the Contents pane, right-click Cities and click Attribute Table.
5)Scroll across the table, if necessary, to look at all the field names (the gray column headings).
This is a different presentation of the same information you saw when you identified cities on the map.
6)Scroll back to the beginning of the table, and then scroll a little way down through the records (the table rows).
This table has a lot of records: in fact, 29,259 of them, as you can see at the bottom. Each record corresponds to a unique feature—that is, a unique city—on the map. So there must be a lot of cities you’re not seeing in the current view.
7)Leave the table open. It will stay docked under the Lesson1a map.
8)In the Contents pane, right-click the Cities layer. On the context menu, click Zoom To Layer.
The map zooms out to the geographic extent of the layer: the entire United States. You can’t distinguish individual city polygons at this scale.
9)On the Map tab, in the Navigate group, click the Previous Extent button.
Select the record for Los Angeles
When you select a record in an attribute table, the corresponding feature is selected on the map. (Likewise, when you select a feature on the map, its record is selected in the table.) Selections are marked with a blue highlight by default.
1)Scroll up to the top of the table. Make sure the table is wide enough that you can see the POP2010 field.
2)Right-click the POP2010 field name. On the context menu, click Sort Descending. Alternatively, double-click the column header to switch between the ascending/descending sort order.
The records are sorted in the order of their populations, from largest to smallest. Los Angeles is now the second record in the table, after New York.
3)At the left edge of the table, click the small gray box next to the Los Angeles record to select it.
On the map, the city of Los Angeles is outlined in blue. You may be able to see the whole city already, but now you can make sure.
4)Close the attribute table by clicking the X to the right of Cities.
5)In the Contents pane, right-click Cities and click Selection > Zoom To Selection.
The map zooms in close on the selected feature and centers it in the view. The city’s odd shape is attributable to years of piecemeal expansion and incorporation. The city has internal “holes” where it surrounds other cities, such as Beverly Hills, or unincorporated areas. It also has a long, narrow southern corridor that connects it to its harbor at the Port of Los Angeles.
6)On the Map tab, in the Selection group, click the Clear button
Filter the display of cities using a definition query
One of your project requirements is that the new park be inside the Los Angeles city limits. Therefore, you’re more interested in Los Angeles than in other cities. A layer property called a definition query allows you to show only those features in a layer that interest you.
1)In the Contents pane, right-click the Cities layer and click Properties.
2)In the Layer Properties dialog box, click Definition Query.
3)Click Add Clause to begin building your query.
You build a query on an attribute table by specifying a field and setting a logical or arithmetic condition that values in that field must satisfy. In this case, you want to find records with the value of Los Angeles in the NAME field.
4)In the list of field names, use the drop-down arrow to click NAME.
5)Click is Equal to in the second drop-down menu.
6)Type Los Angeles in the third box. You can also use the menu to select the city name.
7)Click Add. Do not click OK yet.
8)Click the General tab. Delete the layer name Cities, and type Los Angeles.
9)Click OK.
On the map, only the city of Los Angeles is shown. The other cities are hidden by the definition query.
10)In the Contents pane, right-click the Los Angeles layer and click Attribute Table.
The table shows only the record for Los Angeles.
11)Close the attribute table.
The other city features haven’t been deleted. Clearing the definition query would display them again. Layer properties affect the display of data in a map, not the essential properties of the data itself: the number of features, their shapes, their locations, and their attributes.
Layers and datasets
A layer points or refers to a dataset stored somewhere on disk (as specified on the Source tab of the Layer Properties dialog box). A layer is not a physical copy of the data. A layer is a representation or rendering of the data. The dataset stores the shapes, locations, and attributes of features; the layer stores display properties, including what the layer is named, which of its features are shown or selected, how those features are symbolized, and whether they are labeled. Changes to layer properties do not affect the dataset that the layer refers to. You can make as many layers as you want from the same dataset and give them different properties. These layers can coexist in the same map document or in many different map documents.
Add a layer of rivers
Now you can add a layer of local rivers to the map and see where the Los Angeles River fits into the picture.
1)From the Catalog pane, browse to the Hydro group in the ESRI.gdb and right-click the River layer. Then click Add To Current Map from the menu.
