Assessment of Persistent Scatterers Behaviour in Co-Polarimetric PAZ Data with Model-Backfeed Method

This study investigates the PAZ SAR data in both VV and HH channels, contributing to PAZ product assessment. It focuses on deformation maps and deformation time series over a test site in Leeuwarden, the Netherlands. To optimize the estimates of the deformation time series and parameters of the temporal model, we developed and applied a model-backfeed method (MBF). This MBF iteratively re-introduces into phase unwrapping the best deformation model of every Constantly Coherent Scatterer, such as Persistent Scatterer (PS), determined by Multiple Hypothesis Testing (MHT). In this regard, distinct temporal behavior of individual scatterers is considered and modeled, thus improving the estimates of deformation time series. 24 co-polarimetric SAR data acquired between 2019 and 2021 are used for our test. The test result shows that PAZ SAR in HH offered 7% more PS than those in VV, and the VV mode identified a bit more PS along line-infrastructure like roads. Besides, by comparison and GNSS-based validation, we find that co-pol PAZ products are generally of a good quality. The MBF method increases the average ensemble coherence by 38% for VV and 35% for HH, and decreases the average spatio-temporal consistency by 2.3% for VV and HH and mitigates phase unwrapping errors, thereby optimize deformation estimates.