Evaluation of ASTER GDEM using GPS benchmarks and SRTM in China

Abstract

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM) has generated one of the most complete high-resolution digital topographic data sets of the world to date. The ASTER GDEM covers land surfaces between 83° N and 83° S at a spatial resolution of 1 arc-second (approximately 30 m at the equator). As an improvement over Shuttle Radar Topography Mission (SRTM) coverage, the ASTER GDEM will be a very useful product for many applications, such as relief analysis, hydrological studies, and radar interferometry. In this article, its absolute vertical accuracy in China was assessed at five study sites using ground control points (GCPs) from high-accuracy GPS benchmarks and also using a DEM-to-DEM comparison with the Consultative Group on International Agriculture Research Consortium for Spatial Information (CGIAR-CSI) SRTM DEM Version 4.1. It is demonstrated that the vertical accuracy of ASTER GDEM is 26 m (root mean square error (RMSE)) against GPS-GCPs, while for the SRTM DEM it is 23 m. Furthermore, height differences in the GDEM-SRTM comparison appear to be overestimated in the areas with a south or southwest aspect in the five study areas. To a certain extent, the error can be attributed to variations in heights due to land-cover effects and undefined inland waterbodies. But the ASTER GDEM needs further error-mitigating improvements to meet the expected accuracy specification. However, as for its unprecedented detail, it is believed that the ASTER GDEM offers a major alternative in accessibility to high-quality elevation data.

Acknowledgements

Part of this work was carried out at the University of Glasgow. It was supported by the Natural Environmental Research Council (NERC) through the Generic Atmosphere Solutions for Radar Measurements (GAS) project (Ref: NE/H001085/1) and was also supported in part by the programme of Introducing Talents of Discipline to Universities (the 111 Project), a China National Natural Science Foundation of China (NSFC) project (No. 41074005), and a China 973 project (2006CB701301). Part of this work was also supported by the ESA-MOST DRAGON-2 project (ID: 5343). We are grateful to Editor Arthur Roberts and two anonymous reviewees for constructive reviews. We also thank Yangmao Wen, Yang Liu, Qiang Yuan, Wei Tu, Xuechen Luan, and Jimei Yang at Wuhan University for their useful discussions. Figures 1, 2(a), 3(a), 4(a), 5(a), and 6(a) were prepared using the public domain Generic Mapping Tools (Wessel and Smith 1998). The original data of ASTER GDEM are the property of METI and NASA and freely available from Earth Remote Sensing Data Analysis Center (ERSDAC, Japan) and NASA's Land Processes Distributed Active Archive Center (LPDAAC), and the hole-filled SRTM for globe Version 4 is available at no charge from the CGIAR-CSI SRTM 90 m Database. The GlobCover products are made available to the public by ESA and cover the period December 2004–June 2006: © ESA GlobCover Project, led by MEDIAS-France.