symbolizing your data...5. click the color scheme dropdown arrow and click a color scheme. 6. click...

IN THIS CHAPTER

133

Symbolizing your data 6• A map gallery

• Drawing all features with one symbol

• Drawing features to showcategories like names or types

• Managing categories

• Ways to map quantitative data

• Standard classification schemes

• Drawing features to showquantities like counts or amounts

• Setting a classification

• Drawing features to showmultiple attributes

• Drawing features with charts

• Drawing TINs as surfaces

• Drawing CAD layers

• Advanced symbolization

Choosing how to represent your data on a map may be the most importantmapmaking decision you make. How you represent your data determineswhat your map communicates.

On some maps, you might simply want to show where things are. The easiestway to do this is to draw all the features in a layer with the same symbol. Onother maps, you might draw features based on an attribute value orcharacteristic that identifies them. For example, you could map roads by typeto get a better sense of traffic patterns or map the wildlife habitat suitabilityof a particular bird species, ranked from least to most suitable.

In general, you can draw map features as follows:

� With a single symbol

� To show a category such as a name (unique values maps)

� To represent a quantity such as population (graduated color, graduatedsymbol, and dot density maps)

� To show multiple attributes that are related (multivariate and chart maps)

You can also draw these other data types:

� Images and rasters (see Chapter 14, �Working with rasters�)

� TINs representing a three-dimensional surface

� CAD drawing files

Browse the map gallery on the next few pages to see the various ways youcan symbolize your data.

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A map gallery

Single symbol map Unique values map

Drawing your data with just a single symbol gives you a sense ofhow features are distributed�whether they�re clustered ordispersed�and may reveal hidden patterns.

In the map above, you can easily see where people live andconclude that some areas are more densely populated based onthe number of cities clustered together.

On a unique values map, you draw features based on an attributevalue, or characteristic, that identifies them. In the map above,each land use type is drawn with a specific color. Typically, eachunique value is symbolized with a different color. Drawingfeatures based on unique attribute values shows the following:

� How similar features are distributed�whether they�regrouped or dispersed

� How different feature types are located in relation to eachother

� How much of one category there is compared to othercategories

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Graduated color map Graduated symbol map

When you need to map quantities or amounts of things, youmight choose to use a graduated color map. Graduated colormaps have a series of symbols whose colors change according tothe values of the particular attribute. Graduated color maps aremost useful for showing data that is ranked (for example, 1 to 10,low to high) or has some kind of numerical progression (forexample, measurements, rates, percentages).

The map above uses different shades of color�in a graduatedcolor ramp�to represent different amounts of people. Here,darker shades indicate a greater number of people.

Another way to represent amounts of things is to vary the size ofthe symbol a feature is drawn with. The graduated symbol mapabove uses a larger symbol to show earthquakes with a largermagnitude. Like graduated color maps, graduated symbol mapsare most useful for showing rank or progression of values.However, instead of using color to represent the differences invalues, the size of the symbol varies.

When making a graduated symbol map, it is important to choosethe range of symbol sizes carefully. The largest symbols need tobe small enough that neighboring symbols don�t completelycover one another. At the same time, the range in size from thesmallest to the largest needs to be great enough that the symbolfor each class is distinct.

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Multivariate map

The maps on the previous pages display one attribute, orcharacteristic, of the data�for example, a name or an amount.Multivariate maps display two or more attributes at the sametime. The map above illustrates the level of human impact on thenatural landscape of Australia. Major habitat types are shownwith unique colors, and the level of disturbance for each habitatis shown with a graduated symbol. The larger the symbol, thehigher the human impact is on the particular habitat.

Chart map

Chart maps allow you to symbolize multiple attributes on onemap as well as communicate the relationship among differentattributes. Chart maps display charts�bar and pie charts�overfeatures. The map above shows you the volume and type ofgoods distributed by an exporter throughout Asia.

Pie charts show relationships between parts and the whole andare particularly useful for showing proportions and ratios. Barcharts compare amounts of related values and are well suited toshowing trends over time. Stacked bar charts can show both therelative relationship between data as well as allowing for absolutecomparisons.

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Raster map

Much of the most readily available geographic data is in the formof rasters. A raster can represent almost any geographic features,though most rasters you�ll work with in ArcMap will probably bescanned maps or photographs of the earth�s surface. You mightadd an aerial photograph to your map to provide a realisticbackground to your other data, or you might use satellite imageryto add up-to-the-minute information about weather conditions orflood levels. You can even update your other data by using araster as a guide for editing.

