Comparison and Validation of the Recent Freely Available DEMs over Parts of the Earth’s Lowest Elevation Area: Dead Sea, Jordan

Abstract

The present research study assesses the accuracy of two recent freely available ASTER-GDEM ver.2, SRTM ver.4.1 digital elevation models for parts of the lowest area on the earth on the shores of the Dead Sea, the site located over areas with high variation in topography within the “humratessahan” watershed, where the elevation varies between 700 m above sea level in the north east of the watershed to 210 meter below sea level. The reference elevation data used in this study are topographical points extracted from existing digital vector topographical map published by Royal Jordanian Geographical Center (RJGC). However, the contour lines do not cover the whole area especially in the flat areas where elevation is less than the contour line interval. Therefore, the second reference data created with photogrammetric techniques from stereoscopic pairs of aerial photos had been used for the surface to surface comparison and elevation profiles assessment purpose. It is demonstrated that the vertical accuracy of ASTER-GDEM ver.2 is 22.223 m (Root Mean Square Error (RMSE)) against reference elevation data, while the SRTM ver.4.1 has an RMSE of 15.858 m; the statistics results indicate that the theoretical accuracy is achievable and meets the expected accuracy specification. Furthermore, as for its unprecedented detail, it is believed that the photogrammetric derived DEM offers an alternative in accessibility to high-quality elevation data with vertical accuracy of 0.78 m (Root Mean Square Error (RMSE)).