Comparison of free high resolution digital elevation data sets (ASTER GDEM2, SRTM v2.1/v4.1) and validation against accurate heights from the Australian National Gravity Database

Abstract

Today, several global digital elevation models (DEMs) are freely available on the web. This study compares and evaluates the latest release of the Advanced Spaceborne Thermal Emission Reflectometer DEM (ASTER GDEM2) and two DEMs based on the Shuttle Radar Topography Mission (SRTM) as released by the United States Geological Survey (SRTM3 USGS version 2.1) and by the Consortium for Spatial Information (SRTM CGIAR-CSI version 4.1) over the Australian continent.

The comparison generally shows a very good agreement between both SRTM DEMs; however, data voids contained in the USGS model over steep topographic relief are filled in the CGIAR-CSI model. ASTER GDEM2 has a northeast- to southwest-aligned striping error at the 10 m level and shows an average height bias of –5 m relative to SRTM models. The root-mean square (RMS) height error obtained from the differences between ASTER GDEM2 and SRTM over Australia is found to be around 9.5 m. An external validation of the models with over 228 000 accurate station heights from the Australian National Gravity Database allows estimating each models’ elevation accuracies over Australia: ASTER GDEM2 ∼ 8.5 m, SRTM3 USGS ∼ 6 m, SRTM CGIAR-CSI ∼ 4.5 m (RMS). In addition, the dependence of the DEM accuracy on terrain type and land cover is analysed. Applying a cross-correlation image co-registration technique to 529 1 × 1 degree tiles and 138 2 × 2 degree tiles reveals a mean relative shift of ASTER GDEM2 compared with SRTM of –0.007 and –0.042 arc-seconds in north–south and –0.100 and –0.136 arc-seconds in east–west direction over Australia, respectively.

如今，若干全球数字高程模型（DEM）在互联网上免费提供。本研究比较和评估先进星载热发放反射仪DEM（ASTER GDEM2 ）和基于航天飞机雷达地形测绘使命（SRTM ）的两个DEM的最新版本，其发布由美国地质调查局（USGS SRTM3 2.1版本）及在澳洲大陆上空空间信息公司（SRTM CGIAR-CSI版本4.1 ）进行。比较一般呈现两个SRTM数字高程模型之间的统一；然而，USGS模型中关于陡峭的地形起伏的资料空缺由CGIAR-CSI模型填充。ASTER GDEM2有一个10米等级的东北- 西南方向条纹误差，并显示一个相对于SRTM模型的-5米平均高度偏差。自澳大利亚的ASTERGDEM2和SRTM之间的差异所得到的均方根（RMS）高度误差据发现约9.5米。对超过228000个准确的站高度的模型，由国家重力数据库进行的外部验证，使得在澳洲估计每个模型的高程精确度成为可能：ASTER GDEM2 〜8.5米、 SRTM3 USGS 〜 6米和SRTMCGIAR-CSI 〜4.5米（RMS） 。此外， DEM精度对地形类型和土地覆盖的依赖关系被分析。将互相关图像配准技术运用于529块1 × 1度瓦片和138块2 × 2度瓦片，揭示了ASTER GDEM2的平均相对位移，通过分别与澳大利亚南北向-0.007和-0.042弧秒的SRTM和东西向-0.100和 -0.136弧秒的STRM相比较。

KEYWORDS:

• digital elevation model
• DEM evaluation
• ASTER GDEM2
• SRTM3 USGS v2.1
• SRTM CGIAR-CSI v4.1
• Australian National Gravity Database
• elevation accuracy
• georeferencing

ACKNOWLEDGEMENTS

This study was supported by the Australian Research Council (Grant DP120102441) and through funding from Curtin University's Office of Research and Development. Further, it was created with the support of the Technische Universität München – Institute for Advanced Study, funded by the German Excellence Initiative. We thank Matthew Garthwaite and one anonymous reviewer for the constructive review of our article.