Building 3D Cartogram Globes

 


When we consider traditional cartograms, often our first thoughts are towards maps of poverty or wealth. Furthermore, we very expect to see a vector or raster based representation rather than a real world image. This post explored two aspects of this novel visualisation technique.

Firstly, we can consider the creation of the cartogram. For simplicity’s sake, the dataset used is the simplified world outline provided by www.gadm.org/ and for our imagery we use one of the NASA Earth Marble Images downloaded in the geotiff format.  Using the Cartogram Geoprocessing tool version 2 available at http://arcscripts.esri.com/details.asp?dbid=15638 we are able to perform the cartogram function on the global boundaries vector layer and in parallel any additional spatial layer. The image below being the population cartogram marble. One issue with the cartogram tool is that the skew of the image morphs the image away from its simple rectangular format so the image must be slightly cropped for the benefit of the 3D conversion.

The 3D version of the globe is created using Blender, a free and open-source 3D modelling package with many comparable features to commercial packages such as 3DsMax. Once the cartogram texture is created, it can be mapped to a sphere mesh and subsequently through the use of keyframes can be animated to spin in a smooth and earth-like manner. Further details will be provided later through a tutorial. Further reality could be added to the map though the addition of night lighting and clouds giving the earth a more realistic appearance.

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