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Main concepts of ILWIS 3.0

CHAPTER 2


In chapter one,Introduction to ILWIS, you started with ILWIS, and learned the

basics o the user interace! This chapter presents so"e #ey concepts o ILWIS!

In section 2!$, the two basic data "odels %&ector and raster "odels' that are used in

ILWIS are treated to(ether with the dierent types o ob)ects %i!e! data ob)ects, ser&ice

ob)ects, container ob)ects and special ob)ects'! In section 2!2 the &arious types o "aps

are shown* point, se("ent, poly(on and raster "aps! +ector and raster "aps can be

displayed si"ultaneously in a "ap window! In this section and in section 2! you will

also ha&e a closer loo# at one o the #ey concepts o ILWIS* the use o do"ains! A

do"ain lists e!(! the possible units in a "ap %as class na"es or I-s' or the ran(e opossible &alues in a "ap! A representation, treated in detail in section 2!., contains the

inor"ation that deter"ines how your spatial data should be represented on screen or

in a printout! A coordinate syste" %section 2!/' contains inor"ation on the #ind o

coordinates you are usin( in your "aps! In section 2!0 o this chapter you will pay

special attention to the (eoreerence %containin( inor"ation about the nu"ber o lines

and colu"ns o a raster "ap, the coordinates and the pi1el sie'! In the sections 2!3

and 2!4 you will see how spatial and attribute data are lin#ed and how you can retrie&e

inor"ation ro" both si"ultaneously, by usin( the pi1el inor"ation window! In

section 2!5 the details &iew o the Catalo(is treated! The last section, section 2!$6,

deals with another i"portant concept o ILWIS* dependency lin#s! In ILWIS the"aps, tables and colu"ns created by an operation, #now how they were "ade! This

has so"e "a)or ad&anta(es, such as the possibility to store only the deinition o a

"ap, without storin( the data o the "ap itsel, and the possibility to si"ply

recalculate output "aps when input data has been chan(ed %"a#e output "aps up7to7

date'!

ILWIS 3.0 Users Guide

-ouble7clic# the ILWIS icon on the des#top!

8se the9a&i(atorto (o to the directory* C*:ILWIS !6 -ata:8sers ;uide:Chapter62!

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2.1 Structure of spatial data in ILWIS

In the pre&ious chapter we ha&e loo#ed at how you can display "aps and tables inILWIS! 9ow we will see "ore in depth how the data are structured! We will treat the

structure o spatial data!

Spatial eatures are represented in ILWIS in the ollowin( ways* 7 Points! =any ite"s

can be represented as sin(le points on a "ap! Points "ay reer

to rainall stations, houses, ield obser&ations, sa"plin( points, etc!

7Lines! Linear eatures such as roads, draina(e lines or contour lines!

7Areas! >eatures which occupy a certain area, such as land use units %e!(! orest',

(eolo(ical units, etc!

The spatial entities described abo&e can be represented in di(ital or" in two data

"odels %>i(ure 2!$'* vector modelsor raster models!

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In a vector modelthe position o each spatial eature is deined by %a series o' ? and

@ coordinates!

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inpoint mapsby re(isterin( their location inXand Ycoordinates and by codin( the"

%e!(! a rainall station, ele&ation, etc!'!

Se("entsA line is stored as a series o ? and @ coordinates %points' that best relect itscharacteristics! The points are connected by strai(ht lines! In ILWIS line eatures are

calledsegments! A se("ent is described by the coordinates o its startin( and endin(

points %itsnodes' and the intermediate points! The code o a se("ent deines what

the se("ent represents %e!(! road, state boundary, contour &alue, etc!'!

Poly(onsAreas are represented by their borders or boundary lines, which are in act lines

stored in the sa"e way as se("ents! A poly(on is a closed area o one or "ore

boundary se("entsB and a code!

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either satellite i"a(es, scanned aerial photo(raphs or i"ported raster "aps ro" other

sources! =ost ILWIS analyses are based on the raster data "odel! The results o "ost

o the operations are also raster "aps!

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%&'ect t(pes

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need besides the data itsel! -o"ains, representations, coordinate syste"s and (eo7

reerences are called ser&ice ob)ects!

7 +ector "aps need a nu"ber o ser&ice ob)ects* a do"ain, a representation and a

coordinate syste"!

7 Raster "aps also need these ser&ice ob)ects* a do"ain, a representation and a coor7

dinate syste"! All raster "aps contain inor"ation in discrete cells or pi1els, which

are ordered in rows and colu"ns! To relate these pi1els to "ap coordinates another

ser&ice ob)ect called a (eoreerence is needed!

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2.2 )ispla(ing "aps and La(er Manage"ent )ispla(ing

*ector and raster "aps

Lets us now ha&e a loo# at the dierent types o "aps in ILWIS! In chapter $ you

ha&e seen the Landuse "ap! Re"e"ber that it was a poly(on "ap! Let us now

co"pare the poly(on "ap with a raster "ap, which is obtained by rasteriin( the

poly(on "ap!

The irst i"pression is that both "aps are the sa"e! They are si"ilar with respect to

the inor"ation they contain! @ou can chec# this by clic#in( the sa"e unit in both

"aps! The units o both "aps are also displayed in the sa"e colors! The dierence,


-ouble7clic# poly(on "ap Landuse inthe Catalo(! The -isplay Fptions G Poly(on =ap dialo( bo1 is opened!

Accept the deaults in the -isplay Fptions 7 Poly(on =apdialo( bo1 by clic#in(F! The poly(on "ap is displayed!

Clic# the Title baro the "ap window, #eep the let "ouse button down, and"o&e the "ap window to the side o the screen! Then release the let "ousebutton! This is called dragging!

-ouble7clic# raster "ap Landuse in theCatalo(! The -isplayFptions 7 Raster =apdialo( bo1 is shown in which you can speciy how you

want to see the raster "ap! 9ote that there are less options than in the -isplayFptions G Poly(on =apdialo( bo1!

Accept the deault &alues in the dialo( bo1 by clic#in( F! The raster "ap isdisplayed in another "ap window!

-ra( and successi&ely resie both windows so that they are ne1t to each other!

Clic# the oo" Inbutton in the Toolbaro theraster "ap! Position the "ouse pointer in a section o the "ap near theboundary o se&eral units! Press the let "ouse button, hold it down, and dra(it to deine a s"all area to oo" in on!

Repeat this procedure or the poly(on "ap! oo" in on the sa"e area!

9ow you can see uite so"e dierences between the two "aps! The poly(on "ap

displays s"ooth boundaries between the units, whereas the raster "ap has a bloc#y

appearance! I this is not clear then oo" in urther! The bloc#y appearance o the

raster "ap is due to the re(ular arran(e"ent o the pi1els! @ou are able to see

indi&idual pi1els and the land use unit they represent!

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howe&er, is in the way the inor"ation is stored in both "aps one in &ector or"at

and the other in raster or"at! The best way to e&aluate this is by oo"in( in on both

"aps!

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We can see the indi&idual pi1els e&en "ore clearly when we display another type o

raster "ap* a satellite i"a(e %T"b$*

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since you cannot see two colors o two pi1els on top o each other!

In a satellite i"a(e nearly each o the indi&idual pi1els has a dierent &alue than its

nei(hbours, due to the dierent relectance &alues o the earth surace as recorded by

the sensor o the satellite! To read so"e o the pi1el &alues*

I"a(e The &alues that you can read ro" the "ap are whole nu"bers between 6 and 2//!

