AD-A256 859 USACERL ADP Report EGI-92/01

July 1992 FAEN-GRASS Enhancements

US Army Corps of Engineers

Constr uction Engineering Research Laborato, y

GRASS 4.0 Map Digitizing

User's Manual: v.digit

by

Craig A. Neidig

David P. Gerdes

Chester Kos

The Geographic Resources Analysis Support System

(GRASS) is an image-processing and geographic information system (GIS) originally designed to serve land

managers and environmental planners at Army installations, but now used by a wide variety of public and

private users. Map data are useful for building a GIS

data base. Within the GRASS system, map development entails the production of vector, raster, and support files

to represent map features. One way analog map data

are entered and converted into digital form is by tracing relevant map features with an electronic instrument called

a digitizer. In GRASS version 4.0, the program used to

conduct this conversion is called v.dlgit.

This manual discusses v.dlglt options. The v.dlglt

program is an interactive, menu-driven vector digitizing,

labeling, and editing package. The samples in this

manual require use of a workstation minimally consisting

of a graphics monitor and keyboard, a pointing device N V0 3 19920

(mouse), and a digitizing tablet. Drivers for v.dlglt exist

for Aftek, Calcomp, GeoGraphics, Hitachi, Kurta, Numoni- D

cs, and SummaGraphics digitizers. v.dlglt also operates E

in an X Windows environment.

Approved for public release; distribution is unlimited. 92- 28678

9 J. ' o( I9I1I011il I!|IIII
The contents of this report are not to be used for advertising, publication, or

promotional purposes. Citation of trade names does not constitute an official

endorsement or approval of the use of such commercial products. The

findings of this report are not to be construed as an official Department of

the Army position, unless so designated by other authorized documents.

DESTROY THIS REPORT WHEN IT IS NO LONGER NEEDED

DO NOT RETURN IT TO THE ORIGINATOR
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1. AGENCY USE ONLY (Leave Bank) N2. REPOR( DATE 3. REPORT TYPE AND DATES COVERED July 1992 Final

4. TAITLE AND SUBTITLE 5. FUNDING NUMBERS

GRASS 4.0 Map Digitizing User's Manual: v.digit R-FED-SCS

WU VII

6. AUTHOR(S)

Craig A. Neidig, David P. Gerdes, and Chester Kos

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) S. PERFORMING ORGANIZATION

REPORT NUMBER

U.S. Armny Construction Engineering Research Laboratories (USACERL)AD EG920

PO Box 9005

Champaign, IL 61826-9005

9. SPONSORPING/MNITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSSRING/MONITORING

AGENCY REPORT NUMBER

U.S. Department of Agriculture Soil Conservation Service (USDA SCS)

ATTN: USDA SCS-CGIS

PO Box 2890

Washington, DC 2W013

11. 'SUPPLEMENTARY NOTES

Copies are available from the National Technical Information Service, 5285 Port Royal Road,

Springfield, VA 22161.

12a. nISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE

Approved for public release; distribution is unlimited.

13. ABSTRACT (Maximum 200 words)

The Geographic Resources Analysis Support System (GRASS) is an image-processing and geographic information system (GIS) originally designed to serve land managers and environmental planners at Army

installations, but now used by a wide variety of public and private users. Map data are useful for building a

GIS data base. Within the GRASS system, map development entails the production of vector, raster, and

support files to represent map features. One way analog map data are entered and converted into digital

form is by tracing relevant map features with an electronic instrument called a digitizer. In GRASS version

4.0, the program used to conduct this conversion is called v.digit.

This manual discusses v.digit options. The v.digit program is an interactive, menu-driven vector digitizing,

labeling, and editing package. The samples in this manual require use of a workstation minimally consisting

of a graphics monitor and keyboard, a pointing device (mouse), and a digitizing tablet. Drivers for v.digit

exist for Altek, Calcomp, GeoGraphics, Hitachi, Kurta, Numonics, and SummaGraphics digitizers. v.digit

also operates in an X Windows environment.

14. SUBJECT TERMS 15- NUMBER OF PAGES

GRASS digitizer 56

geographic resources analysis support system v.digit 16. PRICE CODE

T7. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT

OF REPORT OF THIS PAGE OF ABSTRACT

Unclassified Unclassified Unclassified SAR

NSN 7540-01-280-5500 Sadawd Form 298 (Rev. 2-89)

Pwsesbod by ANSI Sid 239.78

298-102
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FOREWORD

This document was developed for the U.S. Department of Agriculture Soil Conservation Service

(USDA SCS) under reimbursable Project R-FED-SCS, "FAEN-GRASS Enhancements"; Work Unit VII.

The SCS technical monitor was Mr. Richard Liston, USDA SCS-CGIS.

This work was performed by the Office of GRASS Integration (EGI) of the Environmental

Sustainment Laboratory (EL), of the U.S. Army Construction Engineering Research Laboratories

(USACERL). The USACERL principal investigator was David Gerdes. Special thanks is owed to the

following USACERL personnel, who offered advice and assistance on this project: Mary Martin, Meridith

McCarthy, Melissa Records, Jeff Rogers, Scott Wade, Michael Higgins, Chester Kos, Marilyn Ruiz, and

Jean Messersmith. Gratitude is also expressed to the Cartography and GIS Division and the National

Cartographic Center of the USDA Soil Conservation Service (USDA SCS-CGIS), who reviewed this report

in manuscript form and provided constructive criticism. Marjorie Larson is Chief, Office of GRASS

Integration (CECER-EGIS), and Dr. Edward Novak is Laboratory Chief, CECER-EL. The USACERL

technical editor was William J. Wolfe, Information Management Office.

COL Daniel Waldo, Jr., is Commander and Director of USACERL, and Dr. L.R. Shaffer is

Technical Director.
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CONTENTS

Page

SF 298 1

FOREWORD 2

1 INTRODUCTION .................................................... 5

2 USING GRASS FOR MAP DEVELOPMENT ................................ 7

3 PREPARING A MAP FOR DIGITIZING ................................... 8

4 USING THE MOUSE AND THE DIGITIZING CURSOR ....................... 9

5 ENTERING v.digit ................................................... 10

6 THE MAIN MENU .................................................. 19

7 THE DIGITIZE MENU ............................................... 21

8 THE EDIT MENU ................................................... 29

9 THE LABEL MENU ................................................. 32

10 THE CUSTOMIZE MENU ............................................. 37

11 THE COLOR MENU ................................................. 40

12 THE DISPLAY MENU ................................................ 42

13 THE TOOLBOX MENU .............................................. 44

14 THE WINDOW MENU ............................................... 46

15 THE ZOOM MENU .................................................. 48

16 THE DEBUG MENU ................................................. 50

17 EXITING v.digit ..................................................... 52

REFERENCES Accesion For 53

DISTRIBUTION NTIS C?,.'3 -II

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GRASS 4.0 MAP DIGITIZING MANUAL: v.digit

1. INTRODUCTION

1.1. Background

The Geographic Resources Analysis Support System (GRASS) is a public domain, image processing

and geographic information system (GIS) originally developed by researchers in the Environmental

Division of the U.S. Army Corps of Engineers Construction Engineering Research Laboratory

(USACERL-EN) in Champaign, IL. The system is used to input, manipulate, analyze, and output geographic data by users in both military and nonmilitary and public and private agencies based in North

America, Europe, and other parts of the world. v.digit is a robust map development software package

used for vector digitizing, editing, and labeling, and the conversion of vector data to raster format. This

document details the capabilities of v.digit, a highly. interactive, menu driven, map digitizing package

included among GRASS software.

Although most GRASS development has been conducted at USACERI,, system integration, development, testing, distribution, training, and support is perfomied by numerous publicly and privatelyoperated sites throughout the world. GRASS version 4.0 implemented significant additions and

modifications to system libraries and programming code. 'This doctment reflects modifications made to

GRASS version 4.0 map development programs.

1.2. Objective

"Ihe objective of this work is to guide the user through the process of using v.digit to develop a GRASS

database.

1.3. Approach

Cuirrent GRASS v.digit nmp development wad (tata import/export functions are examined in this report.

1.4. Scope

"Ibis dotument discusses the 4.0-release version of the GRASS v.digit program, completed in the Summer of 1991. Some elements of this doctunent will he out of date and inaccurate for post-4.0 software

releases. Ad(itionallv, a1though it is plimmicd that future releases of GRASS issued by USACERI, and

the USI )A SC.S will be identical, they may offer somewhat different functions in GRASS 4.0. 'lihe

functions described in this tutonial are those of the USACIRL GRASS 4.0 release, available to all

GRASS users.
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1.5. Mode of Technoleff Transfer

GRASS is being transferred to the field through the following mechanisms: training programs, a user

sipport center, newsletters, extensive documentation, institutional structures at the Army and

interagency levels, comnunication networks, and other forums.

User feedback on GRASS program capabilities, documentation, and other technology transfer mechanisms is important to the development of the system. Users are encouraged to communicate such feedback to the GRASS development staff at USACERL, via existing electronic communication networks

and via the GRASS Information Center at USACERL, P.O. Box 9005, Champaign, IL 61826-9005;

phone 217-373-7220; fax 217-373-7222; or e-mail grassbug@zorro.cecer.armyamil.
-7-

2. USING GRASS FOR MAP DEVELOPMENT

A great amount of information is stored on paper maps. Such data are useful when building a geographic information system (GIS) database; however, managing the large quantities of data needed can

be cumbersome. Map information can be more easily manipulated in digital form by a computer.

Within the GRASS Geographic Information System, map development entails the production of vector,

raster, and support files that are used within GRASS to represent map features. One way that analog

map data is entered and converted into digital form is by manually tracing relevant map features with

an electronic instrument called a digitizer. In GRASS version 4.0, the program used to conduct this

conversion is called vAdigit.

The v.digit program is an interactive, menu driven, vector digitizing, labeling, and editing package.

This manual discusses the vadigit options and guides the user through a sample digitizing session. To

follow the examples in this manual, the user will need a workstation minimally consisting of a graphics

monitor and keyboard, a pointing device (mouse), and a digitizing tablet. An ASCII (dumb) terminal

with keyboard is optional for some hardware platforms, but is recommended so that the graphics monitor is dedicated to display during the digitizing session. Currently, v.digit drivers have been written for

Altek, Calcomp, GeoGmphics, llitachi, Kurta, Numonics, and SummaGraphics digitizers. v.digit also

operates in an X Windows environment. An X-interface to all GRASS programs is currently under

development.

It is assumed that the user is faniliar with the UNIX environment, GRASS, and in particular with the

concepts of vector maps. raster maps, map layers, geographic regions, reference frames, and GRASS

locations aid mapsets. For a review of these concepts refer to An hItroduction to GRASS 4 (Westervelt

and Goran, 1991).

Experienced GRASS users should note that the map development mn(xlules used in GRASS 4.0 are

essentially the same as their predecessors, with some minor modifications aIKl fiunction enhancements.

Program namnes incorporate the new prefix standard adopted for GRASS 4.0; see GRASS 4.0 Progranm

(Westervelt, Martin, and Brinegar, 1991) for a synopsis of this naming scheme. GRASS 4.0 programs

used for map development include:

v.digit, v.import, v.support, vin.ascii, v.out.ascii, wuid v.toa'ast

These progrnins are discussed in detail in the GRA5S 4.0 User's IRefereiwe Mwtutd (Westervelt,

Shapiro, ct al., 1991).
-8-

3. PREPARING A MAP FOR DIGITIZING

Frequently, map data cannot be digitized directly from original source maps. Paper maps may contain

wrinkles, creases, or tears. IlAt and humidity cause shrinking and swelling of unstable media which

can adversely affect the accuracy of the digital representation. Also, analog maps generally contain

many types of thematic information. The analyst must know exactly what map features are to be digitized. To avoid confusion, the user may need to prepare a separate map or maps containing only those

features relevant to the database before digitizing. See Cartographic Issues in the Development of a

Digital GRASS Database (Ruiz and Messersmith, 1990) for an explanation of how maps should be

properly prepared for digitizing, and section 5.1 of this tutorial for a discussion of map registration and

geo-referencing.

The following items should be considered before digitizing commences:

- Use a stable medium (preferably mylar, plastic, etc.) on which the features

to be digitized have been rendered clearly and accurately.

- Use drafting tape to secure the medium to the digitizing tablet.

- Define a geographic region in a standard coordinate system

(TITM, latitudeAongitude, etc.) for the data layer.

