Separating and Unwrapping of Residual Topographical and Time-Series Deformation Phases in PS-InSAR Based on Zero-Temporal Baseline Combination and Time-Domain Differentiation

To separate and unwrap the residual topographical and deformation components from the wrapped phases are the key issues for persistent scatterer interferometric synthetic aperture radar (PS-InSAR) technique. The current methods, such as grid-search method based on the assumption that the deformation in time-domain is linear, or the least squares ambiguity decorrelation adjustment method that needs priori information to construct the pseudo-observations, etc., are still difficult to tradeoff accuracy against efficiency. In this article, we propose a new method to separate and unwrap the differential phases for PS-InSAR by dividing them into residual topographical phase and differential deformation phases and performing the phase unwrapping separately. First, we calculate phase ambiguities caused by residual topographical error by zero-temporal baseline combination and single parameter grid-search method. The calculated residual topographical error is used to separate the differential phases dominated by deformations from the original differential phases of PS-InSAR. Then, we proposed time-domain differentiation to unwrap differential phases dominated by deformations without any assumption of deformation model in time-domain. The performance of the proposed method is tested by both simulated and real datasets. The experimental results show that, compared with classic PS-InSAR, the accuracy of residual topographical error estimation is comparable; however, there is an accuracy improvement of 34.4% for the deformation parameter estimation and 35.7% for nonlinear deformation time-series extraction, as well as an improvement of 20–40 times in computational efficiency.