MT-InSAR monitoring of deep excavations: a feasibility study of analytical kinematic constraints to assess three-dimensional surface movements

Multi-temporal Interferometric Synthetic Aperture Radar (MT-InSAR) has become a valuable tool for monitoring surface movements in urban areas.This study integrates MT-InSAR data from complementary ascending and descending orbits, with kinematic analytical constraints to evaluate three-dimensional ground displacements induced by deep excavations.A case study of metro station construction in Copenhagen's Cityringen is presented, where ground movements were induced by piling and excavation activities.To assess the reliability of MT-InSAR against terrestrial benchmarks, displacement time series from very-high-resolution X-band satellites (TerraSAR-X and Cosmo-SkyMed) are compared with three-dimensional terrestrial measurements.A novel method is then introduced that integrates dual-orbit MT-InSAR measurements with an analytical kinematic model to assess 3D displacement directions, grounded in the physical behaviour of deep excavations.This allows for decomposition of satellite observations along the radar Line-of-Sight (LOS) into vertical and horizontal components around a rectangular excavation.A study of the directional sensitivity of Analytically Constrained InSAR (AC-InSAR) to the variance of LOS measurements is carried out.Finally, the kinematically constrained MT-InSAR results are compared with terrestrial data to demonstrate the feasibility and accuracy of the proposed approach.