tutorial: theme mapping - microimages, inc. · a theme map is a screen display or print that...

ThemeMapping

Tutorial

TNTedit™TNTview®

with

TNTmips®

THEME

MAPPING

Theme Mapping

Before Getting StartedA theme map is a screen display or print that portrays graphical elements usingcolor, patterns, or symbolism to convey information about the relative value of anumeric attribute associated with the element, such as yield, population, orelevation. Generally, a range of styles, such as a color spread, is used to representthe range of values for the attribute. Through a series of exercises, this bookletfamiliarizes you with the powerful theme mapping functions that are part of thevisualization process in TNTmips®, TNTedit™, and TNTview®. Theme mapscan be incorporated in a TNTatlas®, but they can’t be created while running one.

Prerequisite Skills This booklet assumes you have completed the exercises inthe Displaying Geospatial Data and TNT Product Concepts tutorial booklets.The exercises in those booklets provide basic knowledge on how to use the TNTproducts including how to select and view raster, vector, CAD, TIN, and databaseobjects stored in Project Files. Please be sure you remember how to add and removelayers from a multilayer view. You should also know how to set up and select yourprinter. This booklet does not present these basic skills again.

Sample Data The exercises presented in this booklet use sample data distributedwith the TNT products. If you do not have access to a TNT products DVD, youcan download the data from MicroImages’ web site. Many of the exercises usethe COUNTY object in the NEBRASKA Project File in the THEMEMAP directory of DATA. Theobjects in the GS_THEME Project File in this directory are also used.

More Documentation This booklet is intended only as an introduction to thefunctions in Theme Mapping.

TNTmips® Pro and TNTmips Free TNTmips (the Map and Image ProcessingSystem) comes in three versions: the professional version of TNTmips (TNTmipsPro), the low cost TNTmips Basic version, and the TNTmips Free version. Allversions run exactly the same code from the TNT products DVD. If you did notpurchase the professional version (which requires a software license key) orTNTmips Basic, then TNTmips operates in TNTmips Free mode.

This booklet refers to TNTmips, TNTedit, TNTmips Free, and TNTview as “TNT.”Since the display features in all four products are essentially the same, you willbe able to follow these exercises no matter which product you have.

You can print or read this booklet in color from MicroImages’ web site. The website is also your source of the newest tutorial booklets on other topics. You candownload an installation guide, sample data, and the latest version ofTNTmips.

Merri P. Skrdla, Ph.D., 10 August 2012©MicroImages, Inc. 2003–2012

http://www.microimages.com

Theme Mapping

Welcome to Theme MappingGeodata stored as vector, CAD, and TIN objects canmake use of associated database information fordrawing style assignment by attribute value. Data-base information can be quantitative or qualitative.The TNT products provide three methods for usingassociated attributes to assign display styles. Thesemethods are referred to as style By Attribute, ByTheme, and By Script.

Style By Attribute lets you assign a drawing style toeach attribute value. Such displays are best suitedfor qualitative data, such as soil type or land use.Style By Theme requires quantitative attributes andis not available for CAD objects. Style By Script issuitable for quantitative or qualitative attributes, butrequires specific knowledge for constructing scripts(database queries).

Quantitative data presents the possibility of convey-ing where in the range of values an element falls, aswell as whether it is the same or different than otherelements. Theme Mapping is a powerful means tolook at trends and classes present in the databaseinformation associated with vector and shape ob-jects without the need for you to design the scriptsrequired to identify the classes and assign meaning-ful styles. Theme Mapping treats the values in adesignated field statistically and assigns styles tothe classes identified according to the parametersyou specify. The approach used to assign drawingstyles based on the distribution of values in a data-base field is essentially an interactive interface for aspecialized database query.

Themes are maintained using style assignment tablesand style objects just as when drawing style isassigned by attribute. Thus, in order to create or edita theme, you have to be able to write to the file.Consult the TNT Product Concepts booklet for de-tails on copying objects or use your operating sys-tem.

Pages 4–11 provide in-struction for creating atheme map, adding a leg-end, and printing the result.Pages 12–16 lead youthrough adding a computedfield to get new informationout of your existing data-base and creating andprinting a theme map basedon that information. Page17–20 introduce thememapping for points andlines, and pages 21–23describe interactive thememapping tools and options.

launch TNT

use the File Manageror your operating sys-tem to copy the ProjectFiles in the THEMEMAP

data collection to yourlocal drive

STEPS

Vocabulary: A theme mapis a color coded map withthe coloration related to therelative amount of somevariable, or attribute. Anattribute is a distinguishingcharacteristic stored in adatabase and associatedwith an element in a geo-metric object (vector, CAD,shape, or TIN) or with cellsin a raster object. Attributescan be qualitative (soil type,land use) or quantitative(yield, population).

