Using Google Charts with KML

In my last post, I showed how KML icon images could be utilised for proportional symbol mapping. Instead of loading a custom image, images can be requested from the URL based Google Chart API as shown below (download KMZ).

These pie charts are generated on-the-fly. The dataset is the same I used for my OpenLayers and Google Chart mashup. The charts are scaled according to total population and the pie shows the age distribution for each country. If you click on a chart, you'll see a larger version in the balloon:

Since the pie charts are loaded from an external service, the KMZ file is only 10 kB. There are some performance issues since around 200 pie charts are requested from the Google Chart API. I hope to see chart functionality as an integral part of KML and various geobrowsers in the future.

The map is also viewable in Google Maps and Microsoft Live Maps (Virtual Earth). The KML IconScale element is not supported by these geobrowsers, so all pie charts have the same size.

You'll obtain more control of the styling by using GeoJSON and OpenLayers.