Shawn Allen of the Stamen Design (I’ve linked to their work before) produced this clever map of trees, cabs, and crime in San Francisco. I’ll let him explain it:
I’ve had this idea to use subtractive blending so that you can see where these three data sets overlap for a while, and decided to scratch the itch this weekend. I’m still not sure if it’s significant or even interesting, but here it is. This is a slightly improved version of the original with a more useful (and attractive!) legend and no base map. The colors have also changed: Trees are cyan and crimes magenta because I felt that the latter should stand out more. And yellow to produce red, which seems to me a more crime-y color.
To see the map in all it’s halftone glory, take a look at the embiggened version.
(Thanks to Jon Christensen.)