minor code. This structure 

covers all DLG data files created and 

maintained by the USGS. In the 

1:2,000,000-scale DLG data files, the 

major code is usually 290, indicating a 

small-scale data base. There are, however, a few exceptions. A listing of all 

feature codes used for the 1:2,000,000-

scale DLG files is contained in Appendix 

A. The minor code describes the feature. 

This same structure is used to enter 

additional information about a feature. 

The feature codes have been assigned 

to various map features in a manner 

designed to facilitate the production of 

small-scale maps (1:2,000,000 to 

1:10,000,000 scale). Two capabilities 

are built into the feature codes. ( 1) 

The size of the feature is included so 

that features can be excluded from a 

given map as a function of the scale and 

(or) intended use of the map. (2) 

Feature codes can be grouped together in 

various ways to produce logical sets of 

information. Examples of these capabilities are presented below. 

First, feature selection by size is 

shown. The feature codes for singleline perennial rivers and streams are 

shown in table 2. 

A map produced at a scale of 

1:2,000,000 might include all streams and 

rivers listed, from feature codes 290 

3003 through 290 3016 (fig. 7A}. However, a map at a scale of 1:5,000,000 

could exclude all rivers and streams of 

less than 50 km (fig. 7B). In this caP.~, 

feature codes 290 3007 through 290 3016 

would be used to produce the map, whereas 

feature codes 290 3003 through 290 3006 

would not be used because these features 

fall below the minimum size for this type 

of feature at this particular scale. 

Finally, at a scale of 1:10,000,000 

feature codes 290 3010 through 290 3016 

may be used; all rivers and streams less 

than 100 km in length (fig. 7C) would 

thereby be excluded. 

11 

Table 2.--DLG feature codes for singleline perennial rivers and 

streams 

Major 

cod! 

Minor 

code Description 

290 

290 

290 

290 

290 

290 

290 

290 

290 

290 

290 

290 

290 

290 

3003 

3004 

3005 

3006 

3007 

3008 

'3009 

3010 

3011 

3012 

3013 

3014 

3015 

3016 

length <20 km. (< 12 mi) 

length 20-<30 km (12-<19 mi) 

length 30-<40 km. (19-<25 mi) 

length 40-<50 km. (25-<31 mi) 

length 50-<60 km (31-<37 mi) 

length 60-<80 km (37-<50 mi) 

length 80-<100 km. (50-<62 mi) 

length 100-<125 km (62-<78 mi) 

length 125-<150 km (78-<93 mi) 

length 150-<200 km (93-<124 mi) 

length 200-<250 km (124-<155 mi) 

length 250-<300 km (155-<186 mi) 

length 300-<350 km. (186-<217 mi) 

length 350+ km (217+ mi) 

The second example, which uses a 

group of feature codes to produce a logical set, can be illustrated by looking at 

the roads and trails data file. Consider 

the feature codes in table 3. 

Table 3.--DLG feature codes for roads and 

trails data file 

Major Minor 

code code 

290 5001 

290 5002 

290 5003 

290 5004 

290 5005 

290 5006 

290 5007 

290 5008 

290 5009 

290 5010 

Description 

Interstate 

Major u.s., limited access, 

divided 

Major State, limited access, 

divided 

Major other, limited access, 

divided 

Toll road 

Interstate connector 

Limited access, divided connector 

Toll connector 

Interstate, under construction 

Interstate, proposed 

The interstate highway system can be 

represented in two ways: ( 1) the road 

segments that are actually classified as 
f. 

o' 

( p 

Figure 7A.--Pecos River, southeastern New Mexico. 

Scale: 1:2,000,000. 

part of the interstate system (feature 

codes 290 5001, 290 5009, and 290 5010) 

and (2) how a motorist might perceive the 

interstate highway system (feature codes 

290 5001 through 290 5010). The map resulting from this second case would show 

a completely connected highway system, 

made up of the interstate system and the 

other roads that act as connectors. 

Figures SA anQ 8B are partial maps illustrating the interstate system plotted 

both ways. 

Feature codes are recorded in separate records, following either an area 

or a line record. However, not all area 

and line records will have a feature 

code. The absence of a feature code 

means that the code for the feature can 

be derived from adjacent, connecting, or 

bounding factors and that no additional 

12 

information is carried in that particular 

record. The main feature code (that 

which defines the feature) will be 

assigned to either an area or a line 

record, depending on what the feature 

represents. Additional feature codes may 

be carried with the main feature code to 

convey more descriptive information about 

the feature. For example, consider 

figure 9. 

Area 34 is an Indian reservation (90 

107). Area 49 is a national scenic 

waterway or wilderness area (90 106). 

Notice that area 49 is also a forest or 

grassland (90 104). 

Line 107 carries feature codes indicating that it is the boundary for a 

national wilderness area (290 6045), a 

national forest (290 6055), and an 

Indian reservation (290 6070). 
Figure 7B.--Rivers and water bodies, 

New Mexico. 

Scale: 1:5,000,000. 

Figure 7C.--Rivers and water bodies, 

New Mexico. 

Scale: 1:10,000,000. 

Multiple feature codes (maximum of 

20) may be entered for any area or line 

record of a DLG data file. When multiple 

codes are entered, they are not entered 

in any specific order. 

13 

COORDINATE SYSTEMS 

The DLG data files are encoded and 

stored by using an internal file reference coordinate system. 

The origin of the internal file 

reference coordinate is in the center of 

the map sheet (fig. 10). All map features (nodes, areas, and lines) are 

specified in terms of these internal 

file reference coordinates. The internal 

file reference coordinate system is in 

units of 0.001 inch at map scale. The 

file-header records contain information 

describing the ground planimetric 

reference system for the file (Albers 

equal area), the longitudes and latitudes of the corner points of the map 

sheet (in degrees and decimal degrees), 

and the file-to-map coordinate projection 

parameters. This information can be used 

to convert the internal file reference 

coordinates to the ground planimetric 

reference system for the Albers equal 

area projection. An example of this 

calculation is given in Appendix G. 

