Continuing with the cartography series we are going to cover the use of thematic mapping on the GeoWeb. There has been a pleasant up tick in thematic maps being used across the GeoWeb and more attention placed on the cartography of them. Real Estate sites have been using choropleth maps (usually labeled heat maps) for the past few years, but we are now beginning to see them crop up in a wide variety of GeoWeb applications.
Guilhem posted up a nice tutorial on how to create a thematic map with the new Google Maps Flash API on his “Leveraging Visionary Paradigms” blog. Bjørn Sandvik has been putting out a flurry of blog content and applications for thematic mapping. Bjorn’s “Thematic Mapping Engine” is a very cool piece of software and another visually appealing 3D thematic generator similar to UUorld’s time space maps.
I was talking to some cartographer friends about the recent proliferation of 3D thematic maps and they had some concerns about their utility and accuracy. Specifically they pointed to testing that has shown people stink at estimating heights of the countries and have the hardest time telling the most basic differences in height.
Same with estimating sizes of oblique-viewed 3D domes for proportional symbols. The problem is further magnified when the data is re-projected to an Earth globe view making the task of estimating heights/sizes of the polygons even harder (since the user has to mentally compensate for the curvature of the earth). In short their concern is we are sacrificing accuracy for eye candy.
I love eye candy just as much as the next person, which begs the question can we leverage a Z dimension in a more effective manner. One example I like is this 3D thematic in Google Earth:
The map shows the results of a project where participants are wired up with a device that “records the wearer’s Galvanic Skin Response (GSR), which is a simple indicator of the emotional arousal in conjunction with their geographical location.” While the 3D lines still have the projection issues, I believe it effectively uses 3D to show the data far more effectively than the 2D version (lines varying in thickness).
Criticality aside I think it is great people are pushing the bounds of cartography and thematics on the GeoWeb. Although the cartographers have a great point that we should be aware of the limitations and inaccuracies inherent in some of these techniques.
(editorial note – I blatantly stole the “Is 3D Crap” title from Steve Coast’s “Is 3D Shit” session at WhereCamp.)
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