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

Areas and Perimeters Examined

If you have trouble understanding the areas and perimeters, recall our rural analogy: Suppose that each polygon represents a field of a farm in which different animals are kept. The questions to be answered are these: How much area does each animal have to graze in, and how much fence is required to keep each animal where it belongs? In the steps that follow, you will use the labeling capabilities of ArcMap to display the areas and perimeters of each of the three polygons.

____ 14. Go back to ArcMap (restart it if necessary and open TextToFeatures.mxd) and add TextToFeature_Polygons. Right-click TextToFeature_Polygons. Click Label Features. What values appear within the polygons? ______, ______, ______. Verify from Figure 4-17 that these are the perimeters of the three polygons. Write the perimeter value on Figure 4-17: P=xx. Be sure you understand where the 40 came from. Going back to our analogy, it would take 40 units of fencing to keep the animals in that polygon: the sum of the perimeters of the two squares.

____ 15. Right-click again on the TextToFeature_Polygons entry, then select Properties. Navigate to the Labels tab if necessary. Change the Label Field to Shape_Area. Click Apply and then OK. Now you will see the polygons labeled with the area (instead of perimeter as before) ______, ______, ______. Inside each polygon on the diagram in your textbook, write the area value: A=yy. Verify that each number you have written in a polygon represents ...