Understanding Thematic Maps: 
An Overview of Spatial Distribution
by David L. Bradshaw
InteractiveGIS

Thematic maps are tools that researchers may use to represent how a set of attribute data is dispersed spatially.  Thematic maps, in the Missional Culturescape site convey information about a single theme as it relates to an area or a population living in that area.

Thematic maps provide an effective way to show the spatial distribution of one or more specific data themes for standard geographic areas.  The map may be qualitative in nature (i.e., predominant denomination types) or quantitative (i.e.., percentage population change).

There are three primary purposes for thematic mapping.  First, to produce a map that provides specific information about particular geographical location. Second, provide a map that allows the reader a means to visualize general information about spatial patterns of a specific geographical location. Third, provide a means that can be used to compare patterns on two or more maps.

Chloropleth maps are perhaps the most common and easily recognized style of thematic mapping.  It is created by shading known bounded areas, such as a state or county, with a color associated to a particular value, say population, with it.  This type of thematic mapping is best used with a discrete data set that can be measured and associated with predetermined layers of geography.  The Missional Culturescape site allows users to produce thematic maps on nine different layers of geography:

·         State or Province

·         Region within the State or Province

·         DMA -- Direct Media Area

·         CBSA - Core based statistical areas (metro and micro areas)

·         County or Parish

·         City Places larger than 10,000 in population

·         Postal Code / Zip Code (5 digits)

·         Census Tract / Division

·         Census Block Group / Subdivision