Vertical Accuracy Assessment of 30-M Resolution Alos, Aster, and SRTM Global Dems Over Northeastern Mindanao, Philippines

Abstract

ABSTRACT:The ALOS World 3D -30m (AW3D30), ASTER Global DEM Version 2 (GDEM2), and SRTM-30m 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 SRTM30m, 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-30m (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-30m 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-30m, 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-30m 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.

Vertical Accuracy and Calibration of Digital Elevation Models (DEMs) for the Piranhas-Assu River Basin, Rio Grande do Norte, Brazil

“…Elevados valores de R², acima de 0,9, são amplamente encontrados na literatura, em estudos de calibração do MDE SRTM a partir dos dados de pontos de controle de alta precisão vertical (e.g., Gorokhovich & Voustianiouk, 2006;Medeiros et al, 2009;Forkuor & Maathuis, 2012;Athmania & Achour, 2012;Santillan & Makinano-Santillan, 2016 Figura 3). Investigando a estratificação dessa variação em classes de altura ortométrica, foi possível observar uma diminuição de ∆H do SRTM não calibrado para o SRTM calibrado, em quase todas as classes, exceto na classe de 120 a 130m.…”

“…Essa precisão é 2 vezes maior do que a divulgada Gorokhovich & Voustianiouk (2006), observaram em estudos realizados nos EUA e na Tailândia, que a precisão vertical do SRTM, eram de duas a quatro vezes maiores que os valores apresentados nas especificações originais deste produto para as regiões estudadas. Para o Nordeste de Mindanau (Filipinas), Santillan & Makinano-Santillan (2016) verificaram que o SRTM para a região possuía uma precisão melhor do que a informada nas especificações originais desse MDE. Eles encontraram uma média de ΔH= 6,21m e RMSE= 8,28m, enquanto que nas especificações a média de ΔH esperado era de 10m e RMSE de 16m.…”

Evaluation of Recently Released Open Global Digital Elevation Models of Hubei, China

“…The validation work about AW3D30 is very limited. Santillan et al [27] conducted a vertical accuracy assessment about AW3D30, ASTER GDEM and SRTM 1 in the Philippines with GPS points. It is found that the AW3D30 has the smallest RMSE of 5.68 m.…”

Uncertainty Analysis of Watershed-Based Flow and Water Quality Modelling with Different DEM Data Sources

“…Considering the DEM sources incorporated in previous studies (Tan et al, 2015, Xu et al, 2016 and the current study, it is clear that the factor controlling the significance of DEM source versus resolution is the vertical accuracy of DEM. Although vertical accuracy of different DEM sources may vary based on the study location (Elkhrachy, 2017, Santillan & Makinano-Santillan, 2016, the overall accuracy could be used as a guidance. When the vertical accuracies of employed sources are more or less similar, such as ASTER and SRTM with vertical accuracy of 17 meters at the 95% confidence level (https://asterweb.jpl.nasa.gov/GDEM.ASP) and less than 16m at the 90% confidence level (https://www2.jpl.nasa.gov/srtm/statistics.html), respectively, DEM resolution may play a critical role.…”