I. Introduction
Over the past few decades, the measurement and detection of ground deformation have been achieved using interferometric synthetic aperture radar (InSAR), which provides broad coverage, high resolutions, and frequent acquisitions [1], [2]. In its early application, small ground deformations could be measured using differential InSAR (DInSAR) [3], [4]. However, DInSAR is limited by temporal decorrelation and atmospheric disturbance, which affects the estimation of ground displacement. DInSAR cannot produce a long-term deformation time series; it can only provide its acquisition pair date. Thus, for the past two decades, InSAR time-series techniques have been developed to obtain better measurements and reduce the effect of this limitation. In general, InSAR time-series techniques can be grouped into two categories, persistent scatterers (PSs) and distributed scatterers (DSs), according to the scattering mechanisms of the ground target [5].