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Geographic Information Systems

Constructing and Sharing Maps

Previous: Introduction to GIS

Following: Mapping Place-Name Data

ArcMap is an easy-to-use program to display map data, symbolize it in useful ways, and output it to common, shareable file formats.



  1. Initializing ArcMap

  2. Adding Prepared Data to a Map

  3. Saving a Map Document

  4. Storing Relative Pathnames in a Map Document

  5. Viewing a Map Layer’s Attribute Table

  6. Sorting Attribute Table Records

  7. Locating Attribute Table Records on the Map

  8. Selecting Features

  9. Identifying Features

  10. Finding Features

  11. Labeling A Map Layer

  12. Creating a Layer File

  13. Symbolizing a Point Layer Using Proportional Symbols

  14. Adding a Basemap to a Map

  15. Finding Data on ArcGIS Online

  16. Disabling Background Processing

  17. Opening ArcToolbox

  18. Exporting a Layer to Google Earth

This tutorial will guide you through constructing, coloring, and saving a simple map using ArcMap, the primary component of ArcGIS, using prepared data. In the process of doing this, you will become familiar with some of the menus and procedures you would use to create maps using your own resources.

Getting the Tutorial Data

Since this tutorial will be using specific maps and data, the first step is to make your own copy of the tutorial data. First go to the network drive  G: (aka Google Drive File Stream), open the folder  Shared drives, then the folder  Amherst Software, then the folder  Maps, and finally the folder  Introduction to GIS. Copy this folder, or at least the subfolder  constructingmaps, to a location with fast access:

  • your local drive  C:, if you are using your own own computer and are off campus. Consider a location like your Desktop rather than the folder  Documents, as the latter is often a link to the network drive  OneDrive.
  • your network drive  G:\My Drive, if you are on campus or using a shared computer. For better performance, right-click on the copied folder and in its contextual menu select the item  Drive File Stream > Available offline, which will keep a local copy of your files in sync with the network files.

Since some — but not all — of the ArcGIS programs have trouble handling names with spaces or special symbols, do not rename the folders unless necessary.

The folder  constructingmaps contains the following files, amongst others:

states.shp counties.shp cities.shp gtopo_1km.tif
states.dbf counties.dbf cities.dbf gtopo_1km.ovr
states.prj counties.prj cities.prj gtopo_1km.tfw

Note that many of these files have the same root name, e.g. states; this means that they must all stay together to work properly.

Each such set of data is known as a shapefile (although only one file has the extension .shp), and is one of the basic data formats that is understood by ArcGIS.

Navigating ArcMap

Beginning with ArcMap

Procedure 1: Initializing ArcMap

  1. Click on the menu Start Menu Icon Start.
  2. Scroll down the menu and click on the item Folder Icon ArcGIS, and then click on the menu item ArcMap Icon ArcMap.
  3. ArcMap will take a while to load. Eventually, the dialog ArcMap Icon ArcMap - Getting Started will appear; if necessary click on the template Blank Map, and then click on the button OK.

The main ArcMap window is divided into two panes:

screenshot of emptymap

The larger pane on the right is the map display area. You can display geographic data here by adding it with the yellow-and-black button Add Data Icon Add Dataor menuing File > Add Data > Add Data Icon Add Data…. It’s located in the Standard toolbar, which is usually docked just below the menus in the ArcMap window.

Procedure 2: Adding Prepared Data to a Map

Prepared data is ready to use with ArcMap, without the need to first establish its geographic basis.

  1. In ArcMap Icon ArcMap, in the toolbar Standard, click on the button Add Data Icon Add Data.
  2. The special file dialog Add Data will now appear. It looks like an ordinary file dialog, but it only lets you see some of your folders, viz. those to which you have explicitly connected. Once you set up these connections, the folders will appear in all subsequent dialogs, and you will thereafter have quick access to them. When you need to set up a connection:
    1. Click on the button Connect to Folder Icon Connect to Folder.
    2. In the new dialog Connect to Folder, navigate to the folder where your data is stored; in this case, it would be the folder  constructingmaps that you previously copied to your U: or C: drive.
    3. Click once on the folder’s name.
    4. Click on the button OK.
  3. If necessary, navigate into the folder  constructingmaps.
  4. Select the file  states.shp; note that only one file with this root name appears, another feature of this special dialog.
  5. Click on the button Add.

A map of the United States including Alaska and Hawaii should now appear in the map display pane. Data such as states that are displayable geographically are called layers, because they overlay each other like transparencies when you add them. Maps can display several different kinds of layers: points, polylines, polygons, images, and others. The layer states consists of polygons defining the boundaries of the fifty states. Each of these polygons is called a feature of the layer.

screenshot of states

The layer’s name will also be listed in the pane on the left, which is called the Table of Contents. By default its name is the data file’s root name, but it can be easily changed by cllcking on it and typing.

Experiment: Change the name of the layer  states by clicking on it, pausing, and then typing something else, e.g. United States.

The Table of Contents provides three views of your data. The primary view is  List by Drawing Order, which shows just the simple names of data layers, corresponding to what is visible (or potentially visible) in the map pane. The secondary view is  List by Source, which lists the full path names of your data files. In addition to data layers, it also shows data you’ve referenced that is undisplayable, such as tables of additional data. Usually you’ll want to stay in the Drawing Order view. The third view, Selection, is a topic for another day.

Experiment: Click on the tabs Display and Source to observe how the view of your data changes.

ArcMap Documents

Before we proceed any further, it’s a really good idea to save your map.

ArcMap documents preserve your current arrangement for use at a later time, and are especially useful after the occasional ArcMap crash.

In addition, ArcMap is aware of the location of a saved map, establishing it as the Home folder so that related files are easy to find.

