| dc.description.abstract | Satellite remote sensing plays an important role during the last decades. Its potential had been demonstrated to be an effective data for land deformation monitoring, by using the synthetic aperture radar (SAR) image. However, the most high-resolution SAR images are costly until Sentinel-1 SAR imagery freely offered by ESA since 2014, which covers wide-area coverage connected to a relatively high spatial resolution, therefore allowing obtains a comprehensive outlook of the deformation phenomena.
In this study, interferometric synthetic aperture radar (InSAR) technique were used to monitor land subsidence over Bangkok Metropolitan Area, Thailand. The application of InSAR technique in measuring land deformation has higher uncertainty when spatial and temporal decorrelation are involved. This study demonstrated that, with applying Sentinel-1A SAR data, image pairs can be collected with smaller perpendicular baselines and lower temporary discrepancy, leading to better measuring results. In this study, Sentinel-1A SAR data were collected from March to December in 2017 with the baseline within 50 m and 120 days. Therefore, spatial and temporal decorrelation have a negligible contribution. Because well co-registration is important for the accurate determination of phase difference and for noise reduction, data in 2017 was only used in this study, due to poor co-registration of data obtained in 2015-2016.
InSAR measuring results reveal that, in Bangkok Metropolitan Area, Samut Prakarn has been subsiding rapidly at the rate of 20-30 mm/yr, and Central Bangkok on the east of Chao Phraya river appears to be subsiding relatively slowly at rates around 15 mm/yr. Results also indicate fast subsiding areas in Bang Kho Laem, Sathon and Yannawa District, with strong subsidence around 40 mm/yr. In addition, the InSAR measurements were compared with Royal Thai Survey Department (RTSD) leveling rates in 2016, showing minor difference between the two data sets. This study maps the recent land subsidence rates over Bangkok Metropolitan Area, and also illustrates the applicability of Sentinel-1 data in land subsidence monitoring, which can be significantly contribute to the hazard prevention and land management for low land areas in Thailand. | en_US |