Comment on LA Homeless Map
I found the LA Homeless Map by Cartifact (http://homeless.cartifact.com/) quite fascinating. However, as I studied the map some, it reminded me of how easily presentation of scale can affect perceptions. Specifically, the sizes of the circles used to generate the map give homeless population as a function of the circle's radius, rather than area (which goes up by r-squared). This means that the "40 people" circles are 4X the area of the "20 people" circles which are 4X the "10 people" circles. While radial or areal size mapping can be argued for any given application, for me, the visual interpretation of the radial presentation was highly distorted and I would have chosen an areal mapping for this application. It also points out the importance of choosing appropriate ways to present data for almost any application (it need not be geospatial). IMHO, not enough time / thought is given to the important subject of human-visualization interaction in our current "instant gratification" world.

While it would be interesting to compare and contrast how the two approaches look and determine which is "more accurately" interpreted by human eyes, I already know the answer for this case. Of course, if one is trying to "sway" public opinion rather than provide an objective view, they might choose to use the exaggerated version.

Todd Jamison
Chief Scientist / CEO
Observera, Inc.