PROJECTION INFORMATION 

The 1:2,000,000-scale data file comprises three zones: Continental United 

States, Hawaiian Islands, and Alaska. 

The base parallel, central meridian, 

standard parallels, and maximum and 

minimum latitude and longitude values for 

each zone are as follows: 

Continental United States 

Base parallel 

Central meridian 

Standard parallels 

Longitude extent 

Latitude extent 

Hawaiian Islands 

Base parallel 

Central meridian 

Standard parallels 

Longitude extent 

Latitude extent 

23° N. 

96° w. 

29.5° N. and 45.5° N. 

66° w. to 125° w. 

24° N. to 50° N. 

30 N. 

157° w. 

8° N. and 18° N. 

154° w. to 162° w. 

18° N. to 23° N. 
Denver 

\ 

Interstate (290-5001) 

----- Under Construction (290-5009) 

Figure 8A.--Interstate highway segments west of Denver, Colo. 

Interstate ~ 

{ 

Connectors "'\ ,.--

.,.,---

/~ 

~I Interstate (290-5001) 

- - - -- Under Constr. (290- 500 9) 

- - Connectors (290-5006) 

Figure 8B.--Interstate highway segments with connectors west of Denver, Colo. 

14 
A 

A 

L 

34 

90 

49 

90 

107 

4569 

290 

3859 

107 

4591 

106 

59 

1507 

6045 

~---------eNooe~ .------------J 

Indian Reservation 

- Feature Code 90 1 07 

-Area 34 

1668 

1311 2 

90 104 

58 34 

4617 

290 

49 

1510 

6055 

0 

3 

4693 

290 

National Forest and 

Wilderness Area 

3 0 

1515 

6070 

- Feature Codes 

90 104 

90 106 

-Area 49 

Figure 9.--Feature code assignment. 

f' / 

' / 

' / 

' / 

' / ffi Center Origin 

/ 

/ ' 

/ ' 

/ ' 1/ ' ' 

Figure 10.--Location of origin of file reference coordinates. 

15 
Projections Information--cont'd. 

Alaska 

Base parallel 

Central meridian 

Standard parallels 

Longitude extent 

latitude extent 

50° N. 

154° w. 

55° N. and 65° N. 

129° w. to 172° E. 

54° N. to 72° N. 

16 

The Clarke, 1866 spheroid is used for the 

map projection. 

(For Alaska, the Aleutian Islands extend 

westward to 172° E. For computational 

simplicity the longitude values ranging 

from 180° to 172°E. have been entered in 

the data files as 180° to 188° [or -180 

to -188].) 
APPENDIXES 

17 
....... 

(X) 

FEATURE 

MAJOR 

CODE 

MINOR 

CODE 

Water bodies •••• 040 0100 

0102 

0104 

0105 

0106 

0107 

0110 

0150 

0199 

Political 

boundaries. 

090 0101 

0197 

0198 

0199 

Administrative 090 0103 

boundaries. 0104 

0105 

0106 

0107 

0108 

APPENDIX A.--DLG Feature Codes 

DESCRIPTION 

AREA ATTRIBUTES 

Perennial lake or pond 

Intermittent lake or pond 

Dry lake or pond 

Alkali flat 

Reservoir 

Intermittent reservoir 

Glacier or snowfield 

Island 

Area not in water body (remainder of map) 

Incorporated city, village, town, borough, or hamlet 

Canada 

Mexico 

Area outside a national boundary 

National park, monument, lakeshore, parkway, battlefield, or recreation area 

National forest or grassland 

National wildlife refuge, game preserve, or fish hatchery 

National scenic waterways or wilderness area 

Indian reservation 

Military reservation 
..... 

1.0 

FEATURE 

Roads and 

trails. 

Political 

boundaries. 

MAJOR 

CODE 

MINOR 

CODE 

APPENDIX A.--DLG Feature Codes--continued 

DESCRIPTION 

PARAMETER CODES 

Line records 

102 o---

103 o---

104 0---

Interstate route number, two or three digits right justified 

u.s. route number, two or three digits right justified 

091 00--

092 0---

State route number, two or three digits right justified 

Area records 

State FIPS code, two digits right justified 

County or county equivalent FIPS code, three digits, right justified 

LINE ATTRIBUTES 

Hypsography ••••• 290 2017 Continental Divide 

Rivers and 290 3001 River/stream (double line, shoreline) 

streams. 3002 River/stream (double line, centerline) 

3003* River/stream (single line), perennial, length <20 km, or <12 mi 

3004 River/stream (single line), perennial, length 20-<30 km, or 12-<19 mi 

3005 River/stream (single line), perennial, length 30-<40 km, or 19-<25 mi 

3006 River/stream (single line), perennial, length 40-<50 km, or 25-<31 mi 

3007 River/stream (single line), perennial, length 50-<60 km, or 31-<37 mi 

3008 River/stream (single line), perennial, length 60-<80 km, or 37-<50 mi 

3009 River/stream (single line), perennial, length 80-~00 km, or 50~<62 mi 

3010 River/stream (single line), perennial, length 100-<125 km, or 62-<78 mi 

*This code was only used in the Alaskan drainage files. 

Note: Listing of FIPS codes available as National Bureau of Standards (U.S.), Federal Information Processing 

Standards Publication (FIPS PUB) 6-3, 39 p. for sale by the National Technical Information Service, u.s. 