For more information on displaying raster data, see Chapter 14,�Working with rasters�.

Density map

Mapping the density of features lets you see the patterns of wherethings are concentrated. This helps you find areas that requireaction or meet some criteria. For example, the map above showswhere the highest concentration of crimes occurs in a city. Usingthis map, the city may choose to increase the number of policepatrols in the areas of high density.

One way to map density is with a dot density map. This type ofmap symbolizes features using dots drawn inside polygons torepresent a quantity. Each dot represents a specific value. Forexample, on the crime map, each dot might represent fiveincidents of crime. When creating a dot density map, you specifyhow many features each dot represents and how big the dots are.You may need to try several combinations of amount and size tosee which one best shows the pattern.

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Color-shaded relief map

One of the ways you can represent a continuous surface, such asterrain elevation or temperature gradient, is to display the surfaceas a color-shaded relief map. This type of map displays elevationranges in graduated colors and shades ridges, valleys, andhillsides using a simulated light source. The shading adds arealistic effect that makes the surface look as though you areviewing it from high above. The combined use of color forelevation and shading for surface morphology results in a highlyinformative, yet easy to interpret, view of your surface.

Computer-aided design map

You can integrate CAD drawings onto your maps seamlessly,without having to convert these files into other GIS formats. Thisis particularly useful if your organization has existing CAD dataresources. For example, some departments in your organizationmay be using a CAD package to help manage facilities and otherinfrastructure. You can let ArcMap draw these layers as theyappear in the CAD package, or you can precisely control how todraw them.

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Drawing allfeatures with onesymbolOften, seeing where somethingis�and where it isn�t�can tellyou exactly what you need toknow. Mapping the location offeatures reveals patterns andtrends that can help you makebetter decisions. For example, abusiness owner might map wherehis customers live. Seeing wherethey live can help him decidewhere to target his advertising.

The easiest way to see wherefeatures are is to draw themusing a single symbol. You candraw any type of data this way.When you create a new layer,ArcMap by default draws it witha single symbol.

Drawing a layer using asingle symbol

1. In the table of contents, right-click the layer you want todraw with a single symboland click Properties.

2. Click the Symbology tab.

3. Click Features.

Because Single symbol is theonly option, ArcMap automati-cally selects it.

4. Click the Symbol button tochange the symbol.

5. In the Symbol Selector dialogbox, click a new symbol orchange specific properties ofthe symbol.

6. Click OK on the SymbolSelector dialog box.

7. Type a Label for the feature.

The label appears next to thesymbol in the table ofcontents.

8. Click OK.

Tip

Changing the symbolTo quickly change the symbolfeatures are drawn with, click thesymbol in the table of contents todisplay the Symbol Selector.

Tip

Changing the colorTo quickly change the color of asymbol, right-click the symbol inthe table of contents to display theColor Selector.

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Drawing featuresto show categorieslike names or typesA category describes a set offeatures with the same attributevalue. For example, given parceldata with an attribute describingland use�for example, residen-tial, commercial, and publicareas�you can use a differentsymbol to represent each uniqueland use type. Drawing featuresthis way allows you to see wherefeatures are and what categorythey belong to. This can be usefulif you�re targeting a specific typeof feature for some action orpolicy. For instance, a cityplanner might use the land usemap to target areas for redevelop-ment.

In general, look for these kindsof attributes when mapping bycategory, or unique value:

� Attributes describing thename, type, or condition of afeature.

� Attributes containingmeasurements or quantitiesthat are already grouped, forexample, �0�99�, �100�199�.

� Attributes that uniquelyidentify features, for example,a county name attribute couldbe used to draw each countywith a unique color. u

Drawing a layer showingunique values

1. In the table of contents, right-click the layer you want todraw showing unique valuesand click Properties.


3. Click Categories.

ArcMap automatically selectsthe Unique values option.

4. Click the Value Fielddropdown arrow and click thefield that contains the valuesyou want to map.

5. Click the Color Schemedropdown arrow and click acolor scheme.

6. Click Add All Values.

This adds all unique values tothe list. Alternatively, click theAdd Values button to choosewhich unique values todisplay.

