Multi-component nonlinear motion estimation in differential SAR tomography – the time-warp method

Abstract

In the differential SAR Tomography (D-TomoSAR) system model the motion history appears as a phase term. In the case of nonlinear motion this phase term is no longer linear, and hence can not be retrieved by spectral estimation. We propose the "time warp" method that rearranges the acquisition dates such that a linear motion is pretended. The multi-component generalization of time warp rewrites the D-TomoSAR system model to an M+l-dimensional standard spectral estimation problem, where M indicates the user defined motion model order, and hence enables the motion estimation for all possible complex motion models. Both simulations and real data (from TerraSAR-X spotlight) examples demonstrate the applicability of the method and show that linear and periodic (seasonal) motion components can be separated and retrieved.