94 / 2023-05-25 15:47:36

Application of GACOS-based SBAS InSAR for Surface Deformation Monitoring in Qingdao City

urban ground settlement,Sentinel-1A,GACOS,SBAS InSAR

With the accelerated urbanization, the geological problem of ground subsidence is becoming more and more prominent. Urban ground subsidence can damage urban infrastructure and restrict the sustainable economic and social development of some regions. For long-period slow ground deformation, SBAS InSAR (Small baseline subsets InSAR, SBAS-InSAR) technique can overcome the problems of interference loss correlation, atmospheric delay and phase noise, and effectively obtain time-series ground subsidence information. In this paper, based on the SBAS InSAR technique, 28 views of Sentinel-1A image data from Qingdao City from January 2019 to December 2020 were processed, a spatial baseline threshold of 223m and a temporal baseline threshold of 90d were set, differential interference processing was performed to obtain 75 interferometric pairs, filtering and deconvolution of the interferometric pairs, and tropospheric delay correction products were used to The GACOS data were atmospherically corrected to obtain the results of ground time series subsidence in the urban area of Qingdao. Results analysis: Firstly, the effectiveness of the atmospheric correction using GACOS was analysed, and the standard deviation (STD) was reduced from 1.31 rad and 3.38 rad to 1.04 rad and 2.59 rad, with a reduction of 21% and 23%. The analysis of the overall subsidence in the study area shows that the overall surface conditions are basically stable, with the subsidence areas concentrated in the coastal area of Jiaozhou Bay, the southwest foothills of Laoshan and the northern part of Chengyang District, while the rest of the subsidence areas are scattered, with a maximum annual mean subsidence rate of -60mm/year and a maximum cumulative subsidence of -111.8mm before the GACOS atmospheric correction, and a maximum annual mean subsidence rate of - 58mm/year and the maximum cumulative settlement is -111.5mm; finally, the key settlement areas are analysed, there are four obvious settlement areas in the coastal area of Jiaozhou Bay, which belongs to the construction area of the reclamation project, and the maximum annual average settlement rate can reach -58mm/year; the maximum annual average settlement rate is -31mm/year in the southwest foothills of Laoshan, which is a large settlement area, where there is an underground The maximum annual average settlement rate is -29mm/year in the northern part of Chengyang District, where there are many waters, residential buildings, schools and factories. Afterwards, the level data was verified for some areas and it was found that the level monitoring and SBAS InSAR monitoring showed approximately the same time-series settlement trends, proving that SBAS InSAR has millimetre-level accuracy in urban monitoring and provides a reliable reference for urban ground settlement monitoring.