7. If you want to have moredescriptive labels, click alabel in the Label column andtype a new one.

8. Click OK.

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Drawing features byreferencing specificsymbols in a style

1. In the table of contents, right-click the layer you want todraw showing unique valuesand click Properties.


3. Click Categories.

4. Click Match to symbols in astyle.

5. Click the Value Fielddropdown arrow and click thefield that contains the valuesyou want to map.

6. Click the Match to symbols inStyle dropdown arrow andclick the style that containssymbol names that matchattribute values.

If the style is not loaded, clickthe Browse button to browsefor it on disk.

7. Click Match Symbols.

This adds all unique valuesthat have a matching symbolin the style. Alternatively, clickthe Add Values button tochoose which unique valuesto display.

8. If you want to have moredescriptive labels, click alabel in the Label column andtype a new one.

9. Click OK.

You can let ArcMap assign asymbol to each unique valuebased on a color scheme youchoose or explicitly assign aspecific symbol to a specificattribute value.

To draw features with specificsymbols, you need to create astyle beforehand that containssymbols named after the attributevalue they represent. Forexample, if you have a datasetthat categorizes roads as eithermajor or minor, then you wouldneed to have line symbols withinthat style named �major� and�minor�. ArcMap will match theattribute value to the line symbolname to draw the feature.Features that don�t have amatching line symbol won�t bedrawn. This way of drawingfeatures is especially useful ifyou want to draw your data thesame way on different maps.

See Also

For more information on creatingstyles, see Chapter 9, �Workingwith styles and symbols�.

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Sorting unique values

1. In the table of contents, right-click the layer whose uniquevalues you want to sort andclick Properties.


3. Click the Value column toshow a context menu.

4. Click Reverse Sorting.

5. Click OK.

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Ordering unique values

1. In the table of contents, right-click the layer whose uniquevalues you want to reorderand click Properties.


3. Click the value you want tomove up or down in the list.

4. Use the up and down arrowsto either promote or demotethe value in the list.

The arrow buttons only movevalues within a heading.

5. Click OK.

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Ordering unique valueheadingsYou can also arrange the headingsfor unique values. Just select aheading and use the arrow keys tomove it.

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ManagingcategoriesIf you�re drawing features bycategory, the number of catego-ries you display will affect whatpatterns are revealed on the map.Most people can easily discernup to seven categories for a givenlayer. The more technical theaudience, the more categoriesthey will be able to identify andthe more easily they will be ableto interpret complex patterns.Conversely, a less technicalaudience may benefit more froma map with fewer categories.

When displaying your data, youcan control how you organizeand display categories for a layer.If you want to display fewercategories, you can combinesimilar categories into onecategory�for example, combinetwo detailed land use categoriesinto a more general one. Combin-ing categories in this manner canmake the patterns more apparent.However, the trade-off is thatsome information may be lost.

Instead of reducing the numberof categories, you might organizeindividual categories into groupsthat you define. This allows youto work with and view them as agroup. Additionally, a map readerwill see the groups listed in thetable of contents.

Combining two or morecategories into one

1. In the table of contents, right-click the layer drawn withunique values for which youwant to combine categoriesand click Properties.


You should already seecategories in the scrolling list.If you don’t, follow the stepsfor ‘Drawing a layer showingunique values’ in this chapter.

3. Click the first value you wantto combine. Hold down theShift or Ctrl key and click theadditional values that youwant to combine.

4. Right-click over the valuesand click Group Values.

The selected values will nowbe combined into onecategory.

5. Click OK.

Splitting up combinedcategories

1. Right-click a combinedcategory.

2. Click Ungroup Values.

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Organizing categories ingroups

1. In the table of contents, right-click the layer drawn withunique values for which youwant to organize categoriesand click Properties.


You should already seecategories in the scrolling list.If you don’t, follow the stepsfor ‘Drawing a layer showingunique values’ in this chapter.

3. Click the first value you wantto group together. Hold downthe Shift or Ctrl key and clickthe additional values that youwant to group.

4. Right-click a selected value,point to Move to Heading,and click New Heading.

5. Type a name for the newheading.

6. Click OK.

7. Click OK on the LayerProperties dialog box.

Tip

Deleting groupsArcMap will automatically deletegroups that contain no attributevalues in them.

Tip

Renaming groupsClick the group heading in thetable of contents and type a newname.