Theme Mapping

Selecting Your First ThemeThemes can be created for point, line, and polygonelements. First we’ll design a vector polygon themebased on population. When a theme has alreadybeen created, you can set the element Style optionto By Theme, and the last selected theme will beused. In order to create a theme, you need to clickon the Edit button next to the Style option. TheSelect Table / Field window then opens if the objecthas never been used for theme mapping. If a themehas been created previously, you go directly to theTheme Mapping Controls window shown on thenext page and see the Select Table / Field windowagain only when you choose New from the Thememenu or click on the Attribute button.

When the Select Table / Field window initiallyopens, all the tables in the database for the selectedelement type are shown in the list at the left of thewindow, and the Field list is blank until you selecta table. You then select a field from those listed andyour theme has been identified. Themes can bedeveloped for quantitative data only. However, you

Vocabulary: A drawingstyle associates a namewith element drawing speci-fications, such as pointsize, line weight, whetherand how to fill polygons, andwhether to use simple orsymbolic representationsfor an element.

STEPS select Main / Display

from the TNTmips menu

choose Options / ViewOptions in the DisplayManager, click on theView tab; turn on the De-fault to redraw primaryviews after any changebutton on the View panel,and click [OK]

click on the New icon,choose 2D Display,and select the COUNTY ob-ject from the NEBRASKA

Project File

click on theLayer Controlsicon for theCOUNTY layer inthe DisplayManager

check thatpolygon Selectis set to All

set polygonStyle to New -by Theme

click on Popu-lation_1990 in theTable list

click on Population inthe Field list

click on [OK] to con-firm your selectionand proceed to the de-sign phase

are not preventedfrom selecting astring field becauseit may contain nu-meric values, such asdata imported from acomma separatedvalues (csv) file. Ifall minimum andmaximum values arelisted as zero whenthe Theme MappingControls windowopens, you havepicked a field that isinappropriate fortheme mapping.

Theme Mapping

Theme Mapping ControlsThe Theme Mapping Controls window opens al-ready customized to the range of values in the fieldyou selected, but with default parameter settings,such as the number of classes and the methods fordetermining the count and the distribution. You cankeep these defaults or make changes to better reflectyour theme mapping needs. You can use Save AsDefault on the Theme menu at any time to alter thedefault settings used for subsequent new themes toyour current settings.

The Options menulets you set whetherthe histogram is dis-played as a curve orwith bars and whetherits scale is linear orlogarithmic.

The Theme menu lets youstart a new theme, open anexisting theme, savechanges with the same or adifferent name, set new de-faults, and close the themewindow.

This panel shows the break-down of values for each classand the drawing style assigned.The panel scrolls when thetheme is divided into more thanfive classes.

The Count choices are: ByReference; By ElementSize, which requires a stan-dard attributes table in orderto be active; and AllRecords, which counts eachrecord only once regardlessof the number of elementsattached to it.

The Distributionchoices are: EqualCount, Equal Inter-val, and User De-fined.

Rounding options are: None,Closest, Down, and Up.

The bottom panel lets you set the drawing style for each classeither automatically or manually. When theme mapping pointsor lines, there is an additional panel for size or width spread.

A graphic representation of thedistribution with class bound-aries indicated by dashed lines.

Click here to select adifferent table / fieldfor the theme map.

Theme Mapping

Modifying and Saving a ThemeLet’s make a couple of changes to thedefault settings for this theme map, whichis designed to convey relative population.Because Nebraska has 93 counties, we canreasonably assign more than the defaultfive population classes. We would have togo to 31 classes, which is a bit excessive,to get an equal number in each class; solet’s just go with eight. You want to be ableto distinguish the classes from one an-other, and it is difficult to readily distin-guish more than 10 or 12 classes with thecolor spread method for assigning draw-ing styles. Let’s also set the roundingfunction to round to the closest multiple of10. Up and down are also offered as round-ing options. The default sets rounding tonone.

Database structure is important in theme mapping.For applications where a single entity, such as a state,may have multiple polygons with a single value thatapplies to all, you want to make sure that there is onlya single record for each state and that all the poly-gons are associated with this one record. A stateoutline map of the USA with upper and lower Michi-gan or California and the islands off its coast pro-vides examples of such situations. The adjustmentsthat need to be made in theme mapping for thesecircum-stancesare dis-c u s s e din a latere x e r -cise.

change the value in theClasses field to 8

choose Closest from theRounding option menuand enter 10 in the field toits right

choose Close from theTheme menu

click on [Yes] when asked“Save changes beforeclosing?”

click on [OK] to acceptthe default name anddescription in the Selecttable to save theme aswindow that opens

click on the Lines tab andcheck that the Select op-tion for line elements isset to All

click on [OK] in the Vec-tor Layer Controls win-dow

STEPS

Vocabulary: A style as-signment table keeps trackof which styles to use whendrawing elements with aparticular attribute value.

