Absolute Surface Elevations Accuracies Assessment of Different DEMs Using Ground Truth Data Over Kingdom of Bahrain

摘要

For small islands, accurate digital elevation model (DEM) can help to understand the sea level rise prediction and scenarios impact on coastal zones, flooding risks assessment, flood inundation modelling, erosion and landslide, and environmental disaster process management. Currently, DEMs are available from several different sources using space borne systems, photogrammetry, surveying, topographic contour lines, etc. The aim of this study focuses on a comparison of absolute surface heights accuracies of four independent DEMs datasets over small island as Kingdom of Bahrain. The first two DEMs were acquired with space borne, Shuttle Radar Topographic Mission (SRTM-V4.1) and Advanced Space borne Thermal Emission and Reflection Radiometer (ASTER-V2.1) with 30 m pixel size. The second two DEMs with 2.5 m (DEM-2.5) and 5 m (DEM-5) spatial resolutions were derived from two different topographic contour lines maps at scales, respectively, 1:5000 and 1:25000 using inverse distance weighted (IDW) interpolation method. For validation purposes, a datasets of 400 ground control points uniformly distributed over the study site were used. They were measured using a Differential Global Position System (DGPS) assuring ± 1 and ± 2 cm accuracies, respectively, for planimetry and altimetry. The obtained results show that the derived DEM-2.5 exhibit the best accuracy ± 0.55 m which is excellent by reference to the tolerance or maximum error ± 0.78 m calculated based on errors sources propagation. As well, the DEM-5 shows very good accuracy ± 1.37 m by reference to the calculated tolerance ± 1.54 m. Then, SRTM shows a satisfactory performance with ± 3.00 m accuracy which is less than the absolute vertical height accuracy (± 5.6 m) advocated by NASA for African continent and Middle-East regions. Finally, the achieved ASTER accuracy ± 8.40 m is better than the estimated error (± 17.01 m) by USGS and JAXA.