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Ways to map quantitative data

Quantitative data is data that describes features in terms of aquantitative value measuring some magnitude of the feature.Unlike categorical data, where features are described by a uniqueattribute value such as a name, quantitative data generallydescribes counts or amounts, ratios, or ranked values. Forexample, data representing precipitation, population, and habitatsuitability can all be mapped quantitatively.

Which quantitative value should you map?

Knowing what type of data you have and what you want to showwill help you determine what quantitative value to map. Ingeneral, you can follow these guidelines:

� Map counts or amounts if you want to see actual measuredvalues as well as relative magnitude. Use care when mappingcounts as the values may be influenced by other factors andcould yield a misleading map. For example, when making amap showing the total sales figures of a product by state, thetotal sales figure is likely to reflect the differences inpopulation among the states.

� Map ratios if you want to minimize differences based on thesize of areas or numbers of features in each area. Ratios arecreated by dividing two data values and are also referred to asnormalizing the data. For example, dividing the 18- to 30-year-old population by the total population yields thepercentage of people aged 18�30. Similarly, dividing a valueby the area of the feature yields a value per unit area, ordensity.

� Map ranks if you�re interested in relative measures and actualvalues are not important. For example, you may know afeature with a rank of �3� is higher than one ranked �2� andlower than a �4�, but you can�t tell how much higher or lower.

Should you map individual values or group themin classes?

When you map quantitative data, you can either assign each valueits own symbol or group values into classes using a differentsymbol for each class.

If you�re only mapping a few values (less than 10), you canassign a unique symbol to each value. This may present a moreaccurate picture of the data, since you�re not predeterminingwhich features are grouped together. More likely, your datavalues will be too numerous to map individually and you�ll wantto group them in classes, or classify the data. A good example ofclassified data is a temperature map you might find in anewspaper. Instead of displaying individual temperatures, thesemaps show temperature bands, where each band represents agiven range in temperature.

Ways to classify your data

How you define the class ranges and breaks�the high and lowvalues that bracket each class�will determine which features fallinto each class and thus what the map will look like. By changingthe classes you can create very different-looking maps. Generally,the goal is to make sure features with similar values are in thesame class.

Two key factors for classifying your data are the classificationscheme you use and the number of classes you create. If youknow your data well, you can manually define your own classes.Alternatively, you can let ArcMap classify your data usingstandard classification schemes. The four most common schemesare natural breaks, quantile, equal interval, and standarddeviation. These are described on the following pages.

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Standard classification schemes

Natural breaks (Jenks)

Classes are based on natural groupings of data values. ArcMap identifies break points by looking for groupings and patterns inherent inthe data. The features are divided into classes whose boundaries are set where there are relatively big jumps in the data values.

Quantile

Each class contains an equal number of features. A quantile classification is well suited to linearly distributed data. Because features aregrouped by the number in each class, the resulting map can be misleading. Similar features can be placed in adjacent classes, or featureswith widely different values can be put in the same class. You can minimize this distortion by increasing the number of classes.

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Equal interval

This classification scheme divides the range of attribute values into equal-sized subranges. For example, if features have attribute valuesranging from 0 to 300 and you have three classes, each class represents a range of 100 with class ranges of 0�100, 101�200, and 201�300. This method emphasizes the amount of an attribute value relative to other values, for example, to show that a store is part of thegroup of stores that made up the top one-third of all sales. It�s best applied to familiar data ranges such as percentages and temperature.

Standard deviation

This classification scheme shows you the amount a feature�s attribute value varies from the mean. ArcMap calculates the mean valueand then generates class breaks by successively adding to it or subtracting from it the standard deviation. A two-color ramp helpsemphasize values above (shown in blue) and below (shown in red) the mean.

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Drawing featuresto show quantitieslike counts oramountsWhen you want your map tocommunicate how much ofsomething there is, you need todraw features using a quantitativemeasure. This measure might bea count; a ratio such as apercentage; or a rank such ashigh, medium, and low.

You can represent quantities on amap by varying the color orsymbol size you use to drawfeatures. For example, you mightuse increasingly darker shades ofblue to represent increasinglyhigher rainfall amounts or largercircles to represent cities withlarger populations.

Generally, you�ll need to classifyyour data when you display it.Classifying data groups featureswith similar values into discreteclasses and displays them withthe same symbol. You can eithermanually define classes or applyone of the standard classificationschemes to do so automatically�just specify the number of classesyou want to show. Once you�vedefined the classes, you can addmore classes, delete classes, orredefine class ranges. u

Representing quantitywith color

1. In the table of contents, right-click the layer you want todraw showing a quantitativevalue and click Properties.


3. Click Quantities.

ArcMap automatically selectsGraduated colors.

