CRInSAR Using Two-Step LAMBDA Algorithm for Nonlinear Deformation Estimation: Case Study of Monitoring Xiangtan Converter Station, China

Deformation monitoring of a converter station of an electrical power transmission system will help to prevent potential damages to power facilities and properties. Corner reflector InSAR (CRInSAR) enables local deformation measurements in low coherence areas like construction-engineering projects. However, the accuracy of CRInSAR will be degraded by the phase unwrapping errors, especially when the deformation is large or dominated by nonlinear component. This letter reports a study that employs CRInSAR technique to monitor the deformations of ten CRs installed in Xiangtan converter station, China, with seven TerraSAR-X Spotlight images. A two-step phase unwrapping tactics is proposed based on the least squares ambiguity decorrelation adjustment (LAMBDA) algorithm to focus on estimating nonlinear deformation without being affected by unwrapping errors. The results reveal that the two-step LAMBDA algorithm can achieve an accuracy of less than 2 mm for CRInSAR deformation monitoring regardless of small- or large-scale deformations, as validated by the trigonometric leveling measurements.