Sensitivity of the C-band SRTM DEM Vertical Accuracy to Terrain Characteristics and Spatial Resolution
This work reports the results of a careful regional analysis of the SRTM DEM (Shuttle Radar Topography Mission – Digital Elevation Model) vertical accuracy as a function of both topography and Land-Use/Land Cover (LULC). Absolute vertical errors appear LULC-dependent, with some values greater than the stated accuracy of the SRTM dataset, mostly over forested areas. The results show that the structure of the errors is well modeled by a cosine power n of the local incidence angle (θloc). SRTM quality is further assessed using slope and topographical similarity indexes. The results show a lower relative accuracy on slope with a R2 = 0.5 and a moderate agreement (Kappa ≈ 0.4) between SRTM- and IGN-derived slopes. The application of a simple cosine squared correction on the 90 m SRTM dataset shows only a slight improvement of the relative accuracy despite a 7 m decrease of the mean absolute elevation error. The accuracy is strongly improved (R2 = 0.93 and Kappa = 0.75) for data resampled at a 150 m to 500 m horizontal resolution. These results support the idea that for regional application purposes the topographic correction as well as the spatial resampling of the SRTM dataset are needed.
KeywordsDEM analysis error structure modelling Burgundy
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