- On the medium, locate and mark at least four, and up to 10, coordinate pairs

(i.e., Fasting, Northing) to be used as map registration points.

- Define a reference frame, or "digitizing window," for the area.

- Have another map of the area available for reference.

Affix the map securely to the digitizing surface with drafting tape, making sure that all portions of the

map to be digitized fall within the "active" area of the board and within the reach of the digitizing cursor. The active area refers to that portion of the tablet in which digitized points can be collected.

(Most digitizers have a buffer, or "dead" area, near their edges where the cursor" will not collect points.)

By placing the map to be digitized near the center of the board, this problem can be avoided. For

extremely large maps that extend beyond the active area of the digitizing tablet, the map may have to

be digitized in pieces; the user must provide a set of map registration points for each map piece. The

map should be taped down with the sides approximately parallel to the bottom and sides of the board.

Most digitizing programs, including v.digit, have transformation algorithms that will adjust for small

deviations in registration between the map coordinates and board coordinates. However, if the maps are

severely skewed on the board, then inaccuracies with registration and subsequent collection of point

coordinates will occur.
-9-

4. USING THE MOUSE AND THE DIGITIZING CURSOR

Many v.digit options make use of a pointing device (mouse). A mouse usually has three buttons: left,

center, and right. (Some mice may have only two buttons; in these cases, use of the middle button is

usually emulated by pressing the left, then right, mouse buttons in quick succession.) Once the mouse is

activated, movement of the mouse corresponds to movement of a pointer on the graphics monitor

screen. In v digit, the pointer appears as a nvywable box or an arrow depending on the function

specified by the user. Movement of the mouse is used to identify an object or to define an area shown

on the monitor. Most vAligit operations using the mouse follow a left-right sequence for first choosing,

and second, accepting the functions. In most functions, the middle button ends or aborts use of the

mouse.

Digitizing is the process of converting analog map data into digital form by tracing the desired features

with a digitizer cursor, sometimes referred to as a "puck." The cursor consists of a transparent

viewfinder or "sight" and a pad containing a set of buttons or keys. Generally, the sight is a clear plastic lens on which two perpendicular intersecting lines or concentric circles are superimposed. TIhe keys

are labeled with letters and/or numbers that correspond to various functions within the digitizing program. The user looks through the sight, much as with a rifle scope, to target the appropriate feature to

be digitized, and presses the keys to execute the appropriate digitizing function.
- 10-

5. ENTERING v~digit

To use v.digit, the user must be in GRASS 4.0 and have entered the proper LXCATION, MAPSET, and

DATABASE in which to work. Help with the start-up procedure and a full explanation of these terms

are available in the GRASS 4.0 User's Reference Manual (Westervelt, Shapiro, et al., 1991).

Once in the proper mapset, the user sees a GRASS default prompt similar to the one below.

Mapset <grassuser>in Location <somewhere>

GRASS 4.0 >

After the prompt, initiate the v.digit program by entering the command:

v.digit

The first message to appear upon entering v.digit is a list of the AVAILABLE DIGITZERS (i.e.,

those for which device drivers have been installed on the system). See the sample screen below.

Available Digitizers

Name: Description:

[1] acme Acme digitizer

[2] none Rmn digit without the digitizer.

1lit return to use digitizer in brackets below

or type in number or name of other digitizer.

Select digitizer [none] : 1

Selected digitizer is: acme

llie v.digit program operates either with or without use of a digitizing board. Most prograin operations

are the samnc in both modes; in the latter case the mouse then serves as the default digitizing instruntc.

The user has the option of using the programr withdet the digitizing board by selecting the option [21

nome. However, for the purposes of this manual, the user should start by working with a digitizing

tablet. Finter the number for the appropriate digitizer at the prompt (here, the fictitiouLs "acmne" brand) -

more than one digitizer may be available for selection. If a digitizer has been previotLLly used, it is

saved as the default option and appears nanmed in the brackets next time v.digit is nrm.

Next, the user is prompted for the name of itle VLCIOR nmap to be used during fhe cutrrent digitizing

session. The user has the option to create a new tile or to mnxlify an existing file. If the name

specified is not foutd anm)ng the existing files, the program assumes that the user wants to create a new

file and asks for confinnation of the new file natne. In the following example, the file test is created.
- 11 -

Enter the name of a map to work with.

If name is entered that does not already exist, it

will be created at this time.

DIGIT FILENAME

Enter 'list' for a list of existing digit files

Hit REIURN to cancel request

> test

<test>

You requested to create new file: 'test'. Is this correc-? (y/n) [n] y

The user is next asked if the vector file chosen is georeferenced in the current LOCATION's coordinate

system. In this manual, the Universal Transverse Mercator (UTM) is used as the sample coordinate

system.

Current mapset is UTM.

Is this map in UTM meters? (y/n) [y] y

Thank You

Creating a new vector file

Other coordinate systems that can be used include an arbitrary (xy), latitude-longitude, and State Plane.

In general, GRASS does not currently penhit the user to mix data stored in different coordinate systems

nider a single LOCATION directory. However, other GRASS programs do enable data within a single

LOC)'ATION to be converted to and from various coordinate systems (e.g., v.transform, etc.). In

v.digit, if the user chooses a coordinate system other than the one originally specified for the user's

current GRASS IDCATION, the program responds with the following warning message and automaticallv returns to the GRASS prompt:

I Sorry, GRASS does not currently support mfixing nmap uniits.

If the coordinate systems are not the sanme, then some type of coordinate transformation needs to be

performed. The user should be aware of the coordinate systems of the maps being considered. Refer to

the GRASS pr(orai g.help and to Ruiz and Mc.sersmnith, 1990 for a discussion of map coordinate systens, projections, and data convcrsions.
- 12-

The next screen appears:

Provide the following information:

Your organization US Army Const. Fng. Rsch. Lab

Todays date (monyr)

Your name

Map's name

Map's date

Map's scale

Other info

Zone

West edge of area 590000

South edge of area 4941000

East edge of area 609000

North edge of area 4928000

AFTER COMPLETING ALL ANSWERS, HIT <ESC>TO CONTINUE

"This screen contains information about the vector file. A newly created layer initially contains several

blank lines. The coordinates on this page define a "digitizing region"; they are automatically entered

and are originally derived from the default region coordinates in the PERMANENT mapset for the

present LOCATION. The user can find the default region coordinates by executing the GRASS cornniand g.region -dp prior to entering the vadigit program. The user should be careful to make sure that

this region incorporates the area of the new vector file; generally, the default is more than adequately

large. Remember, too, that data physically can be digitized outside of the default region but it will not

be visible to the user unless the region is expanded to include it. A sample screen with the categories

filled in is presented below; use the Enter/Return key to move around the screen:

Provide the following information:

Your organization USA-CERL

Todays date (monyr) 7/04/91

Your name U.D. Grassuser

Map's name Test for v.digit

Map' s date 1991

Map's scale 1:24000

Other info USGS topo, 1 of 2

Zone 13

West edge of area 590000.00

South edge of area 4941000.00

Fast edge of area 609000.00

North edge of area 4928000.00

AI.TFR COMPIL JTING ALL ANSWERS, lilT <ESC> IO CONI'INUE

After typing in the relevant infomuttion on this screen, press the <-ISCAlPE>kcy to continuc the digitizing session.
- 13-

The following message appears:

Shall we continue? [y]

Writing plus file ...

Press the Enter/Return key to continue. The string "Writing plus file.. ." means that a dig__plus file is

being created for the new vector file. This file pertains to the spatial topology of the vector data to be

created and references the vector data to the appropriate coordinate system. Once created, the dig-plus

files are not directly modifiable unless the vector file is changed using other options (eg., v.support).

This message does not appear if a previously created vector file is chosen. Answering "no" (or simply

"n") at this time exits the user from v.digit. I-bwever, the header information entered at the beginning

of the current session will be saved.

5.1. REGISTERING THE MAP

The next step is to georeference the map to a particular geographic coordinate system (i.e., to the coordinate system previously specified by the user--here, UIM). This is done by selecting a series of registration points, a convenient source of which is the intersection of UTIM grid lines. Some U.S. Geological Survey (USGS) 7_5' quad sheets (1:24000 scale) and most Defense Mapping Agency (DMA) installation nmaps (1:50000 scale) have these grids inscribed on them. However, most USGS quads only have

the UTM grid ticks demarcated along the border of the map. In the latter case, the user has to use a

straightedge and pencil to carefully draw in the grid intersection for each point. Sometimes the analyst

is confronted with a map in which no arbitrary coordinate grid is represented, or maps of less than

superior quality (such as a photocopy or blue-line drawing). In such cases, the analyst may have to

derive registration points from other maps by cross-registering the "bad' map to the "good" map (eg.,

using obvious physical features visible on both maps such as road intersections, bench marks, etc.). This

can be a tedious and frustrating endeavor; the registration process often involves more than a little bit

of ingenuity and persistence on the part of the analyst.

If this vector file has been worked on in GRASS before, a file of registration points with this same file

name will already have been created and be stored in the reg directory in the mapset of the user who

created the file. If the user specifies the name of an existing file, the program automatically accesses

the registration points that were used in the last digitizing session. The user may use these same registration points, add additional ones, or choose completely new points in the current session, as shown

be'low. See RHiiz and Messersnuith, 1990, )or a more detailed discussion of registration points. (If this

is a new file, the user will NOT see the following message.)

Use set of registered points from last session (yin)?

E'nter y to use the saunc rcgistration points as in the previous session, or enter n to register the map

using new points. 'lhe following screen appears:
- 14 -

MW RREGIS1RATICN POINIS

Enter 4 - 10 points : points registered 0

Point # X coord Y coord

1 590000.00___ 4915000.00

2 590000.00___- 4927000.00

3 599000.00___ 4927000.00

4 599000.00___- 4915000.00

5 0.00 --------- 0 .0

6 0.00 -------- 0.00

7 0.00 --------- 0.00

8 0.00 --------- 0.00

9 0.00 --------- 0.00

10 0.00 --------- 0.00

Enter 0.0 to delete a coordinate set.

Those marked by '*' are registered.

AFTER OvPLETING ALL R, HIT <ESC> TO (G rINLTUJE

(CR -Ct rI-C> 10 CANCEL)

-----------------------------------------------------------------

Reading from the map, type in the (xy) coordinates for each registration point using the keyboard.

Move through the list (alternate xy pairs) by entering <RERURN>. Remember, in most cases X refers

to [UTh] EASIINGS and Y to [UlTM] NORTHINGS. v.digit requires that at least four points be

registered; ten points are the most that may be entered. It is a good practice to enter as many registradon points as possible since some points will probably have to be eliminated because of accuracy problems. These points are used to construct a surface grid system for the map. The points should be distributed throughout the map to avoid amplifying accuracy errors that can be caused by choosing points

clustered closely together over a relatively small (and perhaps unrepresentative) section of the map area

being registered.

Also, it is convenient to enter the coordinates in some order; again, each analyst will have his/her own

style for executing these tasks. For example, begin by entering the coordinates of the registration point

nearest the lower left (usually southwest) comer of the map, and continue entering points in a clockwise

direction until all of the coordinates are entered. In this example, as is common practice, a USGS 7.5'

quad sheet has been used to select the registration points. Only four registration points are used in this

case. Note the progression in the direction of the UJIM (xy) coordinate pairs from the lower left to the

lower right comer of the map.

Once the user has finished entering the coordinates of the registration points, and double-checked them

for typing errors, press the <ESCAPE> key to continue. These first four points can be used to constnmct

a map neatline. See section 13 (The Toolbox Menu) for a discussion of this feature. The next screen

appears:
- 15 -

POINTS '10 RBJISTMR

POINF FASTIN3 (X) NJKIM (Y)

I-> 1. 590000.00 4915000.00

2. 590000.00 4927000.00

3. 599000.00 4927000.00

4. 599000.00 4915000.00

Nunber of points: 4, roints registered: 0

----------------------------------------------------------------- I

USINU DIGITIZER (LRSOR FOR INPUT

Key<0> - registcr point Key<3> - add more points

Key<> - skip point Key<4> - accept residuals

Key<2> - unregister point

----------------------------------------------------------------- I

This screen displays options which deal with the registration points. Depending on the brand of digitizer used, the screen may look slightly different than shown above. The nunbers in brackets at the

bottom of the screen refer to numbered keys or buttons on the digitizer cursor.

