Evaluation of Digital Elevation Models (DEMs) generated from ASTER and SRTM data: A case study of flat alluvium terrain of Bakreshwar-Dubrajpur (W.B.), India

Digital Elevation Models (DEM) provides basic information on elevation of Earth´s surface and are freely available from space borne SRTM (Shuttle Radar Topographic Mission) data - a mission of NASA and from ASTER (Advanced Space borne Thermal Emission and Reflection Radiometer) data - a mission of JAPAN. These data provide valuable information regarding surface topography for better understanding of geospatial features of earth. Considering its significance here an attempt has been made to evaluate DEMs generated from the above two data sources both in terms of horizontal as well as vertical variations in elevation values by taking an area which is comparatively a moderately sloping flat terrain with thin forest cover, Bakreshwar- Dubrajpur of West Bengal, India. DEMs, Shaded Relief and elevation contour maps of the area have been generated and studied using the ERDAS Imagine image processing software and Global Mapper Software. For comparison of elevation accuracy, three sites in the area have been chosen along a profile and on which elevation values have been extracted from SRTM, ASTER and Survey of India Topo sheet. The study has brought out that the the DEM generated from ASTER data provides a better view of terrain ie smaller features and minor elevation variation are discernible better then on SRTM -DEM. This may be attributed due to the crude horizontal spatial resolution of 90 meter of SRTM data as compared to 30 mt to that of ASTER data set. Therefore DEM generated from ASTER data provides better view of geospatial features and also the elevation values are near to ground survey data with variation of about 5%.