This "eans that whene&er we wor# with satellite i"a(es %such as SPFT or Landsat'

the do"ain o these i"a(es is called i"a(e! Domain imageis used or satellite

i"a(es, and scanned blac# and white aerial photo(raphs! Pi1el &alues in a band o a

satellite i"a(e represent relection &alues in a certain wa&elen(th inter&al!

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La(er "anage"ent

In the "ap window, poly(on "ap Landuse is displayed on top o raster "ap T"b$!

A "ap window can contain only one raster "ap, but it can be co"bined with se&eral


In the Catalo(o the =ain window select satellite i"a(e T"b$ and dra( itto the "ap window containin( poly(on "ap Landuse! The -isplay

Fptions 7 Raster =apdialo( bo1 is opened!

Accept the deaults and clic# F! Raster "ap T"b$ is now added to the "apwindow!

In the Layer =ana(e"entpane, dra( and drop the Landuse data layer below theT"b$ data layer! 9ow raster "ap T"b$ is displayed on top o poly(on "apLanduse!

=o&e with the "ouse pointer throu(h the "ap while #eepin( the let "ousebutton pressed! The &alues that can be read ro" the "ap are the &alues oraster "ap T"b$!

-ouble7clic# T"b$ in the Layer =ana(e"entpane! The -isplay FptionsG Raster =apdialo( bo1 o raster "ap T"b$ appears!

In the -isplay Fptions G Raster =apdialo( bo1 clear the Inochec# bo1!This "eans that you will not see the &alues o the pi1els any"ore when

clic#in( in the "ap!Accept all other deaults and clic# F! 9ote that in the Layer =ana(e"ent

pane the i in ront o the T"b$ chec# bo1 has disappeared!

=o&e a(ain with the "ouse pointer throu(h the "ap while #eepin( the let"ouse button pressed! The classes that can be read ro" the "ap &iewer arethe class na"es o poly(on "ap Landuse!

In the Layer =ana(e"entpane, select poly(on "ap Landuse! Press the ri(ht"ouse button and choose the Re"o&e Layerco""and or clic# the Re"o&eLayerbutton in the Toolbaro the"ap window! The Re"o&e Layerbo1 appears with the uestion Re"o&ePoly(on =ap JLanduseK

Are you sureAnswer this uestion with @es!

Fpen the Layers"enu and select the Add Layerco""and or clic# the AddLayerbutton inthe Toolbaro the "ap window! The Add -ata Layer

dialo( bo1 is opened!

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se("ent, poly(on or point "aps! Each o the "aps displayed in a "ap window is

called a data layer!

Let us now loo# at another poly(on "ap! We ha&e already seen the poly(on "ap

Landuse, which has a class do"ain! We will now loo# at the poly(on "ap

Citybloc#, which contains the city bloc#s o a part o the city o Cochaba"ba!

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The contents o se("ent "ap Contour are dierent ro" se("ent "ap -raina(e!

The contour lines are all coded accordin( to their ele&ation! In this case the contents

cannot be represented as classes, but as &alues! The "ap Contour thereore has a

value domain!

>inally, let us ha&e a loo# at a point "ap! The point "ap that will be displayed shows

the location o rainall stations in the area %it is a icti&e "ap, only "eant or this

8serBs ;uideand not representin( the real situation in Cochaba"ba'!

Please note that point "ap Rainall also uses an I- do"ain! The do"ain o a "ap is

always indicated at the top o a -isplay Fptionsdialo( bo1! In the dialo( bo1 there is

an option to show the na"es o the points as well!

Select the Inochec# bo1, accept all other deaults and clic# F! Se("ent"ap Contour is now added to the "ap window!

Clic# the contour lines and read their "eanin(! 9ote that you can also readthe "eanin( o the draina(e lines and the city bloc#s when you clic# the"!

In the Catalo(o the =ain window, select point "ap Rainall and dra( itto the "ap window! The -isplay Fptions 7 Point =apdialo( bo1 appears!

Select the chec# bo1 Te1t! So"e e1tra te1t options appear!

Clic# the >ontbutton! The >ontdialo( bo1 is opened!

In the >ontdialo( bo1, select >ont* Arial, >ont Style* Re(ular andSie* 4!

Clic# Fin the >ontdialo( bo1!

In the -isplay Fptions G Point =apdialo( bo1, select Te1t Color*;reenand clic# the Sy"bolbutton!

In the Sy"boldialo( bo1 select Sy"bol Type* Si"ple, Sy"bol* Suare,Sie* /, >ill Color* ;reen, Line Width* $, and Color* Red!

Clic# Fin the Sy"boldialo( bo1!

Practice so"e "ore with the Layer =ana(e"entpane! Add so"e other

poly(on and se("ent "aps, and see the do"ain used by the "aps! Practicealso in chan(in( the order o the layers by dra((in( a layer up or down

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9ote that the na"es o so"e o the rainall stations are only partially shown, becausethose stations are situated )ust outside the area co&ered by the satellite i"a(e!


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Su""ar( )ispla(ing "aps and La(er Manage"ent

In this e1ercise you learnt the ollowin(*

7 ILWIS allows the display o "any data layers in the sa"e "ap window! A "ap win7

dow can display only one raster "ap, but a raster "ap "ay be displayed to(ether

with "any dierent point, se("ent andDor poly(on "aps!

7 The way in which &arious data layers are displayed in a "ap window can be "anip7

ulated &ia the Layer =ana(e"entpane!

7 In the Layer =ana(e"entpane you can select the layers to be displayed, and

ro" which layers you want to obtain inor"ation! @ou can chan(e the display

options o a layer, the order o the layers and you can add or re"o&e layers!

in the Layer =ana(e"entpane! @ou can also choose not to display a data

layer by clearin( its chec# bo1!

When you ha&e inished, close the "ap window!

ILWIS 3.0 User s Guide3,

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2.3 -&out do"ains

In the pre&ious section you ha&e already seen the our "ost i"portant types o

do"ains* 7Classdo"ains or data ob)ects that contain classes %e!(! land use units,

(eo"or7

pholo(ical units'

7I-do"ains or data ob)ects that contain uniue identiiers %e!(! city bloc# $62,

rainall station La(una'

7+aluedo"ains or data ob)ects that contain "easured, calculated or interpolated

&alues %e!(! hei(ht, concentration'

7 The I"a(edo"ain or satellite i"a(es or scanned aerial photo(raphs containin(&alues between 6 and 2//!

A do"ain stores the set o possible data &aluesB %class na"es, I-s or &alues' that

should be a&ailable in a "ap, table or colu"n!

ILWIS uses do"ains e1tensi&ely and or "any operations you should decide in

ad&ance about the do"ain o a resultin( "ap* a class "ap, an I- "ap, or a &alue

"ap! This enables you to ha&e a direct control o&er your data types, e!(! ha&in( the

do"ain as a separate ob)ect you can ha&e a direct loo# at the #ind o data are storedin your "aps!

MIn se&eral other raster7based ;IS syste"s, and also in the pre&ious -FS &ersionso ILWIS, you always had to re"e"ber what each pi1el represented! >or e1a"ple,

i you had a land use "ap with . classes %in which $ N A(riculture, 2N >orest,

N ;rassland and . N Shrubs' and when you wanted to ind the areas which are

suitable or urther de&elop"ent %e!(! the current shrub area'! Then, to show the

suitable areas you had to use a "ap calculation or"ula %this will be e1plained

in depth in chapters 3 and 4' which had the ollowin( or"* Result NI>>%LanduseN., $, 6'

This or"ula "eant* i the Landuse "ap has a pi1el &alue o . %shrubs', then the

resultin( "ap will ha&e a &alue o $ %"eanin( that it "ay be used or urther

de&elop"ent', and otherwise a &alue o 6 %not suitable'!

