Differential interferometric SAR (DInSAR) technique has been widely known as wide range of land subsidence measurement method. However, the displacement is obtained only along the radar line-of-sight (LOS) direction. Thus, in this paper, we merged the results from PSI and geodetic deformation measurements (GPS and leveling) to estimate the three-dimensinal displacement velocities of Kansai International Airport. We compared the estimated results with GPS/leveling survey data. The root mean squared errors (RMSEs) were 7, 14 and 16 mm/year for the east-west, north-south and vertical components, respectively. It was found our proposed method is effective for land subsidence monitoring.

This paper presents the results of estimating land displacement of the areas after an earthquake by utilizing synthetic aperture radar (SAR) time-series images. We selected the nuclear power station in Fukushima Prefecture, Japan, damaged by the Great East Japan Earthquake in 2011, and the tsunami triggered by the earthquake. The still ongoing displacement of the areas, especially the underground frozen soil wall installed, should be quantitatively estimated. In usual, the displacement estimated by persistent scatterer interferometry (PSI)[1,2] is obtained only in the radar line-of-sight (LOS) direction. We estimated three-dimensional displacement velocities by applying the least-squares method to the results from PSI and Global Positioning System (GPS) data. We used 13 and 17 ALOS-2/PALSAR-2 images acquired on the ascending and descending orbits, respectively in addition to the displacement data measured at 10 GPS stations. The obtained results show that local displacement is estimated, and the displacement along the frozen soil wall is different from the neighboring areas. Consequently, it was shown that combining PSI results and geodetic deformation measurements is effective for monitoring land subsidence.

Leveling provides vertical ground deformation and Global Positioning System (GPS) provides three-dimensional (3-D) deformation with subcentimeter accuracy level, but these measurements are point observations. In order to achieve a high spatial resolution, synthetic aperture radar (SAR) is an effective approach. In particular, Persistent Scatterers Interferometry (PSI) can accurately measure wide range of land subsidence by using multi-temporal SAR images. Thus, in this paper, we will merge the results from PSI and geodetic deformation measurements (GPS and leveling) to estimate the 3- D displacement velocities of Kansai International Airport with high spatial reso lution. We apply the least square (LS) approach to combine the interpolated result from GPS and leveling, and estimated results by PSI from SAR images observed on ascending- and descending-orbits. Finally, we compared the estimated results with leveling survey data. The root mean squared error (RMSE) was 18 mm/year, and it was found that the fusion of the results from PSI and geodetic deformation measurements is effective for land subsidence monitoring.