You’ll therefore want to continue to save them on a regular basis, for example every time you’re satisfied with the current view.

Procedure 3: Saving a Map Document

  1. In ArcMap Icon ArcMap, select the menu File, and click on the menu item Save. You can also simply click on the button  Save.
  2. The first time you save your map document, the dialog Save As will appear. It’s highly advised that you navigate to the same folder containing the shape files you’ve added to the map, in this case  constructingmaps.
  3. Your map document will have a file extension of .mxd . Choose a root name describing your project, e.g. states, and click the button Save.

ArcMap documents do not actually contain the data you add to them, such as the layer  states. Instead, they contain pointers to your data, as well as information about how to display them. That’s why it’s a good practice to keep them together, unless the data is in a standard, shared location such as an archive.

Because ArcMap documents only contain links to your data, another good practice is to make those links relative to the map document. For example, the data might be referenced as being “in the same folder as me” rather than being “in the folder C:\Documents and Settings\username\Desktop\constructingmaps”. Either of these is known as a path to the data; the former is called relative while the latter is called absolute. Relative paths will facilitate moving the folder containing your map file along with all the files linked to it to another location.

Procedure 4: Storing Relative Pathnames in a Map Document

  1. In ArcMap Icon ArcMap, select the menu File, and click on the menu item Map Document Properties....
  2. In the dialog Map Document Properties, click on the checkbox  Store relative path names to data sources.
  3. Click on the button OK.
  4. Back in ArcMap Icon ArcMap, click on the button  Save.

Note that you can only open ArcMap documents by double-clicking on them in the Windows Explorer, or by opening them from within ArcMap Icon ArcMap through the menu File and the menu item Open (or clicking on the button  Open). They may not be added to a map using the button Add Data Icon Add Data, which is reserved for the different pieces of data that make up a map.

The Tools Toolbar

The primary toolbar is called Tools, and it contains the buttons listed below. They provide quick ways to zoom in and out, pan across the map, restore a map to its full extent, and return to previous views of the map:

Button Action
Tool for Zooming In to a Region Zoom in: click a point to zoom in to it by 50%, or click-and-drag a rectangular region to view.
Tool for Zooming Out to a Region Zoom out: click a point to zoom out from it by 50%, or click-and-drag a rectangle to contain the current view.
Tool for Zooming In a Fixed Amount Zoom in to current center by 20%.
Tool for Zooming Out a Fixed Amount Zoom out from current center by 20%.
Tool for Panning Pan (drag) the map.
Tool for Returning to the Full Extent Full extent: zoom out to the full map view.
Tool for Returning to the Previous Extent Go back to previous map view — if you lose your map, this will bring it back.
Tool for Returning to the Next Extent Go forward to next map view.
Tool for Selecting Features Select features.
Clear selected features.
Tool for Getting Feature Information Identify features.
Tool for Returning to the Full Extent Find features.
Go to X-Y Coordinate Position Go to an (X, Y) coordinate position.
Tool for Returning to the Full Extent Measure distance along a path you define with a series of clicks (double-click the last).

The toolbar is shown above docked between the two window panes, but may be located in some other position when you open ArcMap for the first time.

Experiment: Locate the toolbar and drag it into position between the two panes (unless you prefer it somewhere else).

Experiment: Try zooming in and out of the map, panning, and using the full extent button to return to the original map view. Also try using the back and forward buttons to move along the sequence of views you’ve created.

We’ll talk about the other tools later.

Map Scales

The degree to which one has zoomed in to or zoomed out from the map is commonly expressed by comparing a distance on the map to the same distance in the real world. So, for example, the distance from New York to Los Angeles is about 6 centimeters in the computer view above, but roughly 4,000 kilometers in real life. Since 6 cm = 0.00006 Km, we can calculate a ratio of these two numbers that doesn’t depend on units, 0.00006 Km : 4,000 Km = 1 : 70,000,000. This ratio describes what one map unit corresponds to in the real world, and is called the map scale.

ArcMap displays the current map scale in a text field / menu at the top of the screen just to the right of the button Add Data Icon Add Data:

Map Scale text field / menu

Intially the scale for your map will be around 1 : 100,000,000, depending on the size of the map display pane. As you use the zoom buttons in the Tools toolbar, the scale adjusts automatically. It’s also possible to change the map scale by clicking and typing directly in the text field, or by clicking on the adjacent pop-up menu button Pop-up Menu Button and choosing from a list of common values.

Experiment: Observe how the map scale changes as you zoom in and out of the map. Try changing the scale by typing a number in its text box, and by choosing a value from the menu.

Note that as you decrease the second number in the map scale ratio, the scale increases. Cartographers therefore use the following terms to describe scales:

  • At a small scale:
    • the ratio is small;
    • the second number is large;
    • the map is zoomed out;
    • you can see a large area;
    • you see less detail.
  • At a large scale:
    • the ratio is large;
    • the second number is small;
    • the map is zoomed in;
    • you can see a small area;
    • you see greater detail.

Map Layer Attribute Tables

Tables, Records, and Fields

When you add a map layer, you will also bring along an attribute table describing the individual features of the map. For example, every state in the map has a name, and we may want to label them, so we need to know how those names are associated with the polygons.

Layer Menu: Open Attribute TableProcedure 5: Viewing a Map Layer’s Attribute Table

  1. In ArcMap Icon ArcMap, in the Table of Contents, right-click on the name of the layer, e.g.  states.
  2. The layer’s contextual menu will now appear; it provides many actions that apply just to this layer. Select the menu item  Open Attribute Table.

Shortcut: you can also open a layer’s attribute table by holding down the Ctrl key and double-clicking on the layer’s name in the Table of Contents.
An attribute table appears in its own window floating above the map, and it looks something like the following:

screenshot of states attributes

In this table, every feature of the layer is listed in its own row or record. Each column or field represents a different attribute of these features. So, in this case, we see each state name on a different row, along with its population in 2000 and 2005, its federal information-processing code, etc.

