COMPARATIVE ANALYSIS OF GLOBAL DIGITAL ELEVATION MODELS

Global Digital Elevation Models (GDEMs) are datasets of vital importance for regional-scale analysis in areas such as geomorphology, [paleo]climatology, oceanography and biodiversity. In this work a comparative assessment of modern and legacy GDEMs is presented for the following datasets: TERDAT (10' resolution), ETOPO5 (5'), Terrainbase (5'), ETOPO2 (2'), ETOPO1 (1'), GTOPO30, GLOBE, SRTM30_PLUS, GMTED2010 and ACE2 (30''). Analysis were run using GRASS-GIS and Python scripts. These datasets were compared about their statistical values and histogram distribution. Additionally, the GDEMs' elevation was compared against the altitude of the world's ultra prominent peaks (ultras: mountains with a topographic prominence - the vertical distance between its peak and the lowest contour line encircling it and no higher summit - of 1,500m (4,921 ft) or more). In land areas, all 30'' datasets are very similar, although in oceanic areas ACE2 presents a series of peaks in the histogram that do no correspond with the reality. Distribution of land elevation per area has a mean at 1,110m, median at 580m and mode at sea level. Oceanic areas have mean at -3,440m, median at -3,900m and mode at -4,300m (peak of histogram below -1,000m). When compared to the dataset of ultra prominent peaks, GDEMs' elevations show an expected tendency of underestimating the peak's altitude, but differences reach 3,500m. ACE2 has the highest standard deviation (482.89m), while ETOPO1 shows the smaller dispersion (292.2m), although the highest mean difference (555.6m). None of the GDEMs captures the full range of elevation on Earth and they do not represent well the altitude of the most prominent peaks. Such problems could be addressed with a new release of SRTM30 based on the 2013-version of SRTM 03'' or with the forthcoming 12m-resolution WorldDEM from the TanDEM-X mission.

Support: FAPESP #09/17675­-5, CNPq #306294/2012­-5