[S-TT40] 合成開口レーダーとその応用

[STT40-02] Utilization of ALOS-2 InSAR-based displacement measurements for land subsidence estimation through the integration of GEONET data

*Amila KARUNATHILAKE¹、Makoto Ohashi¹、Shin-ichi Kaneta¹、Tatsuro Chiba¹ (1.Advanced Technologies Research Laboratory, Asia Air Survey Co., LTD, SHINURI 21 BLDG, 1-2-2 Manpukuji, Asao-ku, Kawasaki-city, Kanagawa 215-0004 Japan)

キーワード：InSAR, Land-subsidence, ALOS-2, GEONET

An accurate estimation of land subsidence over a large spatial area with differing subsidence rates is very challenging by conventional subsidence estimation methods. Space-borne Interferometric SAR (InSAR) has demonstrated promising results for land subsidence monitoring in both urban and sub-urban regions in the last few decades. However, the accuracy and efficiency of existing studies on subsidence estimation remain unclear due to limited track records, field demonstrations, and availability of reliable coherent scatterers over the monitoring land surface. Therefore, the integration of in-situ measurements to improve the accuracy of InSAR based displacement measurements is important for advancing the utilization of SAR. In this study, we assessed and compared ALOS-2 L-band SAR data under repeat-pass observation geometry with continuously recorded GEONET data to enhance the accuracy of InSAR based displacement measurement. SAR data from both ascending and descending orbital directions, a total of 78 scenes from 2016 to 2023 were used to estimate the displacement by InSAR based method. The vertical displacement component derived from alternative satellite orbital directions was used to estimate the subsidence. GEONET stations located in the same ground area were selected for evaluation. InSAR scatterer coherency greater than 0.6, within 500 m buffer zone from GEONET locations was used to compare time-series displacement measurements over the 8-year observation. The results indicate root-mean-square-error of 2.21 in time-series displacement measurements at the selected GEONET station locations. The displacement estimates from each monitoring method were further analyzed for accuracy improvement. The least square method was used to calculate the adjustment parameters and applied to enhance the accuracy of the displacement measurements. The results demonstrate a significant improvement in the accuracy of the estimated subsidence rates obtained through InSAR.