Department of Commerce, Springfield, VA 22161. 
APPENDIX A.--DLG Feature Codes--continued 

MAJOR MINOR 

FEATURE CODE CODE DESCRIPTION 

LINE ATTRIBUTES--continued 

Rivers and 290 3011 River/stream (single line), perennial, length 125-<150 km, or 78-<93 mi 

streams 3012 River/stream (single line), perennial, length 150-<200 km, or 93-<124 mi 

(cont'd.) 3013 River/stream (single line), perennial, length 200-<250 km, or 124-<155 mi 

3014 River/stream (single line), perennial, length 250-<300 km, or 155-<186 mi 

3015 River/stream (single line), perennial, length 300-<350 km, or 186-<217 mi 

3016 River/stream (single line), perennial, length 350+ km, or 217+ mi 

3017* River/stream (single line), intermittent, length <20 km, or <12 mi 

3018 River/stream (single line), intermittent, length 20-<30 km, or 12-<19 mi 

3019 River/stream (single line), intermittent, length 30-<40 km, or 19-<25 mi 

3020 River/stream (single line), intermittent, length 40-<50 km, or 25-<31 mi 

3021 River/stream (single line), intermittent, length 50-<60 km, or 31-<37 mi 

3022 River/stream (single line), intermittent, length 60-<80 km, or 37-<50 mi 

3023 River/stream (single line), intermittent, length 80-<100 km, or 50-<62 mi 

~ 3024 River/stream (single line), intermittent, length 100-<125 km, or 62-<78 mi 0 3025 River/stream (single line), intermittent, length 125-<150 km, or 78-<93 mi 

3026 River/stream (single line), intermittent, length 150-<200 km, or 93-<124 mi 

3027 River/stream (single line), intermittent, length 200-<250 km, or 124-<155 mi 

3028 River/stream (single line), intermittent, length 250-<300 km, or 155-<186 mi 

3029 River/stream (single line), intermittent, length 300-<350 km, or 186-<217 mi 

3030 River/stream (single line), intermittent, length 350+ km, or 217+ mi 

3035* River/stream, centerline in water body, perennial, length <2 km, or <1 mi 

3036 River/stream, centerline in water body, perennial, length 2-<4 km, or 1-<2 mi 

3037 River/stream, centerline in water body, perennial, length 4-<6 km, or 2-<4 mi 

3038 River/stream, centerline in water body, perennial, length 6-<8 km, or 4-<5 mi 

3039 River/stream, centerline in water body, perennial, length 8-<10 km, or 5-<6 mi 

3040 River/stream, centerline in water body, perennial, length 10-<15 km, or 6-<9 mi 

3041 River/stream, centerline in water body, perennial, length 15-<20 km, or 90-12 mi 

3042 River/stream, centerline in water body, perennial, length 20-<25 km, or 12-<16 mi 

3043 River/stream, centerline in water body, perennial, length 25-<30 km, or 16-<19 mi 

3044 River/stream, centerline in water body, perennial, length 30-<40 km, or 19-<25 mi 

3045 River/stream, centerline in water body, perennial, length 40-<50 km, or 25-<31 mi 

3046 River/stream, centerline in water body, perennial, length 50-<60 km, or 31-<37 mi 

*This code was only used in the Alaskan drainage files. 
N 

...... 

FEATURE 

Rivers and 

streams 

( cont • d.) 

MAJOR 

CODE 

290 

APPENDIX A.--DLG Feature Codes--continued 

MINOR 

CODE DESCRIPTION 

3047 

3048 

3050 

3051 

3052 

3053 

3054 

3055 

3056 

3057 

3058 

3059 

3060 

3061 

3062 

3063 

3070* 

3071 

3072 

3073 

3074 

3075 

3076 

3077 

3078 

3079 

3080 

3081 

3082 

3083 

3086 

3095 

LINE ATTRIBUTES--continued 

River/stream, centerline in water body, perennial, length 60-<80 km, or 37-<50 mi 

R~ver/stream, centerline in water body, perennial, length 80+ km, or 50+ mi 

River/stream, centerline in water body, intermittent, length <2 km, or <1 mi 

River/stream, centerline in water body, intermittent, length 2-<4 km, or 1-<2 mi 

River/stream, centerline in water body, intermittent, length 4-<6 km, or 2-<4 mi 

River/stream, centerline in water body, intermittent, length 5-<8 km, or 4-<5 mi 

River/stream, centerline in water body, intermittent, length 8-<10 km, or 5-<6 mi 

River/stream, centerline in water body, intermittent, length 10-<15 km, or 6- <9 mi 

River/stream, centerline in water body, intermittent, length 15-<20 km, or 9-<12 mi 

River/stream, centerline in water body, intermittent, length 20-<25 km, or 12-<16 mi 

River/stream, centerline in water body, intermittent, length 25-<30 km, or 16-<19 mi 

River/stream, centerline in water body, intermittent, length 30+ km, or 19+ mi 

Braided stream, average width of braid 6+ km, or 4+ mi 

Braided stream, average width of braid 0-<2 km, or 0-<1 mi 

Braided stream, average width of braid 2-<4 km, or 1-<2 mi 

Braided stream, average width of braid 4-<6 km, or 2-<4 mi 

Canal, navigable, length <1 km, or <1 mi 

Canal, navigable, length 1-<10 km, or 1-<6 mi 

Canal, navigable, length 10-<20 km, or 6-<12 mi 

Canal, navigable, length 20-<40 km, or 12-<25 mi 

Canal, navigable, length 40-<60 km, or 25-<37 mi 

Canal, navigable, length 60-<60 km, or 37-<50 mi 

Canal, navigable, length 80+ km, or 50+ mi 

canal, other, length <1 km, or <1 mi 

Canal, other, length 1-<10 km, or 1-<6 mi 

Canal, other, length 10-<20 km, or 6-<12 mi 

Canal, other, length 20-<40 km, or 12-<25 mi 

Canal, other, length 40-<60 km, or 25-<37 mi 

Canal, other, length 60-<80 km, or 37-<50 mi 

Canal, other, length 80+ km, or 50+ mi 

Ditch (perennial) 