Theme Mapping

Keep the Spa-tial Data Dis-play processand the currentlayout openuntil you haveadded a leg-end, printed theresults, andsaved the lay-out (throughthe top of page12).

Making the Transition to a Layout

STEPS

right-click on the groupname in the Display Man-ager window and chooseClose Group

click on the Newicon and choosePage Layout

click on the AddObjects icon in theDisplay Manager, andselect the COUNTY objectfor which you created thetheme in the last exer-cise

click on the Settingsicon for Group 1, thenon the Layout tab of theGroup Settings window

toggle off the Auto-Re-draw button at the upperright of the window andenter 4200000 in the AtScale field (yes, that’s 4.2million)

click on the Redraw iconif vector object has notdrawn

You have now createdand saved a theme map.This theme map breaksthe county populationsfor Nebraska into eightclasses, which are dis-played in an incremen-tal color spread fromcyan (lowest popula-tion) to yellow (highestpopulation). It would be nice to see the actualpopulation ranges associated with each color, whichcan be achieved onscreen in the View window leg-end or by adding a legend object, which is needed toprovide values in a printed map. You need to be ineither Page or Display layout mode to add a legendobject in the View window.

There are five tabbed panels in the Group Settingswindow. We use only Layout-panel options in thisexercise.

Theme Mapping

Start a Legend for Your Theme MapThe Add Legend icon is on the toolbar in the DisplayManager window, along with the icons for addingtext and scale bars, because these icons add a newgroup that contains the specified layer type to thelayout. These layer types require separate groupsbecause they cannot be combined in georeferencedoverlay with other layers and usually require inde-pendent positioning in a layout. The group will benamed to match its legend object. The Add Legendicon adds multi-object legends; other legend typesare selected from the Add menu.

The only tricky part about creating a legend for atheme map is locating the style object for the theme.It is maintained as a subobject of the theme styleassignment table, which is in the database with thetable used to provide the theme values. This is alogical place to store the style object so that thestyles don’t get separated from the theme, however,it’s much deeper in the RVC file structure than youmay have navigated before.

The Legend Layer Controls window opens after youhave selected a legend object and, if it is a newlegend object, the style object for the legend. Theentries you make are retained as defaults.

STEPS choose Add / Legend /

Add Polygon Legend inthe Display Manager

navigate to the ProjectFile that contains thecounty population thememap and enter COUNTY

POPULATION in the New Ob-ject Name field in the “Se-lect legend object to use”window

click on [OK] in the Selectlegend object to use win-dow

navigate to the same fileand click on your COUNTY

object icon in the“Select style object touse” window

next click on the POLYDATA

icon, then thePOPULATION_1990_POPULATION

tableicon, and finally thePOPULATION_1990_POPULATION

styleobject icon

(theme)styleobject

text styles for heading and label text

number ofcolumnsand flow

legend object

backgroundcolor ortransparent

map scalefor sizes

size ofsampleblock

sample block posi-tion relative tomulti-line label

spacebetweenlegend com-ponents

Theme Mapping

Setting Legend ParametersYou could click on the OK button at this point andsee what you’ve got, because the legend labels andsample color blocks are determined by the themestyle object, which means you have a completelegend at this point. However, unless you set somesizing parameters or at least confirm they are appro-priate for this example, you may end up with alegend too small to be legible or so large that itobliterates the map. Also, we’re going to print thistheme map, so the size should be appropriate forletter size paper.

After you click OK in the Legend Layer Controlswindow, you’ll find you have two groups listed inthe Display Manager window. Legends are alwaysplaced in a group by themselves since they lackgeoreference information and also require indepen-dent positioning. The display process automati-cally places newly added groups centered on thepage in Page Layout mode. Groups are automati-

cally tiled in Display Lay-out mode until you startmaking attachments.

STEPS in the Sample Size panel

set Units to mm, Height to3.0, and Width to 4.0

make the following set-tings for spacing: Line2.0, Column 6.0, Label2.5, and Margin 0

choose Layout Map Scaleon the At: option button

set the number of col-umns to 2 and check thatthe orientation option isDown then Across

click on [Label Style]

click on [Font] and choosearial.ttf or a similar fontyou have, then click [OK]

set the Foreground Colorto black, the style to Nor-mal, and the AscenderHeight to 8.0 Points, thenclick [OK]

click on [Colors], click onthe Transparent toggle,then click [OK]

click [OK] in the LegendLayer Controls window

chooseNormal

chooseblack

click here

Theme Mapping

The Group Settings window should still be openfrom the exercise on page 7. The Group Name willautomatically update in this window to that of thelegend object because the group containing the leg-end became the active group when it was added.