Every attribute table will begin with the two structural fields FID and Shape. The first is a Feature Identifier that will always be a unique number to distinguish one feature from another. The second is a summary description of the geography of this feature; hidden behind the text “Polygon” there’s a lot of information about how to draw the lines that comprise it.

All other fields are optional, but their presence is important to enable the true power of GIS. These fields are usually one of two types:

  • Text, such as STATE_NAME; these field values are left-justified.
  • Numeric, such as POP2000: these field values are right-justified.

Note that sometimes fields appear to be numeric but in fact are text, e.g. STATE_FIPS, because they are stored as a sequence of individual digits.

Locating Attribute Table Records

The features in a table are often in a random order. However, you can compare them more easily with each other by sorting them by any one of the attributes in the table.

Field MenuProcedure 6: Sorting Attribute Table Records

  1. In ArcMap Icon ArcMap, in a layer’s Attribute table, pick a field, e.g. STATE_NAME, and double-click on its header, the name of the field at the top of its column.
  2. Note that the column will sort itself in ascending order, from A to Z.

  3. Double-click on the header a second time; the column will now sort itself in descending order, from Z to A.
  4. Locate a field whose values are common to multiple records, e.g. SUB_REGION, and right-click on its header to bring up its contextual menu; you’ll see the same two options listed, Sort Ascending and  Sort Descending, but instead select the third one,  Advanced Sorting….
  5. The dialog  Advanced Table Sorting will now appear; it lets you choose multiple columns on which to sort in sequence:
  6. Advanced Table Sorting Dialog

    1. In the menu Sort by, select a field whose values are common to multiple records, e.g. SUB_REGION.
    2. In the menu Then sort by, select a more specific field, e.g. STATE_NAME.
    3. Click on the button OK.

    Note that now all of the records are sorted according to the first field, and within each group the records are sorted by the second field.

Note that all of the data in a row stays together, even though you’ve sorted on a single column (something that doesn’t automatically happen in a program like Excel); this is a common feature of a database.

Experiment: Sort the data by different fields in the table.

Locating Map Features

Once you have found a feature in a table, you can locate it on the map in a few ways.

The most common is to select it, but you can also flash it and zoom to it.

Field MenuProcedure 7: Locating Attribute Table Records on the Map

  1. In ArcMap Icon ArcMap, in a layer’s Attribute table, scroll to a feature you are interested in, and click on the button  Select Record at the far left end of the record.
  2. The feature is now selected , and its record will be highlighted in an aqua color.

    In addition, the feature will be highlighted in the same color on the map itself; you may have to scroll, zoom, and/or move the attribute table around to see it.

  3. To deselect the record you can either:
    1. Right-click on the button  Select Record and then click on the menu item  Select/Unselect;
    2. In the toolbar Tools, click on the button  Clear Selected Features.
  4. In an intricate map it can sometimes be hard to pick out a selected feature, so sometimes a better way to locate it is to flash it, by right-clicking on the button  Select Record and then click on the menu item  Flash.
  5. Often the best way to locate an item is to zoom directly to it, by right-clicking on the button  Select Record and then clicking on the menu item  Zoom To.

Exploring Map Features

The information in the attribute table can be used in a more focused way to explore map features.

Selecting Map Features

When you don’t have the attribute table open, and you recognize features on the map, you can also select them using the tool Identify Tool Select Features.

Field MenuProcedure 8: Selecting Features

  1. In ArcMap Icon ArcMap, in the toolbar Tools, click on the button Identify Tool Clear Selected Features; this will remove any highlighting remaining from the previous procedures.
  2. Again in the toolbar Tools, click on the tool Identify Tool Select Features.
  3. In the map pane, click on any feature you recognize, e.g. Massachusetts. The feature will be highlighted with the same aqua color seen in the attribute table.
  4. If it’s not already, open the attribute table .
  5. In the attribute table, click on the button Show: Selected. Now only the selected feature will appear, so you don’t have to scroll through the records to find it.

Identifying Map Features

When you don’t have the attribute table open, a quick way to get information about a particular map feature is to use the toolIdentify Tool Identify.

Procedure 9: Identifying Features

  1. In ArcMap Icon ArcMap, in the toolbar Tools, click on the toolIdentify Tool Identify.
  2. The dialog Identify will open; move it to a convenient location that doesn’t obscure the map.
  3. In the menu Identify from:, choose which layers you want to select from:
    1. <Top-most layer>;
    2. <Visible layers>;
    3. <All layers>;
    4. A particular layer.

    With a single layer on the map, these options all have the same effect; there will be more about multiple layers later.

  4. Click on a feature in the map, and the data fields in its row in the attribute table will be displayed.

Finding Map Features

More often than not you won’t recognize a feature on the map, but you can find it without going into the attribute table using the toolTool for Returning to the Full Extent Find.

Procedure 10: Finding Features

  1. In ArcMap Icon ArcMap, in the toolbar Edit, click on the toolTool for Returning to the Full Extent Find.
  2. The dialog Find will open; move it to a convenient location that doesn’t obscure the map.
  3. Click on the tab Features if it’s not already selected.
  4. In the field Find:, type in some piece of information you know about the feature such as its name.
  5. In the menu In:, choose which layers you want to select from:
    1. <Top-most layer>;
    2. <Visible layers>;
    3. <All layers>;
    4. A particular layer.

    With a single layer on the map, these options all have the same effect; there will be more about multiple layers later.

