Comparative assessment of vertical accuracy of SRTM and ASTER GDEM elevation data

Digital Elevation Model (DEM) enables researchers to perform geographical researches in global and regional scales including global changes, natural disasters, environmental monitoring etc. Therefore, DEM data plays a key role in scientific researches. SRTM and ASTER GDEM are two elevation datasets that cover nearly the entire land surface of the earth and are globally available (for almost 80% of the earth). Thus, it is necessary to evaluate the vertical accuracy of such data prior their use and to select the appropriate data in term of the research target. ASTER based digital elevation model has spatial resolution of 30 meters, which seems to provide more precise elevation data than SRTM with 90 meters spatial resolution. Several studies have been performed for evaluating the accuracy of each of these two datasets in various countries of the world. The results of such studies indicate their advantages and limitations over each other. In this study, the vertical accuracy of these two DEMs are evaluated by ground control point in three zones of Iran with different topographic characteristics, which are Eastern Azerbaijan, Sistan and Baluchestan and Bushehr. Results show RMSE of SRTM for study area in Eastern Azerbaijan, Sistan and Baluchestan and Bushehr is 6.1, 7.4 and 2.9 meters and in ASTER GDEM is 8.7, 8.3 and 7.2 meters, respectively. So the STRM data has high vertical accuracy than ASTER GDEM in all three zones. The relation between vertical errors and land characteristics such as slope and aspect are studied and their results are presented in this study. Final results of the study indicates higher vertical accuracy of SRTM in comparison with ASTER GDEM in Iran and it is concluded that SRTM is a more appropriate choice for various applications.