An Evaluation on the Data Quality of Srtm Dem at the Alpine and Plateau Area, North-western of China

This paper evaluates the quality of SRTM3 data for alpine and plateau areas in Northwestern (NW) China against DEM data extracted from topographic maps. These SRTM data were obtained from both the ESRI ArcGIS 9.2 software package and NASA's Jet Propulsion Laboratory website. It shows that these two data sources provide the approximate precision as the DEM based on 1:250000 scale topographic maps in general. In our study area, the ESRI SRTM data have about 38% of raster units with less than 10m absolute elevation error, 58%; <20m, 90%; <49m, 95%; <65m, 99%; <92m, and 99.9%; <143m compared with the topographic maps. The delta surface void filling process conducted on the ESRI SRTM data does not change the error scheme of the total DEM. In relatively low and flat basins, as well as the wide valleys on the plateau, the absolute elevation error is typically less than 5m. Significant errors of more than tens or hundreds of meters were obtained in rugged mountainous areas, even lakes and reservoirs in low land. Furthermore, the author suggested that the slope of terrain has no effect on the error, while the northern slope has higher minus mean error compared with the southern one. At last, elevation errors in glacial, deciduous forest and desert settings present a normal Gaussian distribution with all the peaks at -20 to 0m, and few raster units with absolute errors of more than 100-200m.