4. Click the Value dropdownarrow and click the field thatcontains the quantitativevalue you want to map.

5. To normalize the data, clickthe Normalization dropdownarrow and click a field.

ArcMap divides this field intothe Value to create a ratio.

6. Click the Color Rampdropdown arrow and click aramp to display data with.

7. Click the Classes dropdownarrow and click the number ofclasses you want.

8. Click Classify.

9. In the Classification dialogbox, click the Methoddropdown arrow and click theclassification method youwant.

10.Click OK on the Classificationdialog box.


Right-click over a classto see additional optionssuch as sorting andnumber formatting.

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It�s always a good idea toexamine your data before youmap it. For instance, you mayfind that you have a few ex-tremely high or low values ornull values where no data isavailable. These values can skewa classification and thus thepatterns on the map. Fortunately,you can choose to exclude thesevalues before you classify yourdata.

You may also want to normalizeyour data before you map it.When you normalize data, youdivide it by another attribute tocome up with a ratio. Often,ratios are easier to understandthan the raw data values. Forexample, dividing total popula-tion by area yields the number ofpeople per unit area, or a density.Dividing a store�s sales figure bythe total sales for all stores yieldsa percentage of sales at that store.

Creating your own colorramp for a layer

1. In the table of contents, right-click the layer that shows aquantitative value and clickProperties.



4. Double-click the top symbolin the list and set the startcolor for the ramp.

5. Double-click the bottomsymbol and set the end color.

6. Optionally, double-click anymiddle symbol to set its color.

This lets you create amulticolor ramp.

7. Click all the middle symbolsyou’ve set the color of.

By selecting one or moremiddle symbols, the color ofthose symbols is included inthe new ramp. Otherwise,ArcMap only uses the top andbottom symbols.

8. Right-click a symbol and clickRamp Colors.

9. Optionally, right-click theColor Ramp dropdown andclick Save to save your newramp to your default style.

You only need to save theramp if you want to use itagain on another layer.

10.Click OK.

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See Also

For more information on creatingand managing styles, seeChapter 9, �Working with stylesand symbols�.

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Appearance after the top, middle,and bottom colors have been set.

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Representing quantitywith graduated symbols



3. Click Quantities and clickGraduated symbols.




6. Type the minimum andmaximum symbol sizes.

7. Click the Classes dropdownarrow and click the number ofclasses you want.

8. Click Classify.

9. Click the Method dropdownarrow and click the classifica-tion method you want.

10.Optionally, click Exclusion toremove unwanted valuesfrom the classification (e.g.,null values).

11. Click OK on the Classificationdialog box.

12.Click OK on the LayerProperties dialog box.

Tip

Why don’t the symbols getbigger when I zoom in?As you zoom in on the map, thegraduated symbols will not getbigger. If you want them to getbigger, you need to set a referencescale. Right-click the data frameand click Set Reference Scale. Nowwhen you zoom in, all the symbolsin the data frame will becomelarger.

Tip

With how many digits doyou want to display yourlabels?You can set the number ofsignificant digits for labels byclicking the Label column heading.This reveals a menu that lets youformat the labels.

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Representing quantitywith proportionalsymbols



3. Click Quantities and clickProportional symbols.




6. If the Value represents ameasurement on the map—an area or distance—click theUnit dropdown arrow andclick a unit. Otherwise, skip tostep 9.

7. Click Square or Circle as thesymbol.

8. Click Radius or Area.

For example, click Radius ifyour data represents thedistance an earthquake wasfelt from its epicenter. ClickArea if the value representsan area.

9. Click OK.

Tip

What’s the differencebetween graduatedsymbols and proportionalsymbols?When you draw features withgraduated symbols, the quantita-tive values are grouped intoclasses. Within a class, all featuresare drawn with the same symbol.Thus, you can�t discern the valueof individual features; you canonly tell that its value is within acertain range.

Proportional symbols representdata values more precisely. Thesize of a proportional symbolreflects the actual data value. Forexample, you might map earth-quakes using proportional circles,where the radius of the circle isbased on the magnitude of thequake. The difficulty with propor-tional symbols arises when youhave too many values; the symbolsmay become indistinguishable.Also, the symbols for high valuescan become so large as to obscureeach other.

