Monday, September 23, 2013

Monday Map: Service Area Cartogram


The thirteen Division of Solid Waste Services' Service Areas are typically shown on a map by their geographic size and shape.  Service Areas encompass the roads that must be traveled to make collections and the households that actually receive collection service.

What if we wanted to show the relative size of a Service Area based on household count? One way would be to attach a table of actual household count numbers to the map, letting your eyes and brain figure it out.

Another method is the Cartogram. A Cartogram is a map on which a thematic variable, such as household count, is substituted for land area. That is, the Service Area would be displayed not by Square Feet, but by how many households get Montgomery County-provided collection service.  As you can see, the land area size and shape as we know it are distorted. However, it is easy to see how “big” an area is based on household count. Notice how the downcounty became bigger and the upcounty became much smaller.

-- Angie Braun, GIS Specialist

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