  6. In the button group Search:, choose which attribute field you want to search for this information:
    1. All fields;
    2. In field:, and then choose one of the available fields from the menu;
  7. Click the button Find, and a list of matching features will be displayed at the bottom of the dialog.
  8. Click on the feature of interest and the map will flash its location.
  9. If you right-click on the feature of interest, a contextual menu will appear, and you can choose some other options, such as  Zoom To.

Labeling Map Layers

There is, of course, a more general way to identify features on a map, and that is by labeling them on the map itself.

Every map you’ve ever seen probably includes labels that give names to the features on the map.

ArcGIS can label a layer with any of the data in its attribute table, and it will intelligently position them to avoid overlap with other layers’ labels.

The general properties of a layer, such as labeling and the data source, are controlled through the dialog  Layer Properties, which you will see a lot of from this point onward.

Layer Menu: Properties...Procedure 11: Labeling a Map Layer

  1. In ArcMap Icon ArcMap, in the Table of Contents, right-click on the name of the layer, e.g.  states.
  2. The layer’s contextual menu will now appear; it provides many actions that apply just to this layer. Select the menu item  Properties....
  3. Shortcut: you can also open a Layer Properties dialog by double-clicking on the layer’s name in the Table of Contents.

  4. In the dialog  Layer Properties, click on the tab Labels, which looks like the following:
  5. screenshot of label tab

  6. For labels to appear on your map, you must click on the checkbox Label features in this layer.
  7. Placement PropertiesLabelIn the section Text String, in the menu Label Field, choose which attribute you want to use for the labels.

    For example, select STATE_ABBR to use state abbreviations, which are smaller than the state name and will fit the map more easily.
  8. In the section Text Symbol, choose a font, font style, font color, and font size.

    Labels appear at the chosen size relative to the computer screen and independent of the map scale, so you will probably need to adjust them when you are nearing completion of the map and know how much room you have for them.
  9. By default labels will not overlap and will disappear when necessary. Also by default every part of a feature will be labeled (e.g. all of the Hawaiian islands). These options and more can be changed by clicking on the button Placement Properties… and making appropriate adjustments.
  10. Click the button OK (or Apply if you want to see the effect without closing the dialog).
  11. Once you have chosen the attribute that you want to use to label the layer, you can quickly turn the labels off and on in the Table of Contents, by right-clicking on the name of the layer, e.g.  states, and then, in the layer’s contextual menu, selecting the menu item  Label Features.

Zoom into the map to verify that the labels you’ve added appear at an appropriate scale.

Symbolizing Map Layers

Symbolizing Polygons Using Categories

Right-click on the map layer again and select Properties to bring up the Layer Properties screen. Now select the Symbology tab.

screenshot of symbology tab

At present, the map is colored using a single color (symbol) for every feature (state polygon). If we simply wanted to change this color, we could click on the colored rectangle and select a different color. However, what we want to do is color the states different colors. To color the states different random colors, select Categories (which will bring up a new screen), set the Value Field to STATE_NAME--because we want to give different colors to states with different names. Then choose a Color Scheme on the right that consists of patches of distinct colors.

screenshot of unique values options

Click the Add All Values button and OK. Each state will now be colored by one of the colors from the scheme you chose. You can go back to the original single color for all states through the Symbology tab by selecting Features then Single Symbol then OK.

Checklist for Coloring states random colors

  • Right-click the states layer and select Properties
  • Click the Symbology tab
  • Select Categories
  • Select STATE_NAME as the Value Field
  • Select a Color Scheme with patches of colors
  • Click Add All Values

Symbolizing Polygons Using Quantitative Fields

Right-click the states layer, select Properties and then the Symbology tab. Select Quantities on the left.

screenshot of quantitative options

Begin by selecting the quantitative variable for coloring the map as the Value in the Fields section.

Coloring a map using a quantitative variable is more complicated than coloring it using random different colors. There are three basic choices to make:

  1. You need to select a color scheme from the ones provided. Generally you will select a color ramp whose values vary in a continuous way to indicate change in the quantitative variable.
  2. You need to decide how many value classes you want to use. This will group the values into a discrete set of ranges.
  3. Finally, you need to decide what method you will use to classify the values (choose the value ranges). ArcMap provides several ways to do this automatically, as well as the option of letting you set the break points between categories manually.

Such a map is sometimes called a heat map because of its common use to describe temperature, though usually with a blue-to-red (cold to hot) color ramp.

Classification Methods

ArcMap will by default use five categories and the natural breaks method for dividing the values into five categories. The natural breaks method tries to draw the lines between categories of values where they naturally break. If you want more categories, you can easily change the number. Usually between five and eight categories works reasonably well. If you use too many categories, the color values may be difficult to distinguish.

To use a different method of classifying values, click the Classify button over on the right side of the screen.

screenshot of classifcation screen

The quantile method creates categories with near-equal numbers of features in each. If we use it to create five categories of states and there are 51 states (50 states and the District of Columbia), we will get categories that each contain ten or eleven states. The equal-interval method divides the values into categories whose value ranges are the same. Choose one of these methods and click OK on this screen and then on the Layer Properties screen. The map will be colored--or symbolized according to the choices you made.

Checklist for coloring a map using a quantitative field

  • Right-click the states layer and select Properties, then the Symbology tab
  • Click Quantities
  • Select the field you want to use in Field Value
  • Select the number of Classes
  • Choose a Color Ramp
  • Click Classify to change the classification scheme

Eliminating the Size Dependence of Data Display

When looking at a map like the previous one, which displays population as a color spread out over the entire state, our brains automatically integrate the area, emphasizing larger states over smaller states, even if they have the same population. Compare, for example North Dakota and Alaska —  which one looks like it has the larger population? They actually have the same population, with only a 2% difference.

