Standardized choropleth map

http://www.directionsmag.com/articles/choropleth-mapping-with-exploratory-data-analysis/123579

Standardized choropleth maps are different from choropleth maps because they normalize this data according to a certain area.  By analyzing data in the form of a percent or per unit area we can compare areas of different size to see how they compare to one another.  For choropleth maps this is a better mapping technique for analyzing data due to the modifiable areal unit problem (MAUP) that exists.

In the map above, the population per square kilometer is depicted for an area broken up into multiple area.  Because this data is standardized, our eyes are quickly drawn to the areas higher population per square mile (the darker colored areas).  Because there are higher population per kilometer values in almost a linear fashion, I would assume that there is some central road or water source that exists close to these areas.