Waterloo bridge monitoring: Comparing measurements from earth and space

Abstract

Satellite radar imagery is becoming more accessible, and at improving spatial and time resolutions. Interferometric Synthetic Aperture Radar (InSAR) has the capability to provide wide-area, high density, millimetre-level displacement measurements (obtained even in darkness and adverse weather conditions). This paper examines advances in InSAR satellite measurement technologies to understand their relevance, utilisation, and limitations for bridge monitoring. Waterloo Bridge is presented as a case study to explore how InSAR data sets can be combined with traditional measurement techniques including sensors installed on the bridge and automated total stations. A novel approach to InSAR bridge monitoring was adopted by the installation of physical reflectors at key points of interest on the structure, in order to supplement the bridge's own reflection characteristics and ensure that the InSAR measurements could be directly compared and combined with in-situ measurements. The interpretation and integration of InSAR data sets with civil infrastructure data is more than a trivial task. Key assumptions and their implications for data interpretation are discussed, with a view to how this technology could be employed in the future.