DEM extraction from archive aerial photos : Accuracy assessment in areas of complex topography

The aim of this study is to analyze the accuracy of a Digital Elevation Model (DEM) created with photogrammetric techniques from stereoscopic pairs of aerial photos in areas with complex geomorphologic characteristics. The evaluation of DEM and derived geomorphometric parameters was conducted by comparison with other standard DEM products (i.e. TINITALY/01 and ASTER GDEM-V2) and by accuracy assessment based on Check Points (CPs). The validation process includes the comparison of elevation profiles, the calculation of DEM accuracies, and the evaluation of the effect of slope and aspect on the DEM accuracy. The produced DEM accurately represent complex terrain (RMSE = 4.90 m), thus providing information suitable for local-scale geomorphometric analysis. The obtained accuracy resulted slightly worse than TINITALY/01 (RMSE = 2.53 m), but significantly better than ASTER GDEM (RMSE = 12.95 m). These results confirm that photo-based DEM extraction can be a very competitive and precise methodology if other expensive high-resolution data are not accessible.