Evaluation of SRTM3 and GTOPO30 Terrain Data in Germany

Abstract

High-resolution terrain data are crucial for gravity field modelling in mountainous regions. In areas without national digital elevation models (DEMs) available, fill-ins from global models have to be used. For this purpose, the global models GTOPO30 (30″ resolution) and SRTM3 (3″ resolution) are considered. The SRTM3 model has been released recently from the analysis of the Shuttle Radar Topography Mission and covers the latitudes between 60°N and 54°S, while the GTOPO30 model is a global public domain data set completed already in 1996.

In this contribution, 1″ × 1″ national DEMs for Germany are used to evaluate the global models. The differences between the best national models and the SRTM3 data show a standard deviation of 7.9 m with maximum differences up to about 300 m. The largest differences are located in opencast mining areas and result from the different epochs of the DEMs. Histograms of the differences reveal a clear deviation from the normal distribution with a long tail towards too high SRTM3 elevations. The evaluation of GTOPO30 shows that the longitudes should be increased by 30″ (one block) in Germany. For the shifted GTOPO30 DEM, the standard deviation of the differences with respect to the best national model is 6.8 m, roughly 75 % smaller than for the original model.