viewit: computation of seen areas, slope, and aspect for land-use planning

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VIEWIT: computation of

seen areas, slope, and aspect

for land-use planning

Michae l R. Travis Gary H, Elsner

W a y n e D. Iverson Christine G . Johnson

"ACIFIC

SOUTHWESTorest and Range

S E R V IC E

S . D E P AR T M E N T O F A G R IC U L TU R E

0 . BO X 245, B ER K ELEY , C A LIFO R N IA 94701

USDA FOREST SERVICE

GENERAL TECHNICAL

R E P OR T P S W - 11 11975



Travis, Michael R., Gary H. Elsner, Wayne D. Iverson, and Christine G.

Johnson.

1975. VIEWIT: computation of seen areas, slope, and aspect for land-

use planning. USDA Forest Sew. Gen. Tech. Rep. PSW-11, 70 p.,

illus. Pacific Sou thwe st Forest and Range Exp. Stn., Berkeley, Calif.

This user's guide provides instructions for using VIEWIT-a comp uter-ized technique for delineating the terrain visible from a single point or

from multiple observer points, and for doing slope and aspect analyses.

Results are in tabular or in overlay map form. V IEWIT can d o individual

view-area, slope, or aspect analyses or combined analyses, and can produc e

elevation profile charts between any two points in a study area. The guide

explains how to prepare data, select available options, and inte rpre t results.

VIEWIT is designed to operate o n a Univac 110 8 computer w ith Exec-8

operating system. The VIEWIT system is accessible via rem ote terminals to

the USDA Fort Collins Computer Center. For those not having access to

this computer facility, the programs are available on request to: Director,

Pacific Southwest Forest and Range Experiment Station, P. 0. Box 245,

Berkeley, California 94701, Attention, Computer Services Librarian. The

programs will be copied on a magnetic tape to be supplied by th e

requestor.

Oxford: 907.2:U712.01-U681.3

Retrieval Terms: recreation settings, VIEWIT, land-use planning, c om put er

programs, handbooks.

The Authors

MICHAEL R. TR AVIS is a senior programmer in the School of Forestry

and Conservation, University of California, Berkeley, on assignment to this

Pacific Southwest Forest and Range Experiment Station. He was educated

at the University of C alifornia (A.B. degree in physics, 1 96 3 and J.D.

degree, 1968). GARY H. ELSNER is in charge of the Station's forest

recreation research unit, at Berkeley. He received degrees in agricultural

economics at the University o f Arkansas (B.S., 1962 ) and the U niversity o f

California (M.S., 19 64 , and Ph.D., 1966). CHRISTINE G. JOHNSON,

formerly a landscape architect in th e Forest Service's California Region, in

San Francisco, is now with the Federal Highway Administration, in

Boston, Mass. She holds a B.S. degree in landscape architecture (1968)from the University of Massachusetts. WAYNE D. IVERSON is regional

landscape architect, Forest Service California Region, San Francisco. He

earned a B.S. degree (1 955 ) and an M.S. degree (19 56 ) in landsc ape archi-

tecture a t the U niversity of W isconsin.



CONTENTS Page

Foreword ........................................... 1

1. Identifying Boundaries an d Cell Size . . . . . . . . . . . . . . . . . . . . 4 1.1 Subdivide into Grid Cells .......................... 4 1.2 Decide on Cell Size and Shape ...................... 4

2 . Preparing Terrain Data in Com puter-Rea dable Form ........ 4 2.1 Hand Code Elevation Data . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2 Digitize Elevation Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.3 Obtain Digital Terrain Tapes ....................... 5

2.4 Explore Con tract Digitizing . . . . . . . . . . . . . . . . . . . . . . . . 5

3. Implementing VIEWIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3.1 Data Definition and Inp ut Commands . . . . . . . . . . . . . . . . 5

3.2 Decide on Data Analysis Options . . . . . . . . . . . . . . . . . . . . 8

3.2.1 Data Specification Com mand s ................. 8

3.2.2 Analysis Com mand s . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.2.3 Display Option Commands .................... 11

3.2.4 Description of Analysis Op tions . . . . . . . . . . . . . . . . 11

3.2.5 Type of Input Expected for Each Command . . . . . . 17

4. Demand Terminal Use ............................... 18



FOREWORD

VIEWIT is a computerized technique for delineat-

ing the terrain visible from a single point or from

multiple observer points. The results are produced in

either tabular or in overlay map form. VIEWIT can

also be used t o prepare terrain slope and aspect analy-

ses. In addition, the system may be used to do com-bined analyses o f seen area with aspect relative t o the

observer po ints an d weighted by the distance to seen

areas from observer points. The system will also pro-

duce elevation profile charts between any two points

in the study area. Besides these basic capabilities,

VIEWIT has many options for seen-area analyses and

for aspect analyses. The system has been developed

over an eight-year period and the original "seen-area"

program was published in 1968.'

Th e system has been used to help manage and plan

lands which are visually imp ortant. E xamples of ap-

plications include timber harvesting, mining, scenic

tramway routes, bridge proposals, transportation

system alternatives, ski runs, roads, recreation devel-

opments, and fuelbreaks. Additionally, VIEWIT is

being used to determine visual impact, and terrain

slope and aspect inform ation fo r land-use planning.

VIEWIT provides capabilities for several kinds of

analyses o f digital terrain data. The basic inp ut to the

program is a grid of elevation points representing the

area o f interest. A second program input is a series of

user requests that define the form of the elevation

data and cause various operations to be performed.

The system then produces tables and maps showing

the results of these requests.

VIEWIT is designed t o opera te on the Univac 1 108

comp uters w ith Exec-8 operating systems.

What Can VIEWIT Do?

VIEWIT can do these jobs:

1. Verify the consistency of digitized topo-

graphic data through the Data Check option and print

maps in numeric or gray scales as well as tables

showing th ose cells or cell clusters which do n ot m eet

specified tolerances of elevation with their eight

neighboring cells.

2. Expr ess in tables showing square miles, acres,

and hectares the area within the study unit that can

be seen from any single point on the ground or at any

' Amidon, Elliot L., and Gary H. Elsner. 1968. Delineating

landscape view areas . . . a co mputer approach. USDA Forest

S en . Res. Note PSW-180, 5 p., illus. Pacific Southw est Forest

and Range Exp. Stn., Berkeley, Calif.

point above the ground level; map the location of

these seen areas.

3. Express the above information in composite

form from many viewing points within the study area

(viewing points may represent alternative roads, trails,

or other development systems); map these seen areason a numerical printout which indicates the num ber

of times each cell is visible from the viewing points;

map these seen areas on a gray scale printout which

shows all cells visible from 0 to 9 and more than nine

times seen in shades of gray; map these seen areas as a

percentage of times each cell is seen from the total

numb er of observer positions, and print ou t in numer-

ical or gray scale maps or both, thereby providing

further mapping refinement to cells seen more than

10 t imes.

4. Evaluate only a portion of a stud y area (sub-

rectangle) to save time and funds.

5. Evaluate only specified sectors of view suc h

as 0 t o 9 0 , 1 8 0 t o 2 2 0 , or co mbin ations o f

sectors.

6. Evaluate only specified vertical angles of

view.

7. Evaluate only user-specified classes for slope,

aspect and elevation analyses.

8. Develop profile printouts in line with (X,Y)

coordinates or diagonal to these coordinates in any

length specified.

9. Develop tables, numeric maps, and gray shade

maps of elevation values.

10. Develop tables, nume ric maps, and gray shade

maps of slope classes as specified. Slope may be

computed by fitting a plane to the eight neighboring

cells or by finding the maximum slope to these cells.

1 1. Develop tables, nume ric maps, and gray shade

maps of aspects by 36 10-degree classes.


maps of aspect by eight sectors of 4 5 , each centered

on th e principal compass points.


maps of aspect by eight sectors of 4S0, each with

weighting from most desirable to least desirable fro m

any direction which is specified to be mos t desirable.

14. D evelop "aspect relative to the observer"

(vertical tilting and horizontal rotation of the plane

of the grid cell) weighting tables, numeric maps, and

gray shade maps. This weighting is one of the func-

tions of "visual magnitude" weighting. It can be done

for one viewing point or for many.

15. Develop distance-weighting tables, numeric

maps, and gray shade maps. This weighting can be



adjusted to allow for up t o 20 changes in the distance

weights. Weights may relate to foreground, middle-

grou nd, an d backgro und distances or (e.g.) weights

may be specified to give greater weights to middle-

ground or the middle areas. It can be done for one

viewing point o r for many.

16 . Develop combined distanc e, "aspect relative

to the observer" and times seen tables, num eric maps,

and gray shade maps. These three functions com bined

meas ure the relative visual mag nitude o f each grid cell

or the "visual perce ption sensitivity" of each cell.

Examples of Applications

What are some specific situations and examples in

which VIEWIT has been applied? And what parts or

options of the program would be useful if you were

developing a land-use plan for a visually sensitive

unit?

First, after data collection and preparation you

would perform a Data Check to verify accuracy.

Next, select the key viewing points in the unit and

test a combination of distance weighting, "aspect

relative to observer weighting," and times seen table

which would list the total acreages of each of 10

combined weighting categories and then produce a

gray shade map of these combined weightings. This

provides a map of the "visual perception sensitivity"

of the unit in fine detail. (It would possibly take

months to do this work by manual methods-espe-

cially t o com bine th e weightings of numerous viewing

points.)

In almost every land-use planning situation you

would want to develop a slope class map or perhaps

several types of slope class maps. For areas that could

be logged b y tractors the slope class map and the

tables could be ex amine d t o determine area slopes

less than 35 percent. For potential ski areas, slopes

between 10 percent and 8 0 percent could be deter-

mined by VIEWIT.

Fo r othe r uses the aspect options may be valuable.

T he 4 5 aspect map with eight weighted sectors

might be given highest weighting for northeast expo-sure to map out best ski area or vegetative regenera-

tion potential or selected microclimatic conditions.

Overlay the slope an d aspect maps for ski area poten-

tial, and potential areas would be immediately appar-

ent. If maximum exposure to sunlight were a criteri-

on, the southwest exposure map printout in gray

shades would be mo st useful. These are just a few of

the options that may be helpful.

For an example of project application, consider a

powe r transmission line proposal across a section of

land which yo u manage. If the proposal is of a general

nature in location, you may wish to check its poten-

tial visual impact against the "visual perception sensi-

tivity" ma p prepared in land-use planning (or if this

was not done you may want to select key viewing

points and produce a printout map). If the proposal is

a specific one with tower locations designed, you can

set the viewing point at the top of each tower and

develop tables and maps which show the acreage on

which each tower would visually have imp act, or the

combined visual impact of al l the towers. If the

digitized topogra phic da ta is already available and

you have a computer specialist and a high-speed ter-

minal, this table outp ut and mapping could take just

a matter of minutes to prepare in response t o the

special-use proposal. The same visual impact analysis

could quickly be made of a highway proposal, a

proposed building, electronic relay, a clearcut block,

o r a scen ic t r a r n ~ a y . ~

For fire detection planning, the system can be

used to map the seen area of existing fixed fire

detection stations and t o prepare composite seen area

maps with additional or reduced numbers of stations.

These analyses are then helpful in evaluating the

location and height of new stations in specifying a

system of stations.

Should You Use VIEWIT?

Before investing time and fu nds in using VIEWIT,

the po tential user should answer these questions:

1. Are visual resources of great importan ce in theproposed project or land-use planning activity? Will

they have major effects on decisions?

2. Can the visual analysis be handled through

oth er means with less investment?

3. Does th e user have access t o a high-speed print-

er terminal? If not, can the user work with turn-

around times involved in mailing of inpu t and out pu t

data from other offices; or can work be handled by

sho rt details of individuals t o suc h offices?

4. Is the format of output data compatible with

other data output? If not, can i t be converted to

compatible data by manual graphics (outlining areasor coloring in areas of similar ou tp ut characteristics).

5. If the value of visual analyses is marginal, will

the optional outputs, such as slope and aspect maps

and tables, offset the marginal values in favor of using

VIEWIT?

Elsner, Gary H. 1971. Computing visible areas from pro-

posed recreation developments . . . a case study. USDA

Forest Serv. Res. Note PSW-246, 10 p., illus. Pacific South-

west Forest and Range Exp. Stn., Berkeley, Calif.



6. Is there high potential for future use of the

input data after its initial usage? For instance, would

there be possibilities of power transmission, road,

timber sale, electronic relay site, etc., proposals with-

in this land unit? If so, visual impacts could be

determined within minutes or hours of the proposal

at negligible costs.

7. Are there possibilities that several slope andaspect classifications will be needed for planning and

design consideration? This program is flexible in pro-

ducing several kinds of slope and aspect classifications

initially or at later dates with no change in stored

data.

8. Will computer-generated output data be ac-

cepted by management and the public as valued infor-

mation for decisionmaking? Will quantitative esti-

mates of visual impacts of alternative land uses be

useful in developing land-use or project plans?This guide provides detailed instructions on how

to use the VIEWIT system. Appendix I lists a sample

deck of punched cards in the form in which they

would be submitted to the computer, and illustrates

the computer printout. Appendix I1 illustrates the use

of a preprocessor program with data in a form that

cannot be read directly by VIEWIT.The VIEWIT system is accessible via remote terrni-

nals to the USDA Fort Collins Computer Center. For

those not having access to this computer facility, the

programs are available on request to: Director, Pacific

Southwest Forest and Range Experiment Station,

P. 0. Box 245, Berkeley, California 94701, Atten-

tion, Computer Services Librarian. The programs will

be copied on a magnetic tape to be supplied by the

requestor.



1 . IDENTIFYING BOUNDARIES AND CELL SIZE

The f i r s t s t ep i n us i ng VIEWIT i s t o

deci de on the area bounda ries. The area

boundary may be determined by the boundary

o f t he u n i t p l a n and i t s v i s u a l i n f lu e n c e

area . For ins tance , a u n i t p lan o r p ro jec t

boundary may be l im i te d t o p r i ma r i l y t he

Nat ional Forest land on the face of a moun-

t a i n , b u t a c t i v i t i e s on t h a t u n i t co ul d

v i su a l l y impac t a community i n t he va l le ybelow. Ther efor e, th e VIEWIT boundary should

extend beyond the p lan ning u n i t boundary so

that the system can accommodate viewing

po in t s and a l lo w fo r any sc reen ing te r ra in

t h a t l i m i t s t he v i s i b i l i t y o f t h e p r oj e ct

a r ea o r l and un i t .

The second st ep i s t o mark the boundary

on a USGS map (same s ca le as l a t e r used i n

da t a c o l l e c t i o n such as 1 i nch = 1 mi le ,

1 i n c h = 2 m i l e s ) .

1 . 1 Subd iv ide I n t o Gr id Ce l l s

Subd iv ide the rec ta ng le enc los ing the

a re a o f i n t e r e s t i n t o c e l l s . Each c e l l i s

a minimum element fo r analys i s . The c e l l s

may be rec tangular rather than square.

Smal le r c e l l s a l l ow a more accura te ana lys s

o f seen areas, s lop e and aspect, bu t requi r e

more data c ol le c t io n ef f o r t and more computer

c o s t s f o r a n a l y s i s .

1.2 Decide on Ce ll Si ze and Shape

Dec ide on the ce l l s i ze needed fo r t he

p l an n in g e f f o r t . I f the computer output

map i s t o be used as an over lay the topo-

gr aph ic map at l a t e r stages and a high-speed

l i n e p r i n t e r i s t h e o u t pu t method, t h e c e l l s

should be rec tangular t o conform t o the

1/5 inch x 1/6 inch char acte r type o f ap r i n t e r now .

For example:

C e l l S i z e =

1 i nch = 1 m il e 2 1.33 acres @

1/5 inch x 1/6 nc h

2 inches = I m il e 5.4 acres @

1/5 i nch x 1/6 nch

1 :24,000 3.1 acre s @

(7$-min. quad.) 1/5 in ch x 1/6 nc h

1 :62,500 20.6 acr es @

(15-min. quad.) 1/5 inc h x 1/6 nch

To dec ide on map scale t o ce l l s ize ,

cons ider (a) the amount of de ta i l requ i red

f o r t he s tudy ; (b ) t he var ia t i on o r complex-

i t y o f t e r r a i n ; ( c ) t im e and d o l l a r s a v a i l -

able; and (d) whether the data w i l l be used

aga in f o r more de ta i le d s tud ies w i th VIEWIT.

The map sca le chosen f o r th e VIEWIT an al-

yses should be compat ib le wi th th at used f o r

o t he r p l ann i ng v a r i ab l es . I t may a l s o be

impor tan t t o choose a ce l l s i z e and sca le

which i s the same as adjacent p lann ing uni ts .

Not enough experience has been gained as

y e t t o p i n down f i r m l y t he c o st s o f d i g i t -ized t e r r a i n data, but we have found th at

the work may be done on a con tr ac t ba sis f o r

approx imately I+ t o 2 cents per ce l l t h rough

the use o f au tomat ic d i g i t i z in g equ ipment .

The cost may go as high as 4 cents per cel I.

Manual d i g i t i z a t i on ( i n - s e r v i c e by ex pe ri -

enced pe rson nel) has been done a t cos ts o f

up t o 8 c e nt s p er c e l l . This cost data

should change r a p id ly once more expe rien ce

i s ga ined bo th w i t h in -serv ice automatedd i g i t i z i n g and c on tr ac te d d i g i t i z i n g o f

topographic data.

2. PREPARING TERRAIN DATA IN COMPUTER-

READABLE FORM

Once the e le va t io n g r i d loca t ion and

si ze have been chosen, the el ev at io ns must

be pu t i n machine-readable form. This form

w i l l usu al l y be punched cards but could be

magnetic tape i f storage space i s a consid-

era t ion . F requent ly , t he e lev a t io n da ta

w i l l be permanentl y s to red i n card form i n

t he o f f i c e w i t h a t ape o f t h i s i n f o r m a t ion

be ing used a t t he computer f a c i l i t y .

No one spe c i f i c format i s requi red fo r

the ele va t i on data. The user should choose

a form at th a t i s compact, co nvenient, and

has the require d amount o f pre cis ion . For

example, i t may be he lp fu l t o omi t t he la s t

( un i t s ) d i g i t o f e l ev a t i ons t o save space on

the da ta medium and t o record o nly the m ini -

mum necessary row and column i nf or ma ti on on

each data card.

Many a l ternat ive procedures are avai l -

ab le fo r ob ta in in g computer readab le d i g i t a l

topographic data (DTD) . Topographic maps

should be obta ined t o the same scale f o r the

ent i re s tudy a rea . The USGS 74-m in ute maps

are o f ten the most accura te ava i lab le .

Obta inin g these topograph ic maps i s an

i m po r tan t f i r s t s t ep f o r any p rocedu re .

Some o f the ba s ic d i g i t i z a t i o n procedures

are:

I. Overlaying a topographic map on a

I i qh t t ab l e w i t h a dat a g r i d and c odi ng e l e -

v a t i o n va lu es d i r e c t l y i n t o each c e l l .

2 . Us ing automat ic d i g i t i z e r equipment

t o record con tours and th e i r e leva t ion

v al ue s i n l i n e f or m and u t i l i z i n g a d d i t i o n al

s o f tw a r e t o c onve r t and i n t e r po l a t e t o a

un i f o r m g r i d .

3 . O b ta i ni n g t h e d i g i t a l t e r r a i n d a ta

on magnetic tapes from the U. S. Defense

Mapping Agency and usi ng ad di t i on al sof tw aret o a s s i s t i n da t a v e r i f i c a t i o n and i n t er p r e -

t a t i on f o r t he s t udy a r ea .

4. Use o f outs ide consul tant cont ra c t

f o r p r epa r a t i on o f d i g i t i z ed t opog raph ic

data tapes either by manual or automat ic

d i g i t i z i n g e qu ip me nt.

2.1 Hand Code El ev at io n Data

Th is method invo lves us ing a l i g h t t ab le

and t opo grap hic map t o obt ai n computer-



readab le te r r a i n da ta . This procedure may

b e p re fe ra b l e if the s tudy a rea i s sma ll ,

and ind iv idua ls w i th cod ing exper t i se a re

a va i l a b l e .

I. Prepare a gridde d map ove rl ay

( se l e c t a r e cta n gu l a r g r i d , w i t h a r a t i o o f :

1/5 by 1/6 inch i f output i s by h igh-speed

1 i n e p r i n t e r ) .

2. Pla ce 76-minute o r 15-minute map on

Ii g h t t a b l e and o ve r l a y w i t h d a ta g r i d ( t ap e

b o th t o t a b le ) .

3. Code tw o- di gi t (hundreds o f fe et )

e l e va t i o n va lu es i n each ce l l .

4. Have data sheets cardpunched and

v e r i f i e d (OCR forms are a pos sib le opt io n) .

5. Use sim ple computer programs t o read,

f i l l the da ta mat r i x , and t o p r i n t an over lay

da ta map t o ass is t i n check ing o f the da ta

f o r accuracy .

2 .2 D i g i t i ze E l e va t i on D ata

Use d i g i t i z e r s t o reco rd con tou rs and

e le va t ion va lues . Th is procedure i s fas te r

and more complex than the procedure ju s t

descr ibed . I t i s more appropr ia te i f ala rge area i s t o be modeled. I t i nvo lves

hand l in g the infor mat ion on computer-

reada ble tapes, and thus th e ope rat or

should have exper ience i n wr i t in g programs

f o r r e a di n g and w r i t i n g l a rg e d a ta s tora g e

tapes. The fo l l ow in g basic s teps are

invo lved i n us ing t h i s p rocedure.