Intercoastal waterway 

*This code was only used in the Alaskan drainage files. 
N 

N 

FEATURE 

MAJOR 

CODE 

Water bodies •••• 290 

MINOR 

CODE 

4000 

4001* 

4002 

4003 

4004 

4005 

4006 

4007 

4008 

4009 

4010 

4011 

4012 

4013 

4014 

4021* 

4022 

4023 

4024 

4025 

4026 

4027 

4028 

4029 

4030 

4031 

4032 

4033 

4034 

4040* 

4041 

4042 

APPENDIX A.--DLG Feature Codes--continued 

DESCRIPTION 

LINE ATTRIBUTES--continued 

u.s. coastline including Great Lakes 

Perennial water body, lake, reservoit, and island, length <2 km, or <1 mi 

Perennial water body, lake, reservoir, and island, length 2-<4 km, or 1-<2 mi 

Perennial water body, lake, reservoir, and island, length 4-<6 km, or 2-<4 mi 

Perennial water body, lake, reservoir, and island, length 6-<8 km, or 4-<5 mi 

Perennial water body, lake, reservoir, and island, length 8-<10 km, or 5-<6 IDi 

Perennial water body, lake, reservoir, and island, length 10-<15 km, or6-<9 mi 

Perennial water body, lake, reservoir, and island, length 15-<20 km, or -<12 mi 

Perennial water body, lake, reservoir, and island, length 20-<25 km, or 12-<16 mi 

Perennial water body, lake, reservoir, and island, length 25-<30 km, or 16-<19 mi 

Perennial water body, lake, reservoir, and island, length 30-<40 km, or 19-<25 mi 

Perennial water body, lake, reservoir, and island, length 40-<50 km, or 25-<31 mi 

Perennial water body, lake, reservoir, and island, length 50-<60 km, or 31- 37 mi 

Perennial water body, lake, reservoir, and island, length 60-<80 km, or 37- 50 mi 

Perennial water body, lake, reservoir, and island, length 80+ km, or 50+ mi 

Intermittent water body, lake or reservoir, length <2 km, or <1 mi 

Intermittent water body, lake or reservoir, length 2-<4 km, or 1-<2 mi 

Intermittent water body, lake or reservoir, length 4-<6 km, or 2-<4 mi 

Intermittent water body, lake or reservoir, length 6-<8 km, or 4-<5 mi 

Intermittent water body, lake or reservoir, length 8-<10 km, or 5-<6 mi 

Intermittent water ·body, lake or reservoir, length 10-<15 km, or 6-<9 mi 

Intermittent water body, lake or reservoir, length 15-<20 km, or 9-<12 mi 

Intermittent water body, lake or reservoir, length 20-<25 km, or 12-<16 mi 

Intermittent water body, lake or reservoir, length 25-<30 km, or 16-<19 mi 

Intermittent water body, lake or reservoir, length 30-<40 km, or 19-<25 mi 

Intermittent water body, lake or reservoir, length 40-<50 km, or 25-<31 mi 

Intermittent water body, lake or reservoir, length 50-<60 km, or 31-<37 mi 

Intermittent water body, lake or reservoir, length 60-<80 km, or 37-<50 mi 

Intermittent water body, lake or reservoir, length 80+ km, or 50+ mi 

Marsh/swamp and salt marsh, length <10 km, or <6 mi 

Marsh/swamp and salt marsh, length 10-<17 km, or 6-<11 mi 

Marsh/swamp and salt marsh, length 17-<25 km, or 11-<16 mi 

*This code was only used in the Alaskan drainage files. 
t-v 

w 

FEATURE 

Water bodies 

( cont 'd.) 

Roads and 

trails. 

APPENDIX A.--DLG Feature Codes--continued 

MAJOR 

CODE 

MINOR 

CODE DESCRIPTION 

290 4043 

4044 

4045 

4050 

4051 

4052 

4053 

4060* 

4061 

4062 

4063 

4064 

4065 

4066 

290 5001 

5002 

5003 

5004 

5005 

5006 

5007 

5008 

LINE ATTRIBUTES--continued 

Marsh/swamp and salt marsh, length 25-<37 km, or 16-<23 mi 

Marsh/swamp and salt marsh, length 37-<50 km, or 23-<31 mi 

Marsh/swamp and salt marsh, length 50+ km, or 31+ mi 

Dry lake and alkali flat, length <2 km, or <1 mi 

Dry lake and alkali flat, length 2-<4 km, or 1-<2 mi 

Dry lake and alkali flat, length 4-<6 km, or 2-<4 mi 

Dry lake and alkali flat, length 6+ km, or 4+ mi 

Glacier, length <4 km, or <2 mi 

Glacier, length 4-<10 km, or 2-<6 mi 

Glacier, length 10-<17 km, or 6-<11 mi 

Glacier, length 17-<25 km, or 11-<16 mi 

Glacier, length 25-<37 km, or 16-<23 mi 

Glacier, length 37-<50 km, or 23-<31 mi 

Glacier, length 50+ km, or 31+ mi 

Interstate 

Major u.s., limited access, divided 

Major State, limited access, divided 

Major other, limited access, divided 

Toll roadl 

Interstate connectorl 

Limited access, divided connectorl 

Toll connectorl 

5009 Interstate, under construction 

5010 Interstate, proposed 

5013 Minor u.s., limited access, 310 km (500 mi) and longer 

5014 u.s. non-limited access, 310 km (500 mi) and longer 

5015 Minor u.s. limited access, less than 310 km (500 mi) 

*This code was only used in the Alaskan drainage files. 

lRedundant entry used to provide additional information. 
N 

~ 

FEATURE 

Roads and 

trails 

(cont'd.) 

