Geographic Information Systems

Constructing and Sharing Maps

Previous: Introduction to GIS

Following: Mapping Geographically Named 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.

Topics

Procedures

Getting the Tutorial Data
Beginning with ArcMap
Map Layer Attribute Tables
Exploring Map Features
Labeling Map Layers
Coloring Map Layers
Using Multiple Layers
Finding Prepared Data on the Internet
Sharing Maps

Initializing ArcMap
Adding Prepared Data to a Map
Saving a Map Document
Storing Relative Pathnames in a Map Document
Viewing a Map Layer's Attribute Table
Sorting Attribute Table Records
Locating Attribute Table Records on the Map
Selecting Features
Identifying Features
Finding Features
Labeling A Map Layer
Creating a Layer File
Symbolizing a Point Layer Using Proportional Symbols
Finding Data on ArcGIS Online
Exporting a Layer to Google Earth

The aim of this tutorial is to 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 K: (aka \\Software\Winsoft), open the folder Maps, and then open the folder Introduction to GIS. Drag the folder constructingmaps and its contents to your network drive U: (e.g. into the folder My Documents) or the local drive C: (e.g. onto your Desktop). 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
states.dbf	counties.dbf	cities.dbf
states.prj	counties.prj	cities.prj

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.

Beginning with ArcMap

Procedure 1: Initializing ArcMap

Click on the menu Start.
Point at the menu item All Programs, and if you are in the public labs point at the menu item Course-related. Then point at the menu item ArcGIS, and click on the menu item ArcMap.
ArcMap will take a while to load. Eventually, the dialog ArcMap will appear, which allows you to Start using ArcMap with the default setting of A new empty map; 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. 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.

In ArcMap, in the toolbar Standard, click on the button Add Data.
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:

Click on the button Connect to Folder.
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.
Click once on the folder's name.
Click on the button OK.

If necessary, navigate into the folder constructingmaps.
Select the file states.shp; note that only one file with this root name appears, another feature of this special dialog.
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 Display, which shows just the simple names of data layers. The secondary view is 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 Display 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. 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

In ArcMap, select the menu File, and click on the menu item Save. You can also simply click on the button Save.
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.
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

In ArcMap, select the menu File, and click on the menu item Document Properties....
In the dialog Document Properties, click on the button Data Source Options....
In the dialog Data Source Options, in the button group In this map document:, click on the button Store relative path names to data sources.
You may also want to turn on the checkbox Make relative paths the default for new map documents I create. However, this will only apply to the current computer (and it also won't stick around for long in the public labs).
Click on the button OK.
Back in the dialog Document Properties, click on the button OK.

Note that you can only open ArcMap documents by double-clicking on them in the Windows Explorer, or by opening them from within 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, which is reserved for the pieces 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
	Zoom in: click a point to zoom in to it by 50%, or click-and-drag a rectangular region to view.
	Zoom out: click a point to zoom out from it by 50%, or click-and-drag a rectangle to contain the current view.
	Zoom in to current center by 20%.
	Zoom out from current center by 20%.
	Pan (drag) the map.
	Full extent: zoom out to the full map view.
	Go back to previous map view — if you lose your map, this will bring it back.
	Go forward to next map view.
	Select features.
	Clear selected features.
	Identify features.
	Find features.
	Go to an (X, Y) coordinate position.
	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:

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 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. At a large scale a map will appear bigger on the screen (it will be "zoomed in"), and you will see more detail. However, there will be a smaller area visible within the window.

Map Layer Attribute Tables

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.

Procedure 5: Viewing a Map Layer's Attribute Table

In ArcMap, in the Table of Contents, right-click on the name of the layer, e.g. states.
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.

Sorting 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.

Procedure 6: Sorting Attribute Table Records

In 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.

Note that the column will sort itself in ascending order, from A to Z.

Double-click on the header a second time; the column will now sort itself in descending order, from Z to A.
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….
The dialog Advanced Table Sorting will now appear; it lets you choose multiple columns on which to sort in sequence:

Advanced Table Sorting Dialog

In the menu Sort by, select a field whose values are common to multiple records, e.g. SUB_REGION.
In the menu Then sort by, select a more specific field, e.g. STATE_NAME.
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.

Procedure 7: Locating Attribute Table Records on the Map

In 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.

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.

To deselect the record you can either:

Right-click on the button Select Record and then click on the menu item Select/Unselect;
In the toolbar Tools, click on the button Clear Selected Features.

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.
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 Select Features.

Procedure 8: Selecting Features

In ArcMap, in the toolbar Tools, click on the button Clear Selected Features; this will remove any highlighting remaining from the previous procedures.
Again in the toolbar Tools, click on the tool Select Features.
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.
If it's not already, open the attribute table .
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 tool Identify.

