Abstract
Digital terrain models (DTMs) are a fundamental source of information in Earth sciences. DTM-based studies, however, can contain remarkable biases if limitations and inaccuracies in these models are disregarded. In this work, four freely available datasets, including Shuttle Radar Topography Mission C-Band Synthetic Aperture Radar (SRTM C-SAR V3 DEM), Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Map (ASTER GDEM V2), and two nationwide airborne light detection and ranging (LiDAR)-derived DTMs (at 5-m and 1-m spatial resolution, respectively) were analysed in three geomorphologically contrasting, small (3–5 km2) catchments located in Mediterranean landscapes under intensive human influence (Mallorca Island, Spain). Vertical accuracy as well as the influence of each dataset’s characteristics on hydrological and geomorphological modelling applicability were assessed by using ground-truth data, classic geometric and morphometric parameters, and a recently proposed index of sediment connectivity. Overall vertical accuracy—expressed as the root mean squared error (RMSE) and normalised median deviation (NMAD)—revealed the highest accuracy for the 1-m (RMSE = 1.55 m; NMAD = 0.44 m) and 5-m LiDAR DTMs (RMSE = 1.73 m; NMAD = 0.84 m). Vertical accuracy of the SRTM data was lower (RMSE = 6.98 m; NMAD = 5.27 m), but considerably higher than for the ASTER data (RMSE = 16.10 m; NMAD = 11.23 m). All datasets were affected by systematic distortions. Propagation of these errors and coarse horizontal resolution caused negative impacts on flow routing, stream network, and catchment delineation, and to a lower extent, on the distribution of slope values. These limitations should be carefully considered when applying DTMs for catchment hydrogeomorphological modelling.
Highlights
Digital terrain models (DTM) provide a continuous mathematical representation of the Earth’s bare surface [1]
This study examined the vertical accuracy of four DTMs with regard to data source, dataset characteristics, and terrain morphology in three small Mediterranean catchments
The results of this study can be summarised in the following keystone conclusions: 1. The analysed light detection and ranging (LiDAR)-based models and—to a lower extent—SRTM provided reliable sources for most of the discussed hydrological and geomorphological modelling aspects
Summary
Digital terrain models (DTM) provide a continuous mathematical representation of the Earth’s bare surface [1]. Most of the DTMs used in hydrogeomorphological applications are satellite-derived datasets, such as the SRTM DEM [15] and the ASTER GDEM [16], due to their nearly global topographic coverage and unrestricted availability. Their spatial resolution is coarse (~30 m) and their targeted vertical accuracy is ~16 m [17] and ~17 m [18], respectively. Airborne light detection and ranging (LiDAR)-derived DTMs are recognised to overcome these restrictions in spatial resolution and vertical accuracy [19,20,21,22], but their spatial coverage is limited due to their cost-intensive acquisition and processing. A broader range of LiDAR DTM potential applications in catchment hydrology and landscape geomorphology has been identified [26,27]
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