A Global Evaluation of Radar-Derived Digital Elevation Models: SRTM, NASADEM and GLO-30

A new and improved global digital elevation model (DEM) called NASA- DEM has been generated from the Shuttle Radar Topography Mission (SRTM) data to remove topographic artefacts from the SRTM boom os- cillations and to reduce data gaps and biases from unwrapping and system- atic errors. In this paper, we assess NASADEM’s accuracy with respect to ICESat/GLAS and more recent spaceborne lidar elevation datasets from the Global Ecosystem Dynamics Investigation (GEDI) and ICESat-2. We also compare NASADEM to the global TanDEM-X DEM and validate the latter. Our analysis is based on error statistics calculated for each 1◦ × 1◦ DEM tile, which are then summarized as global error percentiles, provid- ing a regional characterization of the NASADEM and TanDEM-X quality. NASADEM is a significant improvement upon the SRTM V3. Over bare ground areas, the median absolute elevation bias and root mean square error (RMSE) decreased to 0.02 and 1.6 meters respectively. For comparison, the TanDEM-X bare ground elevation bias and RMSE were below 0.22 and 1.1 meters. We also investigated NASADEM and TanDEM-X biases associated with the presence of vegetation, highlighting the impact of canopy height and density on InSAR-derived DEMs. These vegetation-induced biases, apparent for both NASADEM and TanDEM-X, provide insight into the potential feasibility of spaceborne interferometric SAR to estimate global forest height.