MAJOR 

CODE 

MINOR 

CODE 

APPENDIX A.--DLG Feature Codes--continued 

DESCRIPTION 

LINE ATTRIBUTES--continued 

290 5016 

5017 

5018 

u.s. non-limited access, less than 310 km (500 mi) 

Other minor u.s. limited access 

Other u.s.2 

5019 Other minor State primary, limited access 

5020 Other State primary 

5021 Minor u.s. parallel, within 10 km (6 mi) 

5022 u.s. parallel, within 10 km (6 mi) 

5023 Minor State parallel, within 10 km (6 mi) 

5024 State parallel, within 10 km (6 mi) 

5028 State secondary (all weather, hard surface) 

5031 Light duty (all weather, improved) 

5041 Unimproved (fair or dry weather) 

5061 Tunnel, road 

5062 Ferry, auto 

Railroads ••••••• 290 5071 

5072 

5073 

5074 

5075 

5078 

5079 

5080 

Class 1, category A, main line 

Class 1, category B, main line 

Class 1, category A, branch line 

Class 1, category B, branch line 

Other railroad 

Tunnel, railroad 

Ferry, railroad 

Class 1, category A, main-line connectorl 

Political 

boundaries. 

290 6000 

6001 

6002 

International treaty line 

National (land) 

National (water) 

lRedundant entry used to provide additional information. 

2u.s. business, alternate, bypass, and routes paralleling u.s. or interstate routes within 10 to 25 km. 
N 

U1 

APPENDIX A.--DLG Feature Codes--continued 

FEATURE 

MAJOR 

CODE 

MINOR 

CODE DESCRIPTION 

Political 

boundaries 

(cont'd.) 

290 6005 

6006 

6009 

6010 

6011 

6012 

6014 

Administrative 290 6021 

boundaries. 6022 

6023 

6024 

6025 

6026 

6027 

6028 

6029 

6030 

6031 

6032 

6033 

6034 

6035 

6036 

6037 

6038 

6039 

6040 

6041 

6042 

6043 

LINE ATTRIBUTES--continued 

State/provincial (land) 

state/provincial (water) 

County, parish, Alaskan borough, or large independent city (land) 

County, parish, Alaskan borough, or large independent city (water) 

Corporate limit (1 million and over population) 

Corporate limit (1/2 to less than 1 million population) 

Small independent city (usually not shown as a county) 

National park, length at longest dimension 0-<2 km, or 0-<1 mi 

National park, length at longest dimension 2-<8 km, or 1-<5 mi 

National park, length at longest dimension 8-<14 km, or 5-<9 mi 

National park, length at longest dimension 4-<20km, or 9-<12 mi 

National park, length at longest dimension 20+ km, or 12+ mi 

National monument, length at longest dimension 0-<2 km, or 0-<1 mi 

National monument, length at longest dimension 2-<8 km, or 1-<5 mi 

National monument, length at longest dimension 8-<14 km, or 5-<9 mi 

National monument, length at longest dimension 14-<20 km, or 12+ mi 

National monument, length at longest dimension 20+ km, o~ 12+ mi 

National seashore or lakeshore, length at longest dimension 0-<2 km, or 0-<1 mi 

National seashore or lakeshore, length at longest dimension 2-<8 km, or 1-<5 mi 

National seashore or lakeshore, length at longest dimension 8-<14 km, or 5-<9 mi 

National seashore or lakeshore, length at longest dimension 4-<20 km, or 9-<12 mi 

National seashore or lakeshore, length at longest dimension 20+ km, or 12+ mi 

National recreation area, length at longest dimension 0-<2 km, or 0-<1 mi 

National recreation area, length at longest dimension 2-<8 km, or 1-<5 mi 

National recreation area, length at longest dimension 8-<14 km, or 5-<9 mi 

National recreation area, length at longest dimension 14-<20 km, or 9-<12 mi 

National recreation area, length at longest dimension 20+ km, or 12+ mi 

National wilderness area, length at longest dimension 0-<2 km, or 0-<1 mi 

National wilderness area, length at longest dimension 2-<8 km, or 1-<5 mi 

National wilderness area, length at longest dimension 8-<14 km, or 5-<9 mi 
1\.) 

0\ 

FEATURE 

MAJOR 

CODE 

Administrative 290 

boundaries 

(cont 'd.) 