To register a point, locate the button labeled "<03' on the cursor. Sight the cross hair of the cursor

over the first point to be registered and press "<O>2'. As each point is registered, an asterisk (*) appears

to the left of it. The program dtso emits an audible "BEEP' to let the user know the point has been

collected. Once a point is registered, v.digit automatically proceeds to the next point. Enter "41' on

the cursor to skip any point. If a mistake has occurred, you can press "<2:' to unregister inaccurate

points so that they can be reregistered or removed from consideration altogether. If more registration

points are needed, choose "<3>' and type in the coordinates of the additional points.

Once a minimum of four points is registered, a fourth column (RESIDUALS) appears on the right side

of the screen listing the residual error associated with each point:
- 16 -

POINIS TO RR3ISTER

POINr EASTINO (X) a 1= U3 (Y) RESIEUAILS

> 1 .- 590000.00 4915000.00 1.79

• 2. 590000.00 4927000.00 1.79

• 3. 599000.00 4927000.00 1.79

• 4. 599000.00 4915000.00 1.79

Numter of points: 4, Points registered: 4

Residual mean average : 1.794367

----------------------------------------------------------- I

USINGT DIGITIZER CURS(R FOR INPUT

Key<D> - register point Key<3> - add more points

Key<> - skip point Key<4> - accept residuals

Key<2> - unregister point

-------------------------------------------------------------------I

The residual is a statistical measure that indicates the accuracy of each registration point in relation to

the others. In this case, the units are expressed as the number of meters of deviation. The magnitude

of the residual error is based on the original scale of the map being digitized. (Ruiz and Messersmith,

1990 gives a more detailed explanation.) For example, as a general rule of thumb, for a standard USGS

7.5' quad sheet (1:24000 scale), the overall residual normally should be less than 9 and ideally less than

3. (Ruiz and Messersmith, 1990 also gives other examples and a more extended discussion of residuals.) Each individual residual should fall within two integers of the other residuals listed. Residuals

can often be lowered by re-registering points ("<03), by elinfinating specific points ("<2•'), or by

adding new points ("<3O). Once the residuals appear satisfactory, choose "<4z' to continue. (As

explained above, the selected points are saved in a file and can be used to re-register the map in a subsequent digitizing session.) The following screen appears:
- 17

This screen is used to verify that the map registration is correct.

Check known points on the map with the digitizer and ccqpare them

with the coordinates at the bottom of this screen.

Cl 1kI MAP: Key '0' to preserve point; Any other Key to continue

Coordinates: X - Current - Y X - Saved - Y

0 595281.67 492082.36 0.00 0.00

----------------------------------------------------------------

GRASS uses the registration points the user has inpuit and accepted to constnrct an entire surface coordinate system for the user's map. (It "registers" the map's surface coordinates to the digitizing tablet's

surface coordinates.) The user can test the accuracy of the georeferencing based on these registration

points by using the screen function sho-vn directly above. The user points to sites with user-known

geographic coordinates on the paper map, and notes the digitizer coordinates correspondilg to these

points listed in the "Current" cohunn; the user-known map coordinates should approxinmate the cornputed coordinate values listed in the "Current" column. Note that as the digitizer cursor is moved the

coordinates under the "Current" heading constantly change. Pressing "<W):' temnprarily freezes the

coordinatcs of that point until the key is pressed again. This option may also be useful when reistering two maps to one another, such as a quad sheet and a photocopy without coordinates. ITe locations

of identifiable features on the photocopy can be pinpointed on the quad sheet and subsequently used as

registration points for the photocopy version. (Unfortunately, the coordinates will have to be written

down since it is not possible to save them directly to a file.) Pressing any key other than "<0Os

proceeds to the next command screen.

----------------------------------------------------------------

USlMi I)I(il'IZIR (Ul•SOR RV( INPUI'

Key '0' for YFS : Key '1' for N)

If sat i slied with the registration, enter 'v' , else 'n'

----------------------------------------------------------------

IThis screen asks the user to verify that the registration is satisfactory alln to respond bI usift one of the

designated cursor keys. Pressing "•1 : sends (lie user back to the registration screen, and "<0:'

accepts the points that were entered.

5.2. DEFININ(; THE WORKING WINIX)W

At this point, the user has entcred v.digit, rogistered the map, and is almost ready to beigin digitizing.

"Ihe "digitizing reg.•ion" that was created earlier (delined by the default region coordinates or others

typed in the dig file header entered by the user just alter entering v.digit) is probably too lange an area
- 18 -

in which to work comfortably. The user now defines a "working window" as a subset of the "digitizing

region." This conforms to the area displayed on the graphic screen, and the parameters can be changed

repeatedly throughout the v.digit session (e.g., using the Zoom or Mndow Menus). The working win4tw does not affect any other GRASS program, nor is it saved after the user exits vAtigit. It exists

only to provide graphic reference and to display small areas in which the user is focusing work.

Understanding the differences between the "digitizing region,' "working window,' "default region;' and

"current region" is important. If necessary, review these concepts before continuing (see, for example,

explanations accessed through the GRASS 4.0 g~help program).

Use the digitizer cursor to pick two points on the map diagonal from each other to define the "working

window" slightly outside the perimeter of the map image. The next two command screens appear in

succession. For example, choose the lower left (southwest) and upper right (northeast) corners of the

area.

IIdentify corners of graphics window.

ILocate digitizer cursor on one corner of desired window.

Then hit any digitizer <KEY>

I----------------------------------------------------------------

When a KEY is depressed, the user hears a "BE01" confirming the selection.

I---------------------------------------------------------------- I

I Nc*v place digitizer cursor on diagonal corner of desired window-.

I Then hit any digitizer <KEY> II

I ---------------------------------------------------------------------------

After choosing the second point, another "BEEP" is emitted, and the pro~ram enters the v.digit mienui.
- 19 -

6. THE MAIN MENU

After the "working window" is selected, the v~digit program enters the Main Menu. The Main Menu

serves as the entry and exit menu for all fuinctions; pertaining to vector data entry and modification.

The layout of the Main Menu screen appear below:

------------------------------------------------------------------ I ZiM S-DIGIT Version 4.0 Wv~n Ivfnu

------------------------------------------------------------------ IMAP INRFAATIN IAMiNI DIGITIZ13D

I Name-: Test, v.digit mianual # #Lines: 0

Scale: 24000 # #Area edges: 0

Person: U.D. Grassuser # #Sites: 0

I Dig. Thresh: 0.0300 in. -I

I N'hp Thresh.: 18.290 meters I Total points: 0

I Digitizer: Enabled

------------------------------------------------------------------

IDigitize Edit Label Cuistmiizc Toolbox Window H-elp Zoomi Qu~it*

I(Thfl3Al. M'b: Press first let ter of desi red conmiand. [Upper CaIse Only]

------------------------------------------------------------------

6.1. MAIN MENU OI'l'ONS

v.digit is composed of a hierarchy of menuis, each of which is composed of a numiber of fields describing tie mienu functions atid options. lihe top) field, or the TITLE field, dfisplavs the version of

GRASS-DiurIb being used and the namec of* the cuirrentix selected mlenui.

'Ihe MAP INFORMATION field is extracted from thle header inforniation typed in by thie user upon

first entering thle digitizing session. It provides a qufick reference to the uiser and also p~rovides thle

current statuis of the dfigitizing and mnap thresholds cuirrently selected (see the Custmize Mlenut for anl

explanation of what the thresholds mecan). 'Ibis field appears only onl thle Main Menu.

'lIh AMOUNTI DI(;ITIZEI)1 field shiows fihe statuts of' thle amnount of each type of featuire (i.e., line.

area, or site) that has been digitized and the total numberlvi of po~ints Comiprisiig these features. This field

appears only onl the Maili and I)~gitize Menitv.

'Ihe OPTIONS field lists the fimctions availablc to thie uiser in any, given mienui. In thle Mifin Menu, it

shows the status of the digitizing device being tied; here, it is the dfigitizer that is enabled. If no (hgitizer haid been selected for uisc, this field wrould state: I~igitizer: I~isubled (see the ('mvqonize Memmmi

options onl howm to toggle thle digitizinig device).

'Ihe GLOB1AL MENU (hottoni field) shows the other mienuis available to the uiser through the currently

selected mcmim. Use the KE.YB)ARD to select ;ui alternate menu by typing in the first letter (UPPER

CASE). Global Menu options may be chosen only whenci they appear on the current mnenui page. O~il\

one mienu is available for uise at any given timec Six options appearing in the (Alobal Menli field at the

lx~ttomi of the Main Meiiu ref-er to specific suhibienius: l0igilize, hFki, label, ('uvtonidze, li(olbox, and

Wi4ndow.
- 20 -

There are six Main Menu global options that are not menu names:

Zoom allows the user to zoom or pan over the vector layer. Since this is a significant function,

however, it is discussed in a separate section.

Help displays menu-specific interactive help to the user.

Quit exits the user from the current vdigit session and automatically saves any work completed

during this time. This option is available only from the Main Menu.

The asterisk, "*", refreshes the terminnal screen.

The exclamation sign (or bang), "!", refreshes the graphics screen. When executed, the following

message appears in the global field:

Wait. Replotting the Screen.

... Press <ESC>key to stop redraw

The screen is erased, and any digitized lines will begin to be redrawn. Pressing the <ESCAPE> key

stops the redraw at that point, and allows the user to use other options. This is especially useful for

large files such as soils, contour lines, or others where it would be inconvenient to wait for the entire

file to redisplay.

"The carat, "^", is used to unlock the monitor when changing (back and front) between the digitizing

(graphic) and (shell) windows on SUN workstations. If the monitor should lock up, pressing the carat

several times should release it. This feature also works on X terminals.

Help, "m", "!, iad "^", are available from anv menu.

Before actually entering D to digitize, try moving through the other menus. Notice that the global

options available within each submenu are slightly different than the ones available in the Main Menu.

"To reiterate, remember that typing the first letter of any of the available options cauLses the ctutrrent

option to be replaced with the new option. When comfortable with the menu and option structure.

proceed to the next section.
-21 -

7. THE DIGITIZE MENU

The aIgitize Menu is where the actual input of vector data occurs. It is accessible from the Main, Bit,

and label Menus. he following sections describe first the use of the digitizing cursor for data input,

followed by the use of the mouse (see also the Customize Menu in section 10). The screen layout of

the Digitize Menu with the default parameters is shown below:

----------------------------------------------------------------------------- IRASS-DIGIT Version 4.0 Digitize Nlnu

------------------------------------------------------------------

AfIVU, digit izer I AM DIGITIZED

Cursor keys: I #Lines: 0

<D> digitize point I #Area edges: 0

,1> quit digitizing j #Sites 0

<2> update monitor -- -------------

<3> toggle point/stremun ode Total points: 0

------------------------------------------------------------------

Digi tize opt ions: I(JRRINT DIGITIZER PARANC.

I<.space> Digi tize

in - Togg I e MI)E INTDE "IYPE

t Toggle IYPE ' point line

I I Au to Label >STRFAM< >AREA FEIXE<

q Ou i t to im iti nienu site

AutoLabel: DISABLED

------------------------------------------------------------------

I dit labe I C(ustoniize Toolbox Window liclp Zoomn *

S(;lI(Ai, NII'J: Press first letter of des i red cclnmind. [Upper Case Oily]

--- - -- - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - -

7.1. DI(;ITIZE' MENU FIEIL)S AND OPTIONS

"lh1e menor has four display fields, which provide the user reference infonnation, function option,; and

intcractivc instnrctions. 'lhe UI'IPI-R-IJ14T field identifies whethcr (he mouse or digitizer is selecteXl,

Wuid if the falter. the I nuid of digitizer benigt used (here the fictitious "A(I'M digitizer"). It also

dcscfrilc, the digiti/cr cursor functions. Each number within brackets refers to the corresponding key

on the cursor:

A11> Digitize 1Point

Axtivates the digilizer for the collection of polints.

<1 --Quit Digitizing

' 'ii iiinates ti I c Ilcclion of points.

<2:-ltlxhate Monittw

Wlen du igitizing ii S'I'RItAM fleN , points are conitimuou'.l\ collected until the user quits digitizinug or togglc', to I'()INI" moel, uid the vector lbing digitizcd dous not appear on the graphics

diiplay nonilon r until the user has quit digilizing. "Ibis key temnporaiily sti;lslpei(k the collection of

v1AinJts during digitizing and displays the line drawn oItn the graphics display ionfitor tip to the

p)i ut last dig itizckd. (Sc the discussion of Pl1int •nd S-t'CAnl modes bweIlow and onm the following

page.)
- 22 -

-d>Toggle PointiStream Mode

Allows the user to switch between POINF and STREAM modes without having to interrupt digitizing and switch to the keyboard. This function is useful for "on-the-fly" digitizing of more

complex features having a combination of straight and curvilinear segments.

