Chapter 6. Overlay Analysis

In this chapter, we will cover the following topics:

  • Punching holes in polygons with a symmetric difference operation
  • Union polygons without merging
  • Union polygons with merging (dissolving)
  • Performing an identity function (difference + intersection)

Introduction

Discovering how two datasets spatially relate to each other when they are placed over one another is called overlay analysis. An overlay can be compared to a sheet of tracing paper. For example, you could overlay the tracing paper on top of your base map and see what areas overlap each other. This process is and was a game changer in spatial analysis and modeling. Computer-aided GIS computations can therefor automatically identify where two geometry sets spatially ...

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