Gridded Population of the World, version 3 (GPWv3) is the third edition of a FREE large-scale data product that demonstrates the spatial distribution of human population across the globe. This includes a major update to the underlying population and spatial data, and in its wake, additional updates have been made, for example, to the Africa accessibility model.

Similarly, in collaboration with the Food and Agriculture Organization of the United Nations (FAO), CIESIN and CIAT have constructed a gridded population projection to 2015...

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http://free-gis-data.blogspot.com/2009/04/global-gridded-population-maps-and-data.html

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