Dot distribution map

Dot distribution maps use dots to represent a certain variable. Many times these maps are used in showing population because the dots do a good job of showing density because a lot of times in the most dense places the dots all come together. A good example of this is in the Detroit Area above, where the population is so dense you can't tell one dot from another. The above map is showing the high populations around the Great Lakes and is trying to determine if this is the cause for the increased pollution in these lakes.

http://www.engin.umich.edu/dept/name/oel/population_eff.htm