>ro" ILWIS 2 onward, you use do"ains and you no lon(er need to #now the relation

between the pi1el &alues and the classes, since ILWIS #eeps trac# o that! In ILWIS,

your "ap calculation or"ula reads*

Result N I>>%LanduseNJ>orestK, JSuitableK,J9ot suitableK'


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without a class na"e are considered undeined! The sa"e class na"e can be used or

se&eral points, se("ents, poly(ons or "appin( units in one "ap! As you willre"e"ber ro" the pre&ious e1ercise, poly(on "ap Landuse had a class do"ain,

which contained the na"es o the dierent land use types!

The -o"ain Classeditor allows you to add new ite"s to the do"ain, and to chan(e or

delete e1istin( ones! Fne should be careul, howe&er, with deletin( do"ain ite"s,

since this "ay cause proble"s in the "aps and tables that use this do"ain! >ore1a"ple, i you delete the >orest ite", there will be poly(ons in the "ap Landuse with

an internal code that is not present any"ore in the do"ain! The orest unit in the "ap

will then be represented as undefined (!and will also loose its color! @ou should

always ta#e care that a do"ain contains all the ite"s that can occur in a "ap or a

table!

A do"ain "ay contain "ore ite"s, howe&er, than are present in the "ap! This is &ery

useul i you ha&e dierent "aps dealin( with the sa"e topic, or e1a"ple "ulti7

te"poral land use "aps o a certain area, or &arious (eolo(ical "aps with the sa"e

le(end!

What is the ad&anta(e o the do"ain approach Let us (i&e an e1a"ple*

MSuppose you ha&e two land use "aps o dierent re(ions in the sa"e country!Suppose in one "ap you ha&e land use types a(riculture, (rassland and shrubs,

and in the other "ap a(riculture, orest and shrubs! In the -FS &ersions o

ILWIS, pi1el &alues o your units "i(ht be A(riculture N $, ;rassland N 2 and

Shrubs N or the irst "ap, and A(riculture N $, >orest N 2 and Shrubs N in thesecond "ap! So, pi1el &alue 2 is once orest and once (rass7land, which is &ery


Fpen the do"ain o poly(on "ap Landuse by double7clic#in( the do"ainLanduse in the Catalo(! The -o"ain Classeditor is opened!

Fpen the >ile"enu in the -o"ain Classeditor, and select the Propertiesco""and or clic# the Propertiesbutton in

the Toolbaro the editor!The Properties o -o"ain Class JLanduseKsheet appears, which describesa"on( others what this do"ain is used or!

Clic# the 8sed

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conusin(M

Howe&er, i you use one do"ain containin( all the possible land use classes, you

do not need to care about pi1el &alues o separate "aps since all the necessary

inor"ation or all your land use "aps is stored in one do"ain! The do"ain then

contains the class na"es* A(riculture, >orest, ;rassland, Shrubs!

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This is the do"ain o the (eo"orpholo(ic "ap! The list o classes in this do"ain

loo#s a bit dierent to the one o the land use classes! @ou see irst a Class 9a"e and

then a Code! Since so"e o the class na"es can be &ery lon(, ILWIS allows the use

o abbre&iations, or codesor the do"ain ite"s! This is &ery handy when you want to

do calculations with "aps, or colu"ns! Instead o ha&in( to write a e1pression li#e*

Result N I>>%;eo"orpholo(yNKAccu"ulation o debris on slopeK,

KPossible landslideK,K9ot a possiblelandslideK'

@ou can now write*

Result N I>>%;eo"orpholo(yNKAdK, KPossible landslideK,K9ot

a possible landslideK'

Codes can be entered, edited and deleted with the Add Ite", Edit Ite"and -elete

Ite"co""ands on the Edit"enu, with the buttons in the Toolbaro the

-o"ain Classeditor or by usin( the ri(ht "ouse "enu on a do"ain

ite"!

More a&out identifier do"ains

I- An identiier do"ain can be used when each ele"ent in a "ap is identiied by a

uniue na"e, i!e! an identiier %I-' ele"ents without an identiier are considered

undeined! Each ite" occurs in principle only once in the "ap! Attributes can be

lin#ed to the uniue na"es, that is to the identiiers! The attribute table contains

additional inor"ation on the uniuely identiied ele"ents and uses the sa"e do"ainas the "ap! An identiier do"ain can be used in point, se("ent, and poly(on "aps,

and in rasteried point, se("ent, and poly(on "aps! The identiier do"ain is ad&ised

or detailed "aps on lar(e scales such as $*/66 or cadastral and inrastructural

purposes!


Clic# the Cancelbutton in the Propertiessheet and close the -o"ainClasseditor!

Fpen another class do"ain* ;eo"orpholo(y!

Close the -o"ain Classeditor!

In the Catalo(, clic# do"ain Citybloc# with the ri(ht "ouse button andselect Fpenro" the conte1t7sensiti&e "enu!

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Let us now loo# in "ore detail at so"e identiier do"ains!

-o"ain Citybloc# is an identiier %I-' do"ain! It is lin#ed to the poly(on "ap with

the city bloc#s, as well as to the table Citybloc#! -o"ain Citybloc# contains the

cadastral codes o the city bloc#s o the central part o Cochaba"ba city!

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In this case the identiiers are uni"ue numbers!

-o"ain Rainall is also an I- do"ain %you can chec# this or instance by openin( the

Propertieso the do"ain'! In this do"ain, the indi&idual ite"s are the uni"ue nameso

the rainall stations! It is not a class do"ain, since each na"e is only &alid or one

rainall station only! I it would be related to "ore rainall stations, the syste" would

not #now to which station the data in the correspondin( table Rainall are reerrin(!

More a&out *alue do"ains

+alue +alue "aps and &alue colu"ns use a &alue do"ain! Ele"ents in &alue "aps %raster,

poly(on, se("ent, or points' or ields in &alue colu"ns represent "easured,

calculated, or interpolated &alues! +alues in a &alue do"ain are deined by a

"ini"u" and "a1i"u" &alue %the &alue ran(e' and a precision &alues s"aller than

the "ini"u" or lar(er than the "a1i"u" are considered undeined!

In this section we will loo# at so"e &alue do"ains!

-o"ain Hei(ht is used or se("ent "ap Contour which contains contour lines! A

&alue do"ain loo#s uite dierent ro" a class or I- do"ain! It is not a list o na"esor codes, but it is a deinition o certain &alues that should be used in a "ap or a

colu"n! In this e1a"ple, do"ain Hei(ht describes the Hei(ht in "eters!

>or the Cochaba"ba area, hei(ht &alues ran(e ro" 2/66 to .066 "eters! These are

the "ini"u" %=in' and "a1i"u" %=a1' &alues o the do"ain Hei(ht!

The Precisiono a &alue do"ain deter"ines the incre"ent between two possible

successi&e &alues! The precision deter"ines or instance the nu"ber o deci"als that

are used to store the &alues! When you use a precision o 6!$ the &alues are stored with


Close do"ain Citybloc#, and open do"ain Rainall!

Close the -o"ain Identiiereditor!

Fpen the do"ain

Hei(ht!

