A new digital elevation model over South Africa based on ground and satellite data

Abstract

This study makes contributions toward development of accurate DEM from ground and satellite data over South Africa. This is achieved by preparing recent satellite-based DEMs (AW3D30, SRTM, ASTER, TanDEM-X, and MERIT), assessing their vertical accuracy, selecting candidate DEMs, modelling errors for the candidate DEMs and fusing candidate DEMs. Following removal of outliers from each DEM, a different number of ground levelling data are used in the assessment of the DEMs (AW3D30 -26,364 points, SRTM -25,727, ASTER -23,773, TanDEM-X -25,964 and MERIT-24,485). The standard deviations of the differences between ground levelling and DEMs heights are ±5.09, ±7.03, ±9.20, ±4.99 and ±8.36 m for AW3D30, SRTM, ASTER, TanDEM-X and MERIT, respectively. AW3D30 and TanDEM-X are therefore selected for fusion. The two candidate DEMs are improved by applying a combination of linear regression, multiple regression, and adaptive terrain-dependent methods using 17,307 model data points. A fused DEM is developed from improved candidate DEMs using a combination of different fusion methods and assessed using 8,657 data points (distinct from the model points). The standard deviation of the height differences between ground levelling and the fused DEM is ±4.290 m, and it is more accurate than all satellite based DEMs considered in this study.