Tip

The maximum valuesymbol is too largeIf the symbol for the maximumvalue fills the space on the dialogbox, it will probably be too big onthe map. Try reducing the symbolsize for the minimum value,normalizing the data, or excludingsome values. If it�s still too large,use graduated symbols instead.

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Representing quantitywith a dot density map



3. Click Quantities and click Dotdensity.

4. Click one or more fieldsunder Field Selection thatcontain the quantitativevalues that you want to map.

5. Click the arrow button to addfields to the field list.

6. Double-click on a dot symbolin the field list to change itsproperties.

7. Type the dot size or click theslider to adjust the size.

8. Type the dot value or click theslider to adjust the value.

9. Check Maintain Density topreserve the dot density.

When checked, as you zoomin, the dot size will increaseso that a given area willvisually appear as dense.Otherwise, the dot size willremain constant.

10.Optionally, click Properties toset the dot placementoptions.

11. Click OK.

Tip

How big should the dotsbe?When creating a dot density map,you specify how many featureseach dot represents and how bigthe dots are. You may need to tryseveral combinations of amountand size to see which one bestshows the pattern. In general, youshould select values that ensure thedots are not so close as to formsolid areas that obscure thepatterns, or so far apart as tomake the variations in density hardto see.

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Setting aclassificationWhen you classify your data, youcan either use one of the standardclassification schemes ArcMapprovides or create custom classesbased on class ranges youspecify. If you choose to letArcMap classify the data, simplychoose the classification schemeyou want and set the number ofclasses. If you want to defineyour own classes, you canmanually add class breaks and setclass ranges that are appropriatefor your data. Alternatively, youcan start with one of the standardclassifications and make adjust-ments as needed.

Why set class ranges manually?There may already be certainstandards or guidelines formapping your data. For example,temperature maps are oftendisplayed with 10 degreetemperature bands. Or you mightwant to emphasize features withparticular values, for example,those above or below a thresholdvalue that determines whethersome action will occur. Whateveryour reason, make sure youclearly specify what the classesmean on the map.

Setting a standardclassification method

1. In the table of contents, right-click the layer that shows aquantitative value for whichyou want to change theclassification.



You should see the currentclassification.

4. Click Classify.

5. Click the Method dropdownarrow and click the classifica-tion method you want.

6. Click the Classes dropdownarrow and click the number ofclasses you want to display.

7. Click OK on the Classificationdialog box.


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Deleting a class break

1. Click Classify from theSymbology tab of the LayerProperties dialog.

2. Click on the class break youwant to delete.

The selected break ishighlighted.

3. Right-click over the histogramand click Delete Break.

Tip

Seeing more data valuesplotted on the histogramIncrease the number of columnsshown to see more data values inthe histogram.

Inserting your own classbreak and setting a range

1. In the table of contents, right-click the layer you want to setclass breaks for.

You should see the currentclassification.

2. Click the Range you want toedit.

Make sure to click the Range,not the Label.

3. Type a new value. This setsthe upper value of the range.

4. Click OK.

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Excluding features fromthe classification

1. Click Classify from theSymbology tab of the LayerProperties dialog.

2. Click Exclusion.

3. Double-click the field you’reusing to draw the layer.

4. Double-click an operator.

5. Double-click the value youwant to exclude.

If you don’t see the value inthe list, click the CompleteList button.

6. Click OK to execute theexpression and excludevalues.

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See Also

For more information on buildingquery expressions, see Chapter 13,�Querying maps�.

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Drawing featuresto show multipleattributesGeographic data usually has anumber of different attributesthat describe the features itcontains. While you�ll commonlyuse one of the attributes tosymbolize the data�for example,show categories or quantities�you may sometimes want to usemore than one. For example, youmight display a road networkusing two attributes: onerepresenting the type of road andthe other representing the trafficvolume along it. In this case, youcould use different line colors torepresent the different types ofroads and also vary the line widthto indicate traffic volume alongeach road.

When you symbolize your datausing more than one attribute,you create a multivariate display.Symbolizing your data this waycan effectively display moreinformation about the data;however, it can also make yourmap more difficult to interpret.Sometimes it might be better tocreate two separate displays thanto try to display the informationtogether.