The automatic tiled placement of groups you get inthe Display Layout mode is replaced by automaticcentering on the page in Page Layout mode. Yourlegend will, thus, initially appear centered overNebraska. You just need to change the VerticalAttachment so it will appear below Nebraska but stillcentered on the page. Printer margins are oftenasymmetric so if you want a group centered, it isbetter to use page than margin attachment.

Positioning the LegendSTEPS click on [To…] in the Ver-

tical Attachment panel

double click on Group 1in the window that opens

set the option menu forVertical Attachment toTop to Bottom

set the Units option menuto millimeters and enter5.0 in the Spacing field

click on [Refresh] in theGroup Settings window(or the Refresh icon onthe View window toolbar)

click on [Close] in theGroup Settings window

All the Groups in the View (with theexception of the active group), aswell as Page and Margin appear inthe window for attachment selection.

page margin

Theme Mapping

Printing a Theme MapSTEPS choose Print from the

Display menu in the Dis-play Manager window

make sure that your de-sired printer and destina-tion are selected on thePrinter panel

click on the Dithering tab,check that the Non-Ras-ter Dither Pattern is set toVector Pattern*, and setthe Print-Raster to Tem-porary if not set that wayalready

click on the Size tab andcheck that the Map Scaleis 4200000

set the media size to A,A4, 8.5 x 11, or lettersize depending on yourprinter and check thatthe orientation is set toportrait

The default printer is always the last selected printer,so you should be set to go from your printingexercise in the Displaying Spatial Data booklet. Itis a good idea to check your Page Setup the first timeyou print in each display session, because someonemay have used your computer and changed thesettings.

Your printed product should be high quality withcrisp lines and text. The text, in fact, should be morereadable than it is on-screen at the same map scale.If you need to be convinced, type 4200000 into theZoom/ViewScale field in the sidebar of the Viewwindow (turn on the Show Sidebar and Show Statustoggles on the Options menu in the View window ifthe Scale field isn’t showing). For your display scaleto be the map scale entered, you need to enter yourscreen dimensions on the Measure tabbed panel ofthe MicroImages X Server Preferences window.

If you want labels for your counties, set the Dynamic LabelsText option button in the Polygons panel of the Vector LayerControls window to By Attribute, click on [Specify] and selectthe CNTY_NAME field in the Counties table. Labels with a 5 pointascender height at the design map scale work well for this ob-ject. Enhanced type is also a good idea for labels so they canbe read over both dark and light polygon fill colors.

*If you let your operatingsystem do the dithering,the Non-Raster DitherPattern button will not beactive and you need toclick on the Model buttonon theprinterpanel tocheckmostsettings.

check that the FullPage toggle is on

click [Print] to beginprinting

portraitorientation

Theme Mapping

Setting Up a New Theme LayoutSTEPS click on the Save

Display icon on theDisplay Manager toolbarand create a new objectin the Project File with theother Nebraska objects

click on the expand icon(+) for the COUNTY layer(you will have to first ex-pand Group 1 if you ex-ited the Display process)

click on the expand iconfor polygons

hold the right mouse but-ton down anywhere overthe name or description ofthe Population_1990 tableand select Propertiesfrom the menu that popsup

click on the Field tab inthe window that opens

We are not going to use the layout you just printedagain in this booklet, but you may as well have alayout that associates the population theme and itslegend. In this exercise, we are going to create asecond theme for the same object. You could exitthe Display process after Step 1 and restart on Step2 on this page by opening the layout when you areready to continue. To open a layout, click on theOpen icon on the Display Manager toolbar andselect the layout.

Although you will be creating a new theme map,which means you’ll also need a new legend, don’tdelete the legend group. This group can be used toadd a new legend that has the same position relativeto the theme map as the original legend. If the groupis deleted, this positioning information is lost.

You don’t need to turn on polygon selection to edita table in the database and we are not going to selectany elements.For future refer-ence, opening atable automati-cally turns onselection for thecorrespondingelement type.

All tables have aright mouse buttonmenu.

You can also openthe Table Propertieswindow by clickingon this icon.

The Table Properties win-dow lets you add and deletefields and set other tableparameters.