1 . D i g i t i z e c on to ur s

2. Check readabi l i t y o f co nto ur t ap es

3. Prepare un i form gr id data f rom con-

tour tapes: (a) check a sample of po in ts by

ove r la y in g coded e le va t i on map on or ig in a l

t o p 0 map; ( b) se l e c t ce l l s i ze ca r e fu l l y i norder t o produce one-to-one ove rla y maps

(1/5 by 1/6 in ch i f outp ut i s by h igh-speed

1 n e p r i n t e r ) .

4. I f necessary d i g i t i z e more contours

and add t o data base

5. Complete data ma tr ix by in te rp o l a t io n

6. Check accuracy o f da ta ma tr ix

7 . Cor rec t da ta mat r i x i f necessary

2 .3 Obta in D ig i ta l Te r ra in Tapes

D i g i t a l t e r r a i n tap es a re a v ai l a b l e f o r

the con t inen t a l Un i ted S ta tes and pa r ts o f

Alaska. The inf orm ati on has been d i g i t i z e d

fr om 1/250,000-scale USGS to po gr ap hi c maps

and i n te rp o l a te d t o prod uce a d a ta p r i n t f o r

about ever y 208.33 f e e t on the ground. The

magnetic tape used i s $-inc h IBM compatible,

reco rded i n odd pa r i ty , b ina r y a t 556 bp i

us in g an int er- rec ord gap o f 0.75 inch. Two

2,400 fe et ree ls o f tape conta in the DTD f o r

one 1/250,000-scale to po gr ap hi c map she et.

Tapes are prov ided t o users f o r them t o copy

and re tu rn o r i g i n a l s t o t h e U. S. Defense

Mapping Agency. The DMA d at a are accur ate

w i th in abou t 6 400 fe e t h o r i zo n ta l l y and *100 fe e t ve r t i ca l l y . Map indexes o f ava i l -

abl e DTD tapes are av ai la bl e from the Nat ional

Cartographic Info rmat ion Center, U.S. Geological

Survey, 507 Nat ion al Center, Reston, Vi r g i n i a

22092. Ob tai nin g the tapes from the Center may

tak e several weeks o r a few months. The VIEWIT

system provides automatic user-oriented access

t o these tapes.

2 .4 Exp lo re Con trac t D i g i t i z i ng

Using consu l tant computer f i rm s f o r d ig-

i t i z i n g t o po gr ap hi c da t a has t h e p o s s i b i l i t y

o f being more economical than th e oth er two

methods. The la rg er the area, th e more

l i ke l y t h a t t h i s method w i l l be th e b e s t

a l te rn at iv e. The fo l l ow in g steps are recorn-

mended:

1. Develop spe ci f ica t io ns or modi fy

e x i s t i n g sp e c i f i ca t i o n s f o r t o po gra ph ic

d i g i t i z a t i o n .

2. Develop a coord inate system gr id on

the topographic map t o be suppl ied t o th e

con t rac to r .

3 . Prepare and execute contract action.

3 . IMPLEMENTING VIEWIT

The f i r s t f o l l o w i n g se c t i o n on d a ta

d e f i n i t i o n and i n p u t i s i nten de d fo r t h e

members o f the an al ys is team w i t h program-

ming knowledge and re sp on si bi l i t i es . Those

u se rs n o t i n vo l ved d i r e c t l y w i t h t h e com-

p u te r a p p l i ca t i o n may w ish t o r e f e r t o t h e

second sect ion on ana lys is op tio ns i n more

d e t a i l and o n l y r ev i ew th e f i r s t s e c t io n .

3 .1 Data De f i n i t i on and Inpu t Cma ndsThe system assumes t h a t the area o f

in te re st has been def in ed by a rect angle

drawn on a map. The recta ngl e i s or ie nt ed

so th a t i t s l ow er edge i s t h e X a x is , i t s

l e f t edge th e Y a x i s , w i th +Y p o i n t i n g n o r t h

and +X p o i n t i n g e as t ( f i g . 1 ).

( I f t he +Y a x i s o f t h e d a t a g r i d i s n ot

a l igne d wi th nor t h , the program can be t o l d

t o compensate f o r t h is , see th e ROTATE

opt io n i n the fo l l ow ing tab le o f commands

and f o l l ow i ng d i scuss ion . )

T h is r e c t a ng l e i s d i v i de d i n t o c e l l s o f

a convenient s ize, and each c e l l has been

assigned an ele va ti on by one o f th e methods

discussed i n Sect ion 2 . The lower le f tmos t

c e l l i s c e l l (1 , l ) . The number o f ce l 1s

across the rec tan gle i s th e number of

columns, NCOLS, and the number o f c e l ls f rom



bot tom t o to p i s t he number o f rows, NROWS.Each c e l l i s DELTAX i nches wid e (on th e map)and DELTAY inches h ig h ( f i g . 2 ) .

Y

2 elta V

delta X

The i 1 l u s t r a t i o n shows a gr i d wi t h NROWS= 8 and NCOLS = 5. The c e l l s i ze i s g i ven i n

map inches; th e system ca lc ul at es t he ground

s i z e fr om t he map scal e, M SCALE.

Table I l i s t s the commands which def i nethe inpu t e l eva t io n da ta mat r ix , and spec i -f i es wh ich a re op t i ona l and wh ich a re

requ ired . The de fa u l t fo r opt i ona l commandsi s g i ve n .

The system can read the e le va t i on datai n a number o f d i f fe re n t ways. I n o t h e rwords, the format o f th e data, on cards ortape , i s no t r es t r i c te d t o one f i xe d scheme.Therefore, t o read the data, the user must

spec i f y the fo rmat o f the da ta t o the system.A number o f commands de f i ne the form at ofthe data; some o f these are r equ ir ed andsome, i f no t spec i f ied , cause a de f au l ta c t i o n t o t a k e p l ac e .

In the s imp le case i n wh ich a da tama t r i x has been punched on to cards by rows,wi th the lower (most southe r ly ) row on thef i r s t ca rd o r ca rds , the user need on l ys p e c i f y NROWS, NCOLS, and FORMAT. I f eleva-t i on s have been punched t o th e near est 100

f e e t, w i t h t he l a s t t wo d ig i t s o m i t t e d f romthe data, the n s pe c i f yi n g ZSCALE=I00. wouldcause the program t o r esca le the e l evat i ons

t o t h e p rop er va lu e. A l l o t h e r o p t i o n s

w o u ld t a ke t h e i r d e f a u l t va lu e .NROWS, NCOLS must be s p e c i f i e d . Th e i r

p rod uc t , w hi ch i s t h e number o f c e l l s i n t h emap, should pr ef er ab ly be less than 60,000f o r g r ea t es t e f f i c i e n c y . The maximum valueo f ei t h e r NROWS o r NCOLS i s 1000. DELTA X

and DELTA Y d e f i n e t h e ce l l s i ze o n t h e m a p .The d e f a u l t va lu es o f o n e - f i f t h i n ch w id eb y on e -s ix t h i n ch h ig h w i l l a l l o w t h e programsystem t o produce maps on a l i n e p r i n t er

w h i ch a re e xa c t o ve r l a ys f o r t h e o r i g i n a lmap; i f the values ar e changed, ov er la y mapsw i l l not be produced.

BY ROWS, BY COLS, RO W RIGHT, ROW LEFT,COL UP, COL DOWN ar e pr ov id ed t o al l o w f o r

t h e f a c t t h a t d i f f e re n t a pproaches t o t h epr ob lem o f d i g i t i z i n g t e r r a i n da t a ar eequa l ly l og i ca l . The de f au l t case is BYROWS, ROW RIGHT, COL UP, w hich assumes t h a t

the data s ta r t s on the data medium a t th elower l e f t co rner , p roceeds across the f i r s trow t o i t s r i g h t , t hen from l e f t t o r i g h t

across the next row up, et c.I f

not, chooseop t ions t ha t co r r ec t l y descr ibe the sequenceof data points on the data medium. I f thenumber o f c e l l s i n th e map exceeds 60,000,da ta shoul d be read BY ROWS onl y; re ad in g i t

BY COLS w i l l be su b st an t i al l y more expensivei n computer t ime.

BCD i s the de fa u l t and w i l l be the usual

case where the d ata a re punched i n a formtha t can be read d i rec t ly by th is sys tem byproper cho ice o f op t ions . I f t he fo rmat o ft h e d a t a i s su ch t h a t re ad ing d i re c t l y i s n o tpossib le , the user must wr i t e a preprocessorp rogram which w i l l read the da ta i n the user ' sformat and write i t i n an acceptab le format .

One such form at i s bi na ry rec ords, as pro-duced by a Fort ran WRITE(IUNIT) l i s t st ate -ment. Thus the preprocessor can w r i t e thedat a i n th i s form, and the user can read i t

i n t o th i s system by spec ify ing BINARY.

The opt ions ment ioned ear l ier apply hereas we l l as i n th e BCD case. That i s, abinary record may be a row (B Y ROWS) o r acolumn (BY COLS). I f by rows, the f i r s tre co rd may be th e l owermost row (COL UP, t hede fa u l t ) or the topmost row, i n which case

the us er must spec i f y COL DOWN. The binaryd a t a must be i n f l o a t i n g p o in t f o rm at ; t h i smeans tha t the preprocessor must wr i t e f l oa t -ing-point numbers.

I n some cases the inp ut da ta ma tr ix maybe l ar ge r th an t he memory space i n the com-p u t e r a va i l a b l e t o t h e user . I f t h i s i s t hecase then the preprocessor should handle thedata a row (or a co lumn) a t a t ime wi t h anarr ay d imensioned t o the length o f a row (ora column) and not fo r the en t i r e mat r i x . The

VIEWIT system wi l l then automat ica l ly handleda ta mat r ixes which are la rg e r than ava i l ab lecore.

FORMAT i s r equ i red i f the d ata i s BCD.I t i s a F o r tr a n fo rm at , w i t h t h e e nc l o s in gparentheses bu t wi th ou t the word "FORMAT,"which describes one row o r column o f the

data. More than one card o r card image perrow o r column can be used, so lo ng as t heformat spe ci f i es th is . For example, i f t he

da ta ar e read by ROWS and NCOLS=llO, w i t ht h e r i g ht mo s t d i g i t o f t h e e l e v at i o n s o mi t te d(so e leva t ions a re g iven t o the neares t 10

feet and f i t i n fou r co lumns) , the fo l l ow ingcommand might describe the data: FORMAT=

(5 (20F4 .0/ ) ,10F4 .0 ) . ' Th is w i l l cause f i vecards t o be read per row.

The command, F OR MA T =' ( ~O F ~, O ) 'ould alsowork i n th at case. (Consult an experienced

Fo r t ra n programmer i f t h is i s confusing. ) The



T a b l e 1 --C om ma nd s d e f i n i n g i n p u t e l e v a t i o n d a t a m a t r i x , o p t i o n a l co mm an ds , a nd d e f a u l t s

Command MeaningRequ i r e d o r

o p t i o n a lD e f a u l t

NROWS Number of rows Requ i r e d

NCOLS Number of co lum ns Requ i r e d

DELTA X X s i z e o f c e l l ( o n m ap ) O p t i o n a l OELTAX = 1 / 5 i n c h

DELTA Y

BY ROWS

BY COLS

BCD

BINARY

Y s i z e of c e l l

D a t a ap p e a rs o n e r o w p e r r e c o r d o r r e c o r d s o nt h e d a t a m e di um

D a t a a p p e a rs b y c o l um n s , o n e c o l . p e r r e c o r d

o r r e c o rd s

T he d a t a i s i n c o de d fo r m ( c a r d s , o r c a r di m ag e s o n t a p e o r d r u m )

Th e d a t a a p p e a r s ( o n t a p e o r d ru m ) w i t h o neb i n a r y r e c o r d p e r r o w ( o r p e r c o lu m n i f BYCO LS was s pec i f i ed )

O p t i o n a l

O p t i o n a l

O p t i o n a l

IO p t i o n a l

O p t i o n a lIDELTAY = 1 / 6 i n c h

BY ROWS i s ass um edi f n e i t h e r BY ROWS

no r BY COLS i ss p e c i f i e d

BCD i s assumed

i f n e i t h e r i ss p e c i f i e d

ROW RIGHT

ROW LEFT

E ac h r ow a p p ea r s o n t h e d a t a m e diu m fr o m l e f t t or i g h t ( f r o m w e st t o e a s t, a s o n t h e map )

Rows a p p e a r o n t h e d a t a m e d iu m w i t h t h e d a t a f r o m

r i g h t t o l e f t ( e a s t t o w e st )

O p t i o n a l

O p t i o n a lI ROW RIGHT i s

assumed i f n e i t h e ri s s o e c i f i e d

COL UP

COL DOWN

E ac h c o lum n ap

b o tt om t o t o p

Columns appears o u t h )

pea r s on t( s o u th t o

f r o m t o p

h en o

t o

d a t a mr t h )

b o t t o m

ed ium f r om

( n o r t h t o

O p t i o n a l

O p t i o n a l1CDL UP i s a ss um e d

i f n e i t h e r i s

s p e c i f i e d

M SCALE M a p s c a l e O p t i o n a l M SCALE = 24000

FORMAT A l e g a l F o r t r a n fo r m a t w h ic h w i l l r e a d on e r o w

( o r o ne c o l u m n i f BY COLS ) o f t h e e l e v a t i o n d a t af r o m t h e i n p u t m ed iu m . T he d a t a m u s t b e re a d b yF s p e c i f i ca t i o n s , n o t I ( t h a t i s , 3 - d i g i t f i e l d s

m us t be r ead as F 3 . 0 , no t as 13 )

R e q u i r e d ifd a t a i s BOC,

i g n o r e d i f

d a t a i sB INARY

-- -

Z SCALE A m u l t i p l i e r w h i ch w i l l b e a p p l i ed t o e ac he l e v a t i o n v a l u e r ea d i n

O p t i o n a l ZSCALE = I.0

F I LE

ROTATE

T he nam e o f t h e E x ec -8 f i l e o n w h i c h t h e e l e v a -t i o n d a t a w i l l b e f ou n d. T h i s m u st b e c a t a l o g e d

o r t e mp o ra r y f i l e a t t a c h ed t o t h e r u n e x e c u ti n gt h i s s ys te m .

T he a n g l e t h a t N o r t h m ake s c l o c k w i s e o f t h e + Y

a x i s

O p t i o n a l

O p t i o n a l

The d e f a u l t f i l ename i s ZDATA

ROTATE = 0

MEMORY The max imum amount o f e x t r a memory th e V IEWIT

s y s te m s h o u l d a s k f o r f r om t h e E x e c- 8 o p e r a t i n gs ys te m i n o r d e r t o r e ad i n t h e d a ta

O p t i o n a l MEMORY = 60000

format can be up t o 120 char acte rs long i f

necessary.

Z SCALE al l ows omission of le s s- si gn if i

can t d i g i t s f rom the da ta . I n the example

j us t desc r i bed , Z SCALE = 10. would be

spec i f i ed to resca le the da ta. T ha t i s ,

l l .4 1 7 f e e t would be punched as 1142, read

as 1142. and sc al ed t o 11420. ZSCALE app lis

t o bo th b i na ry and BCD data.

FILE i s p rovi ded t o a l l ow the user t o

have several data f i l e s i n the same run. I n

the usua l case, the user w i l l s imp ly c rea tea temporary f i l e named ZDATA and p lace h i s

dat a cards thereon.

MSCALE i s t he re ci pr oc al o f the map

rep resen ta t i ve f r ac t i on . The de fau l t o f

24000 i s cor rec t f o r 74-minute maps.

ROTATE i s prov ided i n case the dat a g r i d

i s no t a l igned w i th the compass d i rec t io ns .

The d e f a u l t va lu e (ROTATE=0) means t h a t t he

p o s i t i v e Y ax i s o f the g r i d i s no r th . For

example, i f t he d i r e c t i o n n o r t h a c t u a l l y

points between + Y and +X , as the draw ing

shows, then the user would so ec if v

( f i g

VIEWIT can handle data g ri ds o f any size .

However, th e computer has a l i m i t e d amount o f

memory available. I f t he da ta f i t i n t o t h i s,

then they are a l l kept i n memory. I f not,

por t i ons o f the da ta (ca l l ed 'pages ' ) a re

kept i n memory, and other p or ti on s are store d

on auxi 1 ia ry storage (d i sk or drum storage).

This mode o f op era tio n invo lves g rea ter

cos ts f o r t r ans fe r r i ng da ta to and f rom

memory, b ut le ss er memory co st s. VIEWIT

assumes, as a de fa ul t value, t h a t i t can ask

the Exec-8 ope rat ing system f o r up t o 60,000



w or ds o f e x t r a memory t o s t o r e t he da t a g r i d .I f the data gr i d has more than 60,000 ce l l s ,the pagi ng mode i s used. Depending on th e

t o t a l amount of memory ava i l ab le on the com-pu t e r f o r t he us er and on t he r e l a t i v e c os t so f computat ion, in pu t/o utp ut , and memory, i t

w i l l somet imes be less expens ive t o processl a r g e d a t a g r i d s b y s e t t i n g t h e v a lu e o f

MEMORY t o some l a r g e r number. MEMORY ca nnotbe s e t l a r ge r t han t he t o t a l amount o f us e r

memory ( i f t h e da t a g r i d i s t h i s l a rg e ), o rt h e Exec-8 s ys te m w i l l k i l l t h e u s e r ' s jo b .

The f i n a l command re la t i ng t o read ingel ev at io n da ta i s READ. Thi s command i s

g i ve n a f t e r a l l d a t a fo rm at s p e c i f i c a t i o n shave been prov ide d and causes the system t oask f o r s u f f i c i en t memory spac e f o r t he da t afrom the Exec V I I I sup er vis or y system. Whenth i s space i s made ava i lab le , t he da ta a rer ead i n as s pec i f i ed . T h i s p r oc ess o f speci -

f y i n g and read in g da ta can on l y be done once

per program execut ion. O f course, the pro-gram system can be re-executed as many t imesas des i red .

The user should, t o summarize, de f i ne thee x t e n t o f t h e e l e v a t i o n a r r a y and i t s f or ma ton th e da ta medium, the n cause i t t o be read .

A t t h i s p o i n t i t becomes pos s ib l e t o exerc ise

t h e a n a l y t i c a l o p t i o n s .

3.2 Dec ide on Data Analys i s Opt ions

Two pr in c i pa l c lasses o f ana lys i s can beperform ed w i t h the dat a. Each has a number

o f v a r i a t i o n s . I n a d d i t i o n , s ev e ra l o t h e rk ind s o f ana lyses a re ava i lab le . The two

p r i n c i p a l o p ti on s a re ( a) v i s i b i l i t y and

(b) s lope/aspec t analyses. To understand theuse o f t hese op t ions and the var ious d isp layso f t h e i r r es u l t s , t he us e r m us t unde rs tand

the method used by the system.Two f i e l ds o r v a l ues a r e as s oc i a t ed w i t h

eac h c e l l o f t he map. One f i e l d i s e l ev a t i on ,which i s read usi ng t he commands discusse de a r l i e r . The o t he r f i e l d i s a v ai l ab l e f o reach ana ly s is op t ion t o p lace a number in ;t he s i gn i f i can ce o f t he number var i es depend-in g on t he o p t i on chosen.

The user can d isp lay a table showing thef requenc y o f oc cu r rence o f eac h v a l ue f o r a l lc e l l s b y th e TABLE command. A numeri c map

s howi ng t he c on t en ts o f t he num er ic f i e l d f o reach c e l l can be pr i n t e d by t he MAP command.A gray-sca le map o f t he same in form at io n i s

pr oduc ed b y t he GMAP command.

The c on ten t s o f t he numeri c f i e l d f o reach c e l l i s i n i t i a l l y z er o. I t can be r es et

t o z er o by th e u ser by th e CLEAR command.This i s somet imes necessary.

The sequence t o be fo l l owe d i s : Per formt he des i r ed ana l y s i s . Then p r i n t a t ab l e , o r

a numeric map, o r a gr ay- sca le map, o r two o fthese, or a1 1 t h r e e i f des i red , i n any o rder .

Then erase the numeric in for ma t io n and per-fo rm the nex t ana lys i s . The excep t io n t ot h i s i s v i s i b i l i t y a na ly si s; i t may be desir-

ab l e t o per f o r m s ev e ra l o f t hes e be f o r ep r i n t i n g a t a b l e o r map.

3.2. 1 Data Sp ec if ic at io n Commands

The f o l l o w i n g i s a l i s t o f t h e d a ta

sp ec i f ic at io n commands assoc iated w i th dataana l y s i s :

Command Meanin q

X MIN These fo ur c m a n d s taken

toge ther de f ine a subrec tang le

X MAX w i t h i n th e da ta upon whichana lys is w i l be perfor med, and

Y MIN maps and tabl es w i l l be l i mi te d

t o th i s subrec tang le . TheY MAX d e f a u l t va lues a r e X MIN=I,

Y MIN=I, X MAX=NCOLS, Y MAX=

NROWS, so t h a t t he d e f a u l t sub-r e c t an g l e i s t h e e n t i r e d a t aarra y. The subrect angle can bechanged a t any t ime, bu t chang-i n g i t a f t e r an ana l y si s bu t

be f o r e p r i n t i n g a map o r t ab l ew i l l p r oduc e us el ess r e s u l t s .Wel l thought out use of thesecommands w i l l save many d o l l a r s

i n comput ing when th e da tam a t r i x i s l a r ge .

T ITLE S p ec i fi e s a ru n t i t l e o f up t o120 charac te rs which w i l l bep r i n t ed a t t he t op o f each page.

The d e f a u l t i s a b la nk t i t l e .

