DEM Generation from High Resolution Satellite Imagery

Abstract

Digital height models (DHM) covering larger areas can be generated by means of optical or synthetic aperture radar (SAR) images taken from space. An overview of the sensors and the characteristics of generated height models is given. With very high resolution optical satellite stereo pairs a system accuracy of 1.0 ground sampling distance (GSD) standard deviation can be reached. Of course this is not the accuracy of a DEM, which is also influenced by interpolation and includes areas with limited contrast and vegetation, leading to lower quality. In addition, the difference between digital surface models (DSMs), describing the visible surface, and digital terrain models (DTMs), describing the bare ground, has to be respected. The same problem exists for SAR images used by either interferometric SAR (InSAR) or by radargrammetry if no InSAR configuration is available. It has to be ascertained whether existing regional or nearly worldwide DEMs can be used instead of especially produced elevation models. The SRTM DEM and ASTER GDEM are both available, free of charge via the Internet, but their resolution and accuracy are limited. Higher resolution DEMs, such as the SPOT DEM (also named Reference 3D) or NextMap, are not free of charge and they do not cover the whole earth. This will also be the case for the TanDEM-X height model, which will be available in 2014. If more detailed DEMs are required, they can be determined by automatic image matching of very high resolution satellite imagery.