Satellite sensors provide currently reliable elevation data over large areas, with spatial resolutions below 100 m and reported accuracies of approximately 10 m. However, the vertical accuracy of these quasi-global digital elevation models (DEM) varies depending on the terrain and land cover, decreasing in mountain areas, and may influence the quality of products derived from these data, like stream channel network or relief forms. In this paper, we investigated two global elevation data sets: SRTM-X DEM and ASTER GDEM, assessing their vertical accuracy and reliability of terrain features extracted automatically from the elevation data. The research was carried out in the Pieniny Mts., a small mountain range in southern Poland, with elevations ranging from about 400 m to 1000 m a.s.l One particular attribute of this mountain range that may create several problems in deriving accurate terrain features is a deep, narrow and windy gorge of the Dunajec river. We found that the vertical accuracy of SRTM-X DEM is significantly better than of the ASTER GDEM (Root Mean Square errors of 12.05 m and 17.43 m, respectively). Both DEMs allow to extract terrain features with a similar accuracy in areas of moderately steep and gentle slopes, yet fail to properly represent the floor of the Dunajec gorge as relative vertical errors along the river may exceed 100 m. Therefore, we conclude that while both models provide statistically reliable description of the terrain surface, they require additional corrections for hydrological or terrain modeling. © Geoinformatics International.
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