Research And Application Of Urban Surface Deformation Inversion Based On InSAR Technology

Due to the constraints of spatio-temporal incoherence and atmospheric effects,the conventional differential interferometric synthetic aperture radar(D-InSAR)cannot accurately retrieve the slowly accumulating surface deformation information of cities.In order to overcome the defects of D-InSAR in retrieving the surface deformation information of long time series,the permanent scatterer InSAR(PS-InSAR)technology and the small baseline subset InSAR(SBAS-InSAR)technology were born.Both PS-InSAR and SBAS-InSAR are used to analyze point targets in image data,remove residual phase in point targets with different models and methods.The time series surface deformation information is retrieved by extracting the deformation information of the point target.With the support of image data provided by many satellite SAR systems,improving the validity and reliability of PS-InSAR and SBAS-InSAR inversion of urban surface deformation information is a problem that needs to be studied at present.First,for dual-polarization data,this paper studies the inversion of surface deformation information in different urban areas based on PS-InSAR and SBAS-InSAR.Second,the surface deformation error caused by SBAS-InSAR in SARscape with manual selection of ground control points is studied.The detailed researches are as follows:For the inversion of the surface deformation of dual-polarization data in different urban areas,using Sentinel-1A VV and VH polarization data as the data source.The surface deformation inversion of 13 dual-polarization data covering the urban area of Shanghai was carried out by using PS-InSAR.And the surface deformation inversion of 30dual-polarization data covering the urban area of Nanchang was carried out by using PS-InSAR and SBAS-InSAR.By analyzing the inversion results and intermediate results,it can be known that:(1)The monitoring results of the two study areas show that the surface deformation in the study area remains stable generally during the monitoring period,and some areas have suffered small-scale surface uplift and subsidence;(2)Among the inversion results of surface deformation of two polarization data in two study areas,the lack of surface deformation information in the VH polarization data is more serious,which cannot reflect the deformation information in some areas;(3)In the quality comparison of two kinds of polarization data interference pair coherence coefficient image and unwrapping image,the quality of the VH polarization data is worse than the VV polarization data.Too few effective pixels of the VH polarization data interference pair is the main reason for the missing deformation information;(4)By comparing the inversion results with existing research results and leveling data,it can be known that the inversion results of the VV polarization data in PS-InSAR and SBAS-InSAR are more effective and reliable than the VH polarization data.The VV polarization data is more suitable for inversion of urban surface deformation.For the surface deformation error caused by SBAS-InSAR with manual selection of ground control points,an SBAS-InSAR method combining PS feature points was proposed.The feature points are extracted as the ground control points for track refining by setting the amplitude deviation threshold and coherence threshold in PS-InSAR.This method was used for surface deformation inversion in Nanchang city.The results show that:(1)During the period from March 2017 to December 2018,the surface deformation rate in the study area was concentrated at-1.0 to 2.0 mm/a.A small amount of surface uplift and subsidence occurred in some areas;(2)In the process of subway construction and operation,the initial settlement is relatively low,and then the adjacent surface will have a certain degree of uplift dues to the pouring of the concrete structure and the rebound uplift deformation of the basement.Due to the impact of groundwater extraction and urban construction,surface subsidence occurs in some areas;(3)This method is highly consistent with PS-InSAR in inversion results and deformation trends,and improve the accuracy of inversion.To ensure its validity and reliability in inversion of urban surface deformation.