Accuracy evaluation of open DEM products based on airborne LiDAR data

Objectives: Digital elevation model (DEM) is the foundation of many geoscientific applications. Currently there are limited studies with the accuracy evaluation of various open DEM products. This study aims to analyze the accuracy of five open DEM products (including ASTER, AW3D30, MERIT, SRTM, and TanDEM-X 90m). Methods: The five products were compared to airborne LiDAR derived reference DEM and digital surface model (DSM) respectively. Statistical measures including mean error (ME), root mean square error (RMSE), as well as LE90 were used. Results: The results demonstrate significant differences in the accuracy among five open DEM products. None of them meet the designed accuracy in this mountain forest study area. When used as DEM, all five DEM products have severe overestimation of the terrain elevation. Among them, the MERIT (ME=2.82m， LE90=12.19m) and SRTM (ME=4.74m， LE90=11.75m) has much higher accuracy than the other three. TanDEM-X 90m DEM has the worst accuracy (ME=10.39m， LE90=22.83m). When used as DSM, all five DEM products underestimated the elevation of surface objects. Among them, the TanDEM-X 90m (ME=-3.69m， LE90=16.99m) and AW3D30 (ME=-5.34m， LE90=16.81m) have much higher accuracy than the other three products. The spatial distribution of elevation errors are influenced by the type of land cover. Errors in forested areas are higher than in residential areas. Compared to slope, the height of ground objects has more impact on the elevation errors. Conclusion: When used as DEM, the MERIT and SRTM products have higher accuracy, while when used as DSM, the TanDEM-X 90m and AW3D30 have higher accuracy.