MINOR 

CODE 

6044 

6045 

6051 

6052 

6053 

6054 

6055 

6056 

6057 

6058 

6059 

6060 

6061 

6062 

6063 

6064 

6065 

6066 

6067 

6068 

6069 

6070 

6081 

6082 

6087 

6088 

6089 

6090 

6091 

6092 

6093 

6094 

APPENDIX A.--DLG Feature Codes--continued 

DESCRIPTION 

LINE ATTRIBUTES--continued 

National wilderness area, length at longest dimension 14-<20 km, or 9-<12 mi 

National wilderness area, length at longest dimension 20+ km, or 12+ mi 

National forest, length at longest dimension 0-<2 km, or O~<mi 

National forest, length at longest dimension 2-<8 km, or 1-<5 mi 

National forest, length at longest dimension 8-<14 km, or 5-<9 mi 

National forest, length at longest dimension 14-<20 km, or 9-<12 mi 

National forest, length at longest dimension 20+ km, or 12+ mi 

National grassland, length at longest dimension 0-<2 km, or 0-<1 mi 

National grassland, length at longest dimension 2-<8 km, or 1-<5 mi 

National grassland, length at longest dimension 8-<14 km, or 5-<9 mi 

National grassland, length at longest dimension 14-<20 km, or 9-<12 mi 

National grassland, length at longest dimension 20+ km, or 12+ mi 

National wildlife refuge, length at longest dimension 0-<2 km, or 0-<1 mi 

National wildlife refuge, length at longest dimension 2-<8 km, or 1-<5 mi 

National wildlife refuge, length at longest dimension 8-<14 km, or 5-<9 mi 

National wildlife refuge, length at longest dimension 14-<20 km, or 9-<12 mi 

National wildlife refuge, length at longest dimension 20+ km, or 12+ mi 

Federal Indian reservation, length at longest dimension 0-<2 km, or 0-<1 mi 

Federal Indian reservation, length at longest dimension 2-<8 km, or 1-<5 mi 

Federal Indian reservation, length at longest dimension 8-<14 km, or 5-<9 mi 

Federal Indian reservation, length at longest dimension 14-<20 km, or 9-<12 mi 

Federal Indian reservation, length at longest dimension 20+ km, or 12+ mi 

Federal Military reservation, areas of 1-<405 ha, or 1-<1000 acres 

Federal Military reservation, areas of 405+ ha, or 1000+ acres 

National park, closure line 

National monument, closure line 

National seashore or lakeshore, closure line 

National recreation area, closure line 

National wilderness area, closure line 

National forest, closure line 

National grassland, closure line 

National wildlife refuge, closure line 
N 

-..J 

FEATURE 

Administrative 

boundaries 

(cont'd.) 

Cultural 

features. 

MAJOR 

CODE 

290 

290 

MINOR 

CODE 

6095 

6097 

7001 

APPENDIX A.--DLG Feature Codes--continued 

DESCRIPTION 

LINE ATTRIBUTES--continued 

Indian reservation, closure line 

Military reservation, closure line 

Commmercial airfield 

7002 Military airfield 

7020 Alaska pipeline 
N 

00 

APPENDIX B.--DLG Record Formats 

[DLG data files are available in two forms: standard ASCII and IBM binary. ASCII files contain 

fixed length records of 144 characters. Binary files are IBM standard variable-length records. 

The following format table describes both types of DLG data files.] 

Logical Record Type A 

Physical record i format 

ASCII BINARY 

Data 

Element Contents 

Type 

(FORTRAN 

notation) 

Format Format 

record * (bytes) record * (bytes) Comment 

1 

2 

3 

4 

5 

Name of digital cartographic ALPHA 

unit. 

DLG level code INTEGER* 2 

Code defining ground INTEGER* 2 

planimetric reference 

system. 

Code defining zone in ground INTEGER* 2 

planimetric reference 

system. 

Map projection parameters. REAL* 8 

Filler 

A.l 

A.2 

(1-6) 

A.2 

(7-12) 

A.2 

(13-18) 

A.2 

Al44 A 

I6 A 

1I6 A 

I6 A 

25o24.15 A 

6 spaces 

144 

2 

2 

2 

120 

Characters 1-40, name of digital 

cartographic unit. Characters 

42-51, date of original source 

material (for example, 1956) 

followed by latest revision date 

(if applicable) (for example 

1956, 1965). Characters 53-60, 

scale of the source material 

(for example, 62500). 

Characters 61-144, unused. The 

name of the map will be . used 

when practical. 

Code = 3, DLG 3 

Code = 3, Albers conical equal 

area 

Codes 9999 

Definition of the parameters 

for this projection are given 

in Appendix c. 

Filler for ASCII format only. 

linteger fields with a value of zero will have leading zeros suppressed. For example, an I6 field would be •bbbbbO.• (b 

blank) 

2Any field with the format of 024.15 which has a value of zero will be represented as •bbbO.Obbbbbbbbbbbbbbbbbb.• (b = 

blank) 
...., 

\D 

Data 

Element 

6 

7 

8 

9 

10 

Contents 

Map Projection parameters 

(cont'd). 

Code defining units of 

measure for ground 

planimetric coordinates 

throughout the file. 

Resolution 

Accuracy code for 

planimetric data. 

Number (n) of registration 

points. 

Filler 

An (4,2) array containing 

the latitude and the 

longitude of coordinates of 

registration points. 

Filler 

APPENDIX B.--DLG Record Formats--continued 

Logical Record Type A--continued 

Type 

(FORTRAN 

notation) 

REAL* 8 

INTEGER* 2 

REAL* 8 

INTEGER* 2 

INTEGER* 2 

REAL* 8 

Physical record t format 

ASCII BINARY 

Format Format 

record i (bytes) record t (bytes) 

A.3 

(1-144) 

A.4 

(1-96) 

A.4 

(97-102) 

A.4 

(103-126) 

A.4 

(127-136) 

A.4 

(133-138) 

A.5 

(1-44) 

A.6 

(1-48) 

6D24.15 

4D24.15 

I6 

D24.15 

.L6 

I6 

6 spaces 

3(2D24.15) 

96 spaces 

A 

A 

A 2 

A 8 

A 2 

A 2 

A 64 

Comment 

Definition of the parameters for 

this projection are given in 

Appendix c. 

Code 2, meters 

The smallest unit of ground 

coordinate of data element that 

is recorded in file. 

Code = 0, unknown accuracy 

n = 4 

ASCII only 

The array is stored row-wise and 

coordinates are in geographic 

longitude and latitude in units 

of degrees and decimal degrees. 

ASCII only. 
w 

0 

Data 

Element 

1 

2 

3 

APPENDIX B.--DLG Record Formats--continued 

Contents 

Type 

(FORTRAN 

notation) 

Parameters (Al,A2,A3,A4) on REAL* 8 

file-to-map projection 

transformation; the explicit 

form of the transformation 

is: 

x=A1x+A2y+A3 

y=Aly+A2x+A4 

where: 

x,y are coordinates in 

file reference system and 

XY are coordinates in map 

projection reference 

system. 

Number (m) of registration 

points. 

Filler 

An (4,3) array containing 

identifications and 

coordinates of registration 

points. Coordinates are 

expressed in the file 

reference coordinate system. 