ILWIS 3.0 User s Guide+0

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$ deci"al! @ou can also store &alues with a certain step sie, or e1a"ple only the

&alues endin( on /, $6, $/, 26, 2/, etc! In that case you use a precision o /! @ou can

use any &alue or the precision, as lon( as it "a#es sense with respect to the "ini"u"

and "a1i"u" &alue, and the "eanin( o the &alues! >or instance, it would be uite

useless to use a precision o 6!66$ or the do"ain Hei(ht, since the altitude o the

contour lines are in "eters on the topo(raphic "ap ro" which they were di(itied!

It is i"portant to #eep in "ind, that i you use &ery s"all &alues or the precision %or

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The "ost i"portant syste"7deined &alue do"ain is the one called $alue! In act you

can "a#e all other &alue do"ains with this do"ain! The others are (i&en to pre&ent

you ro" needin( to deine do"ains too oten! Let us loo# at so"e e1a"ples!

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There are so"e do"ain types that we ha&e not yet treated so ar, because they are

speciic or certain operations! They will be discussed later on in this boo#! A

co"plete o&er&iew o do"ains can be obtained ro" the ILWIS Helptopic JILWIS

Fb)ects, -o"ainsK!

Su""ar( -&out do"ains

7 A do"ain stores the set o possible data &aluesB that are used by a "ap, table

andDor colu"n! All ILWIS data ob)ects %&ector "aps, raster "aps and tables' always

ha&e a do"ain!

7 The sa"e do"ain can be used by a &ector "ap, a raster "ap and a table!

7 The our "ost i"portant types o do"ains are* class do"ains, identiier do"ains,

&alue do"ains and the i"a(e do"ain!

7Classdo"ains are used or data ob)ects that contain classes! A class do"ain "ay

or instance store the na"es o land use units or (eo"orpholo(ical units!

7I-do"ains are used or data ob)ects that contain uniue identiiers! An I- do"ain

"ay or instance store the uniue I-s o city bloc#s, or the uniue I-s o rainall

stations!

7+aluedo"ains are used or data ob)ects that contain "easured, calculated or inter7

polated &alues! A &alue do"ain "ay or instance store the &alues %ran(e and preci7

sion' needed to deine hei(hts or to deine concentrations!

7 The syste"I"a(edo"ain is used or satellite i"a(es or scanned aerial photo7

(raphs containin( &alues between 6 and 2//! This do"ain is a special type o

&alue do"ain, as the i"a(e do"ain cannot contain undeined &alues!

7 Class and I- do"ains are always user7deined! +alue do"ains can be user7deined,

or syste"7deined!


&alue do"ains also undeined &alues can be used in the

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2.+ -&out representations

A representation contains the inor"ation that deter"ines how your spatial datashould be represented on screen or in a printout! Representations are ser&ice ob)ects

lin#ed to a do"ain! The do"ain deter"ines what is in a "ap %or a table or a colu"n',

and the representation deines the colors o the do"ain ite"s! There are dierent

types o representations dependin( on the type o do"ain!

More a&out representation class

Class Class do"ains ha&e the "ost strai(htorward representation! A "ap with a class

do"ain should ha&e a representation, otherwise it is i"possible or ILWIS to #now

how to display it! A representation or a class do"ain is always user7deined! The usershould set the color or each class in the class do"ain!

-ouble7clic# poly(on "ap Landuse in the Catalo(! The -isplay FptionsG Poly(on =ap dialo( bo1 is opened!

Accept the deaults in the -isplay Fptions 7 Poly(on =apdialo( bo1 byclic#in( F! The poly(on "ap is displayed!

The Layer =ana(e"entpane shows the Le(endo the Landuse"ap,which is in act, representation Landuse! -ouble7clic# the word Le(endin

the Layer =ana(e"entpane! The Representation Classeditor is opened

Practice with chan(in( colors as e1plained abo&e! Chan(e also so"e colorsby usin( the Edit Ite"%s'button or by openin(the Edit"enu and select7in( Edit Ite"%s'!

Select the Se("enttab and loo# at the representation! Ater that, select thePointtab! Since we can use the sa"e do"ain, and the sa"e representation orraster, poly(on, se("ent and point "aps, these options can used to see what aline would loo# li#e, or a point, or an area!

Ha&e a loo# at the other "enu ite"s and try so"e!

Ater that, close representation Landuse!

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Each ite" in the do"ain has a color assi(ned to it! The colors can be edited by

clic#in( on an ite", and then chan(in( the RedD;reenD

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>or an identiier "ap such as the "ap Citybloc# it would be useless to spend "uch

ti"e in deinin( the color o each indi&idual ite" by hand, since dierent colors do

not represent any the"atic dierence! The colors are only used to "a#e a

dierentiation between the units! Thereore, a user7deined representation is not

needed!

>urther"ore, you will (enerally display I- "aps by one o the attributes ound in the

attribute table o the "ap! >or "ore inor"ation see section 3!2!

More a&out representation *alue

+alue =aps with a &alue do"ain ha&e a representation &alue! @ou can "a#e two types o

representations or &alue "aps* 7arepresentation value, in which boundaries and

inter"ediate li"its appear in &al7

ues

7arepresentation gradual, in which boundaries and inter"ediate li"its appear in

percenta(es! I you use it on a &alue "ap, the percenta(es o the reuency distribu7

tion o pi1el &alues are ta#en ro" the histo(ra"!

In the Catalo(, double7clic# poly(on "ap Citybloc#! In the -isplayFptions 7 Poly(on =apdialo( bo1, you see se&eral options* Sin(le Color,

or =ultiple Color 3, $/or $!

Select the option =ultiple Colors, $ and clic# F!

Close poly(on "ap Citybloc#!

In the Catalo(, clic# do"ain Hei(ht with the ri(ht "ouse button, andselect the Propertiesco""and ro" the conte1t7sensiti&e "enu! The

Propertiessheet is opened! As you can see, do"ain Hei(ht has a represen7

tation &alue called Hei(ht!

Close the Propertiessheet and open representation Hei(htby double7clic#7

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A representation or a &alue do"ain is deined on the basis o a nu"ber o li"itin(

&alues between which the color chan(es ro" one color to another in a nu"ber o

user7deined steps! In this e1a"ple the li"its are 2/66 %the "ini"u" o the do"ain',/66, and .066 %the "a1i"u" &alue o the do"ain'! @ou can insert as "any

inter"ediate li"its as you wish!


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There are also a nu"ber osystem#defined representationsa&ailable! These

representations all use percenta(es as li"its %representations o type (radual', so that

they can be used on dierent types o &alue ran(es!

Clic# the Custo"ie Catalo(button in the Standard toolbaro the =ainwindow! The Custo"ie Catalo(sheet appears!

Fn the Selectiontab, select ob)ect type Representation in the list bo1,select the chec# bo1 Include Syste" Fb)ectsand clic# F! 9ow you will

see only the representations, includin( the syste"7deined ones!

Fpen so"e o these representations to see how the colors are assi(ned to di7erent percenta(e &alues!

Clic# a(ain on the Custo"ie Catalo(button! Select all the ob)ects ro"

the list, clear the chec# bo1Include Syste" Fb)ectsand clic# F!

In the Catalo(, double7clic# the se("ent "ap Contour! The -isplayFptions G Se("ent =apdialo( bo1 is opened!

Select a syste"7deined representation, or e1a"ple RepresentationRedand clic# F! 9ow the contour lines are displayed accordin( to that repre7

sentation!

-ouble7clic# the word Le(endin the Layer =ana(e"entpane! TheRepresentation ;radualeditor is opened! It is not possible to edit this rep7

resentation because it is a syste"7deined one and syste"7deined represen7

Select the Li"it /66, open the Edit"enu and select the Edit Li"itco"7"and orclic# the Edit Li"itbutton in theToolbaro the Representation +alueeditor!