Procedure 9: Identifying Features

In ArcMap, in the toolbar Tools, click on the tool Identify.
The dialog Identify will open; move it to a convenient location that doesn't obscure the map.
In the menu Identify from:, choose which layers you want to select from:

<Top-most layer>;
<Visible layers>;
<All layers>;
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.

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 tool Find.

Procedure 10: Finding Features

In ArcMap, in the toolbar Edit, click on the tool Find.
The dialog Find will open; move it to a convenient location that doesn't obscure the map.
Click on the tab Features if it's not already selected.
In the field Find:, type in some piece of information you know about the feature such as its name.
In the menu In:, choose which layers you want to select from:

<Top-most layer>;
<Visible layers>;
<All layers>;
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.

In the button group Search:, choose which attribute field you want to search for this information:

All fields;
In field:, and then choose one of the available fields from the menu;

Click the button Find, and a list of matching features will be displayed at the bottom of the dialog.
Click on the feature of interest and the map will flash its location.
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.

Procedure 11: Labeling a Map Layer

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

Shortcut: you can also open a Layer Properties dialog by double-clicking on the layer's name in the Table of Contents.

In the dialog Layer Properties, click on the tab Labels, which looks like the following:

screenshot of label tab

For labels to appear on your map, you must click on the checkbox Label Features in this layer.
In the area 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.
In the area Text Symbol, choose a font, font size, font color, and font style.
Labels appear at the size you choose, independent of the map scale. This can be a problem when you are zoomed out far enough, as the text can obscure the features they label. You may therefore want to set a scale range for the labels:

In the area Other Options, click on the button Scale Range.
In the dialog Scale Range, click on the button Don't show labels when zoomed:.
You can turn off labels at small scales by clicking in the text field Out beyond and typing a specific numeric value. You can also turn off labels at large scales by clicking in the text field In beyond and typing a specific numeric value.

For example, enter 40,000,000 in the text field Out beyond, and leave the text field In beyond blank.
Click the button OK.

In the dialog Layer Properties, click the button OK

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

Coloring Map Layers

Coloring maps 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

Coloring maps 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:

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.
You need to decide how many value classes you want to use. This will group the values into a discrete set of ranges.
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.

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

Normalizing data

In many cases, instead of coloring a map with a simple demographic field such as "population 2000" or "people over 80," you may want to use the ratio of a field like this to another field, typically either a total field--for proportion of the total population over 80--or an area field--for population density. This is done by specifying that field as the Normalization field

Both the classification method and normalizing your data can make major changes in the way your map looks and in the way it is 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 a layer file

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

In ArcMap, in the Table of Contents, right-click on the name of the layer, e.g. states.
The layer's contextual menu will now appear; select the menu item Save as Layer File....
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.
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

Change the symbology of the layer states to be Features using a Single Symbol with no fill color and a thick, bright red outline .
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.
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.
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.
Finally, remove the more symbolized layer to return to the original single-symbol layer:

In ArcMap, in the Table of Contents, right-click on the more symbolized layer states-pop2000.
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

In ArcMap, in the toolbar Standard, click on the button Add Data.
In the dialog Add Data, navigate into the folder constructingmaps.
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.
Use the tool Identify to learn more about specific cities. You may need to zoom in to spatially distinguish some cities.
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.

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.

Procedure 13: Symbolizing a Point Layer Using Proportional Symbols

In ArcMap, in the Table of Contents, double-click on the layer's name, e.g. cities.
In the dialog Layer Properties, click the tab Symbology.
On the left side, in the list Show:, click on the list item Quantities.
Click on the sub-list item Proportional Symbols.
In the section Fields, in the menu Value:, select an attribute to use, e.g. POP2000.
In the section Symbol, click on the button Min Value,
In the dialog Symbol Selector, choose a symbol type, a color, and a minimum size, e.g. 1.
Click the button OK.
Back in the dialog Layer Properties, click the button OK. The size of the cities' symbols are now based on their populations.
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:

Double-click on the layer you want to change, e.g. cities.
In the dialog Layer Properties, click the tab Display.
In the field Transparent: %, type a percentage value, e.g. 50.
Click the button OK.

Exercise: 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.

In ArcMap, turn off the layer cities so that only the layer states is visible.
In the toolbar Standard, click on the button Add Data.
In the dialog Add Data, make a new connection to the folder K:\Maps (see Adding Prepared Data to a Map for details). This network folder is where Amherst College stores a large amount of data for use in maps.
Navigate into the folder ArcGIS Books-n-Data\ESRI Elevation and Image Data 2008\world_elevation\gtopo30. Note how the icon for the file gtopo_1km shows a grid of pixels, indicating the type of data (image).
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.)
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.