The UPPER-RIGHT field is entitled "AMOUNT DIGITZED." It refers to the number of lines, areas,

and sites digitized (see below), and the number of points used to represent these objects based on the

digitizing thresholds specified (see the Custorize/Display Menus described in sections 10 and 12).

These numbers are continually updated to reflect changes in the features that have been digitized.

The LOWER-RIGHr field entitled "CURRENT DIGITIZER PARAMS" displays the status of the digitizing parameters. Digitizing can occur either in POINT or STREAM mode (see below). Features are

represented either as a LINE, AREA EDGE, or SITE (see below). The parameters currently set are

CAP1TAIUZED and bracketed (> <). The default parameters, shown here, are ">SrREAM< mode and

">z'AREA type. The "AutoLabel:" parameter allows the user to specify a category value for features

at the time they are being digitized (see below), thus eliminating the need to enter the Label Menu,

described in section 9.

The LOWEtR-LEF. field entitled "DIGITIZE OPTIONS" contains the following functions:

<Space>Digitize

Pressing the <SPACE BAR> on the keyboard activates the digitizer to start the collection of

points.

m - Toggle MODE

Selects between the two modes of collecting points during digitizing: STREAM or POINT.

In POINT mode, the digitizer collects points only when the user pushes the <9> key on the cursor, that is, individually, one point at a time. Point mode is used for digitizing straight lines and

simple features where the shape requires only a small number of points to accurately define it

(i.e., straight roads or boundaries, section lines, site loci, etc.).

In STREAM mode, once the <9> key is depressed, the digitizer continually collects points as the

cursor is moved. Stremn mode is used when digitizing curves, complex lines, and other features

where frequent collection of points is needed to capture detail (soil polygons, stremns, etc.).

t - Toggle TYPE

Selects between the three types of features that can be digitized: LINE, AREA ILiGE, or SITE.

It is the decision of the analyst wid herihis supervisor(s) to agree on the level of detail required to

most accurately depict the feature in question.

A LINE is a two-dimensional feature that joins two points together. Features such as roads and

streams are usually represented as lines.

An AREA EDGE is a line feature that defines a perimeter, border, or conunon bxoundary with

other areas. Features like soil polygons are digitized as area edges.

A SITE is used to represent a point locus. Fxamples may include features such as archaeological

sites, endangered species locations, artillery firing points, etc.

I - Auto Label

Toggles between the method of labeling to be used. The default is DISABLEI) (OfT) and the

features must subsequently be labeled using the Label Menu (see section 9). When turned ON,

the user cal specify the category value for line features while they are being digitized. The auto

label method status (ON or (OiU) is shown on the Main D-gitize Menu under CURRFNT' DIGIT17TR PARlMt•lI'R.S.

q - Quit to main menu

Returms to the Main Menu.
- 23 -

7.2. THE DIGITIZING PROCEDURE

The digitizing procedure varies depending on the kind of feature being digitized. There are five possible combinations of digitizing parameters: POINT/SFTE, POINIYLINE, PCNT/AREA EDGE

STREAMLNE, and STREAM/AREA EDGE. Logically, since a point represents only a singular

locus, it would not be used with the STREAM mode.

Along with the visual cues on the graphic screen, v.digit also warmt• the. utser with an audible ;;"BF'

when further action must be taken. Once the <SPACE BAR> on the keyboard is depressed, the G/obal

Menu field shows how many points of a feature have been collected, and the LUIM coordinates for each

respective point. In ST1RF-AM mode these coordinates fly by rapidly. In the following examples,

brackets (Q 1) denote comments that do not appear on screen.

7.2.1. POINT MODE

In POINT mode, SITE type, data collection begins as soon as <0>is pressed. The sequence is:

<space bar> [activate digitizer]

<0> [digitize the site] -I > [end]

[repeat next site] [

<1 > [exit]

"Ihe original Digitize Menu fields are replaced by the following fields:

Site digitizing

# l'oints Fasting Northing

0 0.00 0.00

I1OINT mnode

When the <0> key is depressed, the La-,stinig wuod Northing coordinates flash by very rapidly, and the following query appears:

USING DIGCITZFR CURSOR FOR INPUT

Key '0' for YFS : Key '1' for NO

N(ll ": I new nodes needed

INo you accept this site?

"lie sitc location is first relpesentcd on the graphic screen by a yellow X. (i.e., "X' nmarks the spot).

(Oicck back and fortlh between thc screen and the map to see if the location is correct. If so, press <V>

again; the color of Ihc site "X" changes froin yellow to green, dkenotillE that it has been accepled.

Repeat thc i)Oinlt i ituIt sequence abveC ais neeled. Press <1 > to completely exit point-miode digitizing.

In POINT nmodc. in cither the ILINI or ARI.A I:Xi; types, the first time -- >is pressed activates ite

pr, ,raiil to rcccivc (tLoa. TIhe second time <0> is pressed bIgins the collection of (b'ilt; ilints. "[hrat is,
- 24 -

the sequence to collect points is:

<0> [get ready]

<4> [start digitizing the line]

[repeat next line/areal

<1> [exit]

As each line is digitized and dosed, the segment between the beginning and ending nodes is

highlighted in yellow. The following information appears where the Global Menu field was at the bottorn of the hgitize Menu:

#Points Easting Northing

0 0.00 0.00

POINT mode

As each point is digitized, its sequence number (1,2,3, etc.) appears under the "Points" hez 'ig along

with the UJIM coordinates. After ending, the following query appears in the Global Menu field:

USING DIGITIZER CURSOR FOR INPUT

Key '' for YES : Key '1' for NO

NOE: [0,1 ;] new nodes needed

Do you accept this area line? [if an area edge]

[or]

Do you accept this line? [if a line]

The number of nodes needed depends ocn how the line relates to surrounding lines--if the line's endpoints (i.e., nodes) connect (snap) to two already existing nodes, then it requires no additional nodes; if

one of the line's endpoints is snapped to an existing node but the other endpoint is not, the line requires

one additional node; if both of the line's endpoints are open and not snapped to existing Inxles, then

two new nodes are needed.

Check the map and graphics screen to ensure the line appears correct. When accepted, the line changes

to the color corresponding to its topoflogy (see the Custonize/Color Menu descflbed in sections 10 and

11, for default colors). To exit completely from digitizing, press key <1>at the next prompt:

USING I)IGM1ZER CURSOR FOR INPUIf

Key '0' for YFS : Key '1' for NO

Begin digitizing?
- 25 -

7.2.2. STREAM MODE

In SIREAM mode, LINE or AREA EDGE type, data collection begins as soon as <0> is pressed. The

sequence is:

<Vwece bar> [activate digitizer]

<0> [start digitizing]

<1> [end]

[repeat next line/area]

<1> [exit]

USING DIGITIZER CURSOR FOR INPUT

Key '0' for YES : Key '1' for NO

Begin digitizing?

The line is not displayed on the graphics screen until digitizing is terminated, unless key <2> (update

monitor) is used (see section 7, The Digitize Menu). As each line is closed, the segment between the

beginning and ending nodes is displayed in yellow. After ending, the following query appears in the

Global Menu field:

USING DIGITIZER CURSOR FOR INPU`I'

Key '0' for YES : Key '1' for NO

NO-F: [0,12] new nodes needed

I)o you accept this area line? [if an area edge]

[or]

Do you accept this line? [if a line]

Check between the map and the graphics screen to imake sure the line appears correct. When accepted,

the line changes to die color corresponding to its tolxologv (see the Cutmondze/Color Menus shown in

sections 10 and 11 for the default colors). If the line is not accepted, it is erased.

7.3. DIGITIZING WITH THEI MOUSE

'he mouse Can also be used to pcrfonn cligitizing. Nonnally, the mouse will be used primarily to add

or delete lines (e.g., edit). It can, h•oxwever, lx' used to digitize if a raster (cell) file is used as a data

hackdrop (see the Oisioxtnia, Menu overlay option). This can be accomplished in one of two ways:

either by choosing to ue no digitizer ("none") when first entering the v.digit program (see section 5,

Entering v.digit), or by entli ring the Customize Memi and toggling the digitizing instrumlent from the

digitizer to the mouse (see section 10). 'lhe first alltrnalive is explained in more detail here. If [lie use

of the mouse is selected, then this fact is displayed in the upper-left field of the Digitize Menu screen

(see below).
- 26-

------------------ ----------------------- CRtASS-DIGIT Version 4.0 Digitize Iv&nu

------------------------------------------------------------------ I

Nbuse digitizer PMJ..Nf DIGITIZED

# #Lines: 0

# #Area edges. 0

# #Sites 0

--- -- -- -- -- -- -- --- I Total points: 0

------------------------------------------------------------------ I

IDigitize options: (UIR1N[ DIGITIZJER PAR&AS.

I<space> Digitize

I - Tog glIe Mi1k I MIUE PTIEI

It - TogglIe TYPE >POINf< lineI

I1 - Auto Label s st rearn >AREA HX3iE<

Iq - (u i t t o ma in menu s it e

IAutoLabel: DISABLE)

------------------ ------------------------------------------------ I

IEdit Label Customize Toolbox Window Help Zomo *

I (IBALtvI31U: Pres-. first letter of desired conmand. [Upper Case Oily]

--------- -------------- I------------------------------------------I

Use of the mr-& is kI t i e v- - general principles as usinig the digitizing cursor, and the same menu

optL is apply. The r, r exception to this rule, however, is that the mouse can only be used to digitize

in POIN mode; digitidng in1 STRLEAM mode is not allowed. Heknce, as shown in the samiple screen

above, the Toggle MOD.E option in the Digitize Menu is blank, indicating that it is unavailable for use.

The examples that follow use a three-butlon mouse.

When digitiziir, a SHIE (using type: site), the following instructions appear:

Site digitizing

Buttons:

Left: Dgitize a site

Middle: Ahort/Quit

R~ight: Ab~ort/Quit

#P1oints I Asting Northing

POINF modeXI

As each site locus is selected by pressing the left biutton, a yellow 'X" appears on thc graphics screen.

and the point's Fasting and Northing coordinates appear at the bottomi of the screeni. Ihe lollowinig

message appears:
- 27 -

Do you accept this site?

Buttons:

Left: yes

Middle: no

Right: yes

#Points Easting Northing

1 490000.12 3440000.88

NOTE: 1 new nodes needed

POINI mode

Press the appropriate mouse button to respond.

To digitize an AREA or LINE, the following set of instructions appears:

Begin digitizing?

Buttons:

Left: yes

Middle: no

Right: yes

And:

Point number 0

Buttons:

Left: Mark a point

Middle: (Back up one point)

Right: Quit digitizing

#Points Lasting Northing

POINI' mode

As each point defining the line/area edge is selected, its sequence number and UIM coordinates are

displayed; the line segment between the points is highlighted in yellow. The following screen shows

that four points have been digitized to define a line, along with the UIM coordinates of the last point.
- 28 -

Point number 4

Buttons:

Left: Mark a point

Middle: (Back up one point)

Right: Quit digitizing

#Points Fasting Northing

4 505400.12 3440686.88

POINT mode

If a point does not appear correct, use the middde key to delete it; press the middle key repeatedly to

delete a number of successive points. Upon quitting, the next message appears:

DI you accept this line?

Buttons:

Left: yes

Middle: no

Right: yes

#Points Easting Northing

4 505400.12 3440686.88

NOTE [0,1,2] new nodes needed

POINT mode

Press the appropriate mouse button; continue the digitizing procedure as needed. Practice digitizing

with each of the possible cursor and mouse combinations to become familiar with the differences.
- 29 -

8. THE EDIT MENU

The Edit Menu is used to modify vector files that have been digitized or imported from other sources.

It can be accessed from all the other submenus. The following screen shows the layout of the Fdit

Menu with the default parameters. In the optioms below, the word "line" is used generically and also

refers to area edges.

C(ASS-DIGIT Version 4.0 Edit fAknu

------- =------------------------------------------------------------I

Edit options:

r - Remove line

i - Remove a site

s - Snap line to node

b - Break a line

m- Nive a point

M - Nbve a line or site

t - Re-type a line (AREA/LINE)

d - Display nodes w/in map threshold

R - Renove B13LK of lines

q - Quit to main menu

---------------------------------------------------------------------------.