In the Edit Li"itdialo( bo1, chan(e the color to Lawn;reen and clic# F!Fpen theEdit"enu and select Stretch Steps!The Stretch Stepsdialo( bo1 is shown!

Chan(e the Stretch Steps&alue to 6 and clic# F!

Select the word Stretchin the editor! A drop7down list bo1 appears!

Clic# once "ore to open the list bo1 and select the word 8pper! This "eansthat all &alues between the li"its are displayed in the color o the upper li"it!

>ro" the Edit"enu choose Insert Li"it! The Insert Li"itdialo( bo1 appears!Insert a new li"it %+alue.666, Color;old' and clic# F in the Insert Li"itdialo(

bo1!When inished close representation Hei(ht!

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Su""ar( -&out representations

7 A representation contains inor"ation that deter"ines how your spatial data should

be represented on screen or in a printout! Representations are ser&ice ob)ects lin#ed

to a do"ain! The do"ain deter"ines what is in a "ap %or a table or a colu"n', and

the representation deines which colors these do"ain ite"s should ha&e!

7 There are dierent types o representations, dependin( on the type o do"ain!

7 Class do"ains always ha&e a user7deined representation Class!

7 I- do"ains cannot ha&e a user7deined representation! They can only be displayedin $, 3, $/ or $ dierent colors or by one o their attributes %see section 3!2'!

7 +alue do"ains can ha&e two types o representations*

7 representation +alue, usin( actual &alues as li"its

7 representation ;radual, usin( percenta(e &alues as li"its!

See also chapter $ i you want to #now "ore about representations!


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certain 8T= one!

The Catalo(now only shows coordinate syste"s! Fne coordinate syste" was "ade

especially or the data set* Cochaba"ba! The other three %Latlon, LatlonW;S4. and

8n#nown' are standard ones!

A coordinate syste" deines the possible "ini"u" and "a1i"u" ?Bs and @Bs that

can be used in a "ap, and in case o a coordinate syste" o type pro)ection, you can

also store inor"ation on a "apBs pro)ection, ellipsoid andDor datu"! 9or"ally

locations on the earthBs surace are shown in (eo(raphic coordinates!


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The %eograp&ic Coordinateso the earth are e1pressed in Latitudes and Lon(itudes

%see >i(ure 2!2'!'atitudes%parallels' are "easured ro" the euator and "ay ran(e

ro" 6O to 56O 9 or ro" 6O to 56O S! 'ongitudes%"eridians' are "easured ro" the

;reenwich "eridian and "ay ran(e ro" 6O to $46O E o ro" 6O to $46O W!

Figure 2.2 ;eo(raphic coordinate syste"* the location o A is deter"ined by the Lon(itude %'

and the Latitude %'!

The shape o the earth is li#e a ball %spherical' or li#e a Jhoriontal ru(by ball with

lattened polesK %ellipsoidal'! To represent areas ro" this sphere or ellipsoid into a

plain surace, you need a map projection! The earthBs surace can e&en be better

approached i a pro)ection uses a datu"! With the help o a "ap pro)ection,

(eo(raphic coordinates are con&erted into a "etric coordinate syste", "easurin( the? and @ directions in "eters! Practically e&ery country in the world uses its own

coordinate syste", based on a certain pro)ection! Fne o the "ost used pro)ections is

the so7called niversal )ransverse *ercator%8T='!

The 8T= is an international "etric coordinate syste", which co&ers the whole earth

and di&ides it into 06 ones each co&erin( 0O Lon(itude! or

e1a"ple, point data obtained ro" ;PS %;lobal Positionin( Syste"s' "ay ha&e been

re(istered in (eo(raphic coordinates!

ILWIS has three standard coordinate syste"s*

7Latlon* ;eo(raphical coordinates in de(rees!

7LatlonW;S4.* ;eo(raphical coordinate syste" usin( the W;S4. datu"!

78n#nown* When coordinates are not #nown! This coordinate syste" should not be

used!

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>or "ore inor"ation on types o coordinate syste"s and transor"ations, see section

.!2! In (eneral itBs best to create a coordinate o type pro)ection and speciy the

"ini"u" and "a1i"u" ? and @ coordinates o your study area! Pro)ection

inor"ation "ay be added to the coordinate syste" in a later sta(e or not at all!


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In principle, all "aps o the sa"e area should ha&e the sa"e coordinate syste"!

ILWIS assu"es that all "aps that you want to superi"pose or display to(ether in one

"ap window ha&e the sa"e coordinate syste"! -isplayin( "aps with dierent

coordinate syste"s is possible i pro)ection inor"ation is a&ailable or bothcoordinate syste"s! Then the coordinates o a &ector "ap are transor"ed on the ly

accordin( to the coordinate syste" that the "ap window is usin( at the "o"ent! F

course, you can use the Transor" operationsto per"anently transor" coordinates %see

chapter . or "ore inor"ation'!

The use o pro)ections is urther discussed in chapter .!

Su""ar( -&out coordinate s(ste"s

7 A coordinate syste" is a ser&ice ob)ect or point, se("ent and poly(on "aps, and

or (eoreerences %the latter are used by raster "aps and will be treated in the ne1tsection'! +ector "aps and (eoreerences always need a coordinate syste"!

7 A coordinate syste" deines the possible ?@7coordinates or LatLon7coordinates

that can be used in your "aps and thus stores inor"ation on the #ind o coordi7

nates you are usin( in your "aps! @ou "ay or instance use user7deined coordi7

nates, coordinates deined by a national standard or coordinates o a certain 8T=

one!

9ote that the Pro)ectionin the coordinate syste" Cochaba"ba is 8T=, withthe EllipsoidInternational$52.and that the -atu"is Pro&isional

South A"erica $5/0, with the -atu" Area

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7 A coordinate syste" "ay ha&e inor"ation on the "apBs pro)ection, ellipsoid and

datu"!


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>or such calculations you can also use the Co""and lineo the =ain window!

>or satellite i"a(es, scanned aerial photo(raphs and other i"ported i"a(es, which

"ay not be north7oriented, we ha&e another type o (eoreerence* ageoreference

tiepoints!


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In the satellite i"a(e you will see se&en points displayed, which are related to the

se&en points in the Tie Point Tableo the ;eoReerence Tiepointseditor! >or each point

the ?7 and @7coordinates are (i&en, alon( with the Rowand Colu"nlocations o these

points in the i"a(e! Fn the basis o these coordinates usin( an Aine transor"ation,

all rows and colu"ns will be assi(ned ?7 and @7coordinates, with a certain error,

e1pressed as Si("a! In Chapter 0 we will treat the ;eoReerence Tiepointseditor in "uch

"ore detail!

What is i"portant to note here is that the i"a(e is not oriented perectly to the north!

The i"a(e is distorted with respect to a topo(raphic "ap! When you want to o&erlayi"a(es in co"bination with north oriented "aps, you need to re"o&e the distortion

o the i"a(e by resa"plin( it %see chapter 0'!

The (rid lines are displayed in a rotated way! >ro" this you can conclude that the

i"a(e is distorted and not oriented to the north!

In the Catalo(double7clic# (eoreerenceT"(eo! The -isplay Fptions 7Raster =apdialo( bo1 o T"b$ appears! Accept the deaults and clic# F!

The ;eoReerence Editor* T"(eois opened!

