Abstract
The ALOS World 3D – 30 m (AW3D30), ASTER Global DEM Version 2 (GDEM2), and SRTM-30 m are Digital Elevation Models (DEMs) that have been made available to the general public free of charge. An important feature of these DEMs is their unprecedented horizontal resolution of 30-m and almost global coverage. The very recent release of these DEMs, particularly AW3D30 and SRTM- 30 m, calls for opportunities for the conduct of localized assessment of the DEM’s quality and accuracy to verify their suitability for a wide range of applications in hydrology, geomorphology, archaelogy, and many others. In this study, we conducted a vertical accuracy assessment of these DEMs by comparing the elevation of 274 control points scattered over various sites in northeastern Mindanao, Philippines. The elevations of these control points (referred to the Mean Sea Level, MSL) were obtained through 3rd order differential levelling using a high precision digital level, and their horizontal positions measured using a global positioning system (GPS) receiver. These control points are representative of five (5) land-cover classes namely brushland (45 points), built-up (32), cultivated areas (97), dense vegetation (74), and grassland (26). Results showed that AW3D30 has the lowest Root Mean Square Error (RMSE) of 5.68 m, followed by SRTM-30 m (RMSE = 8.28 m), and ASTER GDEM2 (RMSE = 11.98 m). While all the three DEMs overestimated the true ground elevations, the mean and standard deviations of the differences in elevations were found to be lower in AW3D30 compared to SRTM-30 m and ASTER GDEM2. The superiority of AW3D30 over the other two DEMS was also found to be consistent even under different landcover types, with AW3D30's RMSEs ranging from 4.29 m (built-up) to 6.75 m (dense vegetation). For SRTM-30 m, the RMSE ranges from 5.91 m (built-up) to 10.42 m (brushland); for ASTER GDEM2, the RMSE ranges from 9.27 m (brushland) to 14.88 m (dense vegetation). The results of the vertical accuracy assessment suggest that the AW3D30 is more accurate than SRTM-30 m and ASTER GDEM2, at least for the areas considered in this study. On the other hand, the tendencies of the three DEMs to overestimate true ground elevation can be considered an important finding that users of the DEMs in the Philippines should be aware of, and must be considered into decisions regarding use of these data products in various applications.
Highlights
The Advanced Land Observing Satellite (ALOS) World 3D - 30m (AW3D30), ASTER Global DEM Version 2 (GDEM2), and SRTM-30m are Digital Elevation Models (DEMs) that have become available to the general public free of charge
We present the results of our vertical accuracy assessment of the AW3D30, ASTER GDEM2 and SRTM-30m DEMs covering Northeastern Mindanao, Philippines (Figure 1)
Since the DEMs were generated using data gathered in the year 2000 onwards, we find it appropriate to use the best available land-cover map for the entire Philippines produced by the National Mapping and Resource Information Authority (NAMRIA) for the year 2003 to group the ground control points (GCPs) according to land-cover types
Summary
The ALOS World 3D - 30m (AW3D30), ASTER Global DEM Version 2 (GDEM2), and SRTM-30m are Digital Elevation Models (DEMs) that have become available to the general public free of charge. Assessments of the DEM’s accuracy in many different locations throughout the world are critical for improving the generation of global DEMs (Suwandana et al, 2014). We present the results of our vertical accuracy assessment of the AW3D30, ASTER GDEM2 and SRTM-30m DEMs covering Northeastern Mindanao, Philippines (Figure 1). The effect of varying land-cover on elevation accuracy was assessed
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