| Abstrakt: |
This study evaluates global radar‐derived digital elevation models (DEMs), namely the Shuttle Radar Topography Mission (SRTM), NASADEM and GLO‐30 DEMs. We evaluate their accuracy over bare‐earth terrain and characterize elevation biases induced by forests using global Lidar measurements from the Ice, Cloud, and Land Elevation Satellite (ICESat)'s Geoscience Laser Altimeter System (GLAS), the Global Ecosystem Dynamics Investigation (GEDI) and the ICESat‐2 Advanced Topographic Laser Altimeter System (ATLAS) instruments collected on locally flat terrain. Our analysis is based on error statistics calculated for each 1°×1° $1{}^{\circ}\times 1{}^{\circ}$ DEM tile, which are then summarized as global error percentiles, providing a regional characterization of DEM quality. We find NASADEM to be a significant improvement upon the SRTM V3. Over bare ground areas, the mean elevation bias and root mean square error (RMSE) improved from 0.68 to 2.50 m respectively to 0.00 and 1.5 m as compared to ICESat/GLAS. GLO‐30 is more accurate with bare ground elevation bias and RMSE were below 0.05 and 0.55 m. Similar improvements were observed when compared to GEDI and ICESat‐2 measurements. The DEM biases associated with the presence of vegetation vary linearly with canopy height, and more closely follow the 50th $5{0}^{th}$ percentile of Lidar Relative Height (RH50). Other factors such as canopy density, radar frequency and Lidar technology also contribute to observed elevation biases. This global analysis highlights the potential of various technologies for mapping of Earth's topography, and the need for more advanced remote sensing observations that can resolve vegetation structure and sub‐canopy ground elevation. Plain Language Summary: We compare the accuracy of three global maps of Earth's surface topography that were derived from spaceborne radar missions, namely, SRTM, NASADEM, and GLO30. The accuracy is evaluated using spaceborne Lidar data sets from three missions: ICESAT, ICESAT‐2, and GEDI. Lidars are typically more accurate in estimating elevation of the ground, but their measurements are like sparse point measurements. We evaluated the radar‐derived DEMs separately over bare ground regions and forests. We found that NASADEM is a significant improvement over the SRTM DEM with an error of 1.5 m in bare ground areas. But the GLO30 DEM is more accurate with error of only 0.55 m. The presence of forests causes radar‐derived elevation to be higher than the ground, somewhere mid‐canopy. Key Points: NASA's Digital Elevation Model is better than the Shuttle Radar Topography Mission Digital Elevation Model, but GLO‐30 is the most accurateAll radar‐derived elevations exhibit a strong correlation with forest canopy height with bias similar to the Lidar's relative height 50The Ice, Cloud and land Elevation Satellite‐2 Lidar measurements provide a better Lidar alternative for detecting the ground below forest [ABSTRACT FROM AUTHOR] |
Plný text