Theme Mapping

click on Population in thelist at the left of the win-dow, then on the AddField icon above thelist

change the field name toPopDensity by editingdirectly in the list

set the Field Type toComputed

set the number of Placesto 4 (leave Width at 11)

click on [Edit Expression]

in the Query window type

New Information from Existing TablesWe are going to add a computed field to the Popu-lation_1990 table that calculates population densityfor each of the counties using the Population field inthat table and the area from the standard attributestable (POLYSTATS). Highlighting the Population fieldbefore clicking on Add serves two purposes—thenew field is then the last field instead of beinginserted between the two existing fields, and it picksup its defaults, such as field width, from the Popula-tion field. The factor of a million in the equation isnecessary to get population density expressed inpeople per square kilometer. If you’d rather havepopulation density expressed per square mile, re-

Population_1990.Population 1000000 / POLYSTATS.Area*

Set the Field Typeto Computed.

Click on this button toedit the expression forthe computed field.

Click on theAdd Field but-ton after high-lightingPopulationin the list.

The expression for thiscomputed field is con-structed from table/fieldnames and an operator.

STEPS

place this factor with 386100.

Set the numberof Places to 4.

Click onPopulationbefore youclick on theAdd Fieldbutton sothe new fieldis the thirdfield.

You can alsoedit the fieldname here.

(you can also enter thefield names using Insert /Field in the Query win-dow and selecting thefields as shown below toinsure that spelling iscorrect)

click [OK] in theQuery window

click [OK] in the TableProperties window

Theme Mapping

Theme Map from Computed Field

click on the Vectoricon in the layer rowfor the COUNTY object

on the Polygons panel,select New - by Themefrom the Style menu

click on Population_1990in the Table list thenPopDensity in the Fieldlist of the Select Table /Field window

click on [OK] to confirmyour selection and openthe Theme Mapping Con-trols window

set the number ofclasses to 8

choose Save As fromthe Theme menu

click on [OK] in the Se-lect table to save themeas window that opensto accept the defaultname and description

choose Close from theTheme menu

click on [OK] in the Vec-tor Layer Controls win-dow

You can now use the computed field you created(PopDensity) to provide a new theme and generatea new theme map. To create a new theme, you firstneed to open the Vector Layer Controls window forthe County layer, which you can do by clicking onthe vector icon at the left of the layer row in theDisplay Manager window or by right-clicking onthe vector’s name and selecting Controls from themenu.

You can use Save or Save As to create a new themestyle object after choosing New - by Theme from theStyle option menu in the Vector Layer Controls. For

the populationdensity theme, wewill again set thenumber of classes toeight, but this timewe won’t use round-ing (although you

could round to the near-est 0.01 or 0.001 with-out changing class as-signment).

Once you’ve saved atheme, you can select itfor use again from the

style option menu in the Vector Layer Controls forthat vector object. If you want to use anotherpreviously saved theme after opening the ThemeMapping Controls, choose Open from the Thememenu in that window.

STEPS

Population Population Density

Theme Mapping

A New Legend for Your New Theme

click on the Legendicon at the left of theCOUNTYPOPULATON grouprow

click on [Legend Object],enter Population Densityin the New Object Namefield, and click [OK] in theSelect legend object touse window

click on [Style Object]

navigate up one level,then click on thePOPULATION_1990_POPDENSITY

table icon, and finally thePOPULATION_1990_POPDENSITY

style object icon

confirm or adjust thesettings in the LegendLayer Controls window tomatch those on page 9

click on [Edit Legend]

click on --- Heading ---(top of righthand column)

click on [Add] then [Up]

set the Label option menuto User-Defined

type Population Densityinto the text field, andclick on [OK]

click on [Heading Style] inthe Legend Layer Con-trols window

set the font to Arial, theAscender Height to 14points, and the Verticalspace to 20 points

click on [OK] in the TextStyle Editor window

turn on the Center Head-ings toggle and click [OK]in the Legend Layer Con-trols window

All parameters from the last legend you set upshould be the defaults for this legend. You could,thus, just name the new legend, select the desiredtheme style object, and click on [OK] in the LegendLayer Controls window. But let’s expand yourknowledge of legends a little and add a heading tothis one.

Theme legends change dynamically with the themestyle object. So any changes you make and save inthe number of classes in a theme, the method ofdetermining the distribution, or assigned colors, forexample, will automatically be updated the nexttime the legend is drawn.

Because you created a new legend without deletingthe original legend group, the group positioninginformation is retained, and the new legend willcome up centered under Nebraska when drawn.

First, highlight-- Heading --.

Second, clickon Add.

Fifth,type intext.

Third, clickon Up.

STEPS

Fourth, setLabel optionto User-De-fined.

Theme Mapping

Print Your Second Theme MapWhen creating a new layout, your last used PageSetup is the default for the new layout. These valuesare reset to those saved when you open a layout. The

last layout printed from this bookletwas for the exercise on page 11. Nochanges have been made to map scaleor page orientation, so the print youmake in this exercise should show Ne-braska at the same size, position andorientation as that previous print, butwith different theme styles and the cor-responding legend. It is, however, al-ways a good idea to double check yoursettings when you go to print to insurethey have not changed inadvertently.

