DEM and Slope of UNDESERT countries Burkina Faso, Benin, Niger and Senegal (Source: Ministry of Economy, Trade, and Industry (METI) of Japan; United States National Aeronautics and Space Administration (NASA): Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model Version 2 (GDEM V2)

On June 29, 2009, NASA and the Ministry of Economy, Trade and Industry (METI) of Japan released a Global Digital Elevation Model (GDEM) to users worldwide at no charge as a contribution to the Global Earth Observing System of Systems (GEOSS). This “version 1” ASTER GDEM (GDEM1) was compiled from over 1.2 million scenebased DEMs covering land surfaces between 83°N and 83°S latitudes. A second version of the ASTER GDEM (GDEM2) was released by NASA and METI on 17 October, 2011. Improvements in the GDEM2 result from acquiring 260,000 additional scenes to improve coverage, a smaller correlation kernel to yield higher spatial resolution, and improved water masking. The ASTER GDEM V2 maintains the GeoTIFF format and the same gridding and tile structure as V1, with 30-meter postings and 1 x 1 degree tiles. Version 2 shows significant improvements over the previous release. The GDEM is available for download from NASA Reverb, LP DAAC Global Data Explorer, and J-spacesystems ASTER GDEM Page.

Source: http://www.jspacesystems.or.jp/ersdac/GDEM/ver2Validation/Summary_GDEM2_validation_report_final.pdf ASTER Global Digital Elevation Model Version 2 – Summary of Validation Results Accessed 05/11/2013 And http://asterweb.jpl.nasa.gov/gdem.asp