Methods On High-Accuracy DEM Extraction From Interferometric SAR In Sophisticated Terrain Areas

Synthetic Aperture Radar Interferometry (InSAR) is a landmark achievement with the development of SAR, and has a great potential in development and application. As fastest growing technologies in Earth science and remote sensing, InSAR is a hot research topic as well. With the fast development in SAR sensors, it provides possible massive, rapid and high-resolution SAR acquisitions for InSAR applications such as topographic mapping, surface deformation, hazard monitoring, glaciers movement, forest resources investigation, agriculture monitoring and wetland change mapping etc. Nevertheless, how to effectively generate a high accuracy digital elevation model (DEM) in sophisticated terrain area using InSAR is still a hot research interest.In sophisticated terrain regions, there are many problems in DEM extraction using InSAR. Firstly, due to the SAR side-looking imaging model, a large shadow and serious layover area can be expected in the steep terrain area, which cause real terrain information loss and holes in DEM results. Secondly, in fractured terrain regions, the low coherence in interferograms and accuracy in DEM extraction are unable to support the practical demands. Thirdly, in practical production, because of the difficulty in installing ground control points (GCPs) in sophisticated terrain regions, the above problems are even worse for DEM extraction using InSAR. Regarding to the above problems, research strategies and solutions are proposed in this thesis. The main objects of this thesis includes following three parts:1) Multi-direction InSAR fusion, it is able to fuse multi-direction InSAR data to extract DEM and provide high quality DEM, because a single direction InSAR processing cause DEM information loss due to shadow and layover. And methods on detection and extraction of shadow and layover and shadow effect elimination are studied.2) StereoSAR assisted InSAR, in sophisticated terrain area, this method exploits the advantages of InSAR and StereoSAR respectively to extract DEM comprehensively. Also this method focus on extracting or editing the seed points and structure lines under the stereo environment, improving the quality of interferometric phase unwrapping (PU) resolving, study stereophotogrammetry cooperatively assisted method to improve the quality of InSAR. Furthermore, methods on combination of InSAR and StereoSAR from multi-direction SAR data, construct StereoSAR and InSAR combined adjustment model are studied and proposed as well.3) InSAR technical solutions for DEM extraction in sophisticated terrain area, based on spaceborne and airborne InSAR data, a practical solution for addressing mapping challenges in sophisticated terrains through cross-track and repeat-pass InSAR technology is developed. And this solution is verified in different test areas.The main contributions and innovation of this thesis are summarised as following:1. Multi-direction fusion InSAR, DEM extraction technical method and process on combination of InSAR and StereoSAR from ascending and descending or multi-direction SAR data are proposed. And this method can reduce DEM information loss caused by shadow and layover, etc.2. StereoSAR assisted InSAR technology is proposed and realized to improve DEM accuracy. A method on extraction or editing the seed points and structure lines under the stereo environment improves the quality of interferometric phase unwrapping resolving. Regarding to In view of the consistency, continuity and completeness of phase unwrapping, the stereophotogrammetry synergy methods on correction of wrapped phase and modification of low-coherence area are suggested to improve the quality of the interferometry.3. StereoSAR and InSAR combined adjustment model are constructed, and unify DEM extraction from InSAR and StereoSAR into the same coordinate system, and then improve three dimensional positioning accuracy of the target4. InSAR technical solutions for DEM extraction in sophisticated terrain area are proposed. An InSAR system is designed and developed for DEM extraction. This system integrates functions of above DEM extraction methods. Moreover, through this system, techniques proposed above are applied to DEM extraction from multi-sources InSAR pairs. And its effectiveness, accuracy and robustness are verified through plenty of experiment results from different test areas. It has been successfully applied in DEM generation, such as around1,200km2test area in Shanxi Qinling mountain, around4,400km2mapping area in Hengduan mountain and around2,000km2mapping area in Zoige wetland.