(An example is: TITLE = 'MOUNTRUSHMORE PLANNING UNIT')

M TITLE Spec i f i e s a map t i t l e o f up t o24 characters which wi l l bep r i n t e d i n l a rg e b l oc k l e t t e r sbefore each map. I t i s p r i n te d

i n two l i ne s o f 12 charac te rseach in cl ud in g blanks. The de-f a u l t i s 24 b l ank s. Bo th TITLEand MTITLE can be changed when-

ever desi red . (An example o fMTITLE i s : MTITLE = 'TRUCKEEUNITSLOPE MAP.' T h i s i n st ru c -

t i o n w i l l r e s u l t i n t he p r in t -i n g o f t h e f i r s t 12 c h ar a ct e rswhich are TRUCKEE UNIT on thef i r s t l i n e and t h e second l i n ew i l l t he n co n t a i n t h e n e x t 9characters which are SLOPE MAP.)

XOBS These t wo commands s e t an

o bs er ve r p o i n t l o c a t i o n f o rYOBS v i s i b i l i t y a n al y si s . Th is

in fo rmat ion mus t be spec i f i eda t l e a s t once . XOBS and YOBSar e i n g r i d c o - o rd i na t es .

OBS Serves as an alt er na t i ve way tospe c i f y t he observer loca t ion .OBS = (22,14) i s equiva lent t oXOBS = 22,Y OBS = 14.

RAD IUS Spec i f i e s t he rad ius t o whichv i s i b i l i t y w i l l be determined.I t i s g i v en i n m i les , and mustbe spec i f i ed .



APPEND I X IThis appendix shows a simple VIEWIT ru n i n which the data i s read di r ec t ly by the system.

The pr in t out s show f i r s t , a l i s t i n g o f the cards to be submitted to the computer, ju s t as they

would appear i n the inp ut deck. This i s fol lowed by the actual computer output re su lt in g from

the submission o f these cards.

The pr in to ut s demonstrate how the ele vat ion data is placed on a f i l e named ZDATA by the use o f

the @DATA contro l card . The use r commands f o l l o w t he @XQT card which c a l Is the V I EWIT system in to

execution.These commands f i r s t spe cif y th e si ze and form of the el eva tio n data and cause i t t obe read. They then pe rfor m a number o f simple analyses.

OHOG * * * OE MnN S T R AT I ON R U N * * *0 MS G. N O A T A I N P U T I S F RO M CA RO SI0ASG.T ZOATA. . C R E A T E A T EM PO RA RY F I L E , ' l O A T A m tÂ ¥ O A T A , Z O A T A . . I N S E R T O AT A C A R 0 I M A G E S I N T O F I L E ' ZO A TA .'. . . . . . . . . . . . . . . . . . . . . . .* OATA CARf tS GO HERE. . . . . . . . . . . . . . . . . . . . . . .Â ¥ E N T H y S C A RD I S N E E DE D TO S T O P Â ¥ D AT F RO M I N S E R T I N G C AR DS .Ã ˆ X Q P S W * V I ~ W I T , a N O W R U N T H E V I E N I T S Y S T E MC O M M E N T Ã ‡ ! F I R S O E F I N E A N 0 R E A D T H E O A T A ' ,N RO WS Ã§ 52 N t O L S x i b , Z S C AL E Ã ˆ~ O O . F O R M A T = I ( 3 b F i m 0 ) ! , C OL D OW N, R EA D,C OMMEN T =! NOf E U SE OF Z SC ALE T O BR I N G T H E D AT A T O T H E R I GH T R AN GE' ,C O M M E N T ~ ~ O E F A U L T S U CH AS ROW R I G HT , B CD, ~ S C A L E = ~ U O O OAVE BEEN U SED . ' ,C OM ME NT m'N Ow D E F I N E AN OB SE RV ER P O I N T A N 0 0 0 A V I S I B I L I T Y A N A L Y S I S ' ,M T I T L E s ! S E E N A R E A S M A P ' ,O B S a ( Z 2 , 1 8 ) , R A O I U S s l m 5 , V I E W, C O MM E NT = 'N O W P R I N T A N U MER I C MAP ' ,

M AP , C O M M E N f 'A N O A G R EY , S C A L E M A P ' ? M T I T L E Z " ,MESSAGEa ! GR pY SC ALE SSEE N AR EASMAP' , GMAP,C OMMEN T a ' AOn A SEC OND O B S E R V E R ' Ã ˆ O B S = ( ~ O , ~ Q ) , V I â ‚M T I T L E Ã § I T I M p S E E N I M A P ' , M A P ,C O M M E N T s 'N o w W I T H T HE A V E R A GE M AP O P T I O N I N S T E A D , ' ,A V G M A P , M T T T L E S I A V E R A G E MAPSTIMES S E E N ' , M A P , M T I T L E ~ ! ~ ,

M E S S A G E a t G R ~ Y S C A L E I T I M E S S E E N S A V ER A G E M A P ', G MA P, N UM MA P,C O M M E N T S ~ N U M MAP COMMAND SET MAP MODE BACK TO THE DEFAULT OFE S S E E N ' , C O MM E NT * ' C L E A R C O U NT F I E L D A ND D O A NEW SET OF V, M T I T L E a ' e U B R E C T A N G L E ' , C L E A R, X M I N = 1 0 , Y M I N a l O , Y r t A X = 3 0C O M M E N T a l N O w A L L O P T I O N S A F F E C T O N L Y T H I S S U B R E C T A N G L E . ! , V IC O M ME N T a' N O w GO B A C K T O T H E W HO LE D A T A G R I D ' , X M I N r l , Y M I N a lC O M ME N T Ãˆ I E XA M I N O NL Y C E R T A I N A Z I MU T H SE CT OR S FO R V I S I B I L I T Y

N U MER I C MAPS UF T I M

I S I 6 I L I T Y A N A L Y S E S . '*EW, MAP, TABLE,, X M A X S i b , Y M A X s 5 2 ,

' fC L E A R. M T I T L E = I S E C T O R $ M A P ' , S E C T 0 R ~ ( 9 0 , 1 8 0 ) , S E C TO R = (Z Z 5 ,, 3 1 5. 0 ), V IE W ,MAP, C LEAR , C OMMEN T a ' R ES ET T O SC AN T H E H H OLE C I R C LE ' , N SEC T ,C O M M E N T Ã § ' P R l N A C R O S S - S E C T IO N A L P R O F I L E ' , E N O = ( 3 7 , 5 2 ) , P R O F I L E ,M T I T L E * ' s L O P E $ M A P ' , C O M M E N T a l P R I N T A S L O P E C L A S S M A P ', S L O P E, T A B L E , M AP , GH A P,C OMMEN T = ' F I N O SLOPE C LASSES BY T H E MAXI MU M SLOPE MET H OD R AT H ER T H AN T H E

A V E R A G I N G ME T HO D U S E 0 B E F O R E ' , X S L O PE , T A B L t ,MT I T LE O' M AXT MU M I SL OPE MAP!, MAP, GMAP,C OMMEN T * lAN Q AN ASPEC T MAP BY 1 0 D EGR EE SEC T OR S! , MT I T LE: ' ASPEC T $M AP! ,ASPEC T , MAP. T ABLE, C OMMEN T Ãˆ~N O C OMPASS PO I N T ASPEC T ! , C ASPEC T , T ABLE,M AP , G V AP , c O M M E N T a !A N O R E L A T I V E A S P E C T ' , R A S P E C T a 1 8 0 m , T A B L E , M AP , G MA P,C O M M E N T a ' C H g C K C E L L S W H I C H D I F F E R F R O M T H E A V E R A G E O F T H E I R N E I G H B O R S B Y M O R E THA N 1 5 0 F EE T, !, M T I T L E a f O A T A C HE C KS M AP ' , 0 C H E C K s l S O . , MAP, GMAP, TABLE,C O M ME N T =' N O TI C E T HA T T HE RE I S ONE E S P E C I A L L Y B A D C t L L AT ( l 7 , 3 6 ) ' ,C O M ME N T =! I TS N E I G H B O R S A P P E A R I N t R R O R A L S O B EC A U SE T H I S O N t C E L L A L T E R S T HE A v ER AGE F OR T H OSE C ELLS, ' ,C O M M E N T = ! P R T N T T H E A C T U A L E L E V A T I O N O A T A ! , M E S S A G E = ! E L E V A T I O N S M A P ' , O P R I N T ,X O B S 8 2 2 , Y O f t S a 1 8 ,C O M M E N T = 1 T HI S I S A N A L T E R N A T I V E WAY T O S E T O B S E RV E R P O S T I O N ! ,C O M M E N T = ~ O E M O N S T R A T EW E I G H T E D V I E W O P T I O N S ' , M T I T L E ~ ~ W E I G H T E D $ M A P ! ,

ANON, V I EW, MAP, T ABLE, AWOFF , C OMM EN T = ' OEF I N E D I S T AN C E WEI G H T I N G F U N C T I ON ' ,N O O W T P t T P O I N T a ( 0 . 5 , 1.1, T PO I N T =( l . O , 0 . 51 , C LEAR , 0 w ON , V I EW , MAP, T ABLE,C LEAR , C OMMENT =! NOW BOT H WEI GH T I N G MET H OD S' ,A W ON,VIEW,MAP,A W OFF, 0 W 0Ãˆ-FC OMMEN T * ' OEf - I N E SOME SLOPE C LASSES, ' ,C L A S S ( l ) S ( O . , 2 5 m ) , C L A S S ( 2 ) ~ ( 2 5 ~ ~ 5O a ) , C L A S S ( 3 ) = ( 5 0 , 1 0 0 0 ~ ) , C L A S S a 3 ,

C O M M E N T a l F O f t S L O P E, C L A S S E S A RE T A K E N A S S L O P E S I N P E R C E N T ',M T I T L E = l U S E f 4 S L O P E S M A P ' ,U SLOPE, TABL E, MAP,C OMMEN T s 'N Ow C ALC U LAT E SLO PE BY T H E MAXI MU M SLOP E MET H OD ' , U X SLOPE,T ABLE, MAP,M T I T L E Ã ˆ ' E L e V A T I O N S C L A S M AP ',C O M M E N T * ' O E t I N E SO ME E L E V A T I O N C L A S S E S ' , C L A S S C l ) = ( O , t O O O ) , C L A S S ( 2 ) a ( < 1 0 0 0 , 5 0 0 0 )1 C L A S S ( 3 ) * (5 0 0 0 , 6 0 0 0 ) , C L A S S ( 4 ) a ( 6 0 0 0 ~ 7 0 0 0 ) , C L A S S ( 5 ) = ( 7 0 0 0, 1 0 0 0 0 ) , N CL AS SS

5 , U ELEV, t A B L E , M A P ,C O M M E N T ~ ~ O E ~ I N ESPEC T SEC T OR S AN 0 AN ALYZ E ASPEC T BY T H EM1,C L A S S C l ) ~ C 3 f O m , 3 6 0 a ) , C L A S S ( 2 ) = ( 0 , 1 0 1, N CL A SS s 2,C O M M E N T a 'A S p E c T S O U T S I D E T HE D E F I N E D C L A S SE S W I L L B E P U T I N C LA S S Z E RO ' ,M T I T L E ~ ~ U S E R S A S P E C T S ~ ,U ASPEC T , T ABLE, MAP,C O M ME N T m' E N B O F D E M O N S T R A TI O N O F V I E W I T a ' , S T OP ,W F I N0 0



@ M SG ,N D A T A IN PU T I S F R OM C A R O S I

Ã ˆ A S G , Z O A T A : . C R E A T E A T E M P OR A R Y F I L E , ' Z DA T A ,'

Ã ˆ O A T A , Z D A T A . I N S E R T D A T A C A RD I M A G E S I N T O F I L E 1 Z O A TA . IO A T A T 7 R L 7 0 - 9 0 5 / 1 2 - 1 1 8 ~ 5 1 3 3E N D D A T A , I M A G E C O U N T 1 52

8 X Q T P S w * V I E w I T , , NOW R U N TH E V I t W I T S Y S TE M

G E N E R A L V I S y B I L I T Y P R O G R A M

F O R E S T R E C R E A T I O N A ND L A N D S C A P E M A NA G EM E NT P R O J E C TP A C I F I C S O U T H H E S T F O R E S T AN D RA NG E E X P E R I M E N T S T A T I O NU.S. F O R E S T S E R V I C E , B E RK E L E Y , C A L I F O R N I A

R U N ON O S / 1 ~ / 7 5 A T 0 9 1 3 0 t 2 5

== I N P U T C A a O t C O M M E N T a ' F I R S T D E F I N E AN D R E A R T H E D A T A ' ,

=s I N P U T C A R D ) N RO W S= S2 , N C O L S 3 3 6 , Z S C A LE = 1 00 . , F O R M A T a t ( 3 6 F 2 , 0 ~ ~ , C O L DOWN, R EA D ,

U S E R R E Q u E S T I N R O W S = 5 2

N R OW S S E T T O 52

U S E R R E Q u E S T t N C O L S = 3 6N C O L S S E T T O 3 6

U S ER R E Q ~ I E S T ~Z S C A L E a 1 0 0Z S C A L E S E T f 0 1 0 0 . 0 0 0 0 0

U S E R R E Q U E S T ! F O R M A T a( 3 b F B . O )

D A T A F OR M A T W I L L B E 1(36F2 .01--

U S E R R E Q ~ E S TI C O L D O WC O L U M N S A P P E A R O N T H E O A T A M E D I U M F RO M T O P T O B O TT O M ,

USE!( R E Q u E S T i R E A OO A T A H A S B E e N R E A D I N T O 1 8 7 2 A D D I T I O N A L D B A N K L O C A T I O N S

E A C H C E L L I S ,Z O I N C H E S ( . 5 1 CM ,) W I D E A N D, 1 7 I N C H E S ( . U 2 C M.) H I G H O N T H E M A P,

T H I S C O R R E S P O N D S T O A C E L L (1 00 ,O O F E E T ( 1 2 1 . 9 2 M E T E R S) I N I T S E A S T - W t S T D I M E N S I O N AN D5 3 3 . 3 3 F E E T ( 1 0 1 . 6 0 M E T E R S ) I N I T S NO R TH -S O UT H D I M E N S I O N ON T H E G RO UN D,

E A C H C E L L H A S A N A RE A OF , 0 0 U 8 S Q UA R E M I L E S ( 3 . 0 6 A C R E S , 7 . 5 6 M E C T A R k S ) O N T H E G R O U N D *

T H E D A T A R E G I O N I S 7 .2 0 I N C H E S ( 1 8 . 2 9 CM .) W I D EA N D 8 . 6 7 I N C H E S ( 2 2 . 0 1 C M. 1 H I G H O N T H E M A P,

T H I S C O R R E SP O ND S T O A R E G I O N 2 , 7 3 M I L E S ( 4 . 3 9 K M,) E A S T T O K E S T A N D3 ' 2 8 M I L E S t 5 . 2 8 K M ) N O R T H T O S O U T H O N T H E GR OU ND ,

T H E A R ~ A F T H E R E G I O N I S 8 ,9 5 S QU AR E M I L E S( 5 7 3 0 s 0 3 A C R E S > l U l 5 9 a l U H E C T A R E S ) O N T H E G RO UN D*



8s IN PU T CAftD ) COMMENTx'NO TE USE OF ZSCAL E TO BR IN G THE DATA TO THE RI GH T RANGE.'.

USER REQUEST ) COMMEN aNOTE USE OF ZSCALE TO BRING THE DATA TO THE RIGHT RANGE

ss IN PU T CARD) COMMENTa'OEFAULTS SUCH AS ROW RIGH T, BCD, M S C A L E ~ ~ U O O OAVE BEEN u S E D S ' Ã

USER REQnESTt COMMEN EDEFAU LTS SUCH AS RON RIGH T, BCD, MSC ALf cs2 100 0 HAVE BEEN USED.

x I N P U T C A R D ) C O MK EN T a' NO w D E F I N E AN O BS ER VF R P O I N T AND DO A V I S I B I L I T Y A N A L Y S I S ' ;

USER REQIJESTI COMMEN x

NOW DE FI NE AN OBSERVER P OI NT AND DO A V I S I B I L I T Y A NA LY SI S

8 INP UT CARD1 MTI TLE a 'S EEN AREASMAP ' ,

U S E R R E Q u E S T I M T I T L E xSEEN AREA MAPM A P T I T L E I j l SEEN AREA

MAP

8 s INP UT CARD) OBSx(2 2 , l8 ) , RADIU S=1.5 , V IEW, COMMENTs 'NOW PRI NT A MUMEUIC KA P ' t

USER REQ uES T i OBS x ( 22.00 , 18 .001X OBS SET TO 2 2 AND Y 0138 SET TO 1 8

USER REQuESTI RA DI US 8 1.50R A D I U S S ET TO 1 * 5 0 0 0 0

USER REQUEST# VIEW

V I S I B I L I T Y A N A L Y S I S W I L L B E PER FO RM ED W I TH T HE F O L LO W IN G P A R A M E T E R S )X X ~ ~ X X Ã ‡ X X ~ X ~ X S X X X ~ S X X X ~ B S S ~ ~ ~ ~ X X S X S ~ X S ~ X X X X B ~ ~ S S X Z S S Z X S S X X S X B X S X ~ ~ S

x ons 2 2Y OUS 1 8RADyUS 1 .500 (M IL ES )

2 . 1 1 0 ( K I L O M E T E R S )D ELT A X 2 0

1 7D E L T ACALE 2 4 0 0 0 . 0 0

X M I N 1XMAy 36

Y M I N 1

YMAx 52Z A h L E - 90 .0 0Z B I A S 0SECTORS 0

ANALYSIS COMPLETE.TH IS OBSERVER CAN SEE 1 8 4 CELL S ( .88 SQUARE MILES,

563 .21 ACRES, 139 1.7 1 HECTARES. )

USES REQUEST) COMMEN aNOW PRINT A NUMERIC MAP

INP UT CA f tD) MAP, COMMEMTs 'AKO A GREY SCAL E MAP ', M T IT L E x ' f ,

USER REQIJESTI MAP

MAP OF TIMES SEEN FOR EACH CELL,1 OBSERVFR(S)

MARKS UNOBSERVED CELLS

INVISI~LE CELLS ARE BLANK



USER REQUEST: COMMEN x

AND A GREY gCALE M A P

U S E R R E Q ~ I E S T : G M A P



== I N P I J T C A R D # C O M M E N T u I AD O A S E CO N D 08SERVtR~f08S=(20f20),VIEW,

A N A L Y S I S COMPLETE^

T H I S O B S ER V E R C AN S E E 3 0 7 C E L L S ( 1 1 U 7 S Q U A R E M I L E S ,

9 3 9 1 7 0 A C RE S , 2 3 2 2 1 0 4 H E CT AR E Sl )

U S ER RE Q IJ E ST I M T I t L E =

T I M E S S E E N M APM A P T I T L E 1 3 1 TIMES S E E N

MA P

U SER R EQl jEST : MA P

M AP O F T I M E $ S E E N F O R EA C H C E L L ,

2 O ~ S E R V E R ( S )

MARKS UNOBSERVEO CELLSI N V I S I R L E C EL L S ARE B LA N K



:S I N P U T C AR D: C O M ME N Ta l N OW W I T H TH E A V E RA G E M AP O P T I O N I N S T E A 0 , I p

USER REQUEST: COPMEN 8

NOW W I T H THE AVE RAG E MAP OPTION IN ST EA D,

USE R REQoESTI AVGMAP

V I S I f l I L I T V M A PS W I L L P R I N T T I M E S S E EN AS A P E RC EN TOF THE NUMBER OF OBSERVERS,

U S E R R E Q UE S T : M T I T L E 8

AVER AGE MAP T I M E S SEENM A P T I T L E I s : AVERAGE MAP

T I M E S S E E NUS ER REQIJESTI MAP

M AP OF T I M E $ S E E N F OR E A C H C E L L *

2 O ~ S E R V E R ( S )

M AR U S U N OBSER VED C ELLSI ~ V I S I ~ L E C E L L S A R E B L A N K

T I M E S S EE N IS D I S P L A Y ED AS A PERCE NT OF THE NUMBER OF OBSERVERS,

L E S S T H A N 1 0 % B L A NK1 0 % TO 2 0 % 12 0 % 1 0 3 0% 2i o i ~ ' l o ( S E E N B V A L L O B S E R V E R S )



U S E R R E U u E S T i GM AP

M A P OF T I M E S S E E N F O R E A C H C E L L .

2 O B S E R V E R ( S )

M A R K S U N O B S E R V E D C E L L SI N V I S I B L E C E L L S AR E B LA N K

T I M E S S E E N I S D I S P L A Y E D AS A P E R C E N T O F TH E N UM B ER OF O B S E R V E R S .

L E S S T H A N 1 0 % B LA NK

1 0% T O 2 0 % 12 0 % T O 3 0 % 2

1O ~ X * 1 0 ( S E E N B Y A L L O B S E R V ER S )

G R EY S C A L E p X P L A N A T I O N 1

zzzzzzzzzz zzzzzzzzzz ZZZZZZ2ZZZ zzzzzzzzzz

9 O f t M O R E ~11111WV~W111111111111111111111111111111



0 wm m

wmm

mD W

- 0

a a wm m m

mw

o mm m

mm

-0

w o o 0 0

0.0 w o- m



USER REQUEST: NUMMAPVISIBILITY M A P S WILL PRINT TIMES SEEN A S A NUMBER.

=a IN PU T C AA D l COMMENTÃ‡'NU MAP COMMAND SET MAP MODE BACK TO THE DEFA ULT OF NUM ERIC MAPS OF TI M

aa I N P U T C AR D: E S S E E N ' , C O MM E NT * ' C L E A R CO UN T F I E L D AN D DO A NEW S E T O F V I S I B I L I T Y A N A L Y S E S . '

USER REQUEST: COMMEN *MUM MAP COMMAND SET MAP MODE BACK TO THE D EFAU LT OF NUMERIC MAPS OF T I M E S SEEN

USER REQUEST! COMMEN aC L E AR C OU NT F I E L D A h D D O A NEW S ET O F V I S I B I L I T Y A NA LY SE S .

