article · Geo-spatial Information Science
Global digital elevation models provide critical topographic data, but their accuracy varies considerably depending on terrain type and vegetation cover. An evaluation of four freely available 30-metre resolution elevation models, Copernicus GLO-30, NASADEM, ASTER GDEM, and ALOS World 3D, examined their vertical accuracy against dense LiDAR reference data across Southern and Central Africa. In diverse landscapes across Cape Town, Copernicus achieved the highest vertical accuracy, whereas ASTER showed the poorest performance. In contrast, ASTER and NASADEM proved more accurate within the dense tropical rainforests of Gabon. Copernicus maintained superior vertical accuracy in areas with tree canopy cover under 40 percent, but ASTER and NASADEM outperformed it in heavy canopy exceeding 70 percent. Elevation errors exhibited higher positive correlations in forested terrains compared to mountainous and urban settings.
Accurate elevation models are essential for flood modelling, infrastructure planning, and environmental management. Because free global elevation datasets differ significantly in quality depending on forest density and landscape roughness, understanding these variations allows regional planners and researchers to choose the most reliable dataset for their specific terrain, avoiding costly errors in spatial analysis and engineering projects.
This research provides applied guidance for spatial data analysts, civil engineers, and environmental consultants selecting open-access elevation datasets. The insights are directly applicable today, helping organisations avoid the costs of high-resolution commercial surveys where freely available models suffice, or selecting optimal models for specific biomes such as dense forestry or urban infrastructure. The abstract does not outline a specific commercial product pathway.
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Validation studies of global Digital Elevation Models (DEMs) in the existing literature are limited by the diversity and spread of landscapes, terrain types considered and sparseness of groundtruth. Moreover, there are knowledge gaps on the accuracy variations in rugged and complex landscapes, and previous studies have often not relied on robust internal and external validation measures. Thus, there is still only partial understanding and limited perspective of the reliability and adequacy of global DEMs for several applications. In this study, we utilize a dense spread of LiDAR groundtruth to assess the vertical accuracies of four medium-resolution, readily available, free-access and global coverage 1 arc-second (30 m) DEMs: NASADEM, ASTER GDEM, Copernicus GLO-30, and ALOS World 3D (AW3D). The assessment is carried out at landscapes spread across Cape Town, Southern Africa (urban/industrial, agricultural, mountain, peninsula and grassland/shrubland) and forested national parks in Gabon, Central Africa (low-relief tropical rainforest and high-relief tropical rainforest). The statistical analysis is based on robust accuracy metrics that cater for normal and non-normal elevation error distribution, and error ranking. In Cape Town, Copernicus DEM generally had the least vertical error with an overall Mean Error (ME) of 0.82 m and Root Mean Square Error (RMSE) of 2.34 m while ASTER DEM had the poorest performance. However, ASTER GDEM and NASADEM performed better in the low-relief and high-relief tropical forests of Gabon. Generally, the DEM errors have a moderate to high positive correlation in forests, and a low to moderate positive correlation in mountains and urban areas. Copernicus DEM showed superior vertical accuracy in forests with less than 40% tree cover, while ASTER and NASADEM performed better in denser forests with tree cover greater than 70%. This study is a robust regional assessment of these global DEMs.
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DOI: 10.1080/10095020.2023.2296010
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