Filler 

INTEGER* 2 

ALPHA/ 

INTEGER* 2 

Logical Record Type B 

Physical record # format 

ASCII BINARY 

Format Format 

record # (bytes) record # (bytes) 

B.1 

(1-96) 

B.l 

(97-102) 

B.2 

(l-56) 

4024.15 

I6 

42 spaces 

4(A2,2I6) 

88 spaces 

B 32 

B 2 

--- ---

B 24 

--- ---

Comment 

x,y coordinates resulting from 

this transformation will be the 

units of measure defined by data 

element 6 of Logical Record Type 

A. 

m=4 

ASCII only 

When there are four registration 

points, the identification 

sequence is SW, NW, NE, SE. The 

array is stored row-wise. 

Coordinates in the file 

reference sysstem are usually 

expressed in units of 

thousandths of an inch. 

ASCII only 
w 

...... 

Data 

Element 

1 

2 

Contents 

Number (q) of categories 

(overlays) in the DLG file. 

Filler 

A (1,7) array containing 

names as well as maximum and 

actual number of node, area, 

and line elements in each 

network. 

Filler 

APPENDIX B.--DLG Record Formats--continued 

Type 

(FORTRAN 

notation) 

INTEGER* 4 

ALPHA/ 

INTEGER*2 

Logical Record Type C 

Physical record i format 

ASCII BINARY 

Format Format 

record # (bytes) record # (bytes) 

C.l 

(1-6) 

C.2 

(1-56) 

I6 

138 spaces 

(A20,616) 

88 spaces 

c 4 

c 32 

comment 

q=l 

ASCII only 

This array is stored row-wise. 

The first element is the network 

name consisting of 20 

alphanumeric characters, the 

first 4 of which must be unique. 

Columns 2 and 3 of the array 

contain maximum and actual 

number of nodes in the network. 

Columns 4 and 5 contain maximum 

and actual number of areas in 

the network. Columns 6 and 7 

are the maximum and actual 

number of line segments. 

ASCII only 
w 

"-.) 

Data 

Element 

1 

2 

3 

4 

5 

APPENDIX B.--DLG Record Formats--continued 

Contents 

Type of element code 

Element's internal 

identification number. 

x y file coordinate of node 

point or representative 

point for the area element. 

Type 

(FORTRAl'il 

notation) 

ALPHA 

INTEGER* 2 

INTEGER* 2 

Number (t) of classification INTEGER* 2 

attributes attached to the 

node or area element (t~O). 

Number (k) of pairs of INTEGER* 2 

text characters which are 

attached to the node or area 

element ( k~ 0). 

Filler 

Logical Record Type D.l 

Physical record i format 

ASCII BINARY 

Format Format 

record I (bytes) record i (bytes) 

D.l 

(1-2) 

D.l 

(3-8) 

D.l 

(9-20) 

D.l 

(9-20) 

D.l 

(27-32) 

A2 

I6 

2I6 

!6 

I6 

112 spaces 

D.l 2 

D.l 2 

D.l 4 

D.l 2 

D.l 2 

Comment 

Code = N, for node element 

A, for area element 

Number is unique within each 

element type. 

The representative ~rea point is 

usually contained within the 

the area but is not necessarily 

a centroid. 

Absence of attribute codes is 

indicated by t=O. (For node 

elements in 1:2,000,000-scale 

DLG file, twill always be 0.) 

k=O. There are no text 

attributes for 1:2,000,000-scale 

DLG data. 

ASCII only 
APPENDIX B.--DLG Record Formats--continued 

Logical Record Type 0.2 

Physical record # format 

Type ASCII BINARY 

Data (FORTRAN Format Format 

Element Contents notation) record i (b::£tes) record t (b::£tes) Comment 

1 Code indicating a line ALPHA 0.2 A2 0.2 2 Code • L for line segment 

segment graph element. (l-2) 

2 Line segments internal INTEGER* 2 0.2 16 D.2 2 Number is unique within each 

identification number. (3-8) element type. 

3 Internal identification INTEGER* 2 0.2 !6 0.2 2 Number refers to data element 

number of starting node. (9-14) 2 in Logical Record Type D.l. 

4 Internal identification INTEGER* 2 D.2 I6 D.2 2 Number refers to data element 

number of ending node. (15-20) 2 in Logical Record Type D.l. 

5 Internal identification INTEGER* 2 0.2 I6 0.2 2 Number refers to data element 

number of area left. (21-26) 2 in Logical Record Type D.l. 

w 6 Internal identification INTEGER* 2 D.2 I6 D.2 2 Number refers to data element w number of area right. (27-32) 2 in Logical Record Type D.l. 

7 Number (v) of coordinate INTEGER* 2 0.2 I6 D.2 2 1500~ v ~2 

pairs that define the line (33-35) 

segment. 

8 Number (t) of classification INTEGER* 2 D.2 I6 D.2 2 Absence of classification 

attributes attached to the (39-44) attribute codes is indicated 

line segment (t~O). by t=O. 

9 Number (k) of pairs of text INTEGER* 2f D.2 I6 D.2 2 k=O. There are no text 

characters attached~to the (45-50) attributes for 1:2,000,000-

line segment (k~O). scale DLG data. 

Filler --- --- 94 spaces --- --- ASCII only. 
w 

~ 

Data 

Element 

1 

APPENDIX B.--DLG Record Formats--continued 

Contents 

Type 

(FORTRAN 

notation) 

A (v,2) array containing INTEGER* 2 

coordinate pairs that define 

the image presentation of a 

line element. 

Filler 

Logical Record Type E 

Physical record # format 

ASCII BINARY 

Format Format 

record # (bytes) record # (bytes) 

E.l to E.n 3v(2I6) 

0 to 132 

spaces 

E 4v 

Comment 

Coordinates are expressed in 

file reference system, usually 

in units of thousandths of an 

inch. The array is stoPed 

row-wise. 

ASCII only 

3The number of coordinate pairs, •v•, is given in record D.2. There will be v(2I6) coordinate pairs, of which a maximum 

of 12 pairs will fit on a 144-character ASCII record. The space filler will vary in size depending on the value of •v•. 

