8. Interferometric Synthetic Aperture Radar (InSAR) in the Context of Bridge Monitoring

The structural health of critical transport infrastructure, such as bridges, is difficult to assess and monitor. Existing methods of evaluation rely predominantly on visual inspection and/or the installation of sensors to measure the in-situ performance of structures. There are vast numbers of critical bridge structures that need to be monitored and these are often located in diverse geographical locations which are difficult and costly to access. Recent advances in satellite monitoring using Interferometric Synthetic Aperture Radar (InSAR) monitoring provide the opportunity for global coverage of assets and the measurement of displacement to sub-centimetre accuracy. Such technologies could provide bridge engineers and asset owners with insights about the health and behaviour of their assets. The key to successful implementation of InSAR monitoring of bridges lies in understanding the limitations and opportunities of InSAR, and making a clear case to satellite data providers on what specifications (resolution, frequency, processing assumptions) would unlock using such datasets for wider use in monitoring of infrastructure. This work examines the application of InSAR for bridge monitoring using case studies of several UK bridge structures. These bridge structures differ in structural form, material and environmental context, but each raise key considerations in practical application of InSAR, and the potential to spot unusual signs behaviour that would alert bridge owners to maintenance problems and potential failures.