Saved layouts can be viewed in eitherPage or Display Layout Mode. However, unlesseach group is attached to another group in thelayout, the two displays will not be interchangeable.Horizontal, as well as vertical, attachment of the

legend to the vector object insteadof the page will prevent the shift ofthe legend between layout modes

in this exercise.

STEPS

choose Display / Print inthe Display Manager

click on the Settingsicon for the layout inthe Display Manager andchange the LayoutMode to Display

If you had set the legend backgroundto white rather than transparent onpage 9, there would be a white blockevident behind the legend in Displaylayout mode.

Auto-Tile Groups toggle turned on

The vertical attachmentand spacing specified forthe legend is maintained;horizontal attachment wasto the page.

When this toggleis turned on, youare asked if youwant to proceed.

Auto-Tile Groups toggle off

Theme Mapping

Theme Mapping Point ObservationsSTEPS right-click on the layout

name in the Display Man-ager and choose CloseLayout

click on the New icon,choose 2D Display, andselect the ARTIFACTS objectfrom the GS_THEME ProjectFile

click on the vector’sLayer Controls icon,set the style on thePoints panel to New - ByTheme

click on DATABASE in theTable list, FREQUENCY in theField list, then [OK] in theSelect Table / Field win-dow

change Classes to 10

set the Spread Size at 1to 3 millimeters

select None from the AtScale option menu

confirm that Circle (filled)is the selected Pattern

choose Close from theTheme menu, click on[Yes] and [OK] to acceptthe default name

click on [OK] in the Vec-tor Layer Controls

Your options for point styles include display as abox (outline or filled), circle (outline or filled),crosshair (simple or enhanced), symbol, or by styleassigned individually to each theme class. For Box,Circle, Crosshair, and Symbol, all points are repre-sented by the same symbol, and the symbol size and/or color can vary. If Symbol is chosen on the Patternoption menu, the symbol color can change by themeclass if you are using a symbol design that incorpo-rates variable color using the selected color spread.Nearly all of the symbols provided with the TNTproducts make use of this variable color feature.

As mentioned, theme mapped points can incorpo-rate a size spread as well as a color spread (or othercolor / symbol assignment). When you use thisfeature, as theme class values increase, so does thesize of the points. The spatial distribution of pointsin the object should help you determine a size rangein which the number of smaller points obscured bylater drawn, larger points is acceptable. If you aretheme mapping lines, you can vary the line width

with the themeclass as well asthe color.

Theme Mapping

Points as Variable Color SymbolsTools to create point symbols, line patterns, and fillpatterns are provided in TNTmips, TNTedit, andTNTview. Any of these symbolic element represen-tations can incorporate multiple specified colors. Ofparticular interest for this exercise is the color re-ferred to as “variable color,” which can be includedin point symbols and line and fill patterns. Variablecolor components get their actual colors from an-other source, such as a drawing style assigned byattribute or, in this case, by theme. Many of thesymbols, line patterns, and fill patterns provided as

samples with the TNT prod-ucts incorporate a variablecolor portion, and some aredesigned entirely in vari-able color.

When the Select Symbolwindow opens, you shouldnotice that the majority ofthe symbols are entirelycyan or include cyan as oneof the colors. Cyan, as thecolor assigned to the firsttheme class, is the color cur-

rently used for variable color display for these sym-bols. If you change the first color in the color spread,the color of the variable color portion of the symbolin the Select Pattern window will also change.

STEPS

click on the vectoricon in the layer row

click on [Edit] for pointStyle By Theme(DATABASE_FREQUENCY)

select Symbol from thePattern option menu

choose Stars from theSymbol Set option menu

scroll down, select thesymbol named start1,and click [OK]

set the Spread Size to2.0 to 2.0 millimeters withthe Spread Size toggleon (this returns you toconstant sized symbols)

choose Save As fromthe Theme menu, addstars to the end of thedefault name in the NewObject Name field, andclick [OK]

choose Close from theTheme menu and click[OK] in the Vector LayerControls window

a symbol with“variable color”and color spreadfrom blue to red

a symbol with“variable color”

and colorspread from

cyan to yellow

Theme Mapping

Hydrology with Elevation ThemeSTEPS

right-click on the ARTIFACTS

layer in the Display Man-ager and choose Re-move Layer

click on the AddObjects icon and select_3D_HYDROLOGY from theGS_THEME Project File

click on the vector’sLayer Controls icon, andon the Lines panel, checkthat Select is set to All,then set Style to New -by Theme

