Global DEMs vary from one to another: an evaluation of newly released Copernicus, NASA and AW3D30 DEM on selected terrains of China using ICESat-2 altimetry data

A good understanding of the quality of digital elevation model (DEM) is a perquisite for various applications. This study investigates the accuracy of three most recently released 1-arcsec global DEMs (GDEMs, Copernicus, NASA and AW3D30) in five selected terrains of China, using more than 240,000 high-quality ICESat-2 (Ice, Cloud and land Elevation Satellite) ALT08 points. The results indicate the three GDEMs have similar overall vertical accuracy, with RMSE of 6.73 (Copernicus), 6.59 (NASA) and 6.63 m (AW3D30). While the accuracy varies considerably over study areas and among GDEMs. The results show a clear correlation between the accuracy and terrain slopes, and some relationship between the accuracy and land covers. Our analysis reveals the land cover exerts a greater impact on the accuracy than that of the terrain slope for the study area. Visual inspections of terrain representation indicate Copernicus DEM exhibits the greatest detail of terrain, followed by AW3D30, and then by NASADEM. This study has demonstrated that ICESat-2 altimetry offers an important tool for DEM assessment. The findings provide a timely and comprehensive understanding of the quality of newly released GDEMs, which are informative for the selection of suitable DEMs, and for the improvement of GDEM in future studies.