Digitize Label Customize Toolbox Window Help Zoom *

(t101ALlVNU: Press first letter of desired conmand. [Upper Case Only]

-------------------------------------------------------------------I

8.1. EI)F MENU OPFIONS

Eldit tLsLs a combination of keyboard entries aind cursor inputs to exec-ute comnland functions. Type in

the lirst letter of an option name to activate it. Interactive instructions appear on the dumb terminal

screcn (or the shell window if only a graphics monitor is used). Tihe MOUSE is used in all editing

operations. Most editing procedures follow a left-right-left-right button sequence for first choosing, and

second, accepting, the editing function. The mnidlie button is tused to abort the current function. All

colors described below are the I)FFAULT colors for the particular ftnction or feature (see the

(usqtotiize/Color Menus). The features being edited are highlighted in yellow. The user should be very

carefll when using the "remove" functions within lift; if accidentally removed, features may Ibe hard to

recovei or reconstnict.

r - RIemnove Line

Renwves a previously digitized line. ('hoose and accept the line; it disappears from view on the

graphics screen. 'ITis option relpeats automatically for as miawy features as the tuser requfires.

i - Remnove a Site

Relmoves a previotsly digitized site lowation. Choose and accept the site: it will disarppear from

view% on the graphics screen. 'Ihis option repeats automatically for as imany features a.,; the user

requi res.

s - Snap Line to NoIe

aklantal procedure to "snap," or join, tw o selprate noxies together to forin one node. First choose

a lint and nile to snap "fronm" and then a node to snap "to." Ihis option will repeat autonnaticalhl for as many features as the user requires. See the expanded explanation belowv.
- 30 -

b - Break a Line

Breaks an existing line segment into two new segments and inserts a node at the designated location. First choose a line to "break,' and then a "point" on the line to break. A new snapped

node will appear at the designated locus. This option repeats automatically for as many features

as the uet requires.

m - Move a Point

Used to reposition a point in a line. This option does not allow the movement of nodes at the

end of line segments, only the points within a line. Choose a line and a point to move, and a

new position for the point. The point moves to the new location and the shape of the line is

adjusted accordingly. The user may wish to use option "n - Show Pants in Lines!' in the Wndow Menu before moving the point (see section 14).

M - Move a Line or Site

Used to reposition a line or site to a new location. Unlike "m" above, this option retains the

orientation and shape of the original feature, but simply moves the whole feature to a new position. Choose a lin/site to move, and a new location for the line/site. The line/site reappears at

the new location.

d - Display Nodes wAn Map Threshold

Displays nodes that occur within the given distance threshold calculated for the current session.

This is used to verify if nodes from different lines occur close enough to be snapped together,

even though they should not be. This is important if nodes will be automatically snapped together during v.support. The user is allowed to make the map threshold larger but not smaller.

Type the new threshold value after the prompt.

t - Re-type a Line (AREAJLINE)

Changes the type of a line between either an area edge or a line. Use the mouse to point at the

feature to be changed. Choose and accept the line; the color of the feature changes, indicating that its topology has changed. This option repeats automatically for as many features as the user

requires.

R - Remove BLOCK of Lines

Designates a group of lines to be removed, rather than having to delete them individually using the "r" option described above. Use the mouse to define a box around the area where a block of

lines is to be deleted. Choose and accept the area. The program asks for confirmation before

deleting the lines. Only the lines bounded within the box are removed. Exercise extreme caution

when using this option.

q - Quit to main menu

Returns to the Main Menu.

8.2. THE EDITING PROCEDURE

One of the most frequently used procedures in the EiBt Menu is that of snapping adjacent nodes

together to join line segments. It is also the most complicated function, in that it involves nmre than

one segment. The user should be wary when using this finction because it can radically alter the shape of lines if the nodes to be snapped together are t(o) far apart (reler to the Customize Menu in section 10

for a description of the "digitizing" and "snapping" thresholds). An expanded explanation of the pro- cedure is presented here. It should provide an adequate model descfibing the other editing functions.

Before entering the edit menu, the user can display the (digitized data on the graphics monit(o and

search for possible digitizing errors.

After selecting "s - Snap Line to Node" the follhwing scquenc(, aplx'ars [a line "X' has been selected

using t&` ;.1XIuse iointerj:
- 31 -

line to snap FROM:

Buttons:

Left: Ch~oose line

Middle: AbortQuit

Right: Accept chosenlin

Line* X Category: (unlabeled)

1) 'Me selected line is highlighted in yellow and the next query appears [where node "Y' has been

selected]:

Node to snap TO.

Buttons:

Left: Choose node

Mfiddle: Abort~l~uit

Right: Accept chosen node

node#. Y

EAST: [Ul-M Fasting]

NORMI [UIM Northing]

2) With the 1,1-irmouse button, select the node to which you want the line snapped.

3) ihe selected niode is highlighted in yellow; pressing the RIGHT m(115e- button accept% the node mnd

cauises the two adjacent nodes to be snapped. In the case of two "open" nodes- (green), the two will be

joined to form one "closed" node (red). Where a line is being sinappl~xI to an existing closed node, the

scuec is FROM the line TO the nodle. It is not possible to snap existing closedI nodes to each other.

(Sce Also the dliscuission of digitizing and snapping thresholds, in the Cuvtonize Menu in section 10.1.)

Also be aware of the following wamling inessaige (answering "no repeats the above two steps):

Attempting to snap a line to itself. Proceed? [y]

Ipcilywhere two nodes are close together, the wrong line mayi be inadvertently chosen to "Snap

l'1~()4A; if the tuode is snapped then the line may actually "douible-hack" on itself and the original

1~ 'y~ may be destroyed, or a duiplicate line or sliver may be created which cam cause problems

lit-n thle file is to) he conve~rted into a raster layer. If the user mistakenly (lestrovs original toplxogy,

the user may have to redfigitize the muoditieid area. In the case of at self-closing olxy\gon composed of

one, line with two open endpo~ints (nodles), this warning message can be ignored, b-cauise thle polygon is

being closed intentionally on itself'.
- 32 -

9. THE LABEL MENU

Labeling is the process of assigning category values to digitized features. The Label Menu can be

accessed from the Main, Digitize, and bdit Menus (described in sections 6, 7, and 8). The screen layout

of the Label Menul with default option settings is presented below. Colors described for the options

are the defaults (see the Custouze/Color Menus, described in sections 10 and 11), which the user may

change.

-----------------------------------------------------------------

CR(iASS-DIGIT Version 4.0 Label Ntnu

---- --------------------------------------------------------------------- I

ILabel options:

a - Label Areas m - Label Miltiple Lines

II - Label Lines M - Un-Label Miultiple Lines

Is - Label Sites

IA - Un-Label Areas c - Label Contours

L - Un-Libel Lines i- Contour interval: < 5 >

IS - Un-Label Si tes

B - Bulk Label Remaining Lines

Ih - IlighIi gh t Li ne s of ca tegory #

Id - Display Areas of category #

Iq - Return to rmin nmnu

------------------------------------------------------------------ I

IDigitize Editi Customize Toolbox Windou fllp Zoom

I AMf[Al N'IT'4: P'ress first letter of desired comnrnd. [Upper Case Onily]

------------------------------------------------------------ ----- I

9.1. LABEL MENU (VI'lIONS:

a - Label Areas

Assigns at cittegory value to an area. (See the expanded explanation in section 9).2., Labeling

Procedure.)

I - Label Lines

Assigns a cattegony value to a line. Uirst, type the categon. number after the protnpt. Next, move

the po~inter to the line to be labeled (here, unlabeled lines are blue). Choose and accept the line.

'Thle line býeing lab~eled is highighted in yellow, and Mhen accepted turns mtaAentai. No Label

value appears next to the line (etrthe Cvonzfsp' %,M utochang~e the displaty optlion).

Repea labeKling lines with the same category value as needled.

S - Label Sites

Assigns at eategoix value to a site. Hirst. i\ pe the calegor\ ntumber after the promipt. Next. mo\ c

the p 'linter to) the site to be. labe-led (unlabeled sites are g~reen). C7hose the site wkith the left bit

tonl and atccept it with the right. 'Ihe site ben 'dclk is highlighted in ieio ndwhen

Althomeh it is pIaimcd l iat future relmeasc of GRANS issued by IJSA(IT m)ldd the I SIMA S(NS will hr idmnii-l.

these two rcleases imt% 41vi sirricvha dliffeient functions in GRASS 4.0 ''lic tum1tim described in this nmiailw~ are

thoise of tht, I ISA(I I0 (WIASS 4.0 rdcase. av ailab~le to all (MASS users
- 33 -

acceped tunis aqua. No label value appears next to the site (see the Customze/lisplay Menu to

change the display option). Repeat labeling sites with the same category value as needed.

A - Un-Label Areas

Removes a category value from an area or group of areas. Move the pointer inside the area to be

unlabeled. Choose and accept a point within the area. Next, move the pointer to a boundary line

for the area and choose and accept the line. T7he area marker and/or label inside the polygon

disappears and the color of the selected area changes from orange to grey. Repeat as necessary.

L - Un-Label Lines

Removes a category value from a line or group of lines. Move the pointer to the line to be unlabeled. Choose and accept the line; the color changes from magenta to blue. Repeat as necessary.

S - Un-Labe Sites

Wnmoves. a category value from a site or group of sites. Move the pointer to the site to be unflabeled. (hoose and accept the site; the color for the site changes from aqua to green. Repeat as

necessary.

B - Bulk Label Remaining Lines

labels any lines which remain tunlabeled (this option does NOV apply to area edge lines). Upon

choosing this option, the user is a-sk-ed to respond to the foll1~ving prompt:

'Ibiis function will label IATR]Y unlabeled line. Proceed lii

If the aiiswer is yes, enter the category numiber at the prompt. Ns the program proceeds to label,

the color of the remaining lines changes from blue to magenta on the graphics screen. This

option is convenient for labeling a large number of line features having the same category value,

such as roads or streamis. Ile cautious when executifng this option, however, to make sure that all

lines have been labeled properly. 'Ibhis option does NOI' apply to labeling~ area edge lines.

h - Highlight L inesi of Category #

Ty'~pe the category vailue atter the prompt. '[hec lines -with the specilied category value are

highlighted inl yellow.

d - D~isplay Areas of Category #

Ty'pe thle category value alter thle promrpt. '[hec areas w~ith the specified category value are

highlighted in yellow.

m - Label Miultiple Lines

lAbe-ls line segments contiguotti to each other (i.e., connected 7y "snallved" nodes). Type the

categ~ory number after the pronlpt. Use the poin~ter to choose a line to label. 'Ile program

lri"hlii~hts thle connectinig linv's and~ asks the uiser if these are correct. Press the left or fight 1bmttom

to ansxwer ves. '[he highlighted finces will cha~nge color to nia-enta. 'Ibis optioni is convenient for

lablOing" a large numiber of contiguious line features of thle samec category, such as roads or streams

(see ak~ thle Aimtolablx' funlcthirl). Be cautiotis %%hen executifng, this optioni to make sure that all

hueis have been labeled Iprope(rl\. lines that are not directlx coninected to each other (i.e.. have

open" nodes between themi) are not tiaffected by this option, nor are area edge lines.

M - tin-I abel Nlultiple Lines

Ulimlal-clsI liw.legnet %gili" cll' mrtigluns 1)each other (i.e., connectled by "suappe(1' iwxles). Use the

l-x i nfr to choose a line to tinlalx 'elibe prgri highlights any connecting lines% and asks the

user to conirni C these liiics. 'r'ss [ltr left or right buttonl to *umr1swer yes. All the lines, will chkuigc

color toI blue. 1k' caultiotts xx lceu executing this option. 'kl lWoramn doies, NOVF differentiate

btetn dfferent 'aftcgt1 \v allit\ 1i r thek ('ontigtw us lines. AL L lines \\ ill be unlabeled, whether
- 34 -

they have the same category labels or not. Lines that are not directly connected to each other

(i.e., have "open" nodes between them) are not affected by this option, nor are area edge lines.

c - Label Contours

This option allows the rapid labeling of contour line data, such as that impored from DXF or

DLG format files, rather than having to label each interval line individually. The user first selects

a contour interval. (See option i following.) The user is instructed to choose and accept a starting line and an associated elevation value. Then select an ending line and associated elevation

value. The elevation values and the interval must correspond exactly. For example, if there are

five lines to be labeled, the contour interval is 5, and the first line has a value of 250, then the

fifth line must have a value of 270. The program returns an error message if the contour interval

and the starting/ending line elevation values do not match.

i - Contour Interval: < 5>

Selects an interval to label contour lines (see the previous option, c). The interval can be any

unit, e.g., 1, 2, 4, 5, 10, etc. The default setting is 5. The interval specified is completely arbitrary, or in the case of imported DXF or DLG files, recorded as a data attribute. The user should

be aware of the original map data and how it was extracted.

q - Return to main menu

Return to the Main Menu (see section 6).

