The ASTER Global Digital Elevation Model version 2.0 - Early Validation Results

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra spacecraft is capable of collecting in-track stereo using nadir- and aft looking near infrared cameras. Since 2001, these stereo pairs have been used to produce single-scene (60 x 60 km) digital elevation models having vertical (root-mean-squared-error) accuracies generally between 10 m and 25 m. 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 1.0" ASTER GDEM (GDEM v1.0) was compiled from over 1.2 million scene-based DEMs covering land surface between 83°N and 83°S latitudes. This GDEM is a 1 arc-second elevation grid divided and distributed as 1°-by-1° tiles. ** A joint US-Japan validation team assessed the accuracy of the GDEM v1.0, augmented by a team of 20 cooperators selected through an Announcement of Opportunity (AO). In summary, the GDEM v1.0 was found to have an overall accuracy of around 20 meters at the 95% confidence interval. The team also noted several artifacts associated with poor coverage, cloud contamination, water masking issues and the stacking process used to produce the GDEM from individual scene-based DEMs. An independent horizontal resolution study estimated the effective spatial resolution of the GDEM v1.0 to be on the order of 120 meters. ** NASA & METI will release a second version of the ASTER GDEM (v2.0) in mid-October, 2011. The GDEM v2.0 has the same gridding and tile structure as v1.0, but benefits from the inclusion of 300,000 additional scenes to improve coverage, a smaller correlation kernel (5x5 versus 9x9 for v1.0) yielding higher spatial resolution, and improved water masking. This abstract presents early validation results available at the time of submission. Early results indicate: (1) the overall accuracy (both horizontal and vertical) is significantly improved over the GDEM v1.0, (2) the artifacts noted in v1.0 have been substantially reduced in v2.0, (3) improved representation of elevation over and around water bodies, and (4) horizontal resolution is comparable to the Shuttle Radar Topography Mission 1 arc-second elevation model.