Tuesday, July 21, 2015

Solving the Problem of Cartograms

I don't usually like cartograms. I find that the geographical distortions in cartograms quickly lead to geographical illegibility.

The cartogram above, which compares property values between counties across the United States, has shown up a lot recently on my Twitter feed. Now if I hadn't told you that this was a cartogram of the continental United States I bet you would have struggled to identify the country.

After ignoring the Tweets about this cartogram for about a week I finally decided to click on the accompanying link. It turns out I was being very unfair to Metrocosm (the creators of this cartogram). The Metrocosm post on housing values across the United States includes this animated GIF:

Now the cartogram makes much more sense.

I've been converted. I'm now a fan of cartograms. Or to be more specific I like animated cartograms. By simply providing a transition from a regular map projection to a geographically distorted cartogram developers can easily mitigate against the dangers of geographic intelligibility inherent in static cartograms.

Macrocosm have provided another example of a cartogram which uses animated transitions between a traditional map projection and a map distorted by thematic variables. How We Share the World visualizes how the world is divided according to six different socioeconomic variables.

This interactive map allows you to view cartograms of the world with the countries resized based on GDP, Debt, Population, Births, Wealth and the number of Billionaires. The map includes a non-distorted map view1 which again helps to overcome the dangers to geographical legibility in the distorted views.

 1 stop being clever - you know what I mean.

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