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This study focuses on the quality evaluation of two of the best 1 arc-second public global digital elevation models (DEMs), Copernicus GLO-30 DEM and ALOS AW3D30 DSM, from the perspective of their capability to represent the terrain morphology of a complex alpine landscape, located in the alpine Trentino Province, in the Italian Alps. The analysis is performed on an area of 6210 km2, considering a reference DEM derived from a high resolution and accurate airborne Lidar DEM. The quality assessment includes, in addition to a conventional analysis of error statistics on a pixels-by-pixel basis, an ad-hoc analysis on the capability to represent the fine-scale morphology and local roughness. The quality analysis is performed considering the influence of local morphology and of the different land covers. The findings show that the two global DEMs have comparable overall quality, but the relative performances change according to local landscape characteristics. Copernicus DEM performance is on average better than ALOS in correspondence of urbanized areas as well in areas without vegetation cover, with gentle slopes and relatively low short-range roughness. ALOS DEM performance is slightly better than Copernicus in rougher terrain and steeper slopes. In general, both DEMs have poor performances in steep slopes, with a limited capability to describe correctly local morphology. The adoption of these global DEMs for terrain analysis and modelling of earth surface processes should be performed carefully, taking into account the impact of different land covers and of local morphology, including surface roughness. |
