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Maps and Stats

2008-12-14 19:41:22.633997+00 by meuon 2 comments

World Mapper - Interesting maps of stats.

[ related topics: Maps and Mapping ]

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#Comment Re: made: 2008-12-14 21:08:23.902279+00 by: ebradway

That's Danny Dorling et al at CASA with World Cartograms. They are using the Gastner-Newman algorithm published in 2004. The algorithm is based on basic gas diffusion laws - treating the statistical units like particles and the areal unit boundaries like permeable membranes. It creates a field of displacement values based on the statistics (a differential projection) which can be used to transform any data layer place on top.

Initially, Danny asked about using my VB script for ArcGIS - but the algorithm I use doesn't handle world cartograms as well. The algorithm I use, published by Dougenik, Chrisman and Neimeyer in 1985, works by assigning a "mass" to the center of each polygon and shifting each vertex in every other polygon as though it was affected by the "gravity" of these "masses". It's a little easier to implement but less flexible. It also gets really screwed up when you have a polygon or group of polygons that stretches across the break from one side of the map to the other.

In addition to the VB version for ArcGIS, I also have a Python version and an on-the-fly animated cartogram I've been playing with in C++. Maybe I'll get a chance to do something with the C++ version in the new year.

For some reason, WorldMapper took off my favorite cartogram, Incidents of Elephantitis by Country. I have a graphic I downloaded when it was still available but can't find it right now.

#Comment Re: made: 2008-12-14 21:28:24.138246+00 by: topspin

Oddly, when on the labelled map if you "mouseover" Mali it says Mali. When you click on Mali is says "Netherlands, Western Europe."