-ra( and drop raster "ap Landuse in the "ap window! Raster "ap T"b$will be replaced by raster "ap Landuse! @ou will see that the display o (rid

lines and the contour lines now chan(es! They are now displayed in a north7

oriented way!

Close the "ap window!

Close the ;eoReerence Tiepointseditor by openin( the >ile"enu andselectin( the E1it Editorco""and or by clic#in( the E1it Editorbutton

!

-o not close the "ap T"b$!

Clic# the Add Layerbutton! The Add -ata Layerdialo( bo1 appears!

In the Add -ata Layerdialo( bo1, select se("ent "ap Contour and clic#F, and a(ain Fin the -isplay Fptions 7 Se("ent =apdialo( bo1! TheContour "ap is now displayed on top o the i"a(e!

Fpen the Layers"enu and select Add ;rid Lines! The -isplay Fptions G ;riddialo(bo1 is opened!

In the -isplay Fptions G ;riddialo( bo1 chan(e the Colorto @ellow,accept all other deaults and clic# F! The (rid layer is now displayed on topo the two "ap layers!

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Su""ar( -&out georeferences

7 A (eoreerence is needed or raster "aps and uses a coordinate syste"!

7 A (eoreerence is a ser&ice ob)ect, which stores the relation between the rows and

colu"ns in raster "ap%s' and the (round7coordinates %?, @'!

7 Two types o (eoreerences or raster "aps were discussed here*

7;eoreerence corners, used or raster "aps "ade ro" rasteriin( &ector

"aps, and the resultin( "aps ro" operations on these "aps! A (eoreerence

corners is used or raster "aps that are oriented to the north!

7;eoreerence tiepoints, used or satellite i"a(es, scanned aerial photo7(raphsand other i"ported i"a(es, which "ay not be north7oriented!

7 In the chapters 0 and $6 you will see that there are se&eral other types o (eoreer7

ences!


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2. -ttri&ute data

In sections 2!$ and 2!2 we ha&e loo#ed at the way "aps are stored and displayed inILWIS, either as point, se("ent, poly(on or raster "aps! In the sections 2!. up to and

includin( 2!0 we ha&e also loo#ed at the ser&ice ob)ects that contain inor"ation

about these "aps, such as a do"ain, a representation, a coordinate syste" and a

(eoreerence!

In section $! we ha&e also seen that spatial data %"aps' can be lin#ed to non7spatial,

or attribute data %tables'! In order to be able to lin# a "ap with a table, the units o a

"ap "ust be lin#ed to records in a table! The attribute inor"ation can then be added

in colu"ns! In other words, a "ap and its attribute table should use the sa"e do"ain!

Let us briely chec# this a(ain!

In the Catalo(, select do"ain Landuse, table Landuse and poly(on "apLanduse %hold the Ctrl7#ey down while selectin( the ob)ects'!

Clic# the ri(ht "ouse button and select Fpenro" the conte1t7sensiti&e"enu! All three ob)ects are opened!

=o&e the three windows in such a way that you can see all three ne1t to eachother! Resie the windows i necessary!

Clic# se&eral units in the poly(on "ap! 9ote that the class na"es appear in

the "ap, in the table and in the do"ain!

When inished acti&ate the =ain window, open the Window"enu and select-ata Windows, Close All! All three windows will be closed!

In the Catalo(, select table Landuse, clic# it with the ri(ht "ouse buttonand select Properties! The Properties o Table JLanduseK sheet is opened!

9ote that the do"ain o the table is -o"ain Class JLanduseK! Clic# the

Cancelbutton!

Clic# with the ri(ht "ouse button on poly(on "ap Landuse, and select

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So we can conclude that maps and tables can be lined if t&ey &ave t&e same domain!

Howe&er, there is a &ery i"portant restriction that should be "entioned here! It is

only possible to ha&e an attribute table with a class do"ain, or with an I- do"ain!

Tables with a &alue do"ain are not possible! The reason or that is* 7 Suppose you

ha&e deined a &alue do"ain with "ini"u" 6 and "a1i"u" $6666,

and a precision o 6!6$! In that case, a table connected to the "ap should ha&e a &ery

lar(e nu"ber o records %$6666$66 N $,666,666'! The nu"ber o records and the

e1tre"e sie o a table will beco"e a proble"!

7 A "ore i"portant reason, howe&er, is that &alue "aps the"sel&es do not contain

inor"ation to which attributes they can be lin#ed! They are in act attribute "aps,

and not the"atic "aps! The Landuse "ap %with a class do"ain' can ha&e an


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attribute table, in which or each land use type inor"ation is (i&en, such as the

bio"es production per hectare, the &alue o the land per hectare, etc!

7 The Citybloc# "ap %with do"ain I-' can ha&e an attribute table in which inor7"ation is stored or each city bloc#, such as the nu"ber o people li&in( in the

bloc#, the nu"ber o houses, public buildin(s, shops, etc!

7 A &alue "ap, on the other hand, such as the se("ent "ap Contour, contains &al7

ues, representin( a certain pheno"enon %in this case terrain ele&ation'! It is dii7

cult to i"a(ine which attributes could be lin#ed with such inor"ation, other than

purely statistic inor"ation %e!(! the len(th o each line'!

The lin#in( o "aps with attribute tables is useul i you want to substitute the units

o a "ap with an attribute &alue ro" the connected table %a process called

renumbering'! In that case you (enerate an attribute "ap!

Althou(h &alue "aps cannot be lin#ed to attribute tables, you can (enerate tables ro"

&alue "aps! The "ost i"portant ones are cross tables and histo(ra"s! These are not

used, howe&er, to renu"ber the &alue "aps! It would "a#e no sense to replace the -9

&alues %relectance &alues' o a satellite i"a(e with the area attribute ro" its

histo(ra"!

Su""ar( -ttri&ute data

7 =aps and tables can be lin#ed only i they ha&e the sa"e do"ain!

7 Fnly "aps with a class or I- do"ain can be lin#ed to attribute tables! +alue "aps

cannot be lin#ed to tables!

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2.# iel Infor"ation indo

ILWIS has a special tool with which you can e1a"ine "ultiple "aps and lin#edtables si"ultaneously* thepixel information -indo-! A pi1el inor"ation window is

used to interacti&ely inspect coordinates, class na"es, I-s or pi1el &alues, in one or

"ore "aps and attribute &alues o "ap7related tables! A pi1el inor"ation window

shows inor"ation at the position o the "ouse pointer in a "ap window!

A pi1el inor"ation window consists o "any ite"s that you ha&e seen beore in "apand table windows, such as a Control7"enu icon , Title bar, =enu bar, Status bar, etc!


Fpen poly(on "ap Landuse!

In the "ap window, open the >ile"enu and select Fpen Pi1el Inor"ation!The pi1el inor"ation window %>i(ure 2!' is opened!

Position both windows ne1t to each other and "o&e the "ouse pointer o&er

Figure 2.3An ILWIS Pi1el Inor"ation window!

FptionsandHelp!

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So"e special ite"s in this window are*

Top let button* the upper let (ray button in the pi1el inor"ation window can be

used to open the Custo"ie Pi1el Inodialo( bo1!

Inor"ation &iewer* where the inor"ation o the selected data ob)ects or the actual

position o the "ouse pointer in a "ap window is displayed!

=enu bar*the "enus o the ILWIS pi1el inor"ation window are* >ile, Edit,

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I you want to display inor"ation on "aps and tables in the pi1el inor"ationwindow, you "ust "a#e sure that at least one "ap is displayed in a "ap window, and

that the "aps are lin#ed to their attribute tables!