Raster layers have one value for each pixel, in this case representing elevation, and as with vector layers that information can also be displayed:

In the toolbar Tools, click on the tool Identify.
To avoid displaying only information about other layers (such as states), in the dialog Identify, change the menu Identify from: from the default menu item, <Top-most layer>, to another such as <Visible layers> or specifically gtopo-1km.
Click on different locations to determine their elevation.

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). 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.

Finding Prepared Data on the Internet

A lot of geographic data is available on the Internet.

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 (but not exclusively) such data would be labeled as shapefiles, though they are likely to be packaged as a .zip archive that Windows will automatically open.

Experiment: Try doing a web search for data on a subject you are interested in, and include the keyword shapefile; you might very well have some results.

Procedure 14: Finding Data on ArcGIS.com

ArcGIS.com is a relatively new source of data that is easy to use with ArcGIS. It has datasets provided by ESRI (sometimes duplicating what's in K:\Maps), as well as many that are contributed by others.

If necessary, start up a web browser:

Click on the menu Start.
Point at the menu item All Programs.
Locate your preferred web browser, Firefox or Internet Explorer (perhaps in the folder Networking and Communications), and click on it.

In your web browser, visit the web address www.arcgis.com.

At the top of the page, make sure the menu Show:… is set to Show: All Content.
Click in the text field Find maps, applications, and more…, type one or more keywords, e.g. rivers, and click on the link Search for Maps.
Scroll down to review the found items; you'll see a number of data types, which you should pay close attention to:

ArcGIS Desktop 9-usable:

Layers and Layer Packages, downloadable by clicking on the link Open.
Map Services (internet data streams), referenced through a .lyr file downloadable by clicking on the menu More options and then clicking on the link Open in ArcGIS Desktop.

These are also viewable in your web browser with the other link, Open in ArcGIS.com.
Published Maps, which are .mxd files downloadable by clicking on the menu More options and then clicking on the link Open in ArcGIS Desktop.

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 ArcGIS.com, they probably won't be useful to you.

Web browser-viewable Web Maps, which are available in the menu More options as either the link Open in ArcGIS.com or Open in Explorer Online (the latter requires the Microsoft Silverlight browser plug-in). These can be fun to study and play around with, but aren't usable with ArcGIS Desktop 9.
Downloadable Explorer Maps and Explorer Layers, which are incorrectly given the link Open in ArcGIS Desktop, as they can only be viewed in the free program ArcGIS Explorer.

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.

Choose a data set from one of the first two data types, e.g. the map service USA Major Rivers, and click on the link Open.
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.

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

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:

Contrast: Choose an appropriate symbology for your data and background for your maps that will enhance rather than detract from the visibility of your data. Your choice of label font and size will also be important in this regard.
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: 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.

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 view This 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:

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.
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.
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.
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 a few popular sets of data in an easy-to-access format — if you have an internet connection.

You can zoom around the Earth and see images of its surface (taken from airplanes or satellites), roads, and even terrain and buildings in 3D!

ArcGIS is a useful tool to create additional layers that can be viewed in Google Earth, together with its predefined ones.

Procedure 15: Exporting a Layer to Google Earth

Google Earth uses a map format known as KML, which is sometimes compressed to a smaller size using ZIP compression to produce a KMZ file. A free extension is available for ArcMap called Export to KML that will create this format with your layers. Unfortunately, you can only export one layer at a time rather than an entire map.

In ArcMap, turn on the toolbar Export to KML by menuing View > Toolbars > Export to KML. The toolbar is very short, displaying only the Google Earth icon .
Click on the toolbar Export to KML.
In the dialog Export to Google Earth KML, in the menu Select the layer to export:, choose a layer, e.g. USA Major Rivers.
Make sure the checkbox Group and color featuers using the layer's symbology is turned on.
In the menu Select an attribute for labeling features (Optional):, choose an attribute to use for a label, e.g. NAME.
In the text field Name and location of the output KML:, make sure the file is being saved where you can find it.
Click on the button Options.
Click on the tab Labeling and Description Options.
Click on the checkbox Apply feature colors to labels, which will make them more distinguishable from Google Earth's labels.
To create a default balloon information format, click on the button Add ALL Attributes.
In the text field Feature description expression, select and delete the line containing the FID or OBJECTID (usually the first), since that is probably uninteresting to most people.
Click on the button OK.
Back in the dialog Export to Google Earth KML, click on the button OK, which will generate the KML file.
When you are asked "Would you like to open … in Google Earth?, click on the button Yes.
When the layer opens 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.

Within Google Earth, you can right-click on the layer and save it as a KMZ file, which will be much smaller than KML.

The file can also be displayed in the Internet site Google Maps by first putting it in own your web site, then going to http://maps.google.com/, and providing its location (URL) in the field Search the Map.

ArcGIS also has an ArcToolbox tool, Map to KML under Conversion Tools, which will let you export an entire map; however it doesn't include labels.

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 is described in a separate section on using ArcPublisher.

Exercises

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.