I N P U T C A R D 1 , M T I T L E Ã ˆ ~ S U B R E C T A N G L E ~ L EA R, X M I N a 1 0 , Y M I N Ã § l o Y MA Xa 30 ,

USER REQIJEST: M TI T LESUBRECTANGLEM A P T I T L E I;! SUBRECTANGLE

USER REQLIEST! CLE AR

C O UN T F I E L D C L EA R E D F OR C E L L S I N T H E C UR R EN T S U B R E CT A N GL E

USER REQUEST: XM IN a 1 0X M I N S E T T O 1 0

USER REQUEST: YM IN = 1 0Y M I N S E T T O 1 0

USER REQUEST! YMAX a 3 0

YMAX SET TO 3 0

I N P U T C AR D: C O M M E N T ~ ~ N O ML L O P T I O N S A F F EC T O NL Y THS S U B RE C T AN G L E. ' t V IE W, MAP, T A BL E ,

USER REQ UEST: C O W M E N *NOW AL L OPTIONS AFF ECT ONLY T H I S SUBR ECTAN GLE.

USER REQUEST! V IE U

V I S I B I L I T Y A N A L Y S I S W I L L B E P ER FO RM ED W I T H T H E F OL LO W IN G P A R AM E T ER S !s = s s s s s s , 3 : 3 a s ~ ~ s a 3 = ~ ~ s ~ : : s s ~ : ~ ~ a ~ ~ ~ s ~ ~ s a a 5 s ~ ~ ~ : x ~ s 3 ~ ~ ~ : ~ s a a : : - - - - - ------%I

X OR S 2 0Y ORS 2 0R A D T U S 1 . 5 0 0 ( M I L E S )

2 . U ( K I L O M E T E R S )D E L T A X a.2 0D E L T A Y 1 7S C A L E 2 1 0 0 0 . 0 0

X M I N 1 0XM Ax 3 6Y MIN 1 0YMAY 3 0Z A N G L E - 9 0 . 0 0Z B I A S 0SECTORS 0

A N A L Y S I S C O M P L E T E ,T H I S O B S E R V ~ R A N S EE 2 0 5 C E LL S ( ."Ã SQUARE MILES,

62 1. 16 ACRES, 1535.412 HECTARES.)

MAP OF T I ME 8 SEEN FOR EACH CELL .1 O B S E R V E R ( S )

, MARKS UN08SERVEo CELLSI ~ J V I S I B L E EL L S ARE B L A NK



2 3 3

5 0 5

3 0 1 1 1 29 1 1 1 28 1 1 2 7 1 1 1 1 1 1 2 6 1 1 1 1 1 1 2 5 1 1 1 1 I l l 1 24 1 1 1 1 1 1 2 3 1 1 1 1 1 1 1 1 1 1 1 1 2 2 1 1 1 1 1 1 1 1 2 1 1 1 1 1 1 1 1 1 1 1 1 1 2 0 1 1 . 1 1 1 1 1 1 1 1 11 9 1 1 1 1 1 1 1 1 1 1 1 1 ie 1 1 1 1 1 1 1 1 1 1 1 1 1 1 7 1 1 1 1 1 1 1 1 1 1 1 1

1 6 1 1 I l l 1 1 I l l 1 1 1 5 1 1 1 1 1 1 1 1 1 1 1 1 1 1 14 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 10 1 1 1 1 1 1 1 1 1 1 1 1

USER REQUEST! TABLE

TABLE OF NUMBERS OF CELLS AN0 AREAS S E E N BY 1 OBSE RVER (S),

* a INP UT CAR0 1 COMMENTB'NOW G O B A C K TO THE WHOLE D A T A G R I D * , XMINs1, V M I N = l , ~ ^ ' A X s 3 b , YP ( l X^52 ,

USER REQUEST! CONMEN =NOW GO BACK T O THE WHOLE DATA GRID

USER REQUEST! XMIN * 1 XM IN SET TO 1

USER REQUEST! VMIN R 1 YMIN SET T O 1

USER REQuESTl X M A X 8 36

X M A X SET t 0 36

USER REQUEST! Y M A X 8 52 Y M A X SET 9 0 5 2



= I N P U T C A f f O l C O MM E NT m tE X AM I NE O NL Y C E R T A I N A Z IM U T H SE CT OR S F OH V I S I B I L I T Y ' ,

U SER R EQt l E ST t C OM MEN a

E X A M I N E O NL Y C E R T A I N A Z I MU T H S EC TO RS FO R V I S I B I L I T Y

U SER R EQU EST! C LEAR

C OU NT F I E L D C L E A R E D FO R C E L L S I N TH E C UR R EN T S U B R E CT A N G L E

U S E R R EQ IJ ES TI M T I T L E a

SEC T OR M APMA P T I T L E 1 s t S FC TO R

MA P

US ER REQIJEsTI SEC TOR a ( 9 0 . 0 0 , 1 8 0 . 0 0 )

A Z I M U T H S E C T O R 1 I S FROM , 9 0 . 0 0 D E G R L E S TO 1 8 0 . 0 0 O E G R t E S ,

U S E R R E Q u t S T i S E C T O R 8 ( 2 2 5 . 0 0 , 3 l S . 0 0 1A Z I M U T H S E C T O R 2 I S FROM , 22 5 .0 0 D EGR EES TO 31 5 . 00 D EGREES,

U S ER R E Q t l E S T t V I E U

2 02 0

1 5 0 0 ( M I L E S )

2 , U l U ( K I L O M E T E R S )

3 0

. I T2 4 0 0 0 . 0 0

1

A N A L Y S I S C O M P L E T E ,

T H I S O B SE RV E R C A N S E E 1 8 7 C E L L S ( . 8 9 S Q UA R E M I L E S ,

5 7 2 , 3 9 A CR ES , l U l U ~ U 0 E CT AR ES .)

8s I N P u T C A R D ! MAP , C LEAR , C OM M EN T S~ R E SET T O SC AN T H E W HOLE C IR C LE ' , N SEC T ,

U S E R R E Q u E S T l M A P



@@@@ Il l l a Â ¥ @ @11111 # I # IIIII I 1 8 1 1 1 111111 1111 I 8 8 I I 8 I I

1 I I I 8 1 1 1I 8 1 ###@ In 8 Ill 8 8

5 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51 . . a m s s . . e s . . . . n . . . m * . . * . . s . . * m m . . m e .

50 ..........................................................................48

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45 ..........................................................................41 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42 ....................................41 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .......................................39 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36 . * . . # * , * * * . * * * # * * 8 * * 9 * * * . * * * * * * * * *

is . a * * * # 8 . . 8 * * 8 # # * 8 * * # * * @ @ 8 # * * * * * *

34 . * a * * * ~ 8 * * S @ * m * m . * * * @ ~ ~ * * * * * * ~ *

33 a 8 ~ a # # ~ * a * ~ e m # ~ # m ~ ~ @ # a # ~ e ~ * *

32 . * ~ * # a * # m * ~ m * * ~ * * 8 * * * ~ @ ~ * * * ~

31 . . . . . . . . . . . . . . . . . . . . . . . . . . .30 * . . * * * * * * * , , . * * * * . * * # . * * *29 . 1 * . . * . . . . * . . . . . . . . . . . . . . .2 * * ~ ~ ~ a * * ~ ~ e ~ w ~ ~ * * ~ *

27 e w * * * e s v * * m * * s s * e * e * * *

26 * * a * * . . * * * * * * * * * * . * * *

25 * * # m * * s * * * + m * * * * * v * *

24 1 ~ S . . . . ~ . * * . V . * ~ * I . * . I

2 I l l , . * . * . . * . . . . . * . . . * .2 1 1 . . . . . . . . . . . . . . . . . .2 1 1 1 1 1 1 * . . * * * * . . . . . . . .20 1 1 1 1 1 i 1 1 1 1 1 1 119 1 1 1 1 1 1 1 1 1 1 1 1 1 118 1 1 1 I l l 1 1 1 1 1 1 1 1

17 1 1 1 1 1 . 1 1 1 1 1 1 1 1 116 1 1 1 1 1 l l . . . 1 I l l 1 115 1 1 1 1 1 1 1 s ~ . 1 1 1 1 1

-rr-{ 1 1 1 1 1 , 1 1 . * . . 1 1 1 1 1 113 11x1 1 1 1 ' 1 . * * * * 1 1 1 I 112 1 1 1 11-1 411...*..11 11 1 . 1 1 1 1 1 1 , / 1 1

. * . . . .1 1 1

1 0 . 1 1 1 1 1 1 . . . . . . . * 1 1 1 1 1

9 * 1 1 1 . . * * * * 1 1 1 18 * a 1 1 1 1 .......... 17 * . 1 1 1 1 . . . * . . . . * . 1 1 1 16 . . a l l l * . . * . . * e . * * 1 15 * . a 1 1 * * . . . . . . . . . . 1 1

I . . . . * . * . . . . . . 1....3 . . e . * e . . . . . * * . . . . . .

2 . . . . . . . . . * . . . . . . . . .1 . I * ~ e m m . . . . . . * . * . . .



U S E R R E Q u E S T t C L E A R

C O U NT F I E L D C L E A R E D FO R C E L L S I N T HE C U R R EN T S U 8 R E C T A N G LE

USE R REUIJEST: COWMEN :R E S E T T O S C A N TH E K h O L E C I R C L E

U SER R EQ l lEST t N SEC TN O AZ I M U T H SECT O R S.

a: I N P U T C A R D # C O M M E N T U' P R I N T A C R O SS - S E CT I O NA L P R O F I L E ' , E h D = ( 3 7 , 5 2 ) ~ P R O F I L E ,

U S E R R E Q u E S T t C O N P EN 3

P R I N T A C R O g S m S E C T I O N A L P R O F I L E

U S ER R t Q u E S T t EN D = ( 37.00, 5ti.00)X E N D S E T T n 3 6 A ND V EN D SET T O 52

U SE R R E Q lj E S T t P R O F I L

E L E V A T I O N P B O F I L E F R OM P O I N T ( 20, 201 T O P O I N T ( 3 6 , 5 2 ) .

( P O I N T S M A R K E D t A RE . V I S I B L E F R O M TH E. - F I R S T P O I N T )

5 9 0 0 5 8 0 0 5 8 0 0 5 7 0 0

5b0U5 5 0 0 5e0b

5 5 0 0 5 5 0 0 550U5 3 0 0 5 3 0 0 5 3 0 0 5100 5201;5.200SLOG5 0 0 0 5 0 0 0 U900uuoo4800 4800 u s 0 008004900 5 0 0 0 5 0 0 0

5 1 0 0 5 1 0 0 5 1 0 0

5 1 0 0 5 100



a s I N P U T C A p D t M T I T L E a l S L O P E S M A P @ , C O MM E NT x tP R IN T A SLOPE CLASS MAP', SLOPE, T A H L t ; PAP, G fAP ;

USER REQnESTt MTITLE *SLOPE MAPMAP T I T L E 1 8 1 SL OP E

MAPUSER REQ~IESTI COMMEN a

PRINT A SLOPE CLASS MAPUSER REQnEST i SLOPE

USER REQuEST i TABLE

SLOPE CLASS TABLE,0 MEAN$ 0 TO 10 % SLOPE,1 MEANS 1 0 TO 2 0 % SLOPE,2 MEANS 2 0 TO SOX SLOP â‚ ETC,

USER REQUEST# MAP

SLOPE CLASS MAP,BLANK MEANS 0 TO 10 % SLOPE*1 MEAN$ 1 0 TO 20 % SLOPE,2 MEAN$ 2 0 TO 3 0 % SLOPE, ET C8



- -NNNNN U W N N N N - N N N N N e N N C = = N N N W N N = W = i n W -N-NNNNNN-NNN W W N N - - - N - - W W W W e ~ N - - - N N N ~ ~ 4 N N



USER REQUEST: GMAP

SLOPE CLASS MAP.

BLANK MEANS 0 TO 1 0% SLOPE,1 MEAN$ 10 TO 20X SLOPE,2 MEAN8 2 0 TO 30 % SLOPE, ETCn

@Â¥Il I Ill 1111 11111 a I Ill 1111I I Â I 1 1 1 111 1 1111/ !ma@Â¥Il I 1 I 1111 #I11

I l l a II m a I



BS I N P U T CA R D ) C O M M E N T ~ ~ F I N D L OP E C L A S S E S B Y TH E M AX IM UM SL OP E M ET HOD RA TH ER T H A ~ HE

I N P U T C AR D ) A V E R A G I N G M ET HO D U S E D 0 E F O R E ' t X S L O P E P T A B L E *

USER REQUEST! COWMEN =F I N D S L OP E C L A S S E S B Y THE MA XIMU M SLOPE METHOD RATH ER THAN THE AVERAGING METHOD USED BEFORE

USER REQUEST: XSLOP E

MAXIMUM SLOPE CLASS VALUE S COMPUTED FOR CURRENT SUBRECTANGLE.

USER REQIESTI TAB LE

T A B L E OF M A X I M U M S L O P E C L A S S E S.0 MEAN8 0 TO 10 % SLOPE

1 M E AN S 1 0 % T O 2 0 % S LO PE , E T C i

USER REOIJESTI M T IT L E =MAXIMUM SLOPE MAPM A P T I T L E 1 6 1 M A X I M U M

SLOPE MAP

U S E R R E Q l t E S T t H A P

M A P OF M A X I M U M S L O P E C L A S S E SBLANK MEANS 0 TO 1 0% SLOPE

1 M E AN 3 1 0 % T O 2 0 X t E T C.



U S F R R E Q U E S T: G M A P

MAP O F M A X I M U M S L O P E C L A S S E 3

8 L A N K M E A N S 0 T O 1 0% S L O P E

1 MEANS 1 0% T O 20% , E T C ,



S 8 IN PU T CARD # ASPECT, MAP, T ABLE , COMMENTSINOW COMPASS PO IN T ASP ECT I, C A S P E C T , T A 6 L E t

USER REQUEST# ASPECT

ASPECT CLASb VALUES COMPUTED FOR CURRENT SUBRECTANGLE,

USER REQUEST# MAP

ASPECT CLAS9 MAP,

3 6 A S p k C T C L A S S E S#1 MEAN6 0 TO 1 0 DEGREES,2 MEAN9 1 0 TO 20 DEGREES,

ETC +

BLANK &EL LS HAVE NO ASPECT (ARE F LA T) ,



USER REQuESTt TABLE

ASPECT CLAS* TABLEm

3 6 ASPECT CLASSES81 MEAN$ 0 TO 10 DEGREES,2 MEAN$ 1 0 TO 2 0 DEGREES,

E T C *ZERO CELLS HAVE NO ASPECT CARE FL AT )*

CLA$S CELLS AREA1 SQUARE MI LE S ACRES HECTAUES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



USER REQ IJE ST~ COWMENNOW COMPASS POINT ASPECT

USER REQuEsTI CASPE C

A S P E C T C L A ~ $ E SB v P R I N C I P A L COMPASS O I ~ E C T I O N SCALCLILATEDFOR THE CURRENT SUBRECTANGLE*

U S E R R E Q u E S T t T A B L E

TABLE OF ASPECTS B Y PRINCIPAL COMP ASS DI RE CT IO NS ,

THERE ARE 8 4SPkC T CLASSES* EACH REPRESEhTS A u5 DEGREEWIDE RANGE CENTERED ON A COMPASS POINT I

1 t - 2 2 a 5 O t G * FR OM NOR TH2 +*2 2,5 OEGn FROM NE3 +-22. 5 OEG* FROM EASTU +- 22 *5 DEG* FROM SE5 + -2 2* 5 DEG* FROM SOUTH6 +-22. 5 DEG * FROM SN7 t - 2 2 * 5 D EG. F RO M W E S T8 + - 22 *5 OEG* FROM NW

ZERO NO ASPECT (F LA T)

=a I N P U T C A~ OI MAP, G MAP, c O MM E h T= ' A NO R E L A T I V E A S P E C T ' t R A s P ~ c T = 1 8 0 * , T A B LE , f l4pt G F A F t

USER REQIJESTI MAP

MAP OF ASPEeT BY PRINCIP4L COMPASS OIRECTIONS.THERE ARE 8 ASPECT CLASSES, EACH REPRESENTS A US DEGREE

WIDE RANGE CENTERED ON A COMPASS POIN TI1 +- 22 *5 OEGn FROM NORTH2 + - ~ 2 ~ sEG* F ROM NE3 + - 2 2 * 5 O E G * F RO M E A S T4 +-22. 5 DEG * FROM SE5 + *2 2* 5 OEG* FROM SOUTM6 +- 22 *5 DEG* FROM SW7 +-2.?*5 DEG * FROM WEST8 +-2 2.5 DE G* FROM NW

B L A N K N o A S P E C T ( F L A1 )



Command Meanin q

NSECT Disables the az imuth sector

f e at u re o f v i s i b i l i t y a n al ys is .

I t sh ou ld b e g i ve n t o t u r n t h i s

f e a t u r e o f f o r t o d e f i n e a new

s e t o f sec tor s . The de f au l t i s

t o examine t h e f u l l c i r c l e .

SECTOR Spec i f ies the s t ar t and end, i n

degrees c lockwise f rom Nor th, o f

an az imuth sector i n which

v i s i b i l i t y a na ly si s i s t o be

performed . Up t o 20 such

sectors may be defined by

successive sector commands.

For example, t o l i m i t the

v i s i b i l i t y a na ly si s t o t he

d i r ec t ion s f rom NE t o SE,

spec i fy :

N SECT, SECTOR = (45,135)

( f i g . 4)

t o r e t u r n t o e xa mi ni ng t h e

whole c i rc le , spe c i f y N SECT

alone.

Z ANGLE S p e ci f i e s a v e r t i c a l a ng le i n

d eg re es r e l a t i v e t o t h e h o r i -

zont al below which i t i s

assumed that the observer

cannot see or which i s no t

a p p ro p r ia t e f o r t h i s a n a l ys i s.

For example, st a t i ng Z ANGLE =

0 w i l l hav e t he e f f e c t o f mak-

i n g a l l c e l l s a t a l owe r

e le vat ion than the observer

v i s i b l e . Z ANGLE can be f rom

-go0 to +go0. The de fa ul t

v a lue i s -go0, which places no

r e s t r i c t i o n on v i s i b i l i t y .

Z BIAS S p e ci f i es a d i s ta n c e i n f e e t

which i s added t o the observer

p o i nt el e va t io n f o r v i s i b i l i t y

an aly sis . This can be used,

f o r example, t o s imu la te f i r e

towers, tops o f tramways, tops

o f power tran smis sion towers,

a i r p lane o r he l i c op te r v iews .

The Z BIAS may be ne ga ti ve t o

ind ica te sur face excavat ion .

The de fa u l t va lue i s zero .

Command Meaning

X END These commands specify the end

p o i n t o f t h e l i n e a l o ng w hi ch

Y END p r o f i l e s w i l l be drawn by t h e

PROFILE command. P r o f i l e s

END beg in a t t he c u r r en t obse r ve r

p o in t as se t by OBS ( or X OBS,

Y OBS). To dr aw a p r o f i l e

( c ro s s -s e c ti o n o f t h e e l e v a t i o n

data) f rom po i n t (13.43) t o

po in t (51,20), the user could

spec i fy :

0BS=(13,43), END=(51,20),

PROFILE,

NO D W T P Sets the dis t ance weight func-

t i o n t o a s t an da rd w e ig h t o f

1.0 f o r a l l d i st a nc e s. I t

would normal l y on ly be needed

t o r ede f i ne t he d i s tanc e weigh t

f unc t i on .

T POINT Spe cif ies a p a i r o f numberswhich represent a " tu rn ing

po in t " o f t he d i s tanc e we ight

curve. The f i r s t number is the

d is tanc e i n m i l es fr om the

observer, and the second i s a

we igh t between 0. and 1.0. The

user can de f in e d is tance

we igh t i ng f unct i ons w i t h up t o

20 tu rn in g poi nts . The program

connects these poi nts wi th

s t ra ig h t l i n e segments. A

we igh t o f 1 .0 a t a d i stanc e o f

0. from the obser ver and a

we igh t equal t o t he l a s t g i v en

w ei gh t a t a d i s ta n c e o f i n f i n -i t y are assumed. Turning

po in ts mus t be spec i f ie d i n

o r de r o f i nc r eas ing d i s tanc e .

A W ON Enables we igh t i ng by r e la t iv e

a sp ect i n v i s i b i l i t y maps.

Normally , c e l l s a re s imply

counted as seen or not seen.

Wi th we ighted v i s i b i l i t y (by

aspec t o r d is tance o r bo th) ,

c e l l s wh ich are seen are g iven

from 0 t o 10 point s depending

on the we ight ing fu nc t io n .

A W OFF Tur ns o f f we igh t i ng by r e l a t i v e

aspect.

D W ON Enables we i gh t in g v i s i b i l i t y

by d is tance, accord ing t o the

cur rent d is tance we ight

f unc t i on .

D W OFF Turns o f f d is tance we ight ing .

( I n i t i a l l y bo th r e l a t i v e

aspect and dis ta nce weig ht in g

a re o f f . )



Command Mean inq

CLEAR Sets t o zero the conten ts o f

the numeri c f i e l d f o r each ce l l

i n the cu r ren t subrec tangl e .