9.2. THE LABELING PROCEDURE

The Label Menu uses a combination of keyboard entries and cursor inputs to execute functions. Type

the first letter of an option name to activate it. Interactive instructions appear on the dumb tenrinal

-screen (or the shell windlow if only a graphics monitor is used). The moutse is then used to select the

feature to be modified. labeling operations using the nxmuse follow a left-righl-left-right bultton

sequence for first choosing, and second, accepting, (i.e., verifying) the features. The middle button is

used to quit the current finction. The "label" and "unlabel" functions are somewhat redundant. For

example, it is not necessary to "tulabel" a feature befioe giving it a new label; it is possible to relal-wl a

feature directly by using the label option and simply assigning a new category value. The old label is

overwritten by the new one.

Before beginning to label, identify each possible fcature on the original map and the label value that

will be assigned to it. Most analysts have their owin mnncioric procedure for labeling. For features

having no numerical val•ues associated with them (such as soil types, strears, etc.) it is suggested to

label the features sequentially, beginning with calegry vldtc I and continuing as needed. For tho sc

features already possessing a known nueneriid vadlue (sucth ias a contour line, fifin,, polint, etc.) the

analyst may want to retain the original designation.

IMPORTANI': labels can only be positive or negative integcrs; no alpha characters or decimal points

are acceptable. The value zero, 0, is reserved for the category no data. No feature may be, labeled

with a zero. Zero is also ustld to exit (xit of the labcling function (see below).

"Ile labeling procedure is similar for areas, lincs, and sitcsý. Since the labeling of areas is fthe most

complicated, however, it is described in more detail hcre. Ibis should serve ats a;n adelquale model

describing the other labeling functions.

After selecting "a - Label Area." the foilloving sequence appears:
- 35 -

]Enter Category Number (0 to EMD):[O]

Type in the category number for the area, and <REIVRN> The next message appears:

Select point within area:

Buttons:

Left: Choose this position

Middle: AbortAQuit

Right: Accept chosen point position

Point location:

Fast: [UITM Fasting]

North: [LTIM Northing]

On the graphics screen, position the pointer within the chosen area, usually somewhere near the middle

of the feature, and press the LIFI button. A yellow dot appears at the designated locus, and the UTM

coordinates of the point are displayed on the menu screen. If this position is not suitable, simply move

the pointer ind chox)se a new spot. Once the position is satisfactory, press the RIGIWT button to accept

it; the color of the dot changes to orange (this is the AREA MARKFR). The next message appears:

Select a Boundary line:

Buttons:

Left: Choose line

Middle: Abort/auit

Right: Accepl chosen line

Positio4n the pointer on a boundary line defining the area and press the lIti buttton; the chosen line is

highlighted in yellow. The following message appears on the bottom of the ment screen:

Area is not labeled

[ORI if the area has been previously labeled:

Area is labeled category X

[Where "X' is some integer]
- 36 -

If the highlighted line is con'ect, then accept it with the RIGHT button. All the other lines defining the

selected area are highlighted in yellow. Some problems can occur at this stage of the process--if there

are any open nodes around the perimeter of the area, or slivers or overshoots, the program responds

with a BEEP and the following warning message appears:

Could not create area

This message disappears quickly, and the program reverts to the point selection screen. The analyst has

to determine the cause of the error message and may have to perform additional editing and/or digitizing. The Toolbox, 4ndow, and Debug Menus can also be consulted for further assistance (see sections

13, 14, and 16). Provided no errors occur, however, the next message appears:

Accept this area?

Buttons:

Left: yes

Middle: no

Right: yes

Area is Category X

If the area appears satisfactory, press either the LEFF or RIGHT button; the color of the bouncaidt line

changes to orange and the category label appears to the upper right of the area marker. After acccpting

the area, the program returns to the point selection screen. If continuing to label other areas with the

same categor. label, simply repeat the process. To change category values, press the MIDDLE biutton

to quit, type in the new number, and proceed. To end the labeling process altogether, type in zero [01

and <REITURN> at this juncture. In the display default settings, note that if the graphic screen is

redisplayed or the Custongze/LDsplay Menu options are modified, then the category labels disappear,

leaving only the area markers, and the area edges turn color back to grey.
- 37-

10. THE CUSTOMIZE MENU

This menu contains options to modify certain input and display parameters during a digitizing session.

The screen layout of the Custonize Menu and the default settings are presented below. This menu can

be accessed from the Main, Digitize, Bit and Label Menus.

-----------------------------------------------------------------

GRASS-DIGIT Version 4.0 Customize l&nu

-----------------------------------------------------------------

Customize options: Current:

d - Set digitizing threshold 0.0300

s - Set snapping threshold 0.0300

b - Toggle BEEP CN

a - Toggle Auto Window COFF

w - Toggle Windowing device DIGITIZER

p - Toggle Point device NJLSE

d - Toggle Digitizing device DIGITIZER

0 - Select An Overlay Map None

B - Select a Backdrop CELL Map None

- Select a Label Map

D - Enter Display Options Menu

C - Enter Color Options Menu

q - Return from whence we came

-----------------------------------------------------------------

We I p Zoo01 *

GLOBAL vUNU: Press first letter of desired conmand. [Upper Case Only)

I-----------------------------------------------------------------

10.1. CUSTOMIZE MENU OPTIONS

All options in the Customize Menu are selected from the KEYBOARD by pressing the key corresponding to the first letter of the command. The Custonize Metu options set within a digitizing session do

not carry over into the next session. In the descriptions below, the DEFAULT settings are presented

first, followed by the alternate.

d - Set Digitizing Threshold

Sets the amount of space to be left between points collected by the digitizer. To change the digitizing threshold, press "d" and the following message appears in the global field. Fnter the new

threshold value at the prompt. Upon exiting, the new value appears under the "Current" heading.

(Ruiz and Messersmith, 1990 gives a more detailed discussion.)

Current thresholds:

Map: 38.10(X)0() meters.

Dig : 0.0300X - I / 33.333333 of an inch.

Fliter new Dig threshold or <RlI'URN>when finished:

s - Set Snapping Threshold

Sets a threshold value defining the amnount of space less than which two adjacent nodcs automatically will be "snapped," or joined together, to make one node. For example, if the snapping

threshold were set at 0.03 (digitizer) in., nodes placed less than 0.03 in. apart (onl the digitizing

tablet) would be snapped together into a single node, while nodes placed more tham or equal to

0.03 in. apart would be left alone. "lic digitizing threshold and the snapping threshold do not
- 38 -

necessarily have to be the same for any particular scale map, but the default values usually are set

the same. The threshold values chosen depend on the accuracy, resolution, and level of detail

desired in the final digital map (Ruiz and Messersmith, 1990 gives a more detailed discussion).

The format for choosing a new snapping threshold follows that of the digitizing threshold

described above.

b - Toggle BEEP

Selects whether an audio signal is to be emitted from the terminal during the digitizing session.

Many functions in v.digit use a BEEP to indicate their activation. It is recommended to keep the

beep "ON" to determine when certain cursor functions have been selected, e.g., snapping nodes,

editing, etc.

a - Toggle Auto Window

Ajusts the working window to automatically encompass more of an area feature being labeled if

most of the area initially falls outside the original dimensions of the window. This option is used

for labeling areas only (see also section 9, Label Menu).

w - Toggle Windowing Device

Selects whether the DIGITIZER cursor or the MOUSE is used as the windowing device. Once

the working window has been initially selected using the digitizing cursor (see Enterinj' the Digitizing Session), it may be more convenient to use the mouse to choose subsequent windows (see

section 15, The Zoom Menu). If no digitizer is selected when entering the session, then only the

mouse is available for use.

p - Toggle Point Device

Selects whether the MOUSE or the DIGITIZER cursor is used as the pointing device. In most

instances, it is more convenient to use the mouse. If no'digitizer is selected when entering the

session, then only the mouse is available for use in this option.

d - Toggle Digitizing Device

Selects whether the DIGITIZER cursor or the MOUSE is used as the digitizing device. 'lhe

digitizer cursor is normally used for the initial input of vector daita. However, for mnodifying the

data once they have been entered, it may be more convenient to use the mouse. If no digitizer is

selected when entering the session, then only the mouse is available for use in this option.

0 - Select an Overlay Map

Displays a background vector layer for visual comparison and reference. To display a vector

overlay, type "O"; the following prompt appears at the bottom of the menu screen:

Fnter the name of an existing vector file

Enter • 'list' for a list of existing vector files

Ilit RETURN to cancel request >

After choosing the vector file, the following query appears:

Dc you want to automatically redraw backdrop on re-windowv? (y/n) [y]
- 39 -

After responding, this message appears in the global field:

Plotting overlay Map I ... Press <ESC• key to stop I

More than one overlay vector layer can be displayed (although the result might be confusing). If

the automatic redraw option is not selected and the working window is changed, all the overlay

vectors will have to be reselected. The order in which vector overlays are selected is important.

The second vector overlay supersedes the first. Only one overlay vector can be automatically

redrawn. If the working window is changed, the last vector overlay selected for automatic redraw

is the only one that will be redisplayed in the new window.

B - Select a Backdrop CELL Map

Displays a background raster (cell) layer under the current vector file. The background map is

often useful for providing a frame of reference while digitizing and to check how the layers

match each other. Only one backdrop raster map can be displayed at a time. The sequence for

choosing the raster map is the same as for choosing the vector overlay map previously described.

One note of caution: the color table for the raster layer may obscure the vector overlay map if

the overlay color is not changed (see section 11, Color Menu, to change the default color

options).

L - Select a Label Map

This option is not available at this time, but may be included in future GRASS releases.

D - Enter Display Options Menu

Accesses the Display Menu to change the display parameters of features appearing on the graphic

screen (entry is possible only through this menu).

C - Enter Color Options Menu

Accesses the Color Menu to change the color parameters of features appearing on the graphic

screen (entry is possible only through this menu).

q - Return from whence we came

Retimrs to the previous menu.
- 40 -

11. THE COLOR MENU

Featues in v.digit are color coded for ease of identification. The screen layout of the Color Menu is

piesented below. The colors are the default settings of the features as they appear on the graphic screen.

The Color Menu can only be accessed through the Custranize Menu (see section 10).

----------------------------------------------------------------------------

(IRASS-DIGIT Version 4.0 Color Wvlnu

-----------------------------------------------------------------

Color options: Current:

a - Areas grey

I - Lines blue

s - Sites green

A - Labeled areas orange

L - Labeled lines magenta

S - Labeled sites aqua

1 - Nodes w/ 1 line green

2 - Nodes w/ 2 or more lines red

h - Highlight yellow

B - Background black

0 - Overlay map white

r - Reset Defaults

q - Return frorn whence we came

-----------------------------------------------------------------

I [elp Zoom *

GI&BAL NC4,U: Press first letter of desired connand. [Upper Case Only]

-----------------------------------------------------------------

11.1. COLOR MENU OPiIONS

COlors are changed by toggling the appropriate key for the feature to be changed (e.g., press a to

change the color for areas). There are twelve colors that can be selected; they toggle in the following

sequence: grey, magenta, aqua, indigo, violet, white, black, yellow, blue, red, green, orarge. The first

six options a through S are self-explanatory.

"The remaining options are describxe below. Once new options are selected, the graphic screen

automatically refreshes to show the changes.

I - Nodes w/ 1 line

Nodes that form the endpoints of unattached line segments are open or "wusnapped' (here "line"

is used in the generic sense, including also area edge lines). "lhey are color-coded green.

