Drawing 3D bars in KML

The regular polygons from my last blog post can easily be turned into bars by adding an altitude value for each vertex or corner point of the polygon. The technique is similar to the one I used for choropleth mapping (irregular polygons). In a 3D environment, I find bars or extruded polygons much more efficient than proportional symbols (2D). It is easier to spot how the statistical value changes over the surface. Let's map the digital divide:

On this map (KMZ), the height and colour of the bars represents Internet users per 100 population (source: UNdata). We can clearly see the digital divide in the world. Still, because of all the "small" countries in Europe compared to other parts of the world, it is not a fair picture.

Here, I've added another variable: The bar diameter now represents the population in each country, - and the image tells a slightly different story than the image above (KMZ).