Dotted data

This gridded data display is an example of how cartographers tried to resolve the modifiable areal unit problem: the area covered by each cell is the same. However, these cells don’t usually match with the areas in which statistics are tabulating, which means mathematical models are needed to determine the value in each cell.

The present-day GIS map embedded below borrows the “Wurman dots” technique to show the relationship of forested land and population. Filled dots show heavily forested areas, and empty dots show area with little forest coverage. The color represents population: green shows low population while orange shows high population. This multi-variate method allows you to pick out areas with lots of forest and lots of people (like Connecticut), lots of forest and few people (West Virginia), few forests and lots of people (Chicago), and few forests and few people (the coastal Carolinas).