Ground- and Space-Borne Interferometric Radars for Monitoring Cable-Stayed Bridges: A Multi-Scale Monitoring Framework

Maintaining large-scale transport infrastructure is a significant challenge because transport networks consist of many interconnected assets where a localised failure can cause widespread disruption. This study proposes a monitoring framework that connects the wide-area screening capabilities of Interferometric synthetic Aperture Radar (InSAR) with the high-precision diagnostic power of Ground-Based Interferometric Radar (GBIR). Within this architecture, satellite remote sensing is positioned as a continuous observation layer. By taking advantage of frequent revisit times and millimetre-scale sensitivity to movement, the framework uses optimised satellite data acquisition to ensure observations are conducted at scales suitable for bridge monitoring. This offers a practical solution for asset owners to assess infrastructure conditions and plan preventive maintenance across vast networks without the need for frequent expert visitation.

In this integrated framework, GBIR is used to establish a high-fidelity "structural footprint" of the bridge’s health status. While the satellite-based observation is intended to provide long-term tracking and identify general changes [1], the ground-based system captures the rapid structural vibrations required for detailed health characterisation through Operational Modal Analysis (OMA) [2]. This approach is discussed through the case study of the Dong-Yi Bridge, a cable-stayed bridge in South Korea, where GBIR was deployed to record the baseline structural response as a definitive benchmark of the healthy state. The study highlights the potential for a cohesive monitoring pipeline where a radar satellite monitors for anomalous trends, which in turn justifies the targeted deployment of GBIR for in-depth structural inspections. The synergy between these technologies provides a robust and reliable basis for transitioning from schedule-based to trigger-based infrastructure management and informed decision-making.