Discontinuous InSAR Monitoring of Infrastructure using W-band Ground-Based MIMO Radar

Structural health monitoring (SHM) is critical for ensuring safety and preventing structural failures. This study presents the application of discontinuous InSAR using a commercial off-the-shelf W-band ground-based multiple-input multiple-output (MIMO) radar to monitor long-term displacement of a retaining wall. The use of discontinuous InSAR eliminates the need for long-term sensor deployments, as required in continuous monitoring setup. However, discontinuous acquisition can introduce positional shift between campaigns, causing repositioning errors (RE) in the InSAR phase. To address this issue, a data-driven correction method is introduced, utilizing distributed stable points across the scene to estimate and mitigate RE. The proposed approach was first validated in a controlled experiment using movable corner reflectors (CRs). Experimental results exhibited strong agreement between the RE-corrected displacements and actual CR movements. Subsequently, the framework was applied in a long-term SHM campaign targeting a retaining wall undergoing gradual tilting. Results showed that the RE correction effectively reduced phase errors in stable pixels, with the corrected displacement closely aligned with ground-truth data, achieving a root mean square error (RMSE) of 0.47 mm. Despite these results, the method showed limitations with sparse stable point distribution for RE estimation, which affected the accuracy of RE correction across the entire structure.