We will now add "ap ;eo"orpholo(y to the pi1el inor"ation window to read the

inor"ation ro" this "ap, alon( with that o the Landuse "ap!

It is possible to hide or to show "aps and attributes in a pi1el inor"ation window*


To (et "ore inor"ation on a pi1el inor"ation window, press the >$7#ey oropen the Help "enu and select Help on this Window!

-ra( and drop the poly(on "ap ;eo"orpholo(y ro" the Catalo(to thepi1el inor"ation window!

Position the "ouse pointer in the "ap window!

In the pi1el inor"ation window, you can read the inor"ation o the "ap7pin( unit in "ap ;eo"orpholo(y, and o the "appin( unit in "ap

Landuse at the sa"e location!

Clic# the Top let buttonin the pi1el inor"ation window or open theFptions"enu and select the Custo"ieco""and! The Custo"ie Pi1el

Inodialo( bo1 appears! continuously!

-eselect all colu"ns o table ;eo"orpholo(y and clic# F!

When you now "o&e with the "ouse pointer o&er the "ap you will see thatno inor"ation is (i&en on the table ;eo"orpholo(y!

Close the pi1el inor"ation window by double7clic#in( the Control "enuicon!

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The Custo"ie Pi1el Inodialo( bo1 shows a list o "aps, tables and colu"ns that are

presently &isible in the pi1el inor"ation window! The list bo1Show &alues o can be

used to select the "aps, tables or colu"ns you would li#e to see! @ou can select or

deselect the" by clic#in( on the"! Selected ite"s appear hi(hli(hted! With the chec#

bo1es you can deine i the inor"ation is displayed when wor#in( with a =ouse

pointer or with a -i(itiercursor, and whether the inor"ation should be displayed

continuously %while "o&in( o&er the "ap', or only when you clic# a unit!

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Su""ar( iel Infor"ation indo

7 A pi1el inor"ation window is used to interacti&ely inspect coordinates, class

na"es, I-s or pi1el &alues in one or "ore "aps and attribute &alues o "ap7related

tables!

7 A pi1el inor"ation window shows inor"ation at the position o the "ouse pointer

in a "ap window!


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2.4 )etails *ie of a 5atalog

@ou can choose to see the ob)ects in a Catalo(listed in List +iewor in -etails+iew! The List +iewoption (i&es a si"ple list o ob)ect na"es and icons! The

-etails +iewshows detailed inor"ation or each ob)ect!

The -etails +iewis a table with colu"ns that (i&e you e1tra inor"ation onindi&idual ob)ects such as* dependent or not, used do"ainD(eoreerenceDcoordinate

syste", description, e1pression, etc! To chan(e the order o the colu"ns in the

Catalo(*

To chan(e the width o a colu"n in the Catalo(*

-ra( and drop a colu"n header horiontally to another position!

-ra( the &ertical line which separates two colu"n headers to the let or ri(ht!

Clic# colu"n header9a"e! The ob)ects will now be sorted descendin(ly!Clic# the colu"n header9a"eonce "ore! The ob)ects are sorted ascendin(7

ly a(ain!

Clic# the ri(ht "ouse button in the white space o the Catalo(, choose theSort

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The Catalo(is by deault ordered ascendin(ly by9a"ebut you can order the ob)ects

descendin(ly or use another sortin( "ethod %e!(! by Type, Sie, Attribute, etc!'!

Sortin( ascendin(ly and descendin(ly can be used on any colu"n! @ou can also sort

ob)ects when in List +iew! To return to the ori(inal situation*

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7 In ILWIS you can see ob)ects in a Catalo(in List +iewor in -etails +iew!

7 The -etails +iewis a table with colu"ns that (i&e you e1tra inor"ation on indi7

&idual ob)ects!

7 In each Catalo(, you can speciy the &isible ob)ect types, the sortin( "ethod o

ob)ects, and a uery to search or speciic ob)ects!

7 @ou can use predeined ueries but you can also construct your own ueries!


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2.10 %&'ect properties and dependenc( lin6s

As shown in precedin( sections, dierent data ob)ects %point, se("ent, poly(onand raster "aps' and ser&ice ob)ects %do"ains, representations, coordinate

syste"s and (eoreerences' are reuired to or" a "ap in ILWIS! How does

ILWIS #now which ob)ects are lin#ed

Thepropertieso an ob)ect show which ser&ice ob)ects are used or a data ob)ect

or another ser&ice ob)ect! In section 2!2 you saw that or the display o &ector

"aps, you need to ha&e a coordinate syste", a do"ain and a representation

%dependin( on the do"ain' and that a raster "ap reuires the sa"e ob)ects, plus the

(eoreerence! In section 2!3 it was shown that class and I- "aps could also be

lin#ed to attribute tables!

In >i(ures 2!. and 2!/, a sche"atic representation is shown o the properties o

&ector and raster "aps! The properties o &ector "aps with a class do"ain,

identiier and &alue do"ain are shown in >i(ure 2!.!

The ob)ects indicated in the shaded bo1es are the data ob)ects %i!e! point, se("ent,

poly(on "aps and tables' and the ob)ects outside o these bo1es are the ser&ice

ob)ects! The arrows indicate the relations between the ob)ects! >or e1a"ple, in

>i(ure 2!., a do"ain is used by a &ector "ap %either a point, se("ent, or poly(on

"ap', by a table, and by a representation!

All the properties o an ob)ect can be &iewed ro" their Propertiessheet!

Clic# in the Catalo(with the ri(ht "ouse button on class do"ainLanduse, and select Propertiesro" the conte1t7sensiti&e "enu! The

Propertiessheet is opened!

Clic# the 8sed

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A list o ob)ects is shown which use this do"ain Landuse* raster "ap Landuse,

poly(on "ap Landuse, table Landuse, and representation Landuse!

To understand the >i(ures 2!. and 2!/ it is (ood to loo# at the properties o

se&eral "aps!


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Figure 2.+The properties o &ector "aps with a Class, Identiier and +alue do"ain in ILWIS! The data ob)ects are

shown in a shaded bo1!

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Figure 2./The properties o raster "aps with a Class, Identiier, and +alue do"ain in ILWIS! The data ob)ects are

shown in a shaded bo1!

The properties o tables and colu"ns are sche"atically represented in >i(ure 2!0! A

table should ha&e a class or I- do"ain! A table contains a nu"ber o colu"ns! Each


Co"pare the result with >i(ure 2!. and close the Propertiessheet ater7wards!

Repeat this or &alue do"ain Hei(ht! This do"ain is used by se("ent "apContour and by representation Hei(ht! Co"pare with >i(ure 2!.!

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colu"n also has a do"ain %e!(! class, I-, &alue or other special do"ains such as

color, strin(,

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Futput "aps thus #now how they are created and on which input "aps, tables or

colu"ns they

depend! Such output

"aps are called dependent data objects! The sa"e applies or tables and colu"ns! The

operation or e1pression stored inside the dependent data ob)ect is called the definition!

Let us loo# at an e1a"ple! Poly(on "ap Landuse was used in co"bination with the

(eoreerence Cochaba"ba to (enerate a raster "ap Landuse! This is shown

sche"atically in >i(ure 2!3!

The dependent raster "ap, which is the result o the Poly(on to Rasteroperation %i!e! the

Rasterie Poly(on =apoperation', contains inor"ation on the source ob)ects ro"

which it was created! In this case a poly(on "ap and a (eoreerence! Let us chec# this

Clic# in the Catalo(with the ri(ht "ouse button on raster "ap Landuseand select Propertiesro" the conte1t7sensiti&e "enu! The Properties

sheet with the title Properties o -ependent Raster =ap JLanduseKis

opened %see >i(ure 2!4'!

