Validation of digital elevation models (DEMs) and comparison of geomorphic metrics on the southern Central Andean Plateau
Other literature type
(issn: 2196-632X, eissn: 2196-632X)
We validate and compare elevation accuracy and geomorphic metrics of the current generation of satellite-derived digital elevation models (DEMs) on the southern Central Andean Plateau. The plateau has an average elevation of 3.7 km, and is characterized by diverse topography and relief, lack of vegetation, and clear skies that create ideal conditions for remote sensing. At 30 m resolution, the SRTM-C, ASTER GDEM2, stacked ASTER L1A stereopair DEM, ALOS World 3D, and TanDEM-X have been analyzed. The higher resolution datasets include 12 m TanDEM-X, 10 m single-CoSSC TerraSAR-X / TanDEM-X DEMs, and 5 m ALOS World 3D. We assessed vertical accuracy by comparing standard deviations (SD) of the DEM elevation versus 307,509 differential GPS (dGPS) measurements across 4,000 m of elevation. Vertical SD for the 30 m DEMs were 9.48 m (ASTER GDEM2), 6.93 m (ASTER Stack), 3.33 m (SRTM-C), 2.81 m (ALOS World 3D), and 2.42 m (TanDEM-X). Values were generally lower for higher resolution DEMs at 2.02–3.83 m (10 m single-CoSSC TerraSAR-X / TanDEM-X), 1.97 m (12 m TanDEM-X), and 1.64 m (5 m ALOS World3D). Analysis of vertical uncertainty with respect to terrain elevation, slope, and aspect revealed the high performance across these attributes of the 30 m SRTM-C, 30 m and 12 m TanDEM-X, and 30 m and 5 m ALOS World 3D DEMs. Single-CoSSC TerraSAR-X / TanDEM-X 10 m DEMs and the 30 m ASTER GDEM2 displayed slight aspect biases, which were removed in their stacked counterparts (TanDEM-X and ASTER Stack). Based on high vertical accuracy and visual inspection of minimal hillslope artifacts alongside optical satellite data, we selected the 30 m SRTM-C, 12–30 m TanDEM-X, 10 m single-CoSSC TerraSAR-X / TanDEM-X, and 5 m ALOS World 3D for geomorphic metric comparison in a 66 km<sup>2</sup> catchment with a distinct river knickpoint. For trunk channel profiles analyzed with chi plots, consistent <i>m/n</i> values of 0.49–0.57 were found regardless of DEM resolution or SD. Hillslopes were compared through slope and curvature calculations to assess basin-wide differences in their distributions and in the hillslope-to-valley transition related to the knickpoint feature. We find 0.1–0.2 m/m higher slopes downstream of the knickpoint, related to the over-steepened baselevel. While slope and hillslope length measurements vary little between datasets, curvature displays higher magnitude measurements with fining resolution. This is especially true for the optical 5 m ALOS World 3D DEM, which demonstrated high-frequency noise in 2–8 pixel steps through a Fourier frequency analysis. The improvements in accurate space-radar DEMs (e.g., TanDEM-X) for geomorphometry are promising, but airborne or terrestrial data is still necessary for meter-scale analysis.