So, instead of coloring a map with a simple numeric attribute such as “total population ” — an extensive quantity — it’s usually better to divide it by the state’s area to map population density — an intensive quantity. It’s also reasonable to map the ratio of any two extensive attributes where that makes sense, e.g. “people over 80” divided by “total population”, to find the relative fraction of an attribute, which is also an intensive quantity.

In either case, this is easily accomplished in ArcGIS by specifying the field in the denominator as a normalization field.

Such a representation of data is known as a choropleth map, from the Greek for khōra (region) + plēthos (multitude).

Exercise: Normalizing Data

Using data for the female population of each state, normalize it by the male population, and map with an appropriate symbolization.

Both the classification and normalization of your data can make major changes in the way your map looks and in the way it’s interpreted by someone who neglects to read the legend. It’s important to make these choices based on an understanding of the data, with an eye on establishing visual contrast between different data groups.

Creating Layer Files

Once you have colored a layer in a particular way, it’s sometimes useful to save that configuration for future use, such as in another map. A layer document stores a reference to a data set and how it’s currently symbolized. It can be added to a map just like the plain data set.

Procedure 12: Creating a Layer File

  1. In ArcMap Icon ArcMap, in the Table of Contents, right-click on the name of the layer, e.g.  states.
  2. The layer’s contextual menu will now appear; select the menu item Save as Layer File....
  3. The dialog Save Layer will appear. It’s advisable that you navigate to the same folder containing the shape file with which you’ve you’ve been working.
  4. Your layer document will have a file extension of .lyr . Choose a root name describing the data and symbology in this file, e.g. states-pop2000, and click the button Save.

Using Multiple Layers

One of the most powerful features of ArcGIS is its ability to display multiple map layers at once, much like a set of transparencies allows different views to be displayed together in many combinations. To see how this works, we’ll add more and different types of data to your map, beginning with the plain states file you loaded earlier.

Exercise: Comparing Different Symbolizations of the Same Data File

  1. Change the symbology of the layer  states to be Features using a Single Symbol with no fill color and a thick, bright red outline .
  2. Add in the layer file that you created in the previous procedure,  states-pop2000.lyr (see the procedure Adding Prepared Data to a Map for details on adding data). It will be placed above the previous layer in the Table of Contents, which means it will appear in front of it in the map itself. It references the same data set, but includes the symbology you created previously.
  3. In the Table of Contents, you may have noticed the checkboxes to the left of the layers’ names; they are used to turn their display on and off . Click off the upper layer’s checkbox to reveal the lower layer in the map, then click it back on again.
  4. You can also rearrange the layers by clicking on one layer’s name in the Table of Contents and dragging it above or below another layer; this places it in front of or behind the other layer in the map.
  5. Finally, remove the more symbolized layer to return to the original single-symbol layer:
    1. In ArcMap Icon ArcMap, in the Table of Contents, right-click on the more symbolized layer  states-pop2000.
    2. In the layer’s contextual menu, click on the menu item  Remove.

Next we’ll add a different type of data, a set of points:

Exercise: Adding and Symbolizing a Point Layer

  1. In ArcMap Icon ArcMap, in the toolbar Standard, click on the button Add Data Icon Add Data.
  2. In the dialog Add Data, navigate into the folder  constructingmaps.
  3. Note how the file icon for  cities.shp shows points, indicating the type of data to be displayed. Click on  cities.shp, and click the button Add.

    Now many points appear on the map, indicating the different cities in the layer. By default, a point layer will automatically be placed in front of all polygon layers on the map, to avoid being covered over.
  4. Use the tool Identify Tool Identify to learn more about specific cities. You may need to zoom in to spatially distinguish some cities.
  5. In the Table of Contents, just below the layer  cities, you’ll see the same symbol being used to represent the layer on the map. Click on the symbol to open the dialog Symbol Selector, and try out the available options.


Exercise: Displaying a Data Subset

Can you make just the capital cities visible on the map above? (Hint: right-clicking on pretty much anything in ArcGIS will bring up a contextual menu of available options for using it.)

Save your result as a layer file so you can easily reference it later.

The previous step only allows you to select a uniform symbology for the points in a point layer. Like polygons, it’s also possible to vary the symbol based on values in the layer’s attribute table, but in several unique ways such as changing the symbol size.

Proportional Symbols Procedure 13: Symbolizing a Point Layer Using Proportional Symbols

  1. In ArcMap Icon ArcMap, in the Table of Contents, double-click on the layer’s name, e.g.  cities.
  2. In the dialog  Layer Properties, click the tab Symbology.
  3. On the left side, in the list Show:, click on the list item Quantities.
  4. Click on the sub-list item Proportional Symbols.
  5. In the section Fields, in the menu Value:, select an attribute to use, e.g. POP2000.
  6. In the section Symbol, click on the button Min Value,
  7. In the dialog Symbol Selector, choose a symbol type, a color, and a minimum size, e.g. 1.
  8. Click the button OK.
  9. Back in the dialog Layer Properties, click the button OK. The size of the cities’ symbols are now based on their populations.
  10. In this symbolization the smaller symbols are placed on top of the larger ones so they are more visible, however they may still be so thick in some areas that you cannot distinguish the state boundaries behind them. One way to compensate for this is to change their transparency:
    1. Double-click on the layer you want to change, e.g. cities.
    2. In the dialog Layer Properties, click the tab Display.
    3. In the field Transparent: %, type a percentage value, e.g. 50.
    4. Click the button OK.


Procedure: Adding and Symbolizing an Image Layer

We’ll add one type of raster image, representing elevation. It will come from a local repository of map data that we maintain here at Amherst College.