Figure 2. The dependency lin# between ob)ects! The output raster "ap is "ade ro" a poly7

(on "ap and a (eoreerence, usin( the Poly(on to Raster operation!

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e1a"ple in the data set!


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The Raster =aptab (i&es you inor"ation on the ser&ice ob)ects o this "ap and

inor"ation on how the "ap was "ade %i!e! the -einition'*

=apRasteriePoly(on%Landuse!"pa,Cochaba"ba!(r'

Where*=apRasteriePoly(on is the Poly(on to Rasteroperation

Landuse!"pa is the poly(on "ap Landuse used to (enerate this "ap, and

Cochaba"ba!(r is the (eoreerence Cochaba"ba used to (enerate this "ap!

Why does ILWIS #eep trac# o the ob)ects that are used to (enerate another one

When you update input source "aps, tables or colu"ns by editin(, the dependent

output "aps, tables or colu"ns which use these source ob)ects can be easily

recalculated!

Figure 2.# E1a"ple o a Properties sheet!

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This "eans that none o the source ob)ects %i!e! poly(on "ap Landuse and

(eoreerence Cochaba"ba' ha&e been updated since the dependent raster "ap was

(enerated! @ou can &eriy this by e1a"inin( the Catalo(!

9ow we are (oin( to update the source "ap Landuse!


Clic# on the -ependencytab! 9ote that the line below the e1pression=apRasteriePoly(on%Landuse!"pa, Cochaba"ba!(r'says*

Fb)ect is up7to7date!

Close the Propertiessheet o raster "ap Landuse!

Acti&ate the =ain window and chec# the colu"ns -, C, 8and =odiiedinthe Catalo(%-etails +iew'! @ou will see that all the "aps are "odiied on

the sa"e date and ti"e and that raster "ap Landuse is -ependent%-',

Calculated%C' and 8p7to7-ate%8'!

In the Catalo(clic# with the ri(ht "ouse button on poly(on "ap Landuseand select Editro" the conte1t7sensiti&e "enu!

In the Poly(oneditor chan(e or e1a"ple the poly(on La#e, near the 8rbancentre, into 8rban peripheryand close the window aterwards!

Fpen the Propertiessheet o raster "ap Landuse! Fn the -ependencytab you see* Fb)ect is not up7to7date*

Landuse!"pa%day date ti"e'!

Clic# the =a#e 8p7to7-atebutton! A Chec# 8p7to7date"essa(e appearswith the uestion -ependent raster "ap JLanduseK is not up7to7

date! Recalculate it to"a#e itup7to7date

Answer @esto this uestion to recalculate the "ap!

Fpen the Propertiessheet o raster "ap Landuse! Fn the -ependency

tab ou see that the Fb ect is u 7to7datea ain!

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The poly(on "ap is updated now! In the Catalo(o the =ain window you can see

that the poly(on "ap Landuse has been "odiied and that raster "ap Landuse is

now -ependent%-', Calculated%C' and9ot 8p7to7-ate%9'!

It is i"portant to #eep in "ind that dependent "aps are not auto"atically updated!

ILWIS does #eep trac# o the dates and ti"es at which the source ob)ects were

"odiied! Fnly when you clic# the button =a#e 8p7to7-ateon the -ependency tab o

the Propertiessheet, ILWIS will as# you i you want to recalculate the "ap!

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MIn the Preerenceso the =ain window, you can select the chec# bo1 ;i&e aWarnin( when an ob)ect is not up7to7date! I you select this chec# bo1 ILWIS

(i&es you a warnin( when you want to open an ob)ect that is not up7to7date any7

"ore!

There are so"e other i"portant ad&anta(es o the use o dependencies*

7 >or "aps, tables or colu"ns that are created &ia the =apCalcand TabCalc

e1pressions, you can chan(e the deinition o the dependent output data ob)ects so

you can do a si"ilar calculation a(ain with dierent para"eters without ha&in( to

create a new "ap, table, or colu"n!

7 @ou can release dis# space* it is possible to delete the iles that contain the actual

data &alues %e!(! !=P and T

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as $ byte! So you sa&e 5203 N /504. bytes o dis# space, without losin( any

actual inor"ation!

@ou will see that the contents o the sheet ha&e chan(ed! Fn the ;eneraltab, note

the sie o the ob)ect* 4$. bytes! This a"ount o stora(e space is needed or the

inor"ation o the ob)ect deinition ile! Fn the -ependencytab, you now ind a

button Calculate!

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depend lar(ely on the type o do"ain which is used!

7 The lin# between output data ob)ects, obtained ro" other input data ob)ects

throu(h an ILWIS operation is deined by dependency lin#s!

7 =aps, tables and colu"ns are ori(inally when they are di(itied, i"ported or creat7ed by typin(! These ob)ects are called source ob)ects

7 Futput "aps, tables and colu"ns which are created throu(h a calculation or an

operation are called dependent ob)ects!

7 The concept o dependency has a nu"ber o i"portant ad&anta(es*

.asy update* when you ha&e new inor"ation and you edited input "aps, tables

or colu"ns accordin(ly, the dependent output "aps, tables or colu"ns can be

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2.11 7o to use geograpic data in ILWIS

Ater you ha&e loo#ed uite e1tensi&ely at the way (eo(raphical data is stored in a

;eo(raphic Inor"ation Syste" li#e ILWIS, it is i"portant to as# yoursel now what

you will do with it! In (eneral, there are our dierent phases that you ha&e to (o

throu(h when you wor# with (eo(raphic data*

@ou need to ensure that your spatial and non7spatial data is a&ailable in di(ital or"

in your co"puter! How you do this depends lar(ely on the data type! >or instance,

you can di(itie "aps and you can type tabular data! ILWIS can con&ert data iles

deri&ed ro" scannin(, or you can i"port other di(ital or"ats as inputs! Throu(h

i"a(e processin(, ILWIS enables data input ro" re"otely sensed i"a(es! The

aspects o spatial data input will be dealt with in the ne1t chapter %chapter '!

)ata "anage"ent

-ata can be stored in and retrie&ed with ILWIS! The data "ana(e"ent in ILWIS

e"phasies eiciency o stora(e and retrie&al! >ile or"ats used are con&ertible so

dierent data types can be co"bined! =any aspects o data

"ana(e"ent in ILWIS will be treated in chapter . %on spatial

data' and in chapter / %on attribute data'!

-ata analysis is the "ost i"portant eature o ILWIS, ualiyin( it as an analytical

;IS pac#a(e! -ata analysis is the process in which you (enerate inor"ation that is

useul or sol&in( a particular proble"! When the data is in the or" o satellite

i"a(es, the data analysis is also called di(ital i"a(e processin(! The ob)ecti&e is to

(enerate i"a(es that can be interpreted by e1perts, or to (enerate classiication

results, containin( the"atic inor"ation on eatures such as land use, litholo(y, etc!

The &arious ILWIS operations on i"a(e processin( will be co&ered in chapter 0!

Fther data analysis techniues dealin( with "aps, co"bined with tables, will be

treated in the chapters 3 to $2 which ha&e an increasin( de(ree o co"ple1ity!

The inal ob)ecti&e o wor#in( with a ;IS such as ILWIS is to produce useul output

results! 8sin( ILWIS you can show your results on the screen, as hard copy output

%printed data' or as sot copy %iles to be used urther in ILWIS or in other sotware

)ata input

)ata anal(sis

)ata output

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