If •v• equals 12 or is an even multiple of 12, there will be no spaces as filler. 
w 

U1 

Data 

Element 

1 

Contents 

A (t,2) array containing 

major and minor 

classification codes for a 

graph element. 

Filler 

APPENDIX B.--DLG Record Formats--continued 

Type 

(FORTRAN 

notation) 

INTEGER* 2 

Logical Record Type F 

Physical record t format 

ASCII BINARY 

Format Format 

record t (bytes) record t (bytes) 

F.l to F.n 4t(2I6) 

0 to 132 

spaces 

F 4t 

Comment 

The array is stored row-wise; 

the first column contains the 

major classification attribute, 

and the second column contains 

the minor classification 

attribut. 

ASCII only 

4The number of feature (attribute) codes is given as •t• in the D.l and D.2 records. The F logical record is an array of 

t (2I6) codes of which a maximum of 12 (2I6) will fit on a 144 character ASCII record. The space filler will vary 

depending on the value of •t•. If •t• is 12 or an even multiple of 12, there will be no space filling at the end of the 

record. 
APPENDIX c.--DLG Parameter Codes used for 

Albers Conic Equal-Area Projection 

1 

2 

3 

4 

5 

6 

7 

8 

9-15 

Parameter 

Semimajor axis of ellipsoid 

Eccentricity squared of ellipsoid 

Latitude of first standard parallel 

Latitude of second standard parallel 

Longitude of central meridian 

Latitude of projection origin 

False easting 

False northing 

Not usen 

36 
APPENDIX D.--Graphics Format for DLG Data 

The simplified, graphics format that can be used with the GS-CAM 

plotting package is described below. In this format, each line record 

from the DLG format has been reformatted into two record types: one line 

identifier record and multiple latitude-longitude records (one for each 

coordinate pair). If a line record has more than one feature code associated with it in the DLG format, that line record appears in the graphics 

format files multiple times (once for each feature code). The graphics 

format files are organized by feature type. 

Record 1: Line identifier record 

1. Line identifier 

2. Rank (last two digits of feature 

code (described in Appendix A--

unique within category) 

3. Number of points in the line (NP) 

(latitude and longitude) 

4. First five digits of feature code 

(described in Appendix A) 

Record 2: Latitude-longitude record 

1. Latitude (DDMMSSI) 

2. Longitude (DDDMMSSI) 

3. Sequence count 

Position 

1-7 

8-9 

10-lS 

16-20 

(repeated 

1-7 

8-lS 

16-20 

37 

Length 

7 

2 

6 

s 

NP times) 

7 

8 

s 

Format 

I7 

I2 

I6 

IS 

3I2, Al 

I3, 2I2, 

IS 

Al 
APPENDIX•E.--Data Sources and Currency 

The published 1:21 000 1 000-scale National Atlas sectional maps were 

completely revised in 1972-73. Selected information from these maps was 

revised before digitizing. The source and date of the updated 

information are presented below: 

Overlay 

Political Boundaries 

Alaskan borough boundaries 

Administrative Boundaries 

Roads and trails 

Railroads 

Streams 

Alaska 

Water bodies 

Major reservoirs 

Cultural features 

Airports 

Alaska pipeline 

source Currency of Data 

Bureau of the Census 

Administering Federal 

agency 

Various 

Interstate Commerce 

Commission 

Landsat imagery 

National Oceanic and 

Atmospheric Administration 

Sectional Aeronautical 

Charts 

Federal Aviation 

Administration 

USGS maps 

38 

1979 

Various 

1980 

1979 

1979 

1979-80 

1980 

1979 
APPENDIX F.--DLG Record Layout 

Header Records 

A 

8 

c j#Nodes j #Areas J # Unes I 

I I j 

X·Y Coord. #of Length Node Node Feature of Text Code 10# of Node Codes String 

J I J 

Feature Codes 

Text J 

X-Y Coord. #of Length ~ Area Area of Feature of Text r' Record 10# Reference Codes String Point 

I J 

Feature Codes 

Text J 

1 l l 

Right #of #of Length Une Une Start End Left Coord. Feature of Text 

Code 10# Node# Node# Area# Area# Pairs Codes String 

l l J 

H X-Y Coord. String 

----1 Feature Codes 

H Text 

39 
APPENDIX G.--coordinate Conversion 

This appendix illustrates the procedure for converting internal file 

coordinates to ground planimetric reference coordinates. The formulas 

for this conversion are as follows: 

X=Alx+A2y+A3 

Y=Aly-A2x+A4 

where X and Y are the ground planimetric coordinate values and x and y 

are the internal file coordinates. 

The parameters for these formulas (Al, A2, A3, and A4) are contained 

in Header Record B, as double-precision floating-point numbers. 

This example converts four coordinate pairs from 

coordinates to ground planimetric coordinate values 

Equal-Area Projection). The parameters are as follows: 

Al=50.325538142 

A2=6.9275199981 

A3=-1185878.9723 

A4=1314164.3401 

The internal file coordinates to be converted are: 

_x_ J_ 

1st pair -11238 -6583 

2d pair -10405 6583 

3d pair 10405 6583 

4th pair 11238 -6583 

internal file 

(Albers Conic 

The calculation to determine the ground planimteric coordinates for the 

first pair are as follows: 

X=(50.325538142)(-11238)+(6.9275199981)(-6583) 

+(-1185878.9723) 

=-1797041.23 

Y=(50.325538142)(-6583)-(6.9275199981)(-11238) 

+ (1314164. 3401) 

=1060722.79 

The resulting x,y coordinate values for the four pairs given above 

are as follows: 

1st pair 

2d pair 

3d pair 

4th pair 

-1,797,041.23 

-1,663,912.33 

-616,637.88 

-665,924.44 

40 

1,060,722.79 

1,717,538.20 

1,573,376.51 

905,019.86 



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