Surface Subsidence Monitoring Of PS-InSAR Technique

Surface subsidence is a long-term dynamic and continuous geological change process.In recent years,there are obvious hidden dangers of surface subsidence in Caofeidian District of Tangshan City,which has a significant impact on the local ecological environment,people's living activities and social economy.Therefore,it is of great significance for the disaster prevention,mitigation and development of Caofeidian area to use the surface subsidence monitoring technology to monitor the real-time dynamic surface subsidence and predict the trend of subsidence change in combination with subsidence factors.Taking Caofeidian and its surround areas in Hebei Province as the study area,using Sentinel-1A data to do the research and application of PS-InSAR technology for surface subsidence monitoring.Based on the original data of 26 Sentinel-1A used in the research area,the terrain phase is removed by using 90 m resolution SRTM DEM data and POD precise orbit data as auxiliary data,and the permanent scatterer point(PS point)is selected by using the amplitude deviation threshold method of PS-InSAR technology,which is 0.8 and 2499999 PS points have good density and quality.This method selects the resolution unit which can keep the phase stable in the study area and the ground objects which are not subject to the change of time-space baseline,and screens out the low coherence and weak stability ground points.The results show that the threshold method of amplitude dispersion is applicable in the study area;The phase difference interference model of PS points is established and iterative processing is carried out to overcome some problems,which are the influence of atmosphere on interference fringes and spatiotemporal incoherence and the removal of interference phase,noise phase and DEM residual phase,etc.,and the inversion of accumulated settlement and settlement rate on time series.After the results of accumulated settlement and settlement rate are obtained,it can be concluded that the maximum accumulated settlement is 43 mm in two years,and the settlement rate is-26~23 mm/a from 2018 to 2019.the spatial-temporal surface deformation characteristics of four key areas in Caofeidian area,namely,ecological city,Caofeidian industrial area,Tanghai town and Liuzan town,are analyzed,and the accumulated settlement ranges of four areas are-42~39 mm,-43~39 mm,-38~36 mm and-42~40 mm,in which the large area of eco city has subsidence and serious subsidence.