The CLEAR command should be

used between each type o f a nal -

ys is i n the same run. (For

example, the numeric f i e l d

should be cleared between aSLOPE an a lys is and a VIEW

ana lys is . )

CLASS Defines a r b i t r a r y classes

ca l led 'user c lasses ' tha t can

be used t o do slope class ,

aspect c lass , o r e leva t i on

class analyses.

N CLASS Specif ies the number of user-

de f ined c lasses t o use i n a

use r-c las s an al ys is (U SLOPE,

U ASPECT, U ELEV, o r UX SLOPE),

SHOW NZ These two commands control thepr in ti ng of small but nonzero

HIDE NZ values in gray-scal e maps. The

def aul t i s HIDE NZ; specifying

SHOW NZ w i l l cause small values

t o pri nt as the l igh tes t shade

of gray.

HI ANGLE Specifies an upper l i m i t to an

obser ver's angle of view. The

de fau lt val ue of HI ANGLE i s +90

degrees.

LO ANGLE Serves as synonym f o r Z ANGLE.

Either command may be used t o se ta ve rt ic al angle below which the

observer cannot see.

RANK Spec ifies a weight associated

wi th an observer po in t. The

defaul t RANK i s 1 .

MAX IMUM Weighted v i s i b i l i t y is normally

averaged over a l l observers. I f

AVERAGE th is averaging i s undesirable,

the maximum over a set of observ-

ers may be kept by sp ec if yi ng

MAXIMUM. The defaul t state of

averaging may be re in st at ed by

specifying AVERAGE.

3.2 .2 Analysis Commands

The f o l l o w in g commands cause va ri ou s

analyses t o be performed:

Command Act ion

SLOPE cal cul ate s s lope c lass number fo r

each c e l l and places i t i n t he

num er ic f i e l d f o r t h a t c e l l .

ASPECT Ca lc ul at es an asp ect c la ss number

and stores i t f o r each ce l l .

-ommand Act ion

This op t io n g ives 3 6 classes,

each 10 degrees wide, f o r t he

grea tes t reso lu t io n o f aspect .

C ASPECT Cal cul ate s aspect i n ei gh t 45-

degree wide classes, each center-

ed on a major compass di r ec t io n .

I t p rov i des l ess r eso l u t i on thanthe ASPECT opt io n, bu t i s more

us ef ul f o r some purposes.

R ASPECT Ca lc ul at es and st or es , fo r each

ce l l , a number showing the c e l l ' s

aspec t r e l a t i v e t o the spec i f i ed

d i r ec t ion . There a re e ig h t 22.5-

degree wide sectors on each side

o f the g iven d i re ct io n. The two

s id es a re t r ea t e d a l i k e ( t h i s i s

no t the case f o r th e ASPECT or C

ASPECT opt ons). For example,

t h i s may be thought o f as a sun-

i l l um i na t i on ana l ys i s i f the

given angle i s the sun's d i re c-

t i o n or as no rthe ast aspect map

i f R ASPECT a 45,

D CHECK Tes ts each c e l l t o see i f i t

d i f f e r s f r om the average o f i t s

eight closest neighbors by more

than the to lerance g iven. I f so,

a count o f the number o f t imes

the d i f ference exceeds the g iven

amount i s placed i n the numeric

f i e l d . Ce l l s whi ch a re g rea t l y

d i f f e r en t f rom the i r ne ighbors

are p robab ly i n e r ro r . (Normal ly

i ti s e f f i c i e n t t o c heck t h e d at afo r g ross e r ro rs w i th a l a rge to l -

erance before using smaller

values. )

VIEW Per fo rms a v i s i b i l i t y ana lys is

according t o the current para-

meters. The impor tant parameters

ar e observer p o s i t ons, (OBS),

RADIUS, th e number o f s ec to rs and

t h e i r p o s it i o ns , Z ANGLE, Z BIAS,

and whether o r no t r e l a t i v e as-

pect o r d is tanc e weigh t ing i s en-

ab led . For nonweighted v i s i b i l i t y

e i t h e r 0 o r 1 i s added t o the nu-

meri c f i e l d o f each ce l l . F orwei gh ted v i s i b i l i t y , an i n tege r

from 0 t o 10 i s added. Thus th e

conten ts o f each numeric f i e l d

are accumulated over any number

o f v i s i b i l i t y a naly ses , and i n d i -

cate e i th er t imes seen or weight-

ed tim es seen. Sin ce these num-

bers are added, the command CLEAR

should be given before beginning

a s er i es o f v i s i b i l i t y a na lys es

t o ze ro the numeric f i e l d fo r

each cel I. Otherwise, the use r

may be adding, f o r example, tim es



Command Mean ing

seen t o s lope c lass , g i v i ng a

nonsens ica l resu l t .

L i ke a l l o t h e r a n a l y t i c a l and

out put op tio ns, VIEW ac ts on on ly

the current subrectangle.

U SLOPE Causes th e VIEWIT system t o pe r-

fo rm a s lope c lass ana lys is us ing

user-defined classes.

U ASPECT Causes an aspect c lass analysis

t o be per formed us in g user-def ined

classes.

U ELEV Causes th e system t o c l a s s i f y ele -

vat ions by th e user-def ined

classes.

For U SLOPE, the conte nts o f the u ser-d efin ed

c lasses are in te rpre t ed as s lopes i n percent

( f o r example, 100.0 means a 45-degree s lo pe ).

Fo r U ASPECT, th e numbers ar e in te rp re te d as

compass di r e c t ons ( 0 t o 360) i n degrees.

Fo r U ELEV, the numbers a re in te rp re te d as

e l e va t i on s i n f e e t .

XSLOPE Calcu la tess lopec lassnumbers

us in g a nonaveraging method o f

c a l c u la t i ng s lope .

U X SLOPE Calculates s lope c lass numbers

us ing nonaveraging s lope calcula-

t i on , ac c or d ing t o us e r - s peci f i ed

c lasses.

3.2.3 Di sp la y Opt ion Commands

The fo l l ow in g commands are f o r the u-

p l a y o p ti o ns :

Command Meaninq

TABLE Pr in ts a ta bl e showing the

d i s t r i b u t i o n o f t h e c on t en t s o f

t he numeric f i e l d o f a l l c e l l s

i n the cur re nt subrectang le .

An appro pr ia te explanatory

heading i s pr i nte d, depend ing

on the operat i on la s t per formed

on the data . (The user wiI 1

pr obab ly f i nd t h i s op t i on use-

f u l f o r a l l o f t h e t yp es o f

analyses. )

MAP Pr i n ts a numeric map of the con-

t e n ts o f t he co un t f i e l d f o r

each cel l i n the cur re nt sub-

re ct an gl e. The numbers may be

slope clas s, t imes seen, etc .,

depending on the la s t op erat ion

performed. An app rop ria te

heading i s p r i n ted .

Command Meaning

AVG MAP Causes subsequen t MAP commands

t o pr i n t maps o f t imes seen

w i t h each c e l l ' s v a lue p r es ented

as a percent o f the numbers o f

observers . Th is i s esp ec i a l l y

us e fu l i f there are 10 or more

observer po in ts .

NUM MAP Cance ls the AVG MAP command and

re tur ns th e MAP command t o t he

de fa u l t mode o f p r i n t i ng t he

act ual number o f t imes seen f o r

each ce 1 1 .

G MAP Pr i nt s a gray-shaded map o f the

numer ic f i e l d o f each c e l I.

This gives t he same in for ma tio n

as t he MAP command i n a fo rm

which i s more understanda ble as

a whole, es pe ci al ly when seen

f rom a d is tance.

D PRINT Causes the actual e lev at i ons o feach c e l l i n t he c u r r en t s ub rec-

t ang le t o be p r i n ted i n a coded

for m. Th i s i s us e fu l p r i ma r i l y

fo r da ta check ing.

PROF ILE P r i n t s a c r os s -s e c ti o n o r p r o f i l e

o f t h e e l e v a t i o n d a ta f ro m t h e

c u r r en t obs er ve r po in t t o t he

cur ren t end po in t . The cross-

s e c ti o n i s n o t t o s c al e ( i t h as

exaggerated ve r t ic a l sca le) bu t

i s us e fu l f o r da ta c hec king o r

fo r g et t i ng a sense of the shape

o f t h e t e r r a i n o r f o r d et e r -min ing h igh or low po in ts on a

s p e ci f i ed r o u te f o r f u r t h e r

v iew ana lys is .

STATS These th re e commands p r i n t ta bl es

of s ta t is t ica l in fo rmat ion aboutEL STATS the cu rr en t sub rec tan gle . The

table i s fo r examined cel ls i n

V STATS the cu rr en t subre ctangle f o r the

STATS command, f o r v i s i b l e ce l l s

fo r the V STATS command, and f o r

el ev at io ns f o r the EL STATS

command .

3.2.4 Des cr i pt i on of Analys is Opt ions

The fo l low ing sec t ions exp la in the ana ly -

s i s op t ions i n more de ta i l .

SLOPE c a l c u l a te s the s lope o f each c e l l byf i t t i n g a p la ne s urf ac e t o i t s e i g h t n ea re st

ne ighbors . Th is p lane i s a 'bes t f i t ' i n t he

sense that i t minimizes the sum o f (d is tances

f rom the p lane to the ce l ls ) squared. Slope

class es are 10 percent each, so th a t a

s lope of 0 t o 10 pe rc ent i s t he f i r s t c l ass ,

10 t o 20 perce nt i s the second clas s, and so



f o r t h . S l o pe c l a s s num bers a re s to r e d i n t h en u me ri c f i e l d f o r e ac h c e l l w he re t h e y c an b ee xa m in ed w i t h o ne o r a n o t h e r o f t h e p r i n t o u to p t i o n s ( f i g . 5 ) .

C e l l 5 i s t h e c e l l w hose s l o p e i s wa nte d.A p l a n e P i s c h os en t h r o u g h 5 s o t h a t t h e sumo f t h e s q ua re s o f t h e d is t a n c e s f r om the cen-t e r s o f e ach o f t he e i g h t s u r r o un d in g c e l l s t ot h e p l a n e ( dra wn a bo ve as s h o r t v e r t i c a l l i n e s )i s a m in im um . T he s l o p e o f t h e p l a n e i s t h es l o p e f o r t h e c e n te r c e l l .

Each o f t h e a sp e ct o p t i o n s s t a r t s b y f i r s t

f i n d i n g t h e b e s t - f i t p la ne a t ea c h c e l l ; ast h e d i a g r a m a b ov e. T he n, t h e a s p e c t o f t h ec e l l i s t h e d i r e c t i o n i n w h i ch t h i s p l a n es l op e s m os t r a p i d l y . (A c e l l w i t h no s l o p ed oe s n o t h a v e an a s p e c t a t a l I . ) For ASPECT,t h e a sp e ct s a re d i v i d e d i n t o 36 c l a s s e s ( e a c h10 d e g r e e s ) a nd t h e c l a s s n um b er s s t o r e d f o re ac h c e l l ( f i g . 6).

Th e C ASPECT o p t i o n d i v i d e s t h e c i r c l ei n t o e i g h t $ - de g re e s e c t o r s c e n t e r e d o n t h ep r i n c i p a l co mp ass p o i n t s . Th e c l a s s nu mb ersc a n be p r n t e d w i t h TABLE, MAP o r G MAP ( f i g .

7 ) .

T h i s o p t i o n wo ul d b e u se d c h i e f l y t o d e v e lo ps ha de d m aps t o i n d i c a t e a sp e c t b y t r a d i t i o n a ls e c t o rs o f d i r e c t on .

Th e R ASPECT o p t i o n r e q u i r e s t h a t t h e u s e rs p e c i f y a d i r e c t i o n ( i n de gr ee s f ro m n o r t h )and c a l c u l a t e s t h e a sp e ct o f ea c h c e l l r e l a -t i v e t o t h e g i v e n d i r e c t i o n . A ng le s an e q ua ld i s ta n c e on e i t h e r s i d e o f t h e g iv e n d i r e c t i o na r e t r e a t e d a l i k e . T h e re a r e e i g h t c l a ss e s ,e a c h 2 2 .5 ' w i d e, f r o m t h e g i v e n a n g l e o ne i t h e r s i d e t o o p po s i t e t h e g i v e n a ng le . Th ef o l l o w i n g d i ag ra m shows t h e d i v i s i o n o f t h ec i r c l e i n t o r e l a t i v e a sp e ct c l a s se s as su min gt h e u s e r ha s s p e c i f i e d R ASPECT = 9 0 ( f i g . 8 ) .

T h i s o p t i o n w o ul d b e u se d m a i n l y t o d e v el o pw e i g h t i n g o f c e l l s f ro m mo st d e s i r a b l e t ol e a s t d e s i r a b l e a s p ec ts , s uc h a s, n o r t h e a s tf o r s no w r e t e n t i o n o r o pti mu m v e g e t a t i v er e g e n e r a t o n , s o u t h e a s t f o r c am p gr ou nd s( e a r l y m o r n in g su n and p r o t e c t i o n f r om l a t ea f t e r n o o n s u n ).

T he i n f o r m a t i o n d e v e l op e d b y R ASPECT canb e d i s p l a y e d w i t h TA BLE , MAP o r G MAP. The

G MAP d i s p l a y i s e s p e c i a l l y u s e f u l w i t h t h i sa s p e c t o p t i o n . ( G r a y - s c a l e m aps w i t h t h eo t h e r a s p ec t o p t i o n s a r e n o t s a t i s f a c t o r yb e ca u s e t h e m i n d d o es n o t w an t t o s ee t h ed a r k e s t c l a s s as b e i n g j u s t n e x t t o t h el i g h t e s t c l a ss . ) I n p a r t i c u l a r , a map o f t h ei n f o r m a t i o n f r o m t h e R ASPECT ana lys is can bec o n s i d e r e d t o b e a n a p p r o x im a t e s u n- i1 u m i n a -t i o n map o f t h e a r e a u n d e r c o n s i d e r a ti o n ,w he re t h e d i r e c t i o n s p e c i f i e d b y t h e u s e r i st h e s u n ' s a z i m u t h . ( S ha d in g of o ne c e l l b ya n o th e r i s n o t c on s id e re d i n t h i s a n a l y si s - -o n l y t h e a s pe c t o f e ach c e l l . )

F o r b o t h R ASPECT and C ASPECT, c l a s s

z e r o i s u se d f o r c e l l s w i t h n o as pe ct .

D i f f e r e n t i n v e s t i g a t o r s may h av e d i f f e r -e n t i d ea s as t o w ha t c o n s t i t u t e s a go od s e to f s l o p e o r as p e ct c l a s s e s . T h e r e fo r e , t h ec a p a b i l i t y o f u s e r - d e f i n e d c l a s s e s h as be enadded t o V IEWIT. These c la ss es can be usedf o r sl op e, a s pe c t o r e l e v a t i o n a n a l y s i s . T ou se t h i s o p t i o n , f i r s t d e f i n e th e cl a ss e s .T h e re c a n be u p t o 50 u s e r - d e f i n e d c l a s s e s .The u s e r who i n t e n d s t o p r i n t g ra y -s h ad e dm aps s h o u l d n o t d e f i n e m o re t h a n n i n e c l a s s e s ,h ow e ve r, b e ca u se o n l v t h a t m any d i s t i n c t



shades o f gr ay can be produced . (A1 1 numbers

from 9 on up wi 1 1 p r i n t as the darkest shade.)

Classes a re def ine d b y use o f th e CLASS

command. This has a form th at i s s l i g h t l y

d i f fe re n t f rom oth er commands, i n th at i t

takes a 'su bsc r ip t ' (a number spe c i f y in g

wh ic h c las s i s be ing de f i ned ) a f t e r t he word

'CLASS.' The fo l l ow in g i s an example o f the

d e f i n i t i o n o f some c lasses tha t might be used

fo r s lope ana ly s i s :

Th i s examp le s pec i f i es t ha t t h e f i r s t

user c l ass i s f rom 0 t o 35, the second f rom

35 t o 100, and the t h i r d f rom 100 t o 1000.

I t i s a l so necessary t o sp ec i fy NCLASS--this

t e l l s VIEWIT t o use the f i r s t NCLASS c lasses

( i n the example, 3) t o do i t s analyses, maps

and tables.

The CLASS command s im ply a ccep ts any p a i r

o f numbers.as a value f o r the spe c i f i ed c lass .

The i n t e rp re t a t i o n o f th e numbers depends on

the analys is t o be per formed. For s lope, the

numbers are i nte rpr et ed as s lopes i n percent .

I f the c l asses def ined i n the example above

were used fo r s lope c lass ana lys i s , ce l ls

whose slo pe f e l l between 0 and 35 perc ent

would be giv en a slope c la ss number o f I,

c e l l s wi t h s lopes between 35 and 100 percent

a cl as s number of 2, and so f o r t h .

For aspect, the clas s numbers are i nt er -

pret ed as compass di re ct io ns i n degrees. For

example, t o p i ck out c e l l s whose aspect was

mos t ly n or th , the fo l l ow in g commands might be

used :

A l l c e l l s w i t h aspec ts i n t he r ange 350 t o

360 degrees would be giv en a cl as s number o f

I, a11 c e l l s f rom 0 t o 10 degrees , a c lass

number of 2, and a l l oth er c e l l s would be

g iven th e def au l t c las s number o f zero (which

means ' no t i n any def ined c la ss ' ) .

For e lev at io n c lass ana lys is , the c lass

numbers are taken t o be e leva t ion s i n fee t .

The f o ll o w in g example shows how a user mig ht

p i ck ou t a band o f e le vat i ons and break i t

i n t o several subbands:

CLASS(] )=(5000,55OO) ,C~A SS(2 )=(5500 ,600 0),

CLASS(3)=(6000,6500) ,NCLASS=3,U ELEV,TABLE,

MAP,

These examples i l l u s t r a t e a number o f

po in ts about c las s values. Each c las s has

two values assoc iated wi th i t, which are

taken t o be the lower and upper l i m i t o f the

cl as s. So, th e second number should be la rg er

than t he f i r s t ( no check i s made fo r t h i s , bu t

a c la ss def ine d backwards w i l l never be found

t o have any th ing i n i t ) . C lasses need not be

def ined i n incre as in g order , and the re may be

gaps between them. Classes may ov er la p, b u t

i f t hey do, a c e l l w i l l be ass igned t o t he

lowest-numbered cl ass i n which i t f a l l s . C e l ls

which do no t f a l l i n any o f t he f i r s t NCLASS

classes w i l l be given a c las s number of zero,

which w i l l p r i n t as ' 0 ' on the map produced

by t he MAP command, o r as a b lank on t he GMAP

gray-scale map.

For some uses, such as s o i l s t a b i l i t y

analyses, the method o f calc ul at in g s lope

w i t h a be s t - f i t p lane ov er n ine c e l l s ave rages

ou t t oo much de ta i l i n t he t e r r a i n . For such

cases, th e maximum slop e ana lys is opt ion ,

XSLOPE, may be used. Th is o p ti o n ca lc u la t es

t h e sl op e f r om a c e l l t o e ach o f t h e e i g h t

surrounding ce l l s , and keeps the l arg est of

these ei uh t numbers ( f i q. 9) .

Th is s lope i s then p laced i n one o f the

standard 10% s lope c lasses. A l te rn at iv el y ,

t he U X SLOPE op ti o n ca l cu l at e s a maximum

slop e as shown pre vio usl y, and then cl as si -

f i e s i t ac co r ding t o t he c u r r en t s e t o f us er -

s pec i f i ed c las s es .

The XSLOPE and U X SLOPE analyses give

what i s ess en t i a l ly a wors t -case s lope

c l a s s i f i c a t i o n .

For example, assume t h a t th re e logg ing

t ec hn iq ue s ar e a v a i l a b l e . The f i r s t i s a p p l i -

c ab le t o f l a t and n e a r ly f l a t t e r r a i n , t h e

second t o moderate s lopes, and the t h i r d t o

steep slopes. The fo l l ow in g commands w i l l

i s o l a t e each o f these s lope c lasses and p r i n t

a map:

CLASS(\)=(O, 10),C~~ SS(2)=(10,2 5) CLASS(^)=(25,1000),NCLASS=3, U X SLOPE, MAP,

The data check option, D CHECK, ca lcu-

la tes t he ave rage e lev a t i on o f t he e igh t

c e l l s a r ound eac h c e l l . I f t h e e l e v a t i o n

o f t h e c e l l d i f f e r s f ro m t h i s a verage ( e i t h e r

by being hi gher o r lower) by more than the

value spe c i f ied by the user, a c las s number

i s s to r ed f o r t ha t c e l l . Fo r example, i f t he

user gave t he command, DCHECK = 200., then

c e l l s whose e lev a t i on s were w i t h in 200 f e e t o f

the average o f t h e i r neighbors would have

t h e i r numeric f i e l d s f i l l e d w i t h a z er o. C e l l s

whose e levat ions d i f f e r ed by 200 t o 400 fee t



I

would re cei ve a I, by 400 t o 600 feet a 2, ands o f o r t h . These numbers can be displayed withTABLE, MAP, o r G MAP. Depending on th e p re ci -

s io n w i t h wh ich the da t a was ga thered , ce l l swi th a la rge d i f f ere nce c la ss number should be

suspected o f hav ing in cor rec t e leva t ions .They should then be checked a gain s t the or ig i -nal topographic map t o determine i f an e r r o rwas made i n d i g i t i za t i on .

VIEW may be t he most impor tan t ana lys isc ap ab i l i t y f o r most us e rs o f t h i s system. I tp ro duc es v i s i b i l i t y i n f o r m a t io n t h a t can bedisplayed as a seen area map, v i s i b l e f r e-quency map, o r we igh ted v i s i b i l i t y map,depending on the opt ions chosen.