  1. In ArcMap Icon ArcMap, turn off the layer  cities so that only the layer  states is visible.
  2. In the toolbar Standard, click on the button Add Data Icon Add Data.
  3. In the dialog Add Data, navigate into the folder  constructingmaps, and add the file  gtopo_1km by clicking once on its icon and then clicking the button OK. (If you click twice on an image, it may “open” like a folder and provide its three color bands separately, depending on the type of image.) Note how its icon shows a grid of pixels, indicating the type of data (image).
  4. In the dialog Geographic Coordinate Sytems Warning, ignore the information provided and click the button Close. We will consider the implications of this dialog later when we discuss coordinate systems.

    A grayscale representation of elevation will now appear. Note that, by default, an image layer will be placed behind a polygon layer to avoid obscuring it, so initially you may not be able to see some of this layer because it is covered up by the  states layer.
  5. Raster layers have one value for each pixel, in this case representing elevation, and as with vector layers that information can also be displayed:
    1. In the toolbar Tools, click on the toolIdentify Tool Identify.
    2. To avoid displaying only information about other layers (such as  states), in the dialog Identify Tool Identify, change the menu Identify from: from the default menu item, <Top-most layer>, to another such as <Visible layers> or specifically  gtopo-1km.
    3. Click on different locations to determine their elevation.
  6. Raster layers are displayed by assigning each pixel a color based on its value. This can be, for example, the red, green, and blue values of a photograph, each in the range 0 - 255. In the case of a single-valued quantity such as elevation, a grayscale ramp is used by default, where the elevation range shown above in meters, –407 to 8752, is mapped to the black-gray-white values 0 - 255 (the latter shows up as the stretched value in the dialog Identify Tool Identify). A number of other color ramps are available, e.g. , which runs from bluish green at the lowest elevations to red and then white at the highest elevations (suggesting “snow-capped mountains”).

    Double-click on the layer  gtopo_1km to bring up the dialog Layer Properties, click on the tab Symbology, and try out a number of different color ramps.

    Question: Which two places on the surface of the Earth are pinpointed by the maximum and minimum elevations, 8752 and –407? What is the linear unit here?

The colors in the color ramp are associatd with stretch

Exercise: Setting Elevation Limits

Zoom in on New England. We know it’s mountainous here, but you won’t see much contrast because the color ramp is set to the work with all of the mountains in the world. Set a more reasonable range of elevations by finding an appropriate type of stretch for the color ramp.

Finding Prepared Data

A lot of geographic data is available from government, commercial, and other sources, often in a ready-to-use format.


Often you’ll want to provide background for your data, such as streets or terrain, and not have to worry about constructing it yourself.

The company that makes ArcGIS, ESRI, provides a large number of basemaps through Internet servers, which you can easily add to your ArcGIS map.

Procedure 14: Adding a Basemap to a Map

Basemaps are relatively easy to add ArcMap, though it’s best to first add your own data to establish its view and ensure a good choice of background. Then:

  1. In ArcMap Icon ArcMap, in the toolbar Standard, click on the menu arrow Add Datanext to Add Data Icon (or menu File > Add Data), and then  Add Basemap….

    The following dialog will appear:

    Add Basemap Dialog

  2. Double-click on one of these, e.g. Oceans (which will work well with a user-provided land-based elevation layer).

    The basemap should be added to your map, behind most other layers.
  3. Basemap Behind User-Provided Data

  4. There may be multiple pieces added to the map, e.g. a Reference layer that provides labels; if these are in the way, you can turn them off.

    The drawback to using an Internet server for these maps is that they can sometimes be unavailable or slow to load; you may wish to turn them off until you are ready to publish your map.

ArcGIS Online

ArcGiS Online ( is a source of geographic data in formats that are ready-to-use with ArcGIS “Desktop”.

It has datasets provided by ESRI (in particular the same basemaps as above, and others that sometimes duplicate what’s in  G:\Maps), as well as many that are contributed by others.

Procedure 15: Finding Data on ArcGIS Online

ArcGIS Online ( can be accessed both from within ArcGIS Desktop and, more conveniently, from any web browser.

  1. If necessary, start up a web browser:
    1. Click on the menu Start Menu Icon Start.
    2. Point at the menu item All Programs.
    3. Locate your preferred web browser,  Chrome or  Firefox or  Internet Explorer (perhaps in the folder Networking and Communications), and click on it.
  2. In your web browser, visit the web address
  3. At the top of the page, click on the link Gallery.
  4. On the page Gallery you can browse for different types of data amongst the “featured content”, but it’s generally better to search for keywords. In the upper-right corner of the page, click in the text field  Search  for, type one or more keywords, e.g. usa major rivers, and in the menu that pops up, click on the menu item Search All Content.
  5. On the left side of the window, check on the box  Show ArcGIS Desktop Content; otherwise everything displayed will only work within
  6. Scroll down to review the found items; you’ll see a number of data types:
    • ArcGIS Desktop 10-usable, which may be downloadable or referencible internet services:
      • Shapefiles and CSV tables;
      • Layer Packages;
      • Features, Tiles, WMS, KML, and Map Images, which are internet data services;
      • Map Documents, which are .mxd files.

        These documents seem to generally include references to data inaccessible to anyone outside of the author (or a small circle), so unless you can locate all of the data within, they probably won’t be useful to you.
    • Web browser-viewable Web Maps. These can be fun to study and play around with, but aren’t usable with ArcGIS Desktop 10.

    You can click on the titles of these data sets to get more information about them, e.g. their size, author, and any restrictions on their use.

  7. Choose a data set from one of the first two data types, e.g. the layer package USA Major Rivers, click on menu  More options and select the menu item Open in ArcGIS for Desktop.
  8. In the subsequent file download dialog, you can open the file directly (but it will be saved in a temporary location), or you can save it first in a convenient location (e.g. the folder  constructingmaps), and then add it to your map.
  9. The downloaded file will have the name item.pkinfo, which is a reference to the layer on

    As with basemaps, the drawback to using an Internet server as a data source is that they can sometimes be unavailable or slow to load; you may wish to turn them off until you are ready to publish your map.
  10. You can create a free account with ArcGIS Online and create your own publically accessible web maps by uploading materials you create with ArcGIS (beyond the scope of this course). If you are a student, faculty, or staff member of Amherst College or one of the Five Colleges, you can Sign in with your enterprise login.

