Use of Sar Satellite Data in Bridge Monitoring with Application to Urban Areas

In the last 20 years, SAR sensors installed on satellites have been increasingly used to monitor large scale phenomena such as subsidence, uplifting, or landslides. Recently several research