A Multitemporal Baseline Phase Unwrapping Approach for Accurately Monitoring High-Gradient Deformation With Two-Pass DInSAR

The differential interferometric synthetic aperture radar (DInSAR) technique can estimate the Earth’s surface displacement theoretically at centimeter- or millimeter-level accuracy, where the 2-D phase unwrapping (PU) is ineluctable, so that improper PU algorithm would deteriorate the accuracy. Conventional single-baseline (SB) PU-based DInSAR cannot accurately monitor high-gradient deformation due to the limitation of the phase continuity assumption. The conventional multibaseline (MB) PU-based DInSAR, including multifrequency-based two-pass DInSAR and two-stage programming approach (TSPA)-based three-pass DInSAR, is capable of delineating high-gradient deformation but imposes stringent requirements on InSAR data. Under this condition, we present a multitemporal baseline PU approach (MTBA) for two-pass DInSAR from single radar system such that even high-gradient deformation can be delineated at centimeter- or millimeter-level accuracy. The MTBA demonstrates to be valid through a simulation experiment and three strike-slip earthquake events. Furthermore, the MTBA expands the perpendicular baseline-based MB PU for topography mapping into the temporal baseline-based MB PU domain for deformation monitoring, potentially enriching the MB PU theory and extending the application of DInSAR technique.