Time-series InSAR Tropospheric Delay Correction And Its Application In Surface Deformation Monitoring In Plateau Citie

Land subsidence is a geological hazard caused by natural or human factors,manifested as a slow lowering of the ground surface.Compared with traditional leveling measurement methods,InSAR technology has the ability to measure surface deformation with full-time,all-weather,large-scale,and high accuracy.Therefore,this technology has become one of the main technical means for monitoring the health of urban infrastructure and has been widely used in surface deformation monitoring around the world.In radar remote sensing monitoring,the microwave signal transmitted by the satellite at two SAR imaging moments undergoes different degrees of delay phase due to the change of atmospheric refractive index when passing through the atmosphere,which restricts the accuracy of InSAR in surface monitoring.This article uses the combination of time-series InSAR technology and tropospheric delay correction technology to monitor the land subsidence in Kunming and Dali cities and analyze the monitoring results.In order to correct the tropospheric delay error in InSAR deformation monitoring in high-altitude cities and improve the accuracy of InSAR technology in surface deformation monitoring,the core research content and results of this article are as follows:(1)This article collected the Sentinel-1 data set in the ascending and descending orbits from February 2018 to May 2021.Due to the atmospheric impact,the time-space evolution of large-scale land subsidence near Dianchi Lake in Kunming was obtained using the time-series InSAR technology based on GACOS correction.Combined with field investigations and ground data,attribution analysis was carried out.The results showed that the areas with more serious subsidence were concentrated in the exhibition center area along the coast of Dianchi Lake and near Xiaobanqiao,with a maximum deformation rate of-23.12 mm/a and a maximum cumulative deformation amount of-66.98 mm.The main factors causing uneven subsidence are closely related to the dense construction of engineering projects and self-built houses in the lakeside sedimentary area.(2)The power-law function model of ERA-5 data set was used for tropospheric delay correction,and applied in the surface deformation monitoring of Dali City.Through experiments,compared with three commonly used tropospheric delay correction methods,it can be found that the PLE5 model has certain advantages in tropospheric delay correction.After tropospheric delay correction,the surface deformation information from January 2019 to March 2022 in the Dali area was obtained,and the analysis was carried out in areas with more serious subsidence.Overall,the annual average deformation rate in the entire study area ranges from-100 to 100 mm/a,and most areas are in a stable state,with only a small part of the area experiencing surface deformation.They are mainly distributed along the southern coast of Erhai Lake,Binchuan County,and Xiangyun County.The subsidence is relatively concentrated in Binchuan County and Xiangyun County.Due to the long-term mining of deep groundwater,the maximum deformation amount in these two areas reached-281.9mm and-238.9mm,respectively,during the study period.