Integration of Range Split Spectrum Interferometry and conventional InSAR to monitor large gradient surface displacements

Incorrect unwrapping of dense interferometric fringes caused by large gradient displacements make it difficult to measure mining subsidence using conventional Interferometric Synthetic Aperture Radar (InSAR). This paper presents a Range Split Spectrum Interferometry assisted Phase Unwrapping (R-SSIaPU) method for the first time. The R-SSIaPU method takes advantage of (i) the capability of Range Split Spectrum Interferometry of measuring surface displacements with large spatial gradients, and (ii) the capability of conventional InSAR of being sensitive to surface displacements with limited spatial gradients. Both simulated and real experiments show that the R-SSIaPU method can monitor large gradient mining-induced surface movements with high precision. In the case of the Tangjiahui mine, the R-SSIaPU method agreed with GPS with differences of approximately 4.2 cm, whilst conventional InSAR deviated from GPS with differences of nearly 1 m. The R-SSIaPU method makes phase unwrapping less challenge, especially in the cases with large surface displacements. In addition to mining subsidence, it is believed that the R-SSIaPU method can be used to monitor surface displacements caused by landslides, earthquakes, volcanic eruptions, and glacier movements.