Introducing Geographic Information Systems with ArcGIS: A Workbook Approach to Learning GIS, 3rd Edition

Using Topology to Remove Overlaps from the Feature Class

Here we explore a second way of disentangling these two polygons. We make use of the topology rules that accompany geodatabases.

____ 15. Back in ArcCatalog, highlight UTM_Zone_2 in the Catalog Tree. Select File > New > Topology. Read the discussion in the New Topology window. Click Next. Name the new topology Squares_Topology. Click Next again. For the feature classes that will participate in the topology, select (with a check box) only Small_Squares_2. Click Next. Since only one feature class will be involved, there is no need to change the rank values. Click Next. Add the rule Must Not Overlap. The New Topology window should look like Figure 5-14. Click Next. Read the summary. Click Finish After a little computation you will be asked if you want to validate the New Topology. Click Yes.

FIGURE 5-14

____ 16. Launch ArcMap with a Blank Map. Add as data Squares_Topology. When asked if you also want to add the feature classes that participate in the topology, select Yes.

____ 17. Polygons with errors are shown with red borders. Areas of overlap are shown with pink. Turn the two entries in Layers off and on so you can get an idea of what is being shown. (If both are off and there is still an image in the map pane, press the Refresh View button at the lower left of the map window.) Turn both on.

____ 18. Open the attribute ...