Now you can review the Tracts shapefile, which actually consists of seven files that all have the same name, Tracts. These are US Census tracts for Allegheny County, Pennsylvania.
• The Tracts file that has the .shp extension has the features geometry and coordinates. For points, each record has a point and an x,y location. For line and polygon layers, each shape record has coordinates of a line segment or a polygon. Tracts, of course, consist of polygons.
• The Tracts file that has the .dbf extension has the feature attribute table in dBASE format. You can open and edit this file as a Microsoft Excel spreadsheet and as a Microsoft Access database, but such work must be done carefully and without deleting or adding records or changing the order of rows, which could result in corrupted data. The relationship between the .shp and .dbf files of a shapefile depends on the one-to-one physical arrangement of records in both files.
• The .sbx and .shx files contain indexes for speeding up searches and queries. The .prj file is a simple text file that has the map projection parameters of the layer.
• Finally, the .shp.xml file has the layer metadata, and you can open this file in a Web browser to read it.
4 In Computer, navigate up one level to GISTHealth\Data. The remaining folders in the Data folder are file geodatabases. Each file geodatabase includes a .gdb extension. A single file geodatabase can have one or more vector-map layers and data tables.
5 Double-click the UnitedStates.gdb folder icon. You cannot identify the files contained in a file geodatabase in My Computer. Always use ArcCatalog to maintain map layers and data tables stored in a personal geodatabase; otherwise, you will likely corrupt the layers.
6 Close My Computer.
YOUR TURN
Start ArcCatalog and explore the file geodatabases in the Data folder. Preview the feature classes in each geodatabase. Then close ArcCatalog.
Tutorial 1-3
Exploring the ArcMap user interface
To get started, you will open a completed map document that has health and other data to get the feel for ArcMap and health layers.
Open a map document
1 On the taskbar, click Start, and then click All Programs > ArcGIS > ArcMap10.2. Depending on how ArcGIS and ArcMap have been installed, you may have a different navigation menu or a name other than ArcGIS.
2 In the ArcMap - Getting Started dialog box, click Existing Maps > Browse for more.
3 In the Open ArcMap Document dialog box, browse to the drive where you installed the \EsriPress\GISTHealth\Maps folder (for example, C:\EsriPress\GISTHealth\Maps), select Tutorial1-3.mxd, and click Open.
Tutorial1-3.mxd is displayed in the ArcMap application window. The map currently contains the contiguous United States showing demographics related to female-headed households as both point and polygon features and male lung cancer mortality rates. The major components of the ArcMap interface are also identified.
The major components of the ArcMap application window include the following:
• The Menu bar has some items common to most Windows application packages, plus some that are unique to GIS.
• The map display is where the feature classes loaded into the map are drawn.
• The table of contents lists all the data in the map document by layer and allows you to change layer visibility and access layer properties. Currently, the List By Drawing Order button
• The Tools toolbar has frequently used tools and can be docked, if desired, by dragging it by its title bar to any boundary in the ArcMap interface. Similarly, you can undock it by dragging it to the desired location.
• The Status bar displays the map coordinates of the pointer location in the map display. In the preceding graphic, the pointer is over Omaha, Nebraska, and the coordinates for Omaha are displayed on the Status bar.
YOUR TURN
Experiment with turning map layers on and off by selecting and then clearing the check boxes to the left of each map layer in the table of contents. Start with layers currently turned off, from the top down, and turn each one on and then off. Then try various combinations. Keep in mind that the Female-Headed Households with Children layer is a strong indicator of poverty. Of course, not every such household is in poverty, but the tendency is strong. When you are finished, return the map document to its original condition, with layers turned on or off as shown in the preceding figure.
View map-layer attribute tables
1 In the table of contents, right-click Cities with 250,000 or Greater Population and click Open Attribute Table. The attribute table for Cities with 250,000 or Greater Population is displayed. This is the same sort of table you previewed in ArcCatalog.
2 Visually scan the map for a few cities listed in the table. Verify that there is a point plotted for each corresponding record in the table.
3 Close the table.
YOUR TURN
Open a few other tables and scan the contents.
View map layer properties
1 In the table of contents, right-click Cities with 250,000 or Greater Population and click Properties. In the Layer Properties dialog box, click the General tab. Layer Properties is an important dialog box for managing how layers behave and appear in ArcMap. Although there are many properties that can be set, it is good to review a few useful ones for now. For example, in the General window of Layer Properties, you can change the layer name by typing the name of your choice into the Layer Name text box.
2 In the Layer Properties dialog box, click the Source tab. The Source window provides bounding coordinates of the map layer (that is, its extent), the data type, location on the server or computer, geometry type, and projection.
3 Click the Symbology tab. The Symbology window provides many options for symbolizing vector-map layers. The cities layer uses a single symbol chosen by the authors, a purple circular point marker that has a black outline.
4 Click the Fields tab. The Fields window lists the layer’s attribute fields and their properties.