choose the Internal tableand Max_Z field for thetheme and click [OK]

set the color spread fromcyan to orange

choose Save from theTheme menu, and click[OK] to accept the defaultname

choose Close from theTheme menu and click[OK] in the Vector LayerControls window

Theme maps aren’t limited to points and polygons;you can also create themes for lines as we do in thisexercise and the one that follows. Lines are not asfrequently used for theme maps because their at-tributes are more likely to be categorical (such asstate highway or county road or intermittent orperennial stream). Additionally, perhaps the mostimportant quantitative line attribute, namely length,is generally evident without applying a theme. Justas points have a spread size that can be incorporatedas part of the theme drawing style, lines have a spreadwidth that can be applied. Assigning a spread widthto lines makes sense for an attribute such as trafficvolume so that roads / lines that carry more traffic aredrawn wider.

The upper end of the colorspread for lines in thisexample was changedfrom yellow to orange be-cause yellow lines on awhite background arevery difficult to see.

Theme Mapping

Hydrology with Basin Area ThemeYou can base linear themes on the attributes ofsurrounding polygons by first using the TransferAttributes process (Geometric / Attributes / TransferAttributes). The theme in this exercise is based onthe watershed standard basin areas for the streamsand tributaries in the vector object. Standard basinpolygons were generated in TNTmips’ Watershedprocess (Terrain / Watershed), and the areas of thesepolygons were transferred to the hydrology lines toprepare the vector object for your use in this exercise.

Any quantitativepolygon at-tribute, such assoil permeabilityor average slope,can be transferredto points, lines, orpolygons in an-other vector ob-ject and used fortheme mapping ormore sophisti-cated vectoranalysis.

STEPS

click on the LayerControls icon for the_3D_HYDROLOGY object

click on [Edit] for lineStyle Internal_MaxZ

choose New from theTheme menu in theTheme Mapping Controlswindow

click on BasinAreas in theTable list then BasinAreain the Field list of the Se-lect Table / Field window

click [OK] to confirmyour selection andreturn to the ThemeMapping Controlswindow

change the number ofclasses to 6

set the Count to ByReference and checkthat the Color Spreadrange is the same asin the previous exer-cise (cyan to orange)

choose Save As fromthe Theme menu andclick [OK] to accept thedefault name

choose Close from theTheme menu and click[OK] in the VectorLayer Controls window

The standard basinpolygons from the wa-tershed process areshown at the near rightwith the theme map ofthe basin areas associ-ated with each stream atthe far right.

Theme Mapping

Altering Theme Class BoundariesSTEPS right-click on the _3D_HY-

DROLOGY layer name andchoose Remove Layer

click on the AddObjects icon and selectCOUNTY from the NEBRASKA

Project File

click on the vector’sLayer Controls icon, andon the Polygon panel, setStyle to New - by Theme

choose POLYSTATS and AREA

as the table and field, re-spectively

set the end for the colorspread back to yellow

position the mouse overthe boundary line betweenthe two highest classes,then click and hold the leftmouse button as you dragthe boundary to the right

release the mouse whenthe boundary is at about 5x 109 square meters (mini-mum value for highestclass)

repeat for the next boun-dary line to the left, andrelease when the minimumvalue for the fourth class isabout 2.5 x 109

move the other two bound-ary lines until the minimumvalue for the third and sec-ond class are 1.7 x 109

and 1.2 x 109, respectively

choose Theme / Close,click on [Yes] whenprompted

default EqualCount distri-bution for 5classes

user defineddistribution for5 classes

Some data distributions have natural groupings thatare disrupted by the standard options provided. It’stime to show you how to manipulate the position ofthe automatically generated class boundaries so natu-ral groupings can be maintained. The Statisticspanel in the Theme Mapping Controls window pro-vides a histogram in bar graph form of values for theselected field. The bars are drawn in the assignedcolor for the class, and the positions of class bound-aries are shown as dashed lines. These dashed linescan be dragged with the mouse. The range of valuesfor any class affected is automatically updated. Youcan also type values directly into the minimum andmaximum fields to achieve the same effect as drag-ging the class boundary lines. The Distributionoption menu is automatically reset to User-Definedwhen you move any class boundary.