Finding Data on the Internet

It’s always worth searching the Internet for geographic data.

Much of this data must be converted into a format that ArcGIS can properly display, and working with such data will be the topic of the next few sections.

However, many sets of data are “prepared” data, i.e. they are ready to be loaded into ArcGIS and immediately displayed.

Commonly such data would be labeled as shapefiles, though they are likely to be packaged as a .zip archive that Windows will automatically open.

Another relatively new format is the geoTIFF, a standard TIFF image that’s been enhanced with geographic information.

Exercise: Mapping Interesting Data

Look around on ArcGIS Online, or on the Internet using a keyword such as shapefile or geoTIFF, to find another dataset related to your interests and map it. Would it be relevant to add other related datasets? If so, see if you can find and add them to your map. Symbolize them so that they’ll stand out relative to the other datasets on your map.

Sharing Maps

The ArcGIS software is not available to most people, so its documents are not easily sharable. However, there are a number of different ways to save sharable maps depending on the purpose you have in mind. You can print on paper, create an image, create a PDF, or export it to the free applications Google Earth or ArcReader.


Cartography describes the clear, elegant, and even artful design of a map.

With an appropriate choice of content, structure, symbology, and labels, a map can speak volumes while still being easy to read and understand. A map that is just thrown together may be helpful to the author, who knows what to look for, but could be confusing and quickly ignored by an intended audience.

Entire books have been written on designing good maps. In lieu of reading one of them, here are some important considerations to keep in mind when preparing your maps for sharing:

  • Color: Choose an appropriate symbology for your data and background for your maps that will enhance rather than detract from the visibility of your data.

    There are a number of color standards that people respond to perceptually, e.g. darker colors for larger numbers, and others that they expect, e.g. green for forest areas, etc.

    Colorblindness also prevents some people from distinguishing certain colors. So it’s a good idea to pick your color combinations carefully. Visit for some ideas.

    Also note that many journals still only publish black-and-white maps, which may require simplification.
  • Contrast: More generally, the different elements of your map need to be distinguishable from each other. Pick symbols, labels, and graphic element backgrounds so that they are visible when they overlap.
  • Scale: Usually you will want to use a scale such that your data or important background elements have maximal magnification and are centered. If printing on paper, use the dialog Page and Print Setup… to orient the paper as portrait or landscape to match the data.
  • Projection: This is a topic that will be discussed later, but in most cases it’s important to use an appropriate projection that reduces distortion over the area of interest.
  • Standard Map Elements: A number of additional elements that help explain the map, such as a legend, north arrow, and scale bar, should always be included, and these will be described next.
  • Titles and Captions: The names of data layers will be visible in the legend, so make sure they are not the default abbreviated names. In most cases the map itself should also have a descriptive title.
  • Graphics: Other graphic elements are often useful, such as arrows to point out particular features, and can be added using the Draw toolbar.
  • Inset Map: For larger-scale maps, it can be helpful to include a small-scale map as an inset to provide a locational context within a more well-know geography, e.g. a particular region within New England. Thes

Preparing a Map for Sharing

When you publish your map to static formats such as paper, digital images, or PDF, you’ll need to define a size for the output, which you can think of simply as the paper size. Menu File > Page and Print Setup..., and proceed in the usual way to choose Printer, Paper Size, Paper Orientation, etc. In addition, you’ll probably want to check the box Use Printer Paper Settings, since that is usually a good size for sharing.

To see how your map will look on the printed page, go to the View menu and select Layout View.

screenshot of layout viewThis displays the map to fit inside the margins of the paper type chosen. You can change the margins by clicking on them and dragging one of the blue boxes to a new position. Note the thin gray dotted line; it shows the actual limits to printing on the paper size for the printer you’ve chosen.

The map as displayed in the margins is the same one you’ve chosen in the data view, no matter how big or small the margins are. You can use the same tools in the toolbar Tools to change the relative size and position of the map within those margins. Important: in the Layout View, you should have access to the toolbar Layout, which provides similar tools that reference the paper rather than the map — with them you can zoom into the paper without changing the size of the map relative to the paper.

Before sharing your map, it’s a good cartographic practice to add a title, a legend to describe the different layers, a north arrow to show directions, and a scale bar to show the map scale:

  1. Go to the menu Insert and select the menu item Title, and a text box will appear near the top center of the screen. Enter a title and drag the box to an appropriate position.
  2. Next go again to the menu Insert and this time select the menu item Legend. Take all the defaults by clicking the button Next on each of the series of screens. Drag the legend to an appropriate place and resize it if necessary.
  3. Now menu Insert and select the menu item North Arrow...; choose your preferred style, click the button OK, and then move the arrow where you would like it.
  4. Finally menu Insert and then select the menu item Scale Bar...; choose your preferred style, click the button OK, and then move the scale bar where you would like it. Note that by default the scale uses whatever the map units are; you can change that by double-clicking on the bar and choosing a different one.

If necessary, resize the margins around the map to fit these new additions.

ArcMap can have multiple data frames defined in its Table of Contents, but only one of them can be displayed at a time in the Data View.

However, layouts can display the maps from all frames at once, for example to show an overview map in an inset box.

Saving a Map as an Image or Acrobat PDF

The most basic way to share maps is to save them in one of the file formats commonly found on the Internet.

Go to the menu File and choose the menu item Export Map.... Then navigate to the folder in which you want to save the map.