T hi s o p t i o n d et er mi ne s v i s i b i l i t y asfo l lo ws: A c i r c l e o f rad ius RADIUS as spec i -f i ed by the user i s f o rmed around the de f inedobserver po in t . From the observer poi nt , a

r ay i s c rea t ed ou t t h r ough t he i n t e r v en i ngc e l l s t o each p o i n t on t h e r i m o f t he c i r c l e .S in ce t h e e l e v a t i o n o f e ach c e l l on t h i s r a yand i t s d is t anc e f rom the observer a re known,

t he e l ev a t i on /dep r es s i on ang le r e l a t i v e t othe observer can be ca lc ul at ed . Only whent h i s i s eq ua l t o o r g r e a t e r t h an t h e an g le f o rany p reced ing c e l l on the ray can the ce l l i nquest ion be seen.

A d ia gr am i l l u s t r a t e s a m a t r i x o f d a t aw i th an observer po i n t , c i r c le , and one ray( f i g . 1 0 ) .

( Al th ou gh t h i s i l l u s t r a t i o n shows t h e c i r c l el y i n g e n t i r e l y w i t h i n t h e d a ta , t h e sy st emdoes no t requ i re t h i s and i t may be p a r t i a l l y

o r e n t i r e l y o u t s i d e t he c u r r e n t s u b r ec ta n gl eor even the da ta mat r i x . )

Eleva t ion s a long a ra y are determined andsome ce l l s a re shown t o be vi s i b l e and some not( f i g . 1 1 ) .

In th e sim pl est case of the VIEW anal ysis,when a ce l l i s v i s i b l e t he system adds I t ot h e c o n t e n t s o f t h e n u m e r i c f i e l d f o r t h a t

c e l l . Assume, f or example, t ha t the userissues the commands :

VIEW,TABLE,MAP,

observer

The CLEAR ensures t ha t th e numeric f i e l d has

a l l zeroes . Then an observer po s i t i on i sde f i ned and a v i s i b i l i t y ana l y si s per fo rm edf o r a r a d i us o f 16 mile s. The user coul d

have pr in te d a tabl e or map here, bu t e lec tedt o per form another anal ys is f o r a new observerpos i t i on. Since the radius o f examinat ion was

not changed, i t remained a t 1.25 mi les f o r th e

second analysis.

A f t e r th e second VIEW command, each c e l l ' s

numer ic f i e l d cou ld be i n one o f t h ree s ta tes :

a ) S t i l l conta in in g zero, which indicate s

t h a t i t could be seen by neither observer;(b ) con ta in ing 1 , i n d i c a t i n g t h a t i t was seenby one; (c ) con ta in ing 2, i nd ica t in g tha t i t

was seen by bo th obse rv er s. The TABLE com-mand w i l l produce a t ab le showing t he numberand area of ce l ls seen 0, 1 , and 2 t imes. TheMAP command w i l l p r i n t a map where each c e l l

wi 1 be pr in te d as blan k (seen zero t imes), 1,o r 2. O r , i f t he AVG MAP op t i o n has beenspe cif ied , the MAP command w i l l p r i n t a map

where each c e l l w i l l p r i n t as b l ank ( i n v i s -ib le ) , 5 (seen by 50 percent of the observers) ,o r 10 (seen by 100 perc ent o f t he observers).I n add i t i on , t he c e l l s wh ic h we re ou t s i de t hede f i ned r ad i us o f obs er v a ti on f o r a l l obs er v erp o i n t s w i l l be p r i n t e d as a ' . I . I n t h i ssimp lest case, the map coul d be ca l l ed a v i s-ib le f requency map. Any number o f ob ser verpo in ts can be combined f o r one anal ysi s.

A number o f op t i ons r es t r i c t o r m od i f y thev i s i b i l i t y a n al y si s and a f f e c t t he f or m o f

d i s p l a y o f t h e r e s u l t s :

1 , Z ANGLE

The lower l i m i t on v i s i b i l i t y c an a l s obe se t by sp ec if yi ng LO ANGLE, which hasthe same meaning as Z ANGLE. An upperl i m i t of v i s i b i l i t y can be set by spec i fy -ing H I ANGLE, a l i m i t above which theobserver i s not allowed t o look. Thedefau l t , +PO degrees (s tr ai gh t up), i s no ta l imi ta t i on . To use th is feature, the usershould specify ' H I ANGLE = I , followed by anangle between 0 and 90.

2. Z BIAS can be used t o r ai se o r lower the



observer pos it io n. The number give n by

Z BIAS i s added t o the e le vat ion found i n

t h e c e l l as ( X OBS, Y OBS) f o r the vi s i -

b i 1 t y analy sis. (The number i s not per-

manentl y added t o the e le va t i on o f the

spec i f i ed observe r ce l l . ) T h is op t i on

has been used t o show the ef f e c t on v i s i -

b i l i t y o f s k i l i f t towers, ae r i a l t ram-

ways, power transm issi on l ine s, and sim i-

l a r s t r u c t u r e s . I t may al s o be used t os imu la te observa t ion po in ts f rom a i r - '

p lanes and hel i copt ers.

The N SECT and SECTOR commands can be used

t o l i m i t t h e v i s i b i l i t y a n a l ys i s t o us er- spe c-

i f i ed azimuth sectors ra th er than a f u l l 360

c i r c le . N SECT sp eci f ie s no sectors, which i s

the de f au l t case . I t can be used t o re t u rn

from sectore d mode t o an examination o f th e

e n t i r e c i r c l e , o r t o d e f i n e a new s e t o f sec-

t o r s . A f t e r N SECT i s spec i f i ed , each SECTOR

command sp ec if ie s a p a i r o f numbers which i s

the s t a r t and end azimuth ( i n degrees from

nor th) o f a se ct or t o be examined. There can

be up t o 20 such sec tor s. For example, th e

commands:

N SECT, SECTOR=(O. ,go.), SECTOR = (180. ,270.),

w i l l cause a l l subsequent v i s i b i l i t y an aly se so

t o be perfo rmed on l y o n azimuths f rom 0 t o 90

and from 180 t o 270 ( i e., the shaded areas

wou ld be examined fo r v i s i b i l i t y and the b lank

areas would not) ( f ig . 12).

The Z ANGLE, Z BIAS, and SECTOR opt ions

can be used i nd iv id ua l l y o r toge ther f o r any

one o f severa l observer po in t s i n a ser ies , o r

f o r more than one o r a l l . D i f fe r en t observe rpo i n ts can have d i f f e r en t va l ues f o r these

opt ion s, o r the same. The user must on ly re-

member th at t he value sp ec if ie d remains the

same u n t i l i t i s changed.

The o ther se t o f op t ions f o r v i s i b i l i t y

ana l ys i s a re the we i gh t i ng op t ions . The f i r s t

op t i on i s we i ght i ng by aspect r e l a t i v e t o the

observer . Th is func t io n i s enabled by A W ON

and disabled by A W OFF, I n i t i a l l y i t i s d i s -

abled, Wi th t h i s opt ion, the system calcu-

la te s t he aspect o f each c e l l which i s deter -

mined t o be v i s i b l e as exp la i ned e a r l i e r .

Th is aspect i s converted t o an aspect r e l a t i v e

t o the observer , tak i ng in to account the as-

p e ct o f t h e seen c e l l , e l e v a t i o n o f t h a t c e l l ,

and el ev at io n o f the observer. I n most cases,

the observer w i l l see t he c e l l somewhat ob-

l i qu el y ra the r than head-on. Consequent ly the

apparent area of the seen c e l l w i l l be reduced.

Each c e l l i s assigned a maximum o f 10 poi nts ,

and t h i s i s s c al ed a c co r di n g t o t h e r e l a t i v e

aspect. That is, i f t h e c e l l i s t u r ne d p ar -t i a l l y away f rom the observer so tha t i t s

apparen t area i s on l y one -hal f o f i t s ac tua l

area, i t rece ives f i v e po i n ts . Ce l l s tu rned

a t 9 0 t o the observe r, so tha t they a re seen

edge-on, and ce l l s which face away from the

observer, rece ive zero poi nt s. (Thus zero may

i nd i ca te c e l l s seen i n s i l houe t te th a t may be

of ma jor importance i n the ana lys is o f the

t e r r a i n ( f i g . 13 ). )

Ce l l A i s tu rned a t abou t 4 9 t o t he l i n e fr om

the obse rve r i n the h o r i zon ta l p l ane, and

about the same i n the ve r t ic a l p lane. I t

would rece ive about f i v e poin ts. Ce I 1 B i s

oriented away from the observer and would

rece ive zero po in ts .

The score f o r each c e l l , zero t o 10, i sadded t o the numer ic f i e l d f o r tha t c e l l .

A f te r we ighted v i s i b i l i t y ana lyses have been

per fo rmed f o r f i v e observer po i n ts , each c e l l

could have a count o f zero t o 50. A count of

10 cou ld ind ic a te t ha t a ce l l was seen d i re c t -

l y head-on by one observer, and n ot by oth ers

a t a l l , o r more l i k e l y , t ha t the ce l l was seen

ob l iqu e ly by severa l observers.

The numbers developed by t h i s process can

be di sp la ye d by TABLE o r MAP, as be fo re . Be-

cause only 10 d i s t i n c t gray shades are pro-

duced on the l ine -p r in ter , however, a s l i g h t -

l y d i f f e r en t approach i s used fo r G MAP: Thescore fo r each ce l l i s d iv ide d by the number

o f observer po in ts fo r d is p la y purposes. Thus

the number displayed by G MAP w i l l a lways be

i n the range o f zero t o 10. This can be con-

s idered t o be an average o f we igh ted v i s i b i l -

it y over observers.

Weighted v i s i b i l i t y and s im pl e v i s i b i l i t y

analyses should not be combined i n a si ng le

se rie s. The system w i l l al lo w such a combina-

t i o n, b ut th e r e s u lt s w i l l be d i f f i c u l t t o

i n t e r p r e t . The CLEAR command should always be

used between di f ferent k inds of analyses.



The Z ANGLE, Z BIAS, and SECTOR o p t i o n s

c a n be us ed f o r o n e o r m o re o b s e r v e r p o i n t s

f o r w e i gh te d v i s i b i l i t y a n a l y s i s , a nd h av e

t h e same e f f e c t s a s i n t h e s i m p l e ca se .

The s ec on d k i n d o f w e i g h t i n g i s d i s t a n c ew e i g h t i n g . T h i s c an b e u se d a l o n e o r i n com-

b i n a t i o n w i t h r e l a t i v e - a s p e c t w e i g h t i n g . Theo p t i o n a l l o w s t he v i s i b i l i t y o f a c e l l t o b ew e i g h te d b y i t s d i s t a n c e f r o m t h e o b s er v e r.

T o d o so . t h e u s e r m u st d e f i n e a d i s t a n c e -w e i g h t f u n c t i o n w h i c h e x p re s s e s t h e d e s i r e d

r e l a t i o n s h i p b e tw ee n d i s t a n c e and v i s i b i l i t y

R at h er t h a n h a v in g a l i m i t e d s e t o f d i s -

t a n ce f u n c t i o n s , t h e s y s te m a l ow s t h e u s e rd e f i n e an y f u n c t i o n w i t h i n c e r t a i n l i m i t s .

D i s ta n c e -w e i g h t f u n c t i o n s a r e d e f i n e d b y

a p p r o x i m a t i n g th em b y s t r a i g h t l i n e se gm en tsand s p e c i f y i n g t h e i n t e r s e c t i o n s o f t h e se 1 i n e

s eg me nts . T he se p o i n t s , w h i c h a r e c a l l e dt u r n i n g p o i n t s o f t h e f u n c t io n , a r e d e f i n e d b yth e T POINT command. A max imum o f 20 suc ht u r n i n g p o i n t s may b e u se d t o d e f i n e e a chd i s t a n c e - w e i g h t i n g f u n c t i o n . The p r og r am

assu me s t h a t a d i s t a n c e o f z e r o a lw a y s h a s aw e i g h t o f 1 .0 , a nd t h a t t h e l a s t u s e r - s p e c i -f i e d w e i g h t e x t e n d s o u tw a d t o a n i n f i n i t e

d i s t a n c e .

Assum e t h a t t h e u s e r ssues these commands:

NO D W T P , T POINT =( .5 , .O),T POINT = (1.0,

0 . 5 ) , T P OIN T = ( 1 . 5 , 0 . 5 ) , P O I N T= ( 2 , 0 . 25 ) ,

D WON,

T he f i r s t com mand, NO D W T P, s p e c i f i e s n o

d i s ta n c e - w e i g h t t u r n i n g p o i n t s . T h i s s e t s t h ed i s t a n c e - w e i g h t f u n c t i o n b a c k t o i t s i n i t i a l

v a l u e o f 1 .0 f o r a l l d i s t a n c e s . Then t h e u s e r

s p e c i f i e s f o u r p o i n t s o n th e f u n c t i o n ande n a bl es d i s t a n c e w e i g h t i n g ( f i g . 1 4 ).

weight

distance in miles

The l i n e i s a u t o m a t i c a l l y c o nn ec te d t o w e i g h t1 a t d i s t a n c e z e r o and t h e l a s t w e i g h t g i v e n

i s e x t e n d e d o u t w a rd .

T h i s ex am ple a l s o i l l u s t r a t e s t w o r u l e sf o r t h e d e f i n i t i o n o f d i s t a n c e - w e i g h t f u nc -t i o n s : ( a ) w e i g h t s a r e n um b er s b e t w ee n z e r o

a nd 1.0 i n c l u s i v e ; ( b ) t u r n i n g p o i n t s m u s t b ed e f i n e d f r om s m a l l e s t d i s ta n c e s t o g r e a t e rd i s ta n c e s , o t h e rw i s e t h e w e i g h t i n g w i l l n o tf u n c t i o n p r o p e r l y .

When a d i s t a n c e - w e i g h t f u n c t i o n i s d e f i n e d ,D W ON e n a bl es w e i g h t i n g b y d i s t a n c e . As i n

r e l a t i v e - a s p e c t w e i g h ti n g , e a ch c e l l re c e i v e s

a s c o re o f z e r o t o 10 p o i n t s . A w e i g h t o f 1.0c o rr es p o nd s t o 10 p o i n t s , a w e i g h t o f .5 t o 5

p o i n t s , and s o f o r t h . T h i s i n f o r m a t i o n c a n b e

p r i n t e d w i t h TABLE o r MAP, o r d i s p l a y e d a s a na ve ra ge w e ig ht e d v i s i b i l i t y w i t h G MAP as i nt h e ca se o f r e l a t i v e - a s p e c t w e i g h t i n g .

I f t h e u s e r s p e c i f i e s b o t h r e l a t i v e - a s p e c tand d i s t a n c e w e i g h t i n g , t h e t w o w e i g h t i n g p r o -c e ss e s a r e c a r r i e d o u t in d e p e n d e n t l y . E ac h

p r oc es s p r oduc e s a num ber be tw een 0 and 1 .0 .I n t h e c as e o f r e l a t iv e - a s p e c t w e i g h t i n g , t h i snum ber i s t h e a p p ar en t a r e a o f t h e c e l l a s af r a c t i o n o f i t s a re a i f s e e n h ea d -o n . I n d i s -t a n c e w e i g h t i n g , t h e n um be r i s d e r i v e d f r o m

t h e u s e r ' s f u n c t i o n . T he n t h e s e t w o n u mb e rs

a r e m u l t i p l i e d t o pr o du ce a f i n a l w e i g h t i nt h e ra ng e o f 0 t o 1.0. T h i s w e i g h t i s th e n

c o n v e r t e d t o 10 c l a s s e s f r o m 1 t o 10 an d a dd edt o t h e co n te n ts o f t h e n um er i c f i e l d o f t h ec e l l i n q ue s t i o n .

E i t h e r r e l a t iv e - a s p e c t o r d i s t a n c e w e i g ht -i n g o r b o t h ca n be u se d f o r a ny o b s e r v e r p o i n t

o r p o i n t s i n a s e r i e s o f v i s i b i l i t y a n al y se s ,

b u t n e i t h e r s h o u ld b e co mb in ed w i t h a s i m p l ev i s i b i l i t y a n a ly s i s f o r t h e re as on s e x p l a i n e d

e a r l i e r . (A s e r i e s o f v i s i b i l i t y a na ly se se n d s wh en t h e u s e r is s u e s a CLEAR command; upt o t h a t p o i n t n um be rs a c c um u l at e i n t h e n u -m e r i c f i e l d s f o r ea ch a n a l y s is . )

S ince GMAP p r i n t s th e lo wes t shade o fg r ay f o r t he l ow es t c l as s , num bers w h i c h a r ebe low 5 p e r c en t w i l l p r i n t as b l a n k. Th us, i f

t he r e a r e 20 o r m ore obs e rv e r s , o r i f t h e t o t a lo f o b s e rv e r p o i n t s t im e s o b s e rv e r p o i n t r a n ks

e xc ee ds 20, some v i s i b l e c e l l s w i l l b e p r i n t e das b lank . Where t h i s i s undes i r ab le , a new,l i g h t e r s ha de o f g r ay ca n be p r i n t e d f o r c e l l st h a t a r e b e l o w 5 pe r c en t bu t a r e nonz e r o . T h i sop t i on i s s e lec t ed by s p ec i f y i ng 'SHOW N 2 ' f o r-how nonze ro. The d e fa u l t case may be re sto re dby s pec i f y i ng ' H I D E N Z ' .

A t t imes a use r may want t o g i ve an observ -e r p o i n t g r e a t e r w e ig h t t h a n a n o th e r s uc h p o i n t .To do so, use th e 'RANK' command. The d e f a u l tobserver rank is 1 ( one ) . I f t h e u s e r s p e c i -f ies, 'RANK = 2, V I EW , . . . ' t h e n c e l l s s e e nb y th e o b s e rv e r w i l l h av e a co u n t o f 2 r a t h e rthan 1 a dd ed t o t h e v a lu e i n t h e i r n u m e ri c

f i e l d . The va lu e g ive n by the most recen t RANKcommand i s mu l t ip l i e d by whatever m ight o th er -w i s e ha ve b ee n s t o r e d i n o r a dd ed t o a p a r t i c u -l a r c e l l . T h er efo re , i f a c e l l w o u ld h a ve r e -ce ived an inc rement o f 5 ( f o r 50 p e rc e n t ) i n aw e ig h te d v i s i b i l i t y a n a l y s i s , and i f t he r anki s 5, th e n th e c e l l w i l l r e c e i v e an i nc re m en to f I S . A ra nk w i l l a f f e c t a l l o bs erv ers u n t i li t i s changed, so the de fa u l t mus t be res et byspecifying 'RANK = 1 ' .

W eig hte d v i s i b i l i t y a na l ys e s w i t h m oret han one obs e r v e r po i n t av e rage t he f i n a lw eig hte d v i s i b i l i t y o ve r a l l o b s er ve rs . W i ths c a t t e r e d o b s e r v er p o i n t s , t h e r e s u l t s may be



obscured by averagin g them away i n some areas .The user can avoid this by specifying 'MAXIMUM'.This w i l l cause the VIEWIT system t o keep themaximum o f the p revious and present values o ft h e co u n t f i e l d o f a v i s i b l e ce l l r a t h e r t h a nt o add the ol d and new values and then l a t e raverage fo r pr in tou t (as i s done i n the defaul tcase).

The default mode can be restored by speci-f y i n g 'AVERAGE'. The MAXIMUM command, al tho ug h

pr incipa l ly in tended for use wi th weightedvisibi l i ty, can also be used with nonweightedv i s i b i l i t y . Combined wi th the RANK command,MAXIMUM coul d be used t o la bel each c e l l w i t hthe rank of the highest-ranked observer pointwhich saw the cell.

The mode o f MAXIMUM or AVERAGE can bechanged a t any time. However, the user shou ldunderstand the e ff ec t t hi s change wi l l have.The mode i s checked when a v i s i b i l i t y a naly sisi s done, and e i t h e r a sum or maximum i s kept asexp la ine d. The mode i s al so checked fo r mappr in to ut requests, and i f the mode at the timeo f the map command i s AVERAGE, the systemassumes that th e mode was AVERAGE f o r t he v i s i -b i l i t y ana lyses as we l l . I t then d iv ides thecontents of the numeric f i e l d of each ce l l bythe number of observers ( i n the case of weightedmaps, AVG MAP o r GMAP). I f the mode at the timeo f th e map pr i n t o u t command i s MAXIMUM, thesystem does not perf orm any di vi si on .

Users in te res ted i n the s t a t is t i ca l p ro -per t ies o f the i r e leva t ion da ta o r ana lys isresu l t s may p r in t ou t tab les o f s ta t i s t i c a lmeasures by use o f the STATS, V STATS and ELSTATS commands. The i nf or ma ti on pr in ted outincludes the minimum, maximum, mean, standarddev iat io n, v ariance, skewness, and ku rt os is .This in format ion is pr in ted out fo r the eleva-t i on data i n the current subrectangle by speci-f y i n g 'EL STATS'. The inf or ma ti on can be deve l-

oped and pr in ted out f or the count f i e l d ofce l l s in the current subrectangle by specify ingSTATS'. I f the count f i e l d contains the re-su l ts o f one or more v i s i b i l i t y analyses, thes t a t i s t i c s w i l l only be computed on examinedce l l s . Ca lcu la t ion o f s t a t is t i cs can be l im i tedt o ce l l s a lone by spec i f y ing ' V STATS'. Inother words, V STATS w i l l c al cul at e and pr i n tout s ta t i s t i c s fo r ce l l s whose count f i e l d i snonzero.

