Equivalent Stacking of Polarimetric Synthetic Aperture Radar Interferograms Based on Analysis of Persistent and Distributed Scatterers

We propose a method of incorporating the copolarized observations (HH and VV observations) of multipolarimetric SAR acquisitions into persistent scatterer interferometry to estimate the surface displacement and the scatterer height. Interferograms obtained from HH and VV observations were equally weighted on the basis that the magnitude of the backscattered signals from persistent scatterers represented by odd-bounce scattering and even-bounce scattering are the same in the copolarized observations. Moreover, because of the coarser slant-range resolution of multipolarimetric SAR data, distributed scatterers (DSs) should be taken into account to obtain a spatial density of pixels that is sufficient to estimate the parameters of interest. To this aim, we applied a small baseline criterion to create the analyzed data sets, and we used space adaptive filtering to improve the signal-to-noise ratio of the DSs. We applied this method to estimate the ground subsidence rate in an area of groundwater extraction in Japan using the SAR images that are acquired by Advanced Land Observing Satellite/Phased Array Type L-band SAR (PALSAR) in the full polarimetric observation mode.