Monday, March 26, 2007

gCensus-GT - Google Earth visualization for GeoTIFF files and more

Lisa Jordan, a geography professor at Florida State, recently pointed out to me that there's a wealth of GIS data out there in raster data formats that can't be viewed in the free Google Earth client. For example, Columbia University's Socioeconomic Data Analysis Center generates raster imagery for a variety of different data trends. Although it's possible get higher-resolution vector data (like the main gCensus app does), these files tend to be faster to render and provide a quick overview of relevant trends.

To fill this gap, I've just put out the gCensus-GT application (, which allows you to visualize these raster formats in the free version of Google Earth. In addition to the GeoTIFF format SEDAC generates, gCensus-GT should be able to render any raster format supported by the open-source GDAL library ( (but GeoTIFF is the only one I've had test data for). Comments are, as always, welcome.

If you're interested in doing this conversion on your home machine, I've released the core code behind it as a Python module named gdaltokmz; it's available at The module has a few dependencies (notably, the GDAL Python bindings and the ImageMagick graphics tools) and is licensed under the GPL.

1 comment:

Lisa Jordan said...

gCensus-GT is fantastic! I presented some of Imran's work at the Population Association of America meetings in New York this past week in a session on spatial demography (
The session was well attended, and there appears to be considerable interest in using virtual globes in demographic applications. We would like to be able to further use gCensus to query demographic information in a user-friendly way, so that interested users could retrieve population estimates for any geographically defined areas (e.g. radius around a stream, flood risk zones, famine prone regions, etc., see -

gCensus and gCensus-GT are also wonderful resources for the classroom!!