3.2.5 Type o f I np ut Expected f o r Each Command

Th is system prov ides f o r the f ree- fo rm in -

p u t o f us e r commands. Commands need no t s t a r t

o r end i n any pa r t i c u l a r ca rd column, they may

cont inue across card boundar ies, and b lanksar e us ua ll y ignored. Each command i s a wordo f severa l l e t te rs . Cer t a in commands requ i reth a t th e word be se t equa l t o a va lue . Theth re e types o f va lues are: numbers, st r i ng so f charac te rs , and pa i r s o f numbers . Anexample fo l lows:

NROWS=50, NCOLS = 40, BCD, FORMAT = ' (40F2.0) 'Z SCALE = 100.0, READ, RADIUS = 1.50, MT1TI-E =

'SMALL MAP',OBS=( 12, 33. ), VIEW, MAP, OBS = (12,34),VlEW,MTITLE = '',MAP,

Th is example de f ines an e leva t ion a r ray o f50 b y 4 0 l o ca t i o n s , sp e c i f i e s t h a t i t i s i ncard image form (which i s th e de fa ul t and neednot have been spec i f i ed ) , and th a t t he da ta a r ei n 4 0 co n se cu ti ve tw o -d ig i t l oca t ions on eachcard. The e l eva t io ns as read f rom the cardsare t o be mu l t ip l i ed by 100. The da ta a re readby u s i n g t h e d e f a u l t s o f B Y ROWS, e t c . As im pl e v i s i b i l i t y a n a l ys i s i s t h en p er fo rm edwi t h the observer a t (12,33) and a map o f t imes

seen pr in te d w i t h the t i t l e SMALL MAP. Thisana l ys i s i s repea ted f o r a new observer.

The example i l l u s t ra t es these po in ts : Cer -t a i n commands su ch as BCD and READ expe ct nova lue ; any va lue g iven w i l l be ignored. Othercommands expect values o f a c e r t a i n type. Nu-mer ic va lues

.may have any o f th e forms NNN,

NNN. NNN, NNN, o r any o f t he se pr ecede d by aminus s ign . I f the p rogram expects an in teger ,the number g iven w i l l be rounded t o the neares tin teger . Charac te r s t r i ng s a re enc losed bys i n g l e q uo te s, and o n l y i n s id e t h e q u ote s a r eb l a n k s s i g n i f i c a n t . (On ly TITLE, M TITLE FOR-

MAT, FIL E and COMMENT ex pe ct ch ar ac ter s t r i n gvalues.) Commands a r e se pa ra te d by commas,and extra commas between commands are ignored.Card boundaries are ignored (and as a conse-quence, the l as t cm a n d on each cardhave a t r a i l i n g comma, o r t he re must be a com-ma befor e the f i r s t command on th e nex t card,o r b o th ) . Pai rs o f numbers a re enclosed byparentheses and sepa rate d by a comma; ot he r-wise, t h e i r form i s the same as fo r numberss tand ing a lone .

Commands may al s o have a su bs cr i pt , whic hi s a number i n paren thes is fo l lo win g the com-mand name. Cur ren t l y th i s i s on ly used by the

CLASS'command. I f a subs cr i p t i s used w i thany other command i t w i l l b e i g n or e d and awarning message pr inted.

The character ' $ I has a spec ia l func t ioni n s t r i n g s o f c h ar a c t er s - -i t a c t s as a t a b t ot h e n e x t se t o f 12 ch a r a c te r s . T h i s i s i n t en d -

e d f o r u s e w i t h t h e M TITLE and MESSAGE com-mands. Map t i t l e s a re p r i n t ed as two l i ne so f 12 ch a r a c te r s each. To p r i n t t h e t i t l eUSER-CLASS SLOPE MAP on two l i n e s , t h e us ercould use the command

MTITLE='USER-CLASS SLOPE MAP' .where th e two b lanks a f t e r t he word 'CLASS'ensure th a t t he word 'SLOPE' w i l l s t a r t onthe nex t l i ne , o r more s imp ly , the user cou ld

sa y

MTITLE=' USER-CLASS$SLOPE MAP',

wh ich wou Id save hav ing t o coun t charac te rs .

A l l us er commands, whether th ey expect avalue, and i f so what t ype , a re l i s te d here .Because bla nk s a r e ig nore d, th e command ZSCALE can be g i ve n as ZSCALE o r Z S C A L E,



and t he command G MAP may be GMAP o r G MAP

and so fo rt h. The form th at i s shown is con-

side red most readable.

Command Value expected

NROWS number ( integer)

NCOLS number ( integer)

DELTA X number

DELTA Y number

M SCALE number

X MIN number ( integer)

X MAX number ( integer)

Y MIN number ( integer)

Y MAX number ( integer)

BY ROWS none

BY COLS none

B I NARY none

BCD none

R O W LEFT none

RO W RIGHT none

COL UP none

COL DOWN none

FORMAT c h a r a c t e r s t r i n g

T I TLE c h a r a c t e r s t r i n g

M TITLE c h a r a c t e r s t r i n gX O B S number ( integer)

Y O B S number ( integer)

O B S pa i r of numbers ( in t ege rs)

Z SCALE number

RAO I US number

N SECT none

SECTOR pa ir of numbers ( in t ege rs)

Z ANGLE number

Z BIAS number

FILE cha rac te r s t r i ng

X END number (integer)

Y END number ( integer)

EN D pa i r of numbers ( in t ege rs)

N O D W T P none

T POINT pai r of numbers

A W ON none

A W OFF none

D W ON none

D W OFF none

READ none

CLASS pa ir o f numbers

N CLASS number

X SLOPE none

SLOPE none

U SLOPE none

U X SLOPE none

ASPECT none

U ASPECT none

U ELEV noneVIEW none

MAP none

AVG MAP none

NUM MAP none

CLEAR none

TABLE none

G MAP none

D CHECK number

D PRINT none

PROF I LE none

C ASPECT none

R ASPECT number

COMMENT ch ara c ter s t r i n g

4 . DEMAND TERMINAL USE

The VIEWIT system may be used i n ei t h e r

bat ch o r demand computing. Output on li n e

p r i n t e r s may be requested from sm all demand

terminals.

I n a batch run, the system echoes each in -

put card as i t i s read in, and then p r i nt s

each command asi t

i s c a r r i e d o ut .I f

t heuser vio la te s the r ul es o f t he command lan-

guage, th er e are a number o f e r r o r messages

which are reasonably sel f-e xpl ana tor y: An

er r o r message w i l l be p r in ted , a long w i th the

card cont ain ing t he offe nd in g command, w i t h

an ' * I p r i nt e d i n th e v i c i n i t y o f t he e r r o r .

In case o f an er ro r, the system stops execu-

tio n. Execution al so stops when the re ar e no

more commands.

I n a demand run, the echoing of in pu t i s

suppressed. Only the ac tu al re s u l t o f com-

mand execution i s pri nte d. Also, i f VIEWIT

i s b ein g ru n i n a demand mode, when an e r r o r

occurs the system asks the user t o re- ent erth e command o r commands, ra th er th an s top p in g

execution as i t does i n bat ch mode.

Because VIEWIT uses a re l a t i v e l y la rg e

amount o f memory and ot he r computer res our ces

wh il e h and lin g a massive problem, i t should

be used on a demand ter min al w i t h a c e r t a i n

amount o f cau tio n. Gray-scale maps and ot he r

lar ge ove rla y maps tak e a la rg e amount o f

time t o type out on a small demand te rm in al .

However, many of f i c e s do no t have easy access

t o any o ther k ind o f te rmina l. Therefore,

certain features of VIEWIT have been designed

for demand use. These fe at ur es a1 ow th euser t o do analyses and pr i n t out t ables and

small maps on demand ter min als and t o di v e r t

la rg e maps and oth er out put t o high-speed

l i n e p r i n t e r s a t o t h er l oc a ti on s .

I n demand mode, most user in pu t e r r o r s a r e

caught by the system, and the use r can co rr e ct

them ( i n batc h mode, th e VIEWIT system si mp ly

stops when an err or i s detecte d). Several

ad di ti on al user commands have been de fi ne d f o r

demand users:

Command Meaninq

STOP Stops execution of the system.

D IVERT Creates a f i l e and causes a l l

pr i nte d output f rom VIEWIT t o be

s en t t o t he f i l e i ns te ad o f b ei n g

p r i n ted ou t a t the demand termi-

nal ,

SEND Causes th e f i l e cr ea te d by a pre -

ceding DIVERT command t o be se nt

t o a batch te rm ina l t o be p r i n te d

ou t on a l i ne p r i n te r ; t he use r

spec i f i es whi ch ba tch s i t e by se t -



t i n g SEND t o the. s i t e ID (see the

examp Ie beIow)

MESSAGE P r in t s a s t r i n g o f char acte rs i n

l a rge l e t t e r form, w i t h up t o 10

l ines of 12 characters each.

This command i s intended f o r use

w i t h DIVERT and SEND t o l a b e l t he

ba tc h ou tp ut . Als o, MESSAGE can

be used a t any t ime ( i n e i th er

demand o r ba tch mode) t o p r i n t ou tl a rge l e t t e r s f o r any purpose .

The DIVERT and SEND commands are es pec ia l -

l y use fu l f o r map output. The fo l lo wi ng exam-

p l e shows how a user mi ght do a slo pe c la ss

analysis and then p r i n t th e s lope c lass map a t

a high-speed s i t e:

SLOPE, TABLE,

(a t th i s po i n t the user i nspects the tab l e

and decides th at the w i l l be w or th p r i n t -

ing)

The 'DIVERT' command cre at es a f i l e , and

put s th e words VIEWIT OUTPUT a t i t s b egi nni ng

i n la r ge l e t t e r s . The 'MESSAGE' command i n

the example p r i n ts i n l a rge l e t te r s :

SEND TO

JONES AT

TAHOE NF

Command Va lue ex pecte d

SHOW NZ none

HIDE NZ none

HI ANGLE number

LO ANGLE number

INTERFACE (o pt io na l) cha rac ter s t r i n g

OVERLAY (o pt io na l) cha rac ter s t r i n g

RANK number ( i n t e g e r )

MAX IMUM none

AVERAGE none

STATS none

EL STATS none

V STATS none

The TABLE and MAP commands p r i n t a no th er

copy of the s lope c lass t able, and a s lope

c l as s map. Then the SEND command causes t he

f i l e c o n t a i n i n g t he o u t pu t produced b y a l l o f

the above t o be p r i n te d a t ba tch s i te F C~014,

whic h happens t o be the FCCC s i t e ID fo r th e

high-speed terminal i n the F o res t Se rv i ce 's

Ca l i fo rn ia Reg iona l Of f i ce i n San Francisco.

I f an err or occurs a f t e r a 'DIVERT' but

befo re a 'SEND', the er r or message w i l l go

i n t o th e f i l e r a t h e r t ha n t o t h e t er m in a l.

The recommended way t o us e t he se two commands

i s t o type i n DIVERT, then di sp la y commands,

then SEND, a l l on one l i ne . Inspect the l i n e

f o r e r r o r s b e fo r e h i t t i n g t he c ar r i ag e r e t u r n

key; i f there a re e r ro rs , cance l the l ine

( c o n t r o l X ) and retype i t .

I f something seems t o have happened a f t e r

a 'DIVERT', out put can be retu rned t o the

te rm ina l by t yp i ng i n the t ranspa ren t co n t ro l

statement:

The DIVERT command cre ate s a f i l e w i t h a

name o f the f or m PRnnnnnnnnnn, where nnnnnnnnn

i s a 10-d ig i t number. This i s a cata loged

p u b l i c f i l e ; n o rm a ll y t h e SEND command w i l l

f r e e i t and send i t t o t h e s pe c if ie d s i t e w i t ha @SYM operat ion. I f SEND f a i Is , or f o r what-

ever reason, the user could ex p l i c i t l y FREE

and S YM t h e f i l e , o r d e l et e i t , or examine i t

w i t h t h e i n t e r a c t i v e e d i t o r .

In other words, the f i l e created by DIVERT

i s a n o r d i n a r y E x e c - 8 f i l e . I t c a n b e o p e r a t -

ed on i n any way t ha t any l i n e image f i l e

(ca l le d 'SDFF' f i l e ) can be operated on.

Info rma t io n developed by the use of VIEWIT

ana lys is op t io ns can be saved and l a t er en tered

i n t o ove r la y mapp ing systems t o deve lop com-

b ined maps th a t cannot be produced d i r e c t l y by

VIEWIT.

The fo l l ow in g commands are used f o r t h i s

c a p a b i l i t y : XMIN, XMAX, YMIN, YMAX, FORMAT,

FILE, BY ROWS, BY COLS, ROW RIGHT, RO W LEFT,

COL UP, COL DOWN, BINARY, BCD, OVERLAY, INTER-

FACE.

The f o u r commands XMIN, XMAX, YMIN, YMAX

are used t o de f i ne a s ubrec t ang le w i t h in t he

data , such as fo r ana l ys is o p t io ns o f V IEWIT.

The su br ec ta ng le w i l l b e w r i t t e n o u t t o a f i l e

when t he OVERLAY o r INTERFACE command i s g iv en .

( I f no s u br e ct a ng l e i s s p e c i f i e d , t h e e n t i r e

d a ta a rr a y w i l l be w r i t t e n . ) The o r d e r i n w hi ch

t he da t a i s w r i t t en i s det e rm ined by t he com-

mands BY ROWS, BY COLS, ROW RIGHT, ROW LEFT, COL

UP, COL DOWN, wh ic h fu n c ti o n i n e x a c tl y th e

same way as the y do when rea di ng i n data w i t h

t he READ command .

The OVERLAY o r INTERFACE command ( e i t h e r

word may be used) w i 1 l cause the contents o f t he

c ou nt f i e l d o f e ach c e l l i n t he c u r r e n t su br ec -

t a ng l e t o be w r i t t e n o u t t o a f i l e on d i s k s t o r-

age. I f th e f i l e i s t o c on ta in ca rd o r l i n e

images, the n BCD should be sp ec i f ie d. In t h i s

case, a fo rmat must be supp l i ed by spec i f y i ng

FORMAT The form at t h a t was used t o read i n the

da t a c anno t be f u r t he r used s inc e t he ou t p u t



f o rmat must be appropr ia te t o wr i t e ou t i n tegers ;

t h a t i s , i t must have ' I ' f i e l d s p e ci f i ca t i on s .

The format given should be appropriat e t o wri te

out one row (or column i f BY COLS was spec i f i e d )

of the data.

I f BINARY i s sp ec if ie d, th en the INTERFACE

command wi 11 cause each row (o r column i f BY

COLS) o f the curre nt subrectangle t o be wri t t en

out as one binary record.

The F LE command may be used t o sp e c i f y t he

f i l e t o whi ch o ve r la y i n fo r mat i o n w i l l be w r i t t e n

I f the FILE command i s not given, the def au lt

f i l e name of 'OVERLAY.' w i l l be used f o r outp ut

da ta . I f an over lay i s wr i t t e n w i t hou t chang-

ing t he f i l e name, t he in fo rmat ion w i l l f o l l ow

p re v io us d at a w r i t t e n t o t h e same f i l e ( i f a n y ).

I f th e f i l e name i s changed, th e nex t INTERFACE

command w i l l w r i te in t o the beginning of the

new f i l e . That is , i f the user wri tes an over-

l ay i n t o f i l e A, then another i n t o f i l e B, and

t he n r et u rn s t o f i l e A f o r t he t h i r d o ve rl ay ,

t he i n f or mat i o n f ro m th e f i r s t o ve r la y w i l l b e

l o s t .

The INTERFACE command has two forms. Thef i r s t i s s imply :

I NTERFACE,

This form causes the contents o f the count

f i e l d o f each ce l l i n t he cu r ren t subrec tang le

t o be w r i t t e n o u t t o t h e sp e c if i e d o r d e f a u l t

f i le . The order and mode of wr i t in g are deter -

mined by the commands pr ev io us ly menti oned.

The second, o pt io na l f orm o f t he command

provides a label f o r the over lay data:

INTERFACE=' INFORMATION TO LABEL THE F LE' ,

I f t h e o ve rl ay i s BCD , then the contentsof the st r i ng o f characters between quotes

f o l l o w i n g t he INTERFACE command ar e w r i t t e n

t o t h e o ve r l ay f i l e as a card image (8 0 charac-

ter s) , fo l lowed by the data from the curre nt

subrec tangl e. I f BINARY was sp ec if ie d, then

the charac ters a re wr i t t en t o t he f i l e as one

20-word bin ary record (120 characters), f o l ow-

ed by the bina ry data records.

I f the f i l e spe cif ied by the FILE command

( o r t h e d e f a u l t f i l e ) e x i s t s as a ca ta lo ge d o r

t empora ry f i l e , t ha t f i l e w i l l be used. O ther -

wise, a temporary f i l e w i l l be created when the

INTERFACE command i s g iven.

The fo l low ing example i l l us t r a t es the use

o f the INTERFACE command:

Assume th e user has read i n dat a usi ng

these commands:

This w i l l read by rows, bottommost row

f i r s t , f rom l e f t t o r i g h t ( a l l d ef a ul t s) w i th

fo ur cards per row. The data w i l l come from

f i l e 'ZOATA.' (a l so a de fau l t ) .

The user then defines a subrectangle and

calcu la tes s lope c lass va lues:

XMIN = 51, Y MAX = 50, SLOPE, TABLE, MAP,

I f a f t e r seeing the t ab le and map, the

user decides t o save t h i s s lope c lass data f o r

fu r t he r analys is or combination wi th anothersystem, he would do so by

FILE = 'SLOPE.', FORMAT = ' ( 5012) ' ,

COL DOWN, INTERFACE = 'SLOPE CLASS DATA,

50 X 50'9

Af t er these commands are executed, f i l e

'SLOPE' c ont ain s one card image w i t h the la be l

inf orm ati on given between quotes, follow ed by

50 images--each w i t h one row's slo pe clas s

numbers. The topmost row appears f i r s t because

o f th e COL DOWN command. The other op t io ns re -

main a t t h e i r de fau l t values .

Af te r stopping the VIEWIT operator, the

user can c a l l in t o execut ion any other programor system, which can read the data from f i l e

'SLOPE. '

Another f e a t u r e added t o VIEWIT f o r de -

mand use makes i t p o s s i b le f o r t h e u s e r t o

i n t e r r u p t an o p e r a t i o n i n p ro gr es s , T h is i s

p a r t i c u l a r l y u s e fu l i f t h e u se r b eg i ns t o

p r i n t a l o n g t a b l e o r map and t h e n d e c id e s

t h a t h e d oe s n o t wa nt t o see i t . T h i s i s

done as f o l l ow s: F i r s t , ho l d down the

'BREAK' key on th e te rm in al f o r a moment.

T h is w i l l s t o p p r i n t i n g a nd c au se t h e E xec-8

syst e m t o p r i n t o u t a message: '*OUTPUT

INTERRUPT*'. A t t h i s p o i n t t h e us e r sh ou ld

t y p e i n ' @@ XC' f o l l o we d b y a ca r r i a g e r e -

t u r n . T h is w i l l g en e ra te a n i n t e r r u p t w h ic h

w i l l cause t he V IEWIT sys tem t o s top execu-

t i o n o f t he command i n p rogress and ask t he

us er t o subm it a new command. (Seve ral l ines

o f t h e map o r t a b l e b e i n g p r i n t e d may ap pe ar

b e f o r e t h e i n t e r r u p t t a ke s e f f e c t . )

The Exec-8 ru le s f o r t he au tomat i c

assignment o f f i l e s a r e d i f f e r e n t f o r demand

and batc h. Theref ore, th e demand us er shoul d

e x p l i c i t l y a s s i gn t h e t wo f i l e s needed t o

opera te V I EWI T. The recommended c o n t r o l ca rd

sequence t o use i s :

@ASG,A PSWW IEW IT.

@ASG,A PSW*LOG.

@FREE PSWLOG.

@XQT PSWV IEW IT.

(E i t he r '@ASG1 statement may r e s u l t i n

t h e message 'WAITING FOR FA CI LI TY '. I n t h i s

case t he demand user must wa i t u n t i l t he

Exec-8 sys tem makes t he f i l e a v a i la b l e . Th is

w i 1 1 norma l1y t ake on ly a few minutes. )



USER REQuESTi GM A P



USER REQuEST i COWMEN a

A N D R E L A T I V E A S P E C T

USER REQUEST! RASPEC Ã 1 8 0

A S P E C T C L A S S E S C A L C U L A T E D R E L A T I V E TO TH E U S E R - S P E C I F I E D D I R E C T I O N O F 1 8 0 . 0 D E GR E ES

USER REQUEST: TA BL E

T A B L E O F A S fr E CT S R E L A T I V E TO U S E R - S P E C I F I E D D I R E C T I O NTHERE ARE 8 C L A S SE S , E A C H R E P R E S E N T I N G AN G LE S I N TWO 22.5D E GR E E B A N D S, O NE ON E A C H S I D E O F T HE S P E C I F I E D O I R E C T I O N :

1 t - 0 , TO 22 .5 DEG. RE LA T I VE TO THE GI VE N ANGLE2 t - 2 2 . 5 T O 4 5 DE G

3 +-US TO 67.5 OEG4 t - 6 7 . 5 T O 9 0 , D E G5 +-SO. TO 11 2.5 OEG

6 t - 1 1 2 . 5 T O 1 3 5 , DE G7 t - 1 3 5 . T O 1 5 7 . 5 D EG

8 t - 1 5 7 . 5 TO 1 8 0 . D E G

ZERO NO ASPECT (F LA T)

USER REQUEST: MAP

M AP OF C E L L A S PE C T R E L A T I V E TO A U S E R - S P E C I F I E D D I R E C T I O N .THERE ARE 8 CLASSES, EA CH REPRES ENTING ANGLES I N TWO 22 .5D E GR E E B AN D S , O NE O N E A C H S I D E . O F T HE S P E C I F I E D D I R E C T I O N !

