On the use of MTInSAR data and UAV photogrammetry to monitor the behavior of existing bridge portfolios

Bridges play a vital role in road networks, and ensuring their safety and preservation is of utmost importance to both management companies and the scientific community. On the other hand, ensuring a continuous assessment of the bridge portfolios health state requires high costs (e.g.; sensor-based monitoring), which leads to employ different techniques to identify the most critical cases and implementing risk mitigation measures. With this goal in mind, this paper presents the application of two of the most actual and attractive cost-effective techniques for purpose of existing bridge portfolios health state monitoring: (a) multitemporal interferometry via synthetic aperture radar (MTInSAR) data; (b) unmanned aerial vehicle (UAV) photogrammetry. In detail, the paper deals with the use of the two above methodologies, where MTInSAR data can be employed to perform a qualitative assessment of the spatial displacements and velocities characterizing the focused bridges, while UAV flight surveys can be used to identify the occurrence of displacement phenomena (e.g.; landslides) in the area immediately close around the observed structures. After describing pros and cons of the two approaches, an application is provided on an existing bridge, for which MTInSAR temporal series are analyzed over 1 year of observation, while UAV surveys are performed at the start and at the end of the considered period. From the combination and the comparison of the techniques, some insights are provided, opening new scenarios in the field of the structural health monitoring of existing bridges portfolio