Generates a hill-shaded raster surface for thematic choropleth maps using an ArcGIS Python toolbox.
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README.md

Choropleth Hillshade

A Python Geoprocessing Toolbox for ArcGIS

No Maintenance Intended

Generates a hillshaded raster surface for choropleth maps. But why?

  • Show off your within-class variability!
  • Enable thematic maps to have more than just 2 dimensions.
  • Experiment with displaying bivariate data.
  • Skip the colours altogether, if you can handle it.

For input, this geoprocessing tool only requires a polygon feature class (or shapefile) with attributes appropriate for choropleth mapping, such as densities or percentages.

An illuminated/shaded relief raster based on the attribute of choice (e.g. population density per county) is the output of this tool (left), which can be overlayed with the original feature class (right).

ChoroSample

Raster cell size and overall shadow length are set as tool parameters. Compare the different polygon "heights" and the shadows they can cast below:

Shadow4

Shadow5

Shadow6

Other info:

  • Software: This PYT requires ArcGIS for Desktop (ArcMap) 10.1 SP1 or higher, with access to either the Spatial Analyst or 3D Analyst extension.
  • Important ArcMap environment options:
    • Navigate to: ArcMap --> Geoprocessing menu --> Geoprocessing Options... -->
    • Check ON "Overwrite the outputs..."
    • Check OFF "Background Processing"
  • Raster Cell Size tool option: numeric values with units of degrees lat/long; for example, try 0.1 or 0,1 depending on your locale, and then continue to experiment with smaller values.

Inspiration:

  • Stewart, James and Kennelly, Patrick J. (2010). "Illuminated Choropleth Maps". Annals of the Association of American Geographers, 100(3): 513-534.

Authors:

  • Jacob Wasilkowski | Esri St. Louis
  • Jie Cheng | UMASS Medical School

Contributing:

  • Find something wrong or have an idea for a new feature? We welcome submitting new issues and requests.
  • License: MIT. More info here.