Monitoring Large Area Subsidence With PS-InSAR Technique Based On Multi-track Data

With the increasing seriousness of land subsidence, there is several large area of subsidence in our country, e.g, the north China plain, the Yangtze delta and basin of Fenwei. Facing serious land subsidence, In SAR technology has become a kind of high precision, large range and short period of monitoring means. Due to data coverage of one image, there is several problems need to be solved, especially for large regional land subsidence monitoring of thousands of square kilometers. Therefore, how to recover the deformation accurately and how to solve the In SAR technology in large range of synchronous monitoring will become difficult technical problems in In SAR land subsidence monitoring.Based on the above problems, this paper studies the large area subsidence monitoring using PS-In SAR technique with multi-track data. The followings are the main research contents and results:1.The paper analyzes the characteristics and key technology of PS-In SAR, and discussed in detail for PS points selection and unwrapping phase method. In order to improve the reliability of the phase information, we select PS points by amplitude dispersion thresholding together with interferometric phase stability. Secondly, analyze and eliminate the PS candidates through phase space related features. Thirdly, we applied temporal and spatial filter to remove DEM error, atmosphere error, orbit error and space angle error. And the paper chose 3-D phase unwrapping to get the phase information.2.In the paper, we discussed the maximum deformation gradient detection with In SAR subsidence monitoring. Choose different unwrapping gird size in subsidence monitoring for Panjin and Xi’an. Analysis and discussion is given about the subsidence of the profile through the maximum deformation area with different gird size. And the research results show that we can only detect the deformation that is no more than4lbetween two adjacent pixels in actual phase unwrapping.3.To get large subsidence, a method for mosaic of multi-track PS-In SAR results has been introduced in this study. The method not only solves the the differences of PS points position, the deformation magnitude and different reference datum problems in overlapping area, but also proposes an accuracy validation method using the results of adjacent tracks’. The result form three adjacent tracks of Weihe indicates that the the standard deviation is 5.0mm/a, 5.0mm/a.4.The proposed methods have been applied for large subsidence monitoring in Lower Li- aohe with PS-In SAR. 100 m grid size is chosen in 2-D phase unwrapping depending on the deformation gradient. After transforming the coordinate system and validating the datum, a large continuous deformation is acquired and also with time-series of serious subsidence area. Finally, an analysis for deformation reasons will be provided combining with the history of the geological data.