Abstract
Digital Elevation Models (DEMs) are an invaluable source of information in large area studies. Some of the DEMs such as Advanced Spaceborne Thermal Emission Radiometer-Global Digital Elevation Model (ASTER GDEM), shuttle radar topography mission (SRTM), and Global Multi-resolution Terrain Elevation Data 2010 (GMTED2010) are freely available for the scientific community worldwide. Prior to any application, global datasets of DEMs should be evaluated using reference data of higher accuracy. Therefore, the main objective of this study is to assess the quality of the ASTER GDEM (version 2), SRTM (version 4) and systematic subsample GMTED2010 in Tunisia. The validation process, adopted here, is based on two main approaches: internal and external validations. The internal validation is achieved by performing visual inspection of shaded relief images extracted from the three DEMs. At this level, results show that SRTM is essentially similar to ASTER GDEM2 in term of relief features representation. In the second alternative, the vertical accuracy of each DEM is evaluated using 60 Global Positioning System (GPS) validation points. The overall vertical accuracy shows RMSE error of 11.96 m, 8.65 m and 10.86 m for ASTER GDEM2, SRTM and GMTED2010 DEM respectively, in comparison with GPS elevation points.
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