1 t - 0 , T O 2 2 . 5 DE G. R E L A T I V E TO T H E G I V E N A N GL E2 t - 2 2 . 5 TO 4 5 D EG3 t - 4 5 T O 6 7 . 5 D EG4 t - 67 . 5 TO 90 , DEG

5 t - 9 0 . T O 1 1 2 . 5 D E G6 +-112 .5 T O 1 3 5 . D E G

7 t - 1 3 5 . T O 1 5 7 . 5 D EG8 t - 1 5 7 . 5 T O 1 8 0 . 06 .GB L 4 N K NO A S P E C T ( F L A T )

( I F THE' G I V E N AN GL E I S TH E S UN D I R E CT I O N , T H I S I S

A N A P P R O X I M A T E S U N - I L L U M I N A T I O N H AP ,)



a= I N P U T C A R D 1 C O M M EN T n l CH E C K C E L L S W H IC H D I F F E R F RO M T H E AV ER AG E O f T H E I R N E I G h B U U S 8V PORE T H

USER REQ[ jEST l COMMENCHECK CELL S WHI CH D I F FE R FROM THE AVERAGE OF THEI R NEI GHBO RS B Y MORE THAN 1 5 0 F E E T *

USER REQuESTI MT IT LE m

DATA CHECK MAPM AP T I T L E 1 8 1 DA T A CH EC K

MAP

U S E R R E Q u E s T l D C H E C K = 1 5 0

D A T A C H EC K e O M P L ET E 0 , O F 1 8 7 2 C E L L S , 2 5 D I F F E R F RO M T H E A V E R A GE OF T H t I e N E I G P B U H S

USER REQUEST# MAP

DATA CHECK LASS MAP,B L A N K C E L L S P A S S T H E T E S T,1 MEANS CEL LS D I F FE R FROM THE AVERAGE OF THE I R NEI GHBORSB Y AN A MO UN T B E TW E EN TH E S P E C I F I k D T O L E R A f vC t A N 0 T W I C ETHE TOLERANCE*

2 M E AN S T H E D I F F E R E N C E I S 2 * T O L k R A N C E T O 3 * T O LE R A N CE , E T C *



U SE R R E Q ~ I E S T I T A B L E

DATA CHECK CLA SS TAB LE*0 MEANS CELLS PASS THE TEST*1 MEAN$ CELLS DI FF ER FROM THE AVERAGE OF TH EIR N EIGt iBORSBY AN AMOUNT BETWEEN THE SPECIFIED TOLERANCE AN0 TwICFTHE TOLERANCE.2 M EAN S TH E D I F FE R E NC E I S Z ! * T O L t R A h C t TO ~ * T O L E R A N C ~ , T C *

cl,A$s CE LLS AREA # SQUARE M l L t S A C R E S q t C T A R t Sa : : = ~ = ~ = x : a : : a = ~ = : = z = x ~ : = ~ ~ : : = ~ : = = ~ : = ~ = : = = = = = = ~ = ~ = : ~ = = = = = = = ~ = = = : = = ~ = = = = = = = = = = = = = ~ : = = ~ ~ ~ =

0 1 8 4 7 8 . 8 3 5 b 5 3 a 5 0 1 3 9 7 U S0 51 1 5 * 0 7 U 5 * 9 1 1 1 3 . U 5

2 2 m 0 1 6.12 1 5 , 1 33 5 a 0 2 1 5 * 3 0 37 . t32

5 1 * O o 3 .0 b 7.56

b 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

0 0 0 3 * Ob J.56

27 ---- ------------ wo o 3.06 - - - - - - - - - - .56===a===:====z=*===s==x===s======- - - - * - - - - - - - - - - - -= - - - - - - - - - - - - - - - - - - - - - - - - - - - - -= - - - - - - - - - -

=a I N P U T CA RD : C O M M E N T = ~ N O T IC E T H A T T HER E I S ONE t S P E C I A L L Y B AD C k L L AT ( 1 7 ~ 3 4 ) ' 1

USER REQIJEST: C OM MN =N O T I C E T H A T T H ER E I S ON E E S P E C I A L L Y B AO C E L L AT ( 1 7 , 3 6 1

I N P U T C A R D # C O M M E N T a f I T S N E IG H B OR S A P P tA R I N ER RO R AL SO B k C A US E T H I S ONE CkL L AL TEUS T hE A V k

Z= INP UT CAe Ot RAGE FOR THOSE CE L L S * ' ,

USER REQUEST: CONMEN x

I T S N E I G H B O e S A P PE AR I N ERROR AL SO B~ C A U S E HIS ONE CEL L AL TER 3 THE AVERAGE F O d TWOSâ CkLLS.

USER REQUEST# COMMEN @

P R I N T T H E A e T U A L E L E V A T I O N DA T AUSER REQUEST: MESSAG =

E L E V A T I O N M A P



n&

8

u

Iu

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aa

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4k1

IDÃ

a

a

nm

8

Ã

nuB

II

M

Ã

Ill

u

8

M

0

ua

0

Iau

Ã

aÂtÂ

aw#8

Ã

OOOSI x

00601 t008B 1 Ã

OOL171 t

0 0 9 0 1 toos171 Ã

OOt7171OOC01 a00217T +001171 4

O O O f r l Ã

0 0 6 I l *0 0 9 I 1 i

OOLCI Ã

009E1 1

OOStI *OOhSI Ã

OOtf I m

0 0 2 s I *OOIf I A

OOOtI t

00621 8

00921 Â00L?t B

00921 Ã

OOSZI 1

0017?l H

OOf21 HI

OOZZT aOOl?l w

00021 ?00611 i

o o e ~ M

OOLII a0091 1 ÃOOSI I 1

001711 c

OOII I 9

OOZ11 m

OOtI I V

00011 000601 b

00901 t

OOLOI t

00901 9OOSOI t

001701 Â

OOtOl ?00201 fOOlOI Ã

0 0 0 0 1 x0 0 6 6 i

0 0 8 6 t

OOL6 I

0 0 9 6 $0 0 5 6 <OOt76 >OOtb -0 0 2 6 4

0 0 1 6 (

0 0 0 6 I

0 0 6 9 10 0 8 9 t

0 0 1 9 1

0 0 9 9 2OOS6 A

OOB9 X

OOE8 M

0 0 2 9 A

0 0 1 9 n0008 1

OObf s

OOVi MOOLL B0 0 9 f d

0 0 5 1 0

0 0 9 1 N

OOtL w002f 1

OOIL n

OOOL r0 0 6 9 10099 H0 0 1 9 9

0009 40059 3

00179 0

OOi9 3

OOZQ 9

0 0 1 9 V

0 0 0 9 00 0 6 s 6

0 0 9 5 9OOLS L

0 0 9 5 9ooss 5

OOPS 17

OOIS I

0 0 2 s 20 0 1 s I

0 0 0 s00617009BOOf0

00917o o s 0000170 0 t h00?0001B

000170 0 6 s0 0 9 sO O L I

0 0 9 Ioost0017sO O I I

OOZI0 0 1 I0 0 0 s0 0 6 2

0 0 9 2o o i ?0 0 9 2o o s 2OOBZOOIZ0 0 2 2

001Z0 0 0 20 0 6 10 0 9 1OOLI

0 0 9 1OOSI00171oon00210011

0 0 0 100 6

00 9O O L

00 90 0 sOO i 7

O O I

OO?0 0 1



B I I I I I I e I m I I I Â ¥ Â ¥ Â¥ Â 111 III I I I I I I # I I I I I 1 1 1 1 B I D Â I in I I @ @ I 8 8 I I I a @ @ II I I II I I I I I IIIII # Â ¥ Â IIIIi 1 1 # 1 8 I I I I Ill 80 8 I I



ex INP UT CA f tD l XOBSÃ§22 YOBS=l8 ,COMMENTafTH IS I S AN ALTERNATIV E WAY TO SET OBSERVER PU ST IO Nf t

USER REQUEST! XOBS 8 2 2XOBS SET TO 2 2

USER REQUEST! YDBS Ã 1 8Y O0 8 S ET 1 0 1 8

USER REQUEST! COMMEN Ã

TH IS 1 3 AN ALT ERN ATI VE WAY TO SET OBSERVER POSTION

x* IN PU T CAftD: COMMENTÃ‡~DEMONSTRAT WEIGHTED VIEW O P T I O N S ~ , M T I T L E Ã ˆ ~ W E I G H T E D S M A P ~

USE R REQU EST! COWMEN 8

DEMONSTRATE WEIOHTED VIEW OPTIONSUSER REQuEST! M TI TL E *WEIGHTED MAP

MAP T IT L E I$ : WEIGHTEDMAP

3 3 IN PU T CARD: AWDN, VIEW, MAP, TABLE, AHOFF, COM MENTaIOEFIN E DIST ANC E WEIG HTIN G FUN CTI ONI ,

USER REQUEST# AWONV I S I B I L I T Y AN AL YS IS W IL L BE W EIG H TED BY T HE ASPEC T O F EAC H C EL L R EL A T IVE TO T HE O BSERVER .

USER REQtjEST! VIEW

V I S I B I L I T Y A N A L Y SI S W IL L BE PERF OR MED W IT H TH E F OL L O W IN G PARAMET ERS!: S Z X e Z 3 8 3 3 3 ~ 3 ~ 3 S S Z 3 3 3 3 f 3 S 3 Z : 3 3 S Z Z S E 3 f 3 3 8 ~ 3 S 3 3 : 8 3 3 3 8 3 Z 3 Z 3 Ã ‡ S 3 ~ 3 S 3 X ~ 3 3

x 0 6 s 22Y ons 1AR A D ~ U S 1 . 5 0 0 ( M I L E S )

2 .4 1 4 ( K IL O MET ER S)D EL IA X 2 0DELTA Y .17SCALE 24000.00

Z ANBLE -90.002 6 1 ~ 8 0SECTORS 0

V I S I B I L I T Y W I L L BE WEIGH T ED BY ASPECT R EL AT IV E TO T HE O BSER VER,

AN AL YSIS C O MPL ET E.T H IS O BSER VER C AN SEE 1 8 4 C EL L S ( ,88 SQUARE MILE S,

56 3 . 21 ACRES, 1391 . 71 HECTARES.)

USER REQuESTt MAP

MAP OF T IM E$ SEEN WEIG HTED BY ASPECT REL ATI VE TO THE OBSERVERFOR 1 oBSERVER(S1,

EAC H C EL L I $ GIVEN A SCORE OF 0 TO 1 0 FOR EACH OBSERVER,THESE ARE CUMULATED OVER OBSERVER POINTS.

FOR DI SP LA Y TH I S SUM I S DIVIDED BY THE NUMBER OF OBSERVERSSO THAT THE MAP D I S P L A Y S A NUMBER FROM 0 TO 1 0 FOR EACH CELLWHICH I S AN AVERAGE WEIGHTED VI EU OVER ALL OBSERVERS,



I I I I I I f l Ill I Â ¥ Â I IM IIIN @ I 8 8I m a I I I 8 I I I I

I ¥ @ Â I I I@ -18 I 1111 I I

I 8 @I I I I I I I I m I I I IrIi 111 111 I I I IIIII r i a

0 I @ Â ¥ 1 11 8

I # @I I.. I 1 .I l l I



USER REQuEST ! TABLE

T A B L E O F T I M E S S E E N W EI G H T E D BY A S P E C T R E L A T I V E TO T H E O B S ER V E R

FOR 1 f )BSERV ER(S) .

IN PU T CARD! NO DWTP, T PO IN T= (0. 5, I . ) , TPOI NT= ( l , O, 0.51, CLEAR, 0 W O N , v I k w , MAP , TABLE,

USE R REQIIESTI NODWTP

NO DISTANCE 'WEIGHT FUNCT ION TURNING POINTS. FUNCTION WEIGHT WILL BE 1.0 F OR A L L O I S T A ~ C E S .

USER REQuEST ! TPO INT a ( 5 0 , 1 . 0 0 1DISTANCE WEIGHT FUNCTION TURNING POINT I S A T DISTANCE = . 50. AND HAS A- w t 1 6 H T C k

USER REQUEST! TP OI NT a ( 1 , o o t 5 0 1DI ST AN CE WEIGHT FUNC TION TURNING PO IN T 2 I S A T D I S T AN C E = 1.00 AN0 HAS A *tlLHT CF-

USER REQUEST! CLEAR

C OU NT F I E L D C L E A R E D F O R C E L L S I N T HE C UR RE NT S U BR E CT A NG L E

USE S REQUEST ! DWONV I S I B I L I T Y A N A L Y S I S W I L L R E WE I G HE D BY T HE D I S T A N C E O F E A C H C E L L FR OM TH E O B SE R VE RACCORDING TO THE CURRENT D ISTANCE WEIGHT ING FUNCTION,

USES REQUEST! V IEW

V I S I B I L I T Y A N A L Y SI S W I LL BE P ERF ORM ED W I T H T HE F O L L O K IN G P A R A H E T ~ R S ~. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

x 0 8 s 2 2

Y ORS 1 6RADIUS 1.5 00 (M IL ES 1

2 . 4 1 U ( K I L O M E T E R S )D E L t A X 1 2 0

D E L T A Y 1 7S C A L E 2 4 0 0 0 . 0 0

X M I N 1X M Ax 3 6

Y M I N 1YMA y 5 2ZANRLE -90 .00

Z 0 I A S 0S t C T O R S 0

V I 8 I B I L I T Y W I L L BE WEIGHTED BY DISTANCE FROM THE OBSERVER.

A N A L Y S I S C O M P L E T E ,T H I S O B S ER V ER C A N S E E 1 8 4 C E L L S ( . 88 SQUARE MILE S,

56 1 . 21 ACRES, 13 91 . 71 HECTARES.)

USER REQUEST! MA P



o w o m^ a a e a a CO -^ m ............. . - . - - . - . . - - -4- m m m m <X) -0 -

u * m u m m m * * * . . - . . - . . * -m ul m u m m m - - t * - u e m m m a w m m IT .............. ul IT u m m u u 1 l ~ 7 m u m u m m mu- m ...............

m w m I T m IT < J ' w k / ' u l t / i u ' u u l t / i m u ' l J 7 u a I T m w - . . . . - - . - . - . - . . - ..m u t / i m m u m m u l w m u ul ul u m ~ u ~ ~ . . . . - - - . . - . - - . . . -



=a I N P U T C AR D! C L E A R , C O M M E N T ~ ~ N O W B O T H W E I G H T I N G M E T H O OS l l A W ON,VIEWIMAPIA w OFF, D w O F F 1

USER REQUEST! CLEAR

C O UN T F I E L D C L E A R E D F O R C E L L S I N T HE C U R RE N T S UB R E CT A NG L E

USER REQuE ST! COMMEN a

NOW BOTH WEIGHTING METHODS

USER REQUEST: AWONV I S I B I L I T Y A N A L Y S I S W I L L B E W E IG H TE D BY T HE A S P EC T OF E AC H C t L L R E L A T I V E TO T HE O BS ER VE R,

USER REQUEST! V IEW

V I S I B I L I T Y A N A L Y S I S W I L L B E P ER FO RM ED W I T H TH E F O L LO W I NG PA RA M ET ER S!

: : Z X X Z ~ X X ~ X ~ ~ ~ S Z Z Z Z : Z Z ~ Z X X Z Z = : : X S ~ Z E X E : : E ~ Z S : Z X X X X X B S Z X X X S X X X S C : Z : ~ ~

X ORS 2 2

Y ORS 1 8

RADIUS 1 .500 (M IL ES )

2 . ~ 1 1 ( K IL OM E TE RS )

D E L t A X 2 0D E L I A Y . 1 7SCALE 24000,00

X M I N 1XMAf 3 6Y M I N 1

Y MA x 5 2Z A N G L E - 9 0 ,0 0Z B l i S 0

SECTORS 0

V I S I B I L I T Y WILL B E W E IG H T E D B Y A S P EC T R E L A T I V E T O THE OBSERVER,

V I S I B I L I T Y W I L L B E W E IG HT ED B Y D I S T A NC E F RO M T HE O BS ERV ER ,

A N A L Y S I S C O M P L E T E ,T H I S O B S ER V ER C A N S E E 1 6 4 C E L L S ( a86 S Q U A R E M I L E S #

5 6 3 . 2 1 A C RE S , 1 3 9 1 . 7 1 H EC TA RE S. )

USER REQuE ST! MAP

MAP OF T I ME S SEEN WIEGHTED BY D IS TAN CE FROM THE OBSERVER

AND BY ASPEeT R EL AT IV E TO THE OBSERVER FOR 1 OBSERVER(S1 ,

E A C H C E L L I s GI VE N A SCORE OF 0 TO 1 0 FOR EACH OBSERVER.THESE ARE CUMULATED OVER OBSERVER POINTS,FOR D I SP LA Y TH I S SUM I S DIVIDED BY THE NUMBER OF OBSERVERSSO T H AT T H E H A P D I S P L A Y S A NUMBER FROM 0 TO 1 0 FOR EACH CE LL

WHICH I S AN AVERAGE WEIGHTED VIEW OVER ALL OBSERVERS,



N N N .-



USER REQ ( lE .ST t AwOFFW E I G H T I N G BY ASPECT RE LA T I VE TO THE OBSERVER I S TURNED OFF,

USER RfcQtiEST) DWOFFDIS TAN CE WEIGHTING I S TURNED OFF,

== INP UT CARD: COMb 'ENTs 'DEF INE SOME SLOPE CLASSES, ' ,

U S E S R E Qt j t S T t C OW M E N a

DEFINE SOME SLOPE. CLASSES,

== I N P U T C A RD : C L A S S ( l ) = ( O , , Z 5 . ) , C L A S S ( ~ ) = ( 2 5 ~ , 5 0 ~ ) , C L A S S ( 3 ) ~ ( 5 0 ~ 1 0 0 0 , 1 , C L A S S s 3 ,

U SE R R E Q ~ I E S T ~C L A S S ( 1 ) = ( 0 0 . 2 5 .0 0 )C L A S S ( 1 ) W I L L BE FROM 0 0 TO 2 5. 00

USER REQUEST) CLASS ( 2) = ( 2 5 . 0 0 , 5 0 . 0 0 )

C L A S S ( 2 ) W I L L 8E FROM 25 .00 TO 50 .00U S E R R E U u k S T t C L A S S ( 3 ) = ( S0.00, 1000,OO)

C L A S S ( 3 ) W I L L BE FROM 50 .00 TO 100 0 .0 0USER REQt jEST t NCLASS = 3

NCLA SS SET TO 3

INP UT CAR01 COMMENTsIFOR SLOPE, CLASSES ARE TAKEN AS SLOPES I N PERCENT! ,

USER REQUEST) COMMEN =

FOR SLOPE, CL AS SE S ARE TAKEN AS SLOPES I N PERCENT

USER REQUEST! MT IT LE s

USER SLOPE MAPMAP T I T L E I $ l U S t R SLO PE

MAP

== INP UT CARD: U SLOPE, TABLE , MAP,

U S E R R E Qu E S T i U S L OP E

SLOPE CALCULATED BY U S E R - S P E C I F I E D C L A S S E S

USER REQUEST) TABLE

-----

T A B L E OF S L O P E B Y U S E R - D E F I N E D C L A S S E S .

CLASS LOWER

----.---.--I M I T UPPER

------.---.I M I T

1 0 0 2 5 . 0 02 25 .00 50 .003 5 0 . 0 0 1 0 0 0 . 0 0

-----------L A A S C E L L S

- - -AREA) -SQUARE- = = s = ^ = s = a = B a ^ a s s * ^ a = - - - - - - - - s Â ¥ - - - - Â ¥ - * a - - * - e - Â ¥ s - - -- --

M I L ES A CR ES i t C T A R t S! S S S Z I S = S S f S S = s s f S = S f = 2 E Z Z :

1 1 2 7 2 6 . 08 3 8 9 3 . 4 8 9 6 2 0 . 9 62 5 6 7 2 . 71 1 7 3 5 . 5 4 4 2 8 8 . 5 93 3 3 1 6 1 0 1. 01 2 V . 6 0

= ~ = = = = = = ~ = = ~ = = = = ~ ~ ~ ~ ~ = ~ s = s = ~ = = = = ~ : = ~ = s = ~ = = = = = = = s = ~ a z = ~ = = ~ ~ = : = = = = = : = : = ~ = = ~ = ~ = = ~ : = x = = = = =

USER REQUEST! MAP

M A P OF SLOPp B Y USER-SPECIFIED CLASSES,



Ir a i i III 1111 IIIII

I I # IIIIIi I 8 I In

@ I1111

I I I I 8 I I I I # @ I @ Â ¥ Â I@ @ 1 1 1 8 1



* a IN PU T CARD: COMMENTs'NOW C AL CU LA TE SLOPE BY THE MAXIMUM SLOPE METHOD', U X SLOPE,

USER REQuESTt COMMEN =

NOW CAL CUL ATE SLOPE BY THE MAX IMUM SLOPE METHOD

USER REQuEST: UXSLOP

MAXIMUM SLOPE CALCULATED BY USER-SPECIF IED CLASSES.

=* IN PU T CARD: TABLE, MAP,

U SER R EQ u EST i T ABL E

TAB LE OF MAXIMUM SLOPE 8Y USER-DEFINED CLASSES.

CLASS- - - - - L O V R L I M I T UPPER L I M I T* -w- - - - -m-w

1

-----.-----0 0 25 .00

2 2 5 ~ 0 0 5 0.003 5 0 . 0 0 1 0 0 0 . 0 0

USER REQUEST: MAP

MAP OF MA XIM UM SLOPE BY USER-S PECIF I ED CLASSES

viewit: computation of seen areas, slope, and aspect for land-use planning

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