Using SBAS-InSAR for Beijing-Tianjin intercity railway subsidence monitoring

Kurzfassung

The acceleration of urbanization in China, which at expense of over dipping of natural resources as underground water and fossil fuel, has brought some negative aftermaths. One of them is the aggravation subsidence in urban area. Subsidence will put a threat to not only the civilians’ life but also to the sustainable development. When the subsidence is monitored at large scale with high density and frequency, the internal mechanism can be found and the effects could be controlled better. In this thesis, popular time series InSAR methods are presented and compared. Before that, the basic principle of SAR and InSAR is introduced. Moreover, an improved SBAS InSAR algorithm is tested, as well as the CR based quality control. In the last part, the algorithm and quality control method is tested in Beijing-Tianjin Intercity Railway monitoring case, with is verified by terrestrial leveling. In total, the whole thesis is consisting of five parts: (1)Summarize the research currents for InSAR technique. Briefly introducing the basic principle of SAR, InSAR, DInSAR, and PSInSAR; comparisons are made between the techniques and algorithms. Then their limitations are pointed out. (2)Briefly introducing the scatter mechanism for PS, following by the new PS identification method. This method take use and combine amplitude dispersion index, dominant scatter, and coherent index, in such a way that high density and trustable PS can be identified. (3)An improved SBAS InSAR method is presented. Enriching the interferograms by short baseline and multiple master images. Realizing spatial-temporal phase unwrapping by phase function model and Delaunay triangulation. Then, using the PS identification method above, a processing flowchart of monitoring subsidence by time series InSAR is formed. (4)Quality control based on CR. In order to overcome the inconsistency result between terrestrial leveling and InSAR, a stochastic model of between InSAR and leveling deformation result is formed. Moreover, a CR reorganization strategy is introduced through both human interpretation and CR’s statistic characteristics. Finally, the verification and validation is made by using the terrestrial leveling data. (5)An experiment of Beijing-Tianjin Intercity monitoring is applied, to test the application ability in line feature engineering monitoring. After the subsidence result is obtained, the risk assessment is conducted.