Theme Mapping

compare to the illustration on page 14

STEPS return to the Vector

Layer Controls windowand click on [Edit] forPolystats_Area style

choose Theme / Openand selectPOPULATION_1990_POPDENSITY

click on [OK] in the Se-lect Theme Table window

select Equal Interval onthe Distribution optionmenu

choose Theme / SaveAs, add EQINT to the de-fault name in the Selecttable to save theme aswindow, and click [OK]

choose Theme / Close

click on [OK] or [Apply] inthe Vector Layer Con-trols window

We have used the Equal Count distribution for allexercises in this booklet except the one on theprevious page. Let’s take a look at how the resultsdiffer for an Equal Interval distribution. When youchange to this option with the Nebraska PopulationDensity data, you’ll see that four of the eight classeshave no members, and three have only one member,which means that 90 of the 93 counties are in thesame class using an Equal Interval distribution forthis theme. This theme provides a clear example ofwhen you do not want to use an equal intervaldistribution.

Two check buttons are provided near the top of thewindow so that you can eliminate the highest and/orlowest values from consideration when the distribu-tion is determined. This feature is generally usedwhen one or both of these classes are far removedfrom the rest of the distribution or the first or lastclass contains the majority of observations (as illus-trated at the bottom of this page).

Other Distribution Options

all classes included in distribution

first class excluded from distribution

Theme Mapping

Where Next?This tutorial booklet has introduced the basic tech-niques for creating theme maps and has also shownyou how to add a legend and print the resultinglayout. There are many additional features for use increating theme maps that are not presented here. Besure to look at the reference materials available fromTNTmips’ Help menu and using the Search feature onMicroImages’ web site to find out about these addi-tional features.

You should be familiar enough with your data todecide which theme mapping options are appropri-ate for it. You can, of course, become familiar withyour data quite quickly using the Statistics panel inthe Theme Mapping Controls window. The illustra-tions at the right show how results may differ for thesame field values by changing the Count and Distri-bution modes; the differences between some meth-ods are subtle, while differences between other meth-ods are pronounced. All examples shown use statepopulation as the basis for the theme map.

A new record counting mode not previously dis-cussed is shown in the third theme map at the right(Count: By Element Size). The ability to count byelement size is available only if standard attributeshave been calculated for the element type beingtheme mapped. This choice makes it possible toassign the classes so that each covers as close to thesame geographic area as possible based on the at-tribute value distribution in the selected field.

As mentioned earlier in this booklet, you may wantyour theme map to have labels. You can generatedynamic labels in the Display process or permanentlabels in the Editor. Label text can be generated byattribute, such as county name in the Nebraska mapyou worked with, or using a more complex script.You can also design fill patterns, line patterns, andsymbols for use in your theme maps directly in theDisplay process. This topic is covered in the tutorialbooklet on Creating and Using Styles.

MicroImages, Inc.¤®

Advanced Software for Geospatial AnalysisTHEME

MAPPING

Voice: (402)477-9554www.microimages.com

MicroImages, Inc. publishes a complete line of professional software for advanced geospatialdata visualization, analysis, and publishing. Contact us or visit our web site for detailedproduct information.

TNTmips Pro TNTmips is a professional system for fully integrated GIS, image analysis,CAD, TIN, desktop cartography, and geospatial database management.

TNTedit TNTedit provides interactive tools to create, georeference, and edit vector, image,CAD, TIN, and relational database project materials in a wide variety of formats.

TNTview TNTview has the same powerful display features as TNTmips and is perfect forthose who do not need the technical processing and preparation features of TNTmips.

TNTatlas TNTatlas lets you publish and distribute your spatial project materials on CD-ROM at low cost. TNTatlas CDs can be used on any popular computing platform.

TNTmips Basic TNTmips Basic is a very low cost version of TNTmips for students andprofessionals with small projects with large object size limits than TNTmips Free.

TNTmips Free TNTmips Free is a free version of TNTmips for students and professionalswith small projects. You can download TNTmips Free from MicroImages’ web site.

Indexauto-tiling ................................................. 16changing layout modes ............................... 7computed fields ........................................ 13count by element size ............................... 23editing database definition ................. 12, 13equal count distribution ................ 20, 21, 23equal interval distribution .................. 22, 23exclude first or last class .......................... 22first theme ................................................... 4group settings ........................................... 10headings (legends) .................................... 15labeling ............................................... 11, 23layout modes ........................................ 4, 16legend editor, theme maps ........................ 15legends ............................................... 8-9, 15line attributes from polygons ................... 20

lines, theme mapping .......................... 19, 20map scale .................................................... 7points, theme mapping .................. 17-18, 22population density theme ......................... 14population theme map ....................... 5-6, 14positioning groups .................................... 10rounding ..................................................... 6standard attributes .................................... 23style assignment table ................................ 6style objects (legends) .......................... 8, 15symbols ..................................................... 18Theme Mapping Controls ........................... 5transfer attributes ...................................... 20transparent background ........................ 9, 16user-defined distribution .......................... 21variable color symbols ............................. 18

tutorial: theme mapping - microimages, inc. · a theme map is a screen display or print that...

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