2 - Nodes w/ 2 or more lines

Nodes at the intersection of two or more line segments (inch,ding area edge lines) should be

closed or "snapped." ihey are color-coded red.

v.digit distinguishes between nodes which represent "open" and "closed" lines. 3Ihc distinction between

"open" and "closed" nodes is important if the vector layer represents area features to be converted into

a raster layer. Ihe creation of a raster area polygon is not allowed if the lines comprising the polygon

are not properly connected, or closed. '[he creation of raster layers from sites or line segments is not

affected by the presence of open nodes.
-41-

h - Highlight

Many functions in v.digit make use of highlighting. The default highlight color is yellow.

B - Background

Changes the background color field on which the vector lines are displayed. The default c!or is

black.

0 - Overlay Map

Selects the color of any vector files to be displayed as overlay references to the layer currently

being digitized. See also the Custonize Menu described in section 10.

r - Reset Defaults

Resets the default colors back to their original values if changed by the user during a digitizing

session. Upon exiting a session, the color options are automatically reset tc the default values.

Any alternate color options must be specified again by the user on reentering ti - w,-itizing session.

q - Return from whence we came

Returns to the Customize Menu.
- 42-

12. THE DISPLAY MENU

This menu contains options to change the display parameters for features appearing on the graphics

screen during the digitizing session. The screen layout of the Display Menu showing default parameters

is presented below. This menu can only be accessed through the Custloize Menu described in section

10.

----------------------------------------------------------------------------

CRASS-DIGIT Version 4.0 Display Wv~nu

Display options: Current:

a - Area Labels OFF

I 1- Line Labels (1F

s - Site Labels (FF

m - Area Ivhrkers (N

A - Area Border lines OFF

L- Labeled lines CN

i - Li ne s (IN

S - Sites (N

n -Nodes CN

p - Points in lines OFF

r - Reset Defaults

q - Return from whence we came

-----------------------------------------------------------------

IH Ilp Zoom *

jGIfilAL. NF•IJ: Press first let ter of desi red coniand. [Upper Case Only]

-----------------------------------------------------------------

12.1. DISPLAY MENU OP`I'IONS

Display options can be toggled between ON (they appear on the graphics screen) and OFF (they do not

appear). Options set dwring a digitizing session do not carry over to the next; they are autonmtically

reset to the default values. Refer to the Color Menu described in section 11 for the color coding of the

l)splay Menu options. Colors mentioned below are the default colors. In the following descriptions,

the default setting is described first, followed by the alternate.

a - Area Labels

"[his option is normally OFF to prevent cluttering of the screen when many features are being

displayed. When turned ON, the category values alssigned to labeled areas are displayed within

the poIlygons (see the Iahel Menur in section 9). lihe latter setting is recommended when digitizing, labeling, and/or editing areas.

I- Line Labels

"Ibis option is normally OFF to prevent cluttering of the screen when many features are being

displayed. When uinied ON, tihe category values assigned to labeled lines are displayed near the

mTfidpoint of fhe lines (see the la'el Menu in section 9). 'Ihe latter setting is recommended when

digitizing, labeling, and/or editing lines.
- 43-

s - Site Labels

"ITis option is normally OFF to prevent cluttering of the screen when manry features are being

displayed. When turned ON, the category values assigned to labeled sites are displayed to the

upper right of the sites (see the Label Menu in section 9). The latter setting is recommended

when digitizing, labeling, and/or editing sites.

m - Area Markers

Displays the area marker of a labeled area, as represented by a point (default color orange). The

marker is the actual point location in (xy) space within the polygon where a category label has

been placed (see the Label Menu in section 9). This point is used here only as a visual reference,

but does have meaning with regard to feature topology (i.e., raster areas cannot be created

without it). 'Ihe •ser may wish to toggle the display of Area Markers OFF if the user is adding

feature labcls to a map, to prevent the display screen from becoming confusingly cluttered.

A - Area Border Lines

In the OFF setting, area edges are displayed in grey, whether the areas are labeled or not. If

turned ON, the lines that make up labeled areas are displayed in orange. It is recommended to

use the latter setting when digitizing, labeling, and editing areas.

L - Labeled Lines

I)isplays labeled lines in nagenta and undabeled lines in blue. If turned OFF, all lines wrill

display in blue (not reconmlenelld). Area edge lines ,are unaffected, they remain white in color.

i - Lines

Displays unlabeled lines in blue, labeled lines in magenta, and area edes in grey. If turned

OFF, onlv labeled lines appear (magenta) and lines delining area edes ,and unlabeled lines do

not aptvear at all (not recommended).

S - Sites

Displays labeled sites in aqua, and unlabeled sites in green. If tunred OFF. sites will be

represented simply by a red (closed) nwble. The latter option is N(WI" reconnmenlded in order to

avoid confusion with ll noes oil line segmenls amd spurious "floating" jiodes.

n - Nodes

Displays nox's ats po)illns. "()pen" or "uinsnapped" n•des arc displayed in green, wNhile "closed" or

"snapped" ic les are displaved in red. If turned OFF, nodes \will not appear (not recommlendled).

1 - Points in Lines

'Ilis oplion is tionnadh OFF to avoid l.sible confuision xwith n•les. If turned ON, all tile points

that describe a fine are displayed, not just the nodes. *the ixpints arc dislilayed the sa.e c (lor as

thie nodcs Ihxc migh t represent, that is, red for ac "snappxed" or "choed" irle so'fi(cnlt. and gr(e.l

for "'unsnaplped" or "open" Iinies. If a line is conl mposed of a mixture of snappxed and Iunsnlapped

sq-lIkIntsl, thcii thcy are visually represeltel as Utnsnappxed (i.e., the lpoints \\ill aplX'-r gre•en).

"11hC ON settink is sometimes useful ""lvhe breaking or snapping lines during ediling (see. thc Pl.fit

Menut. describc'd in sct'ioli S).

r - Reset DIefuilts

Rescls all oplions to the dclault vahles.

(I - Return tronm i% hence we carnie

Retulns to Ihc (C'I.swnzize Aleiii anid rcereshes th tlispla\ screen if an\ paiamulieters ha\,c Ixen

chancigd.
- 44 -

13. THE TOOLBOX MENU

"This menu provides a number of utilities that help to find and diagnose problems that can occur while

digitizing. In the following descriptions, the default highlight color for all options is yellow. The

Toolbox Menu can be accessed from the Main, Digitize, Edit, and Label Menus.

------------------------------------------------------------------

GRASS-DIGIT Version 4.0 Toolbox Wvenu

------------------------------------------------------------------

Toolbox options:

w - Write out session

R - Register map

B - Build Neat Line

u - Display Unlabeled Areas

o - Display Open area lines

d - Display Duplicate lines

n - Display Node lines

i - Display Islands

q - return from whence we came

------------------------------------------------------------------

Window Help Zoom *

I IJBAL Nf' : Press first letter of desired conmand. [Upper Case Only]

------------------------------------------------------------------

13.1. TOOLBOX MENU OPTIONS

w - Write out sssion

Saves the results of work completed during the current digitizing session. If the se-,'ion lasts for

a long time, this option should be used periodically to prevent loss of data due to an inadvertent

power loss, system shutdown, or other intemiption.

R - Register map

Allows the user to register and re-register one or mor. maps to the dfigitizing board without having to exit and re-enter v.digit. This is tiseftul if the digitized map layer is compoised of multiple

map sheets (e.g., adjacent USGS quad sheets) as is often the case with large installations or geographic areas. lhle procedure is the same as when first registering a map (see Entering v.digit).

If no digitizer is selected upon first entering the v.digit program, this option will not be available

to the user. (It will shv uip as a "blank" space before the option descfiptioln.)

It - Build Neat Line

When the pointts used to register a miap form a rectangle (such as using four UIM grid intersections). this option can be utsed to form lines connecting fltesc four points. TIhe lines create a boxx.

or "fnoat line" arotund the area defined by these lines and acts as a straight boundakr' that other

lines call join. It also serves a visual pxipose to highlight or emphasize a parlicular area ol

interest. If no digitizer is selected uixmii first entering the v.digit prognun, this option will not be,

available to the user. (It will show ill) as a "blank" spxice before the option description.)
- 45 -

u - Display Unlabeled Areas

1-lighlights, in yellow, those polygons that have not been labeled. The option works properly only

after running the GRASS programs v.sipport or vimport. TEhis is because the v~digit program

cannot recognize the polygons until their spatial topology is built by v~support. For complex

features, it may be helpful to first use the "Clear Window' function in thie Window Menu (see

section 14) before choosing ths option.

* - Display Open Area Lines

rinds areas that cannot be properly labeled because there are one or more unsnapped nodes that

prevent the polygons from closing. Edge lines that bound unlabeled areas are highlighted in yellow. It is recommended that this function be used only after labeling all areas and executing the

GRASS program v.support.

d - Display Duplicate Lines

Hlighlights lines which have been accidentally double- digiti zed. See also "n - Display Node

Lines!' below.

n - Display Node Lines

Lllghlights the liles attached to a particular node. Th1is function is useful for tixing to common

6gilzizing problems: overshootis and double-digitizing the samne line. Area-s are built in v.digit bý

following the angles of lilies that attach to nodes; therefore, overshoots cause bad anugle inforniation to be stored. I'his and doutble digitizationi canl also cause slivers of bad data to beý created

(sec section 13.2, Finding E~rrant Nodes).

- lDisplay Islands

I lighlights islands, or ar-a polygons comipletely embedded or enclosed within other piolygons.

'Ibils option is uiseful for locating lakes, soil types, anmd other features that may occur withinl other

featutres.

qj - Return frorn Whence We Came

Returns to the menu uised prior to the 'Thoihox Menu.

13.2. Finding Errant Noides

It is sol netiumes diffticult to locate a problemn nixle when the prograni complains that it caninot label or

build anI area. Mfen the user has to examine each node intersection that compoCse- an area polygon. At

this juncture, it may beuseful to ener tlie 0B~u% Menu (see section 16, and the following~) to locate thenodXes inl question. It is suggested to Zooml as closely' as posible around the suispectedi niode(s) becauise

someI slivers and( line overshootls canII be qutite smiall (see the loom~ Menui, (lescrib-ed in section I15). At

this time, it is also reco mmndedll~ it enter the WindowI Menu (see section 14) and cboisc 11w th"C - Clear

Windmw" option to erase the graphics screen. 'Ilimen choose option "ni - Show Nodes"' to redisplay the

suispect(-d nixlcs (see section 14. The Windmi' Menu). S&nietinies at this po~int. "open ni~xl-s that were

previouisly obsAcured by other nod~es b~conme apparent. - ihese errant iimodes may beK the- caulse of the(

lprol~eni andl can either be remo(ved or snappedt using the 1li/it Menu (see section 8). 'Ibermi reenter the

'Iixlbax M'enu, and chi ose option "ni - D~isplay Nixde Lines." 'Ilime mouse is u~sed to select and accept the4'

n ~xle. Press the RI(I jil mouse burttonm to view hiles couinter-clockwise around the nodelc anid the I .11-T

button to view themin clockwvise. Fach line is highlighted sequentially around the noti Mi lmiIc a descri P

tion of its toI oles' isdsplayed at the Is ttom r f the screen. ( Xershioots are indicated when thme v-isile~(

liles cx ten(flmng fromn a given nixde fail to beý highlighlted in the prope-r sequence arounid theC nlode

P(IIC (1mhIeditized linies are indicated It a lineC is h~(1Iighligted twice iii a row. F or a more detui led descrip

ti nu of tliis procss c( iistrlt the I)'u Menu (see section 16).
- 46 -

14. THE WINDOW MENU

'His menu provides options to modify the graphic screen puaianiters to chieck the accuracy uid comnpleteness of digitized features. Ti~s menu can be accessed through the Main, Digitize, Edit, Label, and

Tool box Menus. The screen layout of the Wndow Menu is presented beow.

