A novel framework for combining polarimetric Sentinel-1 InSAR time series in subsidence monitoring - A case study of Sydney

The city of Sydney, Australia has been growing rapidly over the last decades, with rapid development of residential and transportation infrastructure. Land subsidence associated with the urban development can lead to serious issues which should be thoroughly understood and carefully managed. Hence this study developed an enhanced multi-polarisation time-series InSAR (Pol-TS-InSAR) processing framework to address this challenging application. This is done by integrating the information from different polarimetric channels with different weighting during the TS-InSAR analysis. Ninety dual polarization Sentinel-1 images acquired from 2019 to 2022 are analysed using the developed Pol-TS-InSAR to map the land subsidence in Sydney with the assistance of the GPS measurements. Improvement of measurement points density from Pol-TS-InSAR is observed compared to the single polarimetric TS-InSAR counterpart for all land use types (ranging between 21% and 99%). The comparison between the Pol-TS-InSAR measurements and GPS measurements shows an absolute mean difference and RMS difference of 0.7 mm/yr and 0.9 mm/yr, respectively, in line-of-sight (LoS) direction. The ground subsidence results obtained have been investigated. It is found that the main subsidence factors in Sydney are related to groundwater extraction, mining activities, underground tunnel construction and landfill, which the latter two factors are less aware previously. In additional to these factors, land subsidence related to high-rise building construction has also been observed, even though the impact seems to be less significant than other factors.

Citation: Alex Hay-Man Ng, Ziyue Liu, Zheyuan Du, Hengwei Huang, Hua Wang, Linlin Ge, A novel framework for combining polarimetric Sentinel-1 InSAR time series in subsidence monitoring - A case study of Sydney,Remote Sensing of Environment, Volume 295, 2023, 113694, ISSN 0034-4257. https://doi.org/10.1016/j.rse.2023.113694.