Optimal-condition Analysis For Combing Multi-platform MT-InSAR Deformation Time-series Using SVD And Ground Deformation Models Of Ocean Reclaimed Lands

Since Multi-temporal In SAR(MT-In SAR)has the ability to extract high-precision and high-spatiotemporal-resolution ground deformation signal,it has been applied to ground deformation monitoring.Due to the continuous launch of synthetic aperture radar(SAR)satellites,the combination of multi-platform MT-In SAR deformation time-series makes it possible to obtain decades of deformation in ocean reclaimed lands.Singular value decomposition(SVD)has been proved to be an effective method to combine time-overlapped MT-In SAR deformation time-series.The optimal condition was further explored in the process of combination of two time-overlapped MT-In SAR deformation time-series based on SVD method.The geotechnical model can effectively combine time-gapped MT-In SAR deformation time-series.The accuracy of the deformation values fitted by geotechnical model in the time-gapped period,and the applicability of the geotechnical model in different ocean reclaimed lands were futther discussed.The ocean reclaimed lands of Shanghai is taken as a study area to research the optimal condition analysis of SVD combination with two time-overlapped deformation time-series.Based on using of 61 images acquired by the COSMO-Sky Med(CSK)sensor from December 2013 to March 2016,and 47 images acquired by the Sentinel-1A(S1A)sensor from February 2015 to February 2019(both covering the reclaimed area of Shanghai),we process the two datasets by using the SBAS algorithm and then obtained CSK and S1 A vertical deformation time-series with the incidence angles of two datasets.The SVD method is used to combine the two time-overlap deformation time-series.The precision of the combined time-series under different conditions were investigated by using two strategies of reverse order deletion of data included in CSK MT-In SAR deformation time-series and positive order deletion of data included in CSK MT-In SAR deformation time-series.The results show that it is need to keep at least 5deformation data in the overlapping period of CSK and S1 A time-series,to ensure that the accuracy of the combined deformation time-series is within 5mm.In previous work,some scholars applied the geotechnical model to combine ENVISAT ASAR(ENV,from February 2007 to September 2010)and COSMOSky Med(CSK,from December 2013 to March 2016)MT-In SAR ground deformation time-series of Lingang New City of Shanghai,thus generating long-term ENV+CSK ground deformation time-series.However,there was no MT-In SAR deformation timeseries from September 2010 to December 2013,but only information derived from the used geotechnical model to characterize the ground deformation signals from September 2010 and December 2013.In this work,we used a SAR dataset consisting of Radarsat-2(RST-2)acquisitions collected from January 2012 to October 2016(partially covering the time gap between the ENV and CSK data)to further corroborate the validity of the geotechnical model.As a result,we verified that the geotechnical model is consistent with RST-2 MT-In SAR deformation time-series in the timegapping period.To investigate the applicability of the geotechnical model to the other ocean reclaimed lands,we extended the study area to the ocean reclaimed lands of Shenzhen,located in the Pearl River Delta of China,in this work.Based on three sets of SAR data,collected by the ENV platform(from both ascending and descending orbits,from June2007 to April 2010)and the Sentinel-1A(S1A,from June 2019 to June 2020)sensor(on ascending orbits),we obtained the ground deformation time-series of the reclaimed area of Shenzhen by using SBAS method.The ascending and descending ENV MTIn SAR time-series were also combined by using Min A method to obtainthe up–down(subsidence)ground deformation time-series,and then the up–down time-series was used to estimate the parameters of the geotechnical model,the logarithmic model and exponential decay model adopted to foresee the future ground deformation of the reclaimed area of Shenzhen.Finally,we used the S1 A MT-In SAR deformation to check the validity of the predicted value of three models.The results show that the geotechnical model and the logarithmic model are more reasonable in the prediction of the deformation in the reclaimed area of Shenzhen.Thus,the geotechnical model is also applicable to the description of the ground deformation in the reclaimed area of Shenzhen.