---------------------------------------------------------------- I (MAS-DIGIT Version 4.0 Window tv~nu

I-- -------------------------------------- ---------- --------- -- -- -- -- -- -- -- -- -- ------- IWindow opt ions:

a - Show area markers W - Define new window

IA - Show area labels C - Clear window

Ii - Show l ines c - Display scale

I - Show labeled lines w - VWhere am I

IL - Show line labels 0 - Display f1verlaN Nvhp

B - Di splay Backdrop CIII.. ?vkp

Is - Show sites

IS - Show site labels

n - Show nodes

Iq - Return f rcm whence we cane

----------------------------------------------------------------

ie I-k p Zoem *

IGUfZJAL N'L4J: Press first let ter of desi red cctmiand. [Upper Case O)nlYl

------------------------------------------------------------------

14.1. WIND)OW ME.NU OPTrIONS

Many of the options in the Windm, Menu are redundant with those in the lvbel or h~lbxMenus~.

flkwever, the Window Menu is more often used for q]uick reference than for the acitual nimsxification of'

features. 'Ilic options "a - Show Area Mlarkers' thirough *"S - Show Site Labels"' should be fLuniliar to

the m~er front their use in other menus. The following options require some further explanation, however. A\1l colors described below are the DIT-ALJII, colors for the pariticuilar function or f"eature. See

the Cuvtolnize Menu to change the default color and dlisplay options.

n - Show nodes

l~splays the node~s (line endpo~ints), whether closed (red) or open (green). 1Ibis option is useful

for locating prolleiii nodes when trying to label or create area pmol~ons (see also the lahel. Tool/-

box, and De~bug Menus).

W - D~efine new window

Starts an interactive procedure to define a ncw-\ digitizing wi Tw.'he options arc to zoonin

iniikooin oult or pan (saune as the Znoom Menu). Use either the iiisise or the dnlti/cr ctirsor to

dlefine at WVind~ow.

c - Display scale

Displays at bar scale in the upper-left corner of the current digitizing wlindowv. 'Ilic scale ks metric

(kilometers or meters. (elepending oni the size of the window).
- 47 -

C - Clear window

Erases the contents of the graphics window on the monitor screen. Use this option before

displaying the features to be examined (see options "a" through "n" above). Ihis option is useful

for locating "unsappec!' nodes, errant lines, unlabeled areas, etc., (also se the Toolbox Menu).

w - Where Am I

Activates the pointing device for use as a location finder. The (xy) coordinates are displayed in

the Global Menu field.

0 - Display Overlay Map

Changes the background vector layer to use as reference. This option is available only if the user

has first selected a vector overlay layer using the Cusorrnize/Display Menu.

B - Display Background CELL Map

Changes the background raster layer to use as reference. This option is available only if the user

has first selected a background raster layer using the Custotrnze/Display Menu.

q - Return from whence we came

Returns the user to the previous menu.
- 48 -

15. THE ZOOM MENU

This option provides a number of utilities that allow the user to move through the vector file and to

zoom or pan around designated features within it. The Zoom Menu can be accessed from all the other

menus. The following sequence describes: first, how to use the windowing mode; second, the Zoom

mode; and third, the Pan mode. In the examples below, the mouse is used as the windowing device

(see the Customize Menu).

Upon entering Zoom the following screen appears:

Buttons:

Left: Select new window

Middle: Atort/O(tit

Right: Zoom/Pan MINU

Selecting the LEFI button activates the mouse for use as a WINDOWING device.

Buttons:

lecft: Establish a corner

Middle: Widen view

Right: Accept window,

A "rubber band" box appears in the ctu-rcrn working window with the pointer as its nexus. TO examiine

an area within the current wýorking window, use the LEVFT button to choose a starting corner, aid drag

the pointer to an opposite corner to form a Ibox around the designated area or feature. (lChxosc the

RIGHT Ixbtton to accept the new window. The graphics screen refreshes, and the new area is

displayed. If the user wishes to exam-ine aiu area outside of the current working window. then use the

MIDDLE Ibutton to widen the view. When this option is chosen, the graphics screen is refreshed, aid

thet user sees a recuutugtlar blue field representing the Default Region created for the currenl data layer.

"lhe last working wlindow cxwunined is displayed as a red box within the blue field. StuToumnding the

blue field is a black field reprcsenting the area outside the DefIudt Regioii. Again, use the lkft buton lto

pit a Ibox around the desired area and press the right button to accept it. If a working w\i idw lo )tal\

or partially oiutsi(lc, of the l)e'fult Regioni is selected, the follow\ing waning message appears:

Wind(ow is ohtsidje of defautd. Proceed'? v

After chi ofsing the new window the folio" ing screen again appears:

Bumlttons:

I eftt: ,elect nce\ %\iind w

Middle: Alort/(,•it

ILRight: '/iom/PainME-NUI

Prcssing the RI(;fr Ialllwn t'-ilers the /nliPoin/an iiiwxlc.

Iillions:

I A.cI :Zoomn MI ..NUj

Mliddle: Alx~rt/Otiit

Right: /mni Ml -NU

TO" /00,1 prcss thi' IEFF button.
- 49 -

Buttons:

Left: Zoom in

Middle: AhxKtAit

Right: Zoom out

The ZOOM mode can be used to move as far away from, or in as close to, a feature as required. Fvery

time a button is depressed, the graphic screen is redisplayed with the newly selected area. In ZOOM,

the center point of the current window frame is used as the reference point to zoom around. This point

cannot be changed in the ZOOM mode. It can, however, be changed in the PAN mode, which is examined next. To exit the ZOOM mode, press the MIDDLE button. The following screen again appears:

Buttons:

Left: Zoom MENU

Middle: Abort/Quit

Right: Pan MENU

Press the RIGHT button to enter the PAN mode. Movement across the data layer is determined by the

position of the mouse pointer, and at first may seem counterintuitive. The next screen illustrates the

selection:

Buttons:

Left: Specify new window

Middle: Abort/Quit

Right: Specify new window CFWER

"The LEFT button controls movement over the data layer. Placing the pointer to the LEFT side of the

window appeurs to move features to the RIGHT and vice versa. Likewise, moving the pointer to the

BOTTOM of the window appears to move features UP in the window, and so on. The frame of reference is always toward the CENTER of the current window. Pressing the RIGHT button allows the user

to focus on a specific feature and make it the center of reference.

To exit out of the ZootnlPwa Menu, continue to hit the MIDDLE button until the starting nlenu is

accessed.
- 50-

16. THE DEBUG MENU

The Debug Menu was originally designed for locating and fixing errors in v.digit during the program's

development. It is available in an incomplete and unsupported form, but is useful for finding information about features by referencing their internal topological structure. Within the Debug Menu, the

word line is used generically. That is, all features originally are entered as vector data whether sites

(technically, a line defined by one point), simple lines, or lines defining area perimeters. 'It can be

accessed from any other v.digit menu by pressing the minus or dash, "-, key. The screen layout for

the Debug Menu is presented below:

----------------------------------------------------------------- I ,ASS-DIGIT Version 4.0 Debug klenu

-------------------------------------------------------------------

Debug options:

I - Display line info

n - Display node info

a - I)isplay area info

L - Find line

N - Find node

A - Find area

I - Find isle

d - Display Node-lines

q - Quit to main menu

------------------- ------------------------------------------------ He lp Z7ocn *

GtiLCJAL MVINU: Press first letter of des i red c,(Io nd. [Upper Caase OnI ]

-------------------------------------------------------------------

16.1. DEBUG MENU OPITIONS

After digitizing or importing a vector file, executing tile progranis v.support and v.import may occasionally give a waning message about finding duplicate lalwls for i given line or area. This error can

be caused by two things: either there are ill fatct duplicate laelxs in the file. or a label from a nearby

area or line has been wrongly interpretted as I'loniniz to the feature. "lte first error is only problematic if the label categories for the feaiture are not the saec. In this case. the analyst mlutist decide

which of the multiple labels is correct and re-moCe the other(s). In the latter ctse, the solution may be

as simple as moving the lalbl marker t•,sition using the lahbel ,n'tu. "lhese waming messages supply

the problem feature's intemrl reference numiuher: uising this infonntation the features can be investigaled

using )etug.

I0'bug is divided into two sets of either in(ouise inputs or kc\'oiltrd ctrics. Tlyp in the first letter of an

option name to activate it. 'Ihe first thiee options. "1," "nW," and "'," Iuse the mlous to lxtint to SlX-itic

fealurcs. Interactive instnrctions will appear (n the duntih terminal screen (or the shell wvindko if o•nl\ ai

"graphics monitor is used). Iike the lI/it Menu. lmost dcbutogin 1 operations using tile nouse follow a

left-right button sequence for first. cohlix)mtit,. iud seconld. accpcepul4, the function. 'lbe mniddlc button is

used to quit the currcnt function. All the options are similar; thl following exunjple is for a line: "I -

Di.s0lay Line Info."
- 51 -

OCoose Line:

Buttons:

Left: ChIoose line

Middle: Abort/( it

Right: Accept chosen line

After selecting the feature, it will be highlighted (default color yellow) on the graphics screen. Other

information will appear on the screen where the global menu (bottom menu) had been. It appears in

the following format (again, a line is used as an example).

Line* 8 Category: 2

#8: NI1 8N2 9 Left 0 Right 0

Alt 13 (index 8) Category 2 X 499230.058 Y 3439067.953

The arcane descriptions above refer to the internal coordinates defining the spatial topology of the line.

For example, the Line # is 8, meaning it was the eighth line digitized in the sequence. It has been

labeled category 2. It is linked to two nodes, #8 and #9, and begins at #8. It is the 13th in the series

of labeled features, and the (xy) UTM coordinates of node 8 are provided. The Left and Right fields

refer to area designations; e.g., if the lines bounded labeled areas, what area is "left" of the line and

what area is "right" of the line. However, since this line is not an area edge, the fields are categorized

as "0".

The KEYBOARD comnmands are somewhat more flexible and provide the user more information, for

example: "L - Find Line." Within the Global Menu field the following information will appear:

Fnter <CR> for next line, #of desired line, 'q' quit:

# 1: N1 1N2 1 Left 0 Right 0

Line is NOT labeled

Total lines: 31

The user can proceed through the sequence of features by pressing the <REIlJRN> key, or, if known,

the number of the feature in question. In the examnple above, there are 31 total line features occurring

within the vector data layer. Options "N" and "A" function similarly. Other functions are described in

the following:

I - Find Isle

Highlights "island' polygons, or areas completely surrounded by, or embedded within, other areas,

and describes the lines defining them.

d - Display Node-Lines

Functions similarly to the "l)isplay Node Lines." option within the Toolbox Meau.

q - Return from whence we came

Returns to the previous menu.

After locating the problem features, the user has several options to modify them. One way is to use

other v.digit menus, such as Edit or label and remove or change the suspect feature. Another more

involved procedure is to change the binary vector file into ASCII (American Standard Codc for Infornmtion Interchange) fomlat using the v.out.ascii program. This creates a text file within the dig-ascii

directory within the curren!t napset. The file can then be edited using vi and then cofiverted back to a

binary file using the vin.ascii program. Other progranms like v-support or v.clean can also be usedI.
- 52 -

17. EXITING vdigit

To exit the v.digit program, return to the Main Menu and type Q to "Quit." The following message

appeats:

Leave digit? [7nl

To leav•, type y and <REIfURN> after the query. If any modifications to the vector file have been performed, the following sequence appears in rapid succession:

Compressing Data: DONE

Compressing NODES. LINES. AREAS. ISLES. ATIS. Writing Plus File... DONE.

Do you want to compress the Alts file [n]

This query refers to the vector file in the digatt directory in the user's GRASS mapset. In most cases,

the user wants to answer with the default, [n]. This way, all information about the file, both old and

new, is retained, although it is only the newer that is accessed in future sessions. LUhtil you are certain

that the file is entirely completed, answer n.

If the user answers y, the program deletes the attributes from the file that are not represented in the

current version of the vector file. Examples of such items include the old labels for relabeled features,

changes in topology, etc. The effect is to "clean" the attribute file for the vector layer created or

modified during the just completed digitizing session. In this way the attribute file is brought in line

with the most current version of the map. In addition, if error messages about duplicate attributes are

encountered when running v.support, they can sometimes be eliminated by answering positively to the

above prompt. Upon exiting v.digit, you will be returned to the GRASS prompt.
-53-

REFERENCES

Ruiz, Marilyn S., and Jean M. Messersmith, Cartographic Issues in the Development of a Digital GRASS

Database, Special Report (SR) N-90/16 (U.S. Army Construction Engineering Research Laboratories

[USACERL], September 1990).

Westervelt, James, and William D. Goran, Introduction to GRASS 4, Draft Automated Data Processing (ADP)

Report (USACEP.L, July 1991).

Westervelt, James, Mary Martin, and Deborah Brinegar, "GRASS 4.0 Programs," in GRASS User's Reference

Manual, ADP Report N-87/22 rev (USACERL, September 1988, last revised December 1991).

Westervelt, James, Michael Shapiro, William D. Goran, et a!., GRASS User's Reference Manual, ADP Report

N-87/22 rev (USACERL, September 1988, last revised December 1991).
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