ASTER GDEM (Global Digital Elevation Model) has been produced as a joint activity of the Ministry of Economy, Trade, and Industry (METI) of Japan and the United States National Aeronautics and Space Administration (NASA).
The ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) instrument was built by METI and launched onboard NASA’s Terra spacecraft in December 1999. It has an along-track stereoscopic capability using its near infrared spectral band and its nadir-viewing and backward-viewing telescopes to acquire stereo image data with a base-to-height ratio of 0.6. The spatial resolution is 15 m in the horizontal plane. One nadir-looking ASTER VNIR scene consists of 4,100 samples by 4,200 lines, corresponding to about 60 km-by-60 km ground area.
The methodology used to produce the ASTER GDEM involved automated processing of the entire 1.5-million-scene ASTER archive, including stereo-correlation to produce 1,264,118 individual scene-based ASTER DEMs, cloud masking to remove cloudy pixels, stacking all cloud-screened DEMs, removing residual bad values and outliers, averaging selected data to create final pixel values, and then correcting residual anomalies before partitioning the data into 1°-by-1° tiles. It took approximately one year to complete production of the beta version of the ASTER GDEM using a fully automated approach.
The ASTER GDEM covers land surfaces between 83°N and 83°S and is composed of 22,600 1°-by-1° tiles. Tiles that contain at least 0.01% land area are included. The ASTER GDEM is in GeoTIFF format with geographic lat/long coordinates.
|Grid||Coordinate system||Accuracy°||Data format|
|1”||WGS84 / EGM96||30 m||20 m||GeoTIFF (16bit)|
° Pre-production estimated accuracies for this global product were 20 meters at 95 % confidence for vertical data and 30 meters at 95 % confidence for horizontal data. Initial studies to validate and characterize the ASTER GDEM confirm that pre-production accuracy estimates are generally achieved for most of the global land surface, although results do vary and true accuracies do not meet pre-production estimates for some areas. In addition, Version 1 of the ASTER GDEM does contain certain residual anomalies and artifacts that affect the accuracy of the product and may be impediments to effective utilization for certain applications. Consequently, METI and NASA acknowledge that Version 1 of the ASTER GDEM should be viewed as “experimental” or “research grade.” Nevertheless, they are confident that the ASTER GDEM represents an important contribution to the global earth observation community.
ASTER GDEM is available free of charge. More info including download links can be found here.
GISAT offers SRTM DEM products fulfilling customer specific requirements – e.g. mosaicking tiles into larger areas, reprojections to desired coordinate systems, resampling into defined grid, etc.