Comparison and validation of the recent freely-available ASTER- GDEM ver1, SRTM ver4.1 and GEODATA DEM-9S ver3 digital elevation models over Australia

Western Australian Centre for Geodesy & The Institute for Geoscience Research, Curtin University of Technology, GPO Box U1987, Perth WA 6845, Australia, * Tel: (08) 9266 2218; Fax: (08) 9266 2703; Email: [email protected] 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 This study investigates the quality (in terms of elevation accuracy and systematic errors) of three recent publicly available elevation model data sets over Australia: the 9 arc second national GEODATA DEM9S ver3 from Geoscience Australia and the Australian National University (ANU), the 3 arc second SRTM ver4.1 from CGIAR-CSI, and the 1 arc second ASTER-GDEM ver1 from NASA/METI. The main features of these data sets are reported from a geodetic point of view. Comparison at about 1 billion locations identifies artefacts (e.g., residual cloud patterns and stripe effects) in ASTER. For DEM-9S, the comparisons against the space-collected SRTM and ASTER models demonstrate that signal omission (due to the ~270 m spacing) may cause errors of the order of 100-200 m in some rugged areas of Australia. Based on a set of geodetic ground control points (GCPs) over Western Australia, the vertical accuracy of DEM-9S is ~9 m, SRTM ~6 m and ASTER ~15 m. However, these values vary as a function of the terrain type and shape. Thus, CGIAR-CSI SRTM ver4.1 may represent a viable alternative to DEM-9S for some applications. While ASTER GDEM has an unprecedented horizontal resolution of ~30m, systematic errors present in this research-grade version of the ASTER GDEM ver1 will impede its immediate use for some applications.