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

Making Copies of the Feature Class

____ 8. Using ArcCatalog, in the Catalog Tree, highlight Small_Squares. Press Ctrl-C. Highlight UTM_Zone_2. Press Ctrl-V. Okay the Data Transfer Window. Check that Small_Squares_1 has been added to the Catalog. Also make Small_Squares_2.

____ 9. Examine the geography of Small_Squares. What you are seeing is a larger square with a small square laid on top of it. Esri refers to these features as non-planar. By this it is meant that these features do not tessellate a plane. That is, here it is not the case that the larger square has a hole in it in which the smaller square fits. The larger square is a complete square; the smaller square is also a complete square. Verify this by looking at the table and examining areas and perimeters. Fill in the following.

Large polygon perimeter: _______________ Large polygon area: _______________

Small polygon perimeter: _______________ Small polygon area: _______________

So you can see by the areas and perimeters that each of these squares is independent of the other, although they, in part, cover the same area of the Earth. We couldn’t, for example, grow corn on one and wheat on the other. In general, in a given feature class we want disjoint polygons, so this is a bit of a challenge. Not having disjoint polygons is a problem that occurs whenever we digitize polygons inside polygons.