If your intent is to use the map on a computer, such as in a web page or a PowerPoint presentation, where printing is a secondary consideration:

  • If you have raster images in your map, select JPEG as the format; it will provide lossy but excellent compression.
  • Otherwise choose PNG, which produces good compressed files from vector graphics (it also does a reasonable job on raster graphics).

Choose an image resolution of about 100 dots per inch (dpi), good for display on most computers.

If your intent is to use the map in a paper or a poster that will be printed, for example with Microsoft Word or Adobe InDesign, you will want to save it in an image format that preserves lots of detail; TIFF works well. Choose a resolution of at least 300 dpi.

If you would like the map to be a stand-alone document, then the Acrobat format PDF is a good choice. These files can be easily displayed by most people with the Adobe Reader software, and it’s readily downloaded by web browsers. PDF will preserve more of the details of the map, and so it’s a good way to distribute it if it will later be printed. A PDF map even provides some degree of interactivity, e.g. turning layers on and off. Important: make sure you click on the tab Format and then choose the checkbox Embed All Document Fonts; this will help keep the document readable by everyone.

Experiment: Try producing all three of these file formats, and compare them. In the PDF document, note the tab on the left called Layers; click on it and then click on the “eye” icon next to one of your layers, and observe what happens.

Saving a Layer for Google Earth

The free application Google Earth has become very popular, as it provides imagery of the Earth’s surface (taken from airplanes or satellites) in an easy-to-access format — if you have an internet connection.

It’s also a lot of fun to use, as you can zoom around the Earth and view it from different perspectives, including terrain and buildings in 3D!

ArcGIS is a useful program to create additional layers that can be viewed in Google Earth.

Exporting to Google Earth makes use of a special geoprocessing tool, an extra program that transforms geographic data into new formats from which additional information can be extracted.

Geoprocessing tools are stored in a collection called ArcToolbox.

The next two procedures are preliminary steps useful for most geoprocessing activities.

Procedure 16: Disabling Background Processing

By default geoprocessing tools run in the background so that you can continue using ArcMap for other things, but it’s harder to monitor and there can be occasional failures that don’t otherwise occur. So until you’re used to these tools, it’s better to run them in the foreground, even though it will then be the only thing that ArcGIS is doing.

  1. Menu Geoprocessing, then select the menu item Geoprocessing Options….
  2. In the dialog Geoprocessing Options, in the area Background Processing, click off the checkbox  Enable.
  3. Click on the button OK.

ArcToolboxProcedure 17: Opening ArcToolbox

The majority of geoprocessing tools can be found in ArcToolbox, a large collection of “plug-ins” for ArcGIS.

  1. In the standard toolbar, click on the button  ArcToolbox, which will open it up.
  2. Note the large variety of tool groups available; clicking on any one of them will reveal subgroups of tools, inside of which you will find individual tools.
  3. You may want to “pin” the ArcToolbox window to the right edge of the ArcMap window, which will keep it out of the way until you need it:
    1. Begin to drag the edge of the window  ArcToolbox, and a set of “pinner” buttons will appear; move the cursor on top of the Winder Right Edge Pinner right-edge pinner and release.
    2. ArcToolbox TabClick the button Auto Hide at the top of the window, so that it will go away automatically when you aren’t pointing at it.
    3. To reopen ArcToolbox, simply point at the sideways tab along the right edge, shown here:

ArcToolbox ToolsProcedure 18: Exporting a Layer to Google Earth

Google Earth uses a geographic format known as Keyhole Markup Language, KML for short, which is sometimes compressed to a smaller size using ZIP compression to produce a KMZ file. ArcToolbox provides tools to export both individual layers as well as entire maps.

  1. In ArcMap Icon ArcMap, open  ArcToolbox as described in the previous procedure.
  2. Click on  Conversion Tools, then on  To KML, and finally on Layer to KML.
  3. In the dialog  Layer to KML, there are a number of fields that let you specify the items you want to process and any information that may be required.

    Note the button Show  Help >>, which opens the right-hand panel to provide an explanation of the purpose of the tool and, when you click on each item, what it is expected:

    Layer to KML Dialog

    In the field/menu  Layer, select a layer or map to export, e.g.  USA Major Rivers.
  4. In the menu  Output File, choose the output path of the file you want to create, e.g.  rivers.kmz; it’s usually easiest to click on the button Document Open Browse to choose a folder and the name and type of the file.
  5. Click the button OK; when geoprocessing is run in the foreground, a dialog will appear describing the process and listing any errors that occur:

    Layer to KML Processing

    When geoprocessing is run in the background, to see the results or any errors you must menu Geoprocessing, then select the menu item Results.
  6. Click the button Close to dismiss the dialog.
  7. Navigate to the folder where you stored the KMZ file, and double-click on it to open it in Google Earth.

    When the layer appears in Google Earth, you should be to see the labels when you zoom in far enough, and an information balloon should appear when you click on any feature. Note that the labels are stored as a separate layer from the features, so you can click them off if you want to.
  8. The KMZ file can also be displayed in the World-Wide Web site Google Maps by first putting it in own your web site, copying its web address (URL), and then visiting and pasting the URL in the field  Search.

    The button  Link will provide a URL for the Google map with your layer added, allowing you to share it.

Interactive Maps

It is also possible to create an interactive map that allows the viewer of the map to explore it by zooming and viewing attributes, very similar to what you have been doing already with ArcMap.

Such interactive maps use the free program ArcReader, though it’s only available for Windows.

Creating an ArcReader map involves using the extension ArcPublisher.


If you are interested in applying what you’ve learned to some slightly different kinds of maps, here are some additional exercises. They use map files in the exercises folder in the Introduction to GIS folder.

Previous: Introduction to GIS

Constructing and Sharing Maps

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