Drawing a layer to showboth categories andquantities

1. In the table of contents, right-click the layer you want todraw showing multipleattributes and click Proper-ties.


3. Click Multiple Attributes.

ArcMap automatically selectsthe Quantity by categoryoption.

4. Click the first Value Fieldsdropdown arrow and click thefield that contains the valuesyou want to map.

5. Click the Color Schemedropdown arrow and click acolor scheme.

6. Click Add All Values.

7. Click Symbol Size or ColorRamp, depending on how youwant to symbolize thequantitative value. Thisexample shows Symbol Size.

8. Click the Value dropdownarrow and click the quantita-tive value you want to map.

Set other options as de-scribed in ‘Drawing featuresto show quantities like countsor amounts’.

9. Click OK.

10.Click OK.

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Drawing featureswith chartsPie charts, bar charts, andstacked bar charts can presentlarge amounts of quantitativedata in an eye-catching fashion.For example, if you�re mappingpopulation by county, you canuse a pie chart to show thepercentage of the population byethnic group for each county.

Generally, you�ll draw a layerwith charts when your layer hasa number of related numericattributes that you wish tocompare. Use pie charts if youwant to show how much of thetotal amount each category takesup. Use bar charts to showrelative amounts, rather than aproportion of a total.

Drawing pie charts

1. In the table of contents, right-click the layer you want todraw showing quantitativevalues and click Properties.


3. Click Charts and click Pie.



6. Click the Color Schemedropdown arrow and click thecolors you want to use.

You can double-click anindividual symbol in the list tochange its properties.

7. Check the box to prevent thecharts from overlapping.

8. Click Size.

9. Click the Variation Type youwant.

You can either draw all piesthe same size or vary the sizebased on the sum of theattributes or a particularattribute value.

10.Type in a size or click thearrows to set the size.

11.Click OK.

12.Click OK.

Tip

Charting negative valuesAvoid using pie or stacked barcharts with data containingnegative values.

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Drawing bar and columncharts



3. Click Charts and click Bar/Column.






8. Click Size.

9. Type in a maximum length orclick the arrows to set thelength.

10.Click OK.

11. Click OK.

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Click Properties toswitch between barsand columns.

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Drawing stacked charts



3. Click Charts and clickStacked.






8. Click Size.

9. Type in a maximum length orclick the arrows to set thelength.

10.Click OK.

11.Click OK.

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Click Properties toswitch between barsand columns.

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Drawing TINs assurfacesTINs represent continuoussurfaces such as terrain elevationor temperature gradient. Typi-cally, you display a TIN usingcolor-shaded relief. This lets youeasily see the ridges, valleys, andhillsides and their respectiveheights. Seeing the data this waycan help explain why other mapfeatures are where they are.

You can display any one of threesurface characteristics�slope,aspect, and elevation�on yourmap and even simulate shadedrelief.

Geographic features that crossthe surface�such as a river,road, or shoreline�can beexplicitly represented in a TINwith a breakline. These featuresform the edges of triangles andtherefore influence the surface attheir location. Since the underly-ing triangulation defines thesurface, you might want to take acloser look at it. You can alsodisplay the internal structure of aTIN�for example, nodes andbreaklines�independently or ontop of the shaded relief display.

Drawing a color-shadedrelief surface

1. In the table of contents, right-click the TIN layer that youwant to draw and clickProperties.


By default, ArcMap displaysthe face elevation andbreakline edges of the TIN.

3. Click an entry in the list to seeits symbolization properties.

4. Modify the symbolizationproperties as necessary. Forexample, set a new colorramp or change the numberof classes.

5. Click the Add button to drawadditional elements of theTIN—for example, nodes.

6. Click the renderer thatrepresents the TIN featureyou want to draw.

7. Click Add.

8. Click Dismiss when you arefinished adding renderers.

The list will update to showwhat you want to draw. u

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9. Click an element in the list.

10.Click the Up or Down arrowto change its draw order.

The TIN features at the top ofthe list will draw on top ofthose below them.

11. Click OK.

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How are slope and aspectmeasured?Slope values range between 0 and90 degrees, where 0 indicates noslope. Aspect is also measured indegrees. North is 0 degrees, east is90 degrees, south is 180 degrees,and west is 270 degrees.

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Drawing CADlayersYou can display CAD drawingson your map just like other datatypes. You can decide whichCAD layers to draw and how todraw the entities on the layer.

Depending on how you added theCAD data to your map, you havetwo display options:

� If you added the CADdrawing file for display only,you can only choose whichCAD layers to show or hide.ArcMap draws all entitiesaccording to the colorspecified in the drawing file.You can�t override thisdrawing behavior.

� If you added the CADdrawing as features�point,line, or polygon�becauseyou are interested in using thedata for geographic analysis,you have access to all thesymbolization options asother feature layers. Forexample, you can draw thepolygon entities with a singlesymbol or classified by aunique value.

Displaying a CADdrawing file

1. In the table of contents, right-click the CAD drawing layerand click Properties.

2. Click the Display tab.

3. Click and drag the sliders toadjust the CAD display.

4. Click the Drawing Layers tab.

5. Check the CAD layers thatyou want to display.

6. Click OK.

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Drawing CAD features aspoints, lines, or polygons

1. In the table of contents, right-click the CAD dataset andclick Properties.


The drawing options avail-able to you are the same asother feature layers.

3. Modify the drawing propertiesas necessary.

See the previous topics inthis chapter for more detailedinstructions.

4. Click the Drawing Layers tab.

5. Check the CAD layers thatyou want to display.

6. Click OK.

See Also

For more information on symboliz-ing the features in a CAD dataset,see �Drawing features to showcategories like names or types� inthis chapter.

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Adjusting transparencyYou can also use the Effectstoolbar to adjust the transparencyof CAD layers.

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AdvancedsymbolizationArcMap provides a few othertools that let you control howlayers draw. You can:

� Draw layers transparently.

� Set a reference scale forsymbols so they�ll, forexample, get larger as youzoom in on the map.

� Order the drawing sequenceof multilevel road networkswith complex symbology.

Transparency is especially usefulfor drawing raster layers overother layers on your map,allowing you to see the rasterlayer while still viewing underly-ing features.

When you set a reference scale,symbols and text will appearlarger as you zoom in on yourdata frame and smaller as youzoom out on your data frame. Sofor example, text labels will getlarger if you zoom in to a scalethat is larger than the referencescale.

The current scale of the dataframe is used as the referencescale to which all symbols andtext in the data frame will bemade relative. Setting a referencescale is like �freezing� thesymbol and text sizes used inyour data frame so that the way u

Drawing a layertransparently

1. Click the View menu, point toToolbars, and click Effects.

The Effects toolbar appears.

2. Click the Layer dropdownarrow and click the layer youwant to adjust.

3. Click Adjust Transparency.

4. Drag the slider bar to adjustthe transparency.

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they look at the reference scale ismaintained at all scales.

One reason to set a referencescale is if you want the detail inyour data frame to look the sameonscreen in Data view as it willwhen you print it out. Let�s sayyou are creating a map forpublication that will be printedout at a scale of 1:25,000. If youset your data frame�s scale to be1:25,000 and then choose SetReference Scale, the symbols andtext sizes in your data frame willappear on-screen at the same sizein relation to each other that theywill have in your printed map.

When a reference scale is set, alllayers (except for raster layers) inthe current data frame will havetheir symbols scaled relative tothe reference scale. However, youcan disable scaling for individuallayers: double-click the layer, goto the Display tab, and uncheck�Scale symbols when a referencescale is set.�

Setting a reference scalefor symbols

1. Set the scale of the dataframe to the scale you wantto use as the reference scale.

2. Right-click the data frame inthe table of contents and clickSet Reference Scale.

With (left) and without (right) a reference scale set.

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2Clearing a referencescale

1. Right-click the data frame inthe table of contents and clickClear Reference Scale.

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Arranging the drawingorder of complexsymbols and features

1. In the table of contents, right-click a data frame and clickAdvanced Drawing Options.

2. Check Draw using advanceddrawing options.

3. Click each symbol and set theappropriate properties.

Use the pictures to help youdecide how you want thesymbols to interact as theydraw.

4. Click Apply to view yourchanges.

5. Click OK.

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Symbolizing your dataSymbolizing by unique values willhelp when drawing layers withcomplex intersecting features.

Tip

What does AdvancedDrawing Options provide?Use the Advanced DrawingOptions to order the drawingsequence of multilevel roadnetworks with complex symbology.You can drag and reorder thedrawing sequence, join featuresdrawn with the same multilayeredsymbol, and merge features drawnwith a variety of multilayeredsymbols.

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symbolizing your data...5. click the color scheme dropdown arrow and click a color scheme. 6. click...

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