Digital elevation model validation with no ground control: application to the topodata dem in Brazil

Digital Elevation Model (DEM) validation is often carried out by comparing the data with a set of ground control points. However, the quality of a DEM can also be considered in terms of shape realism. Beyond visual analysis, it can be verified that physical and statistical properties of the terrestrial relief are fulfilled. This approach is applied to an extract of Topodata, a DEM obtained by resampling the SRTM DEM over the Brazilian territory with a geostatistical approach. Several statistical indicators are computed, and they show that the quality of Topodata in terms of shape rendering is improved with regards to SRTM

DTM generation with Radarsat-2 Data without GCP

Digital terain models (DTMs) were extracted from high-resolution Radarsat-2 stereo high-resolution images. The metadata supplied by MacDonald, Dettwiler and Associates Ltd. were used to replace the ground control data used to compute for the deterministic geometric model. The DTMs are then evaluated with 0.2-m accurate lidar elevation data. Because DTMs included the height of land covers, elevation linear errors with 68 and 90 percent confidence level (LE68 and LE90) were both computed over the full study site and the bare surfaces. Comparisons were also performed with the same rigorous model using accurate differential GPS as ground control points (GCPs). Using the radargrammetric model using eight dGPS GCPs achieved the best results (3.3 m LE68) than using only the metadata (3.9 m LE68). However, this accuracy is compensated by the fact that the user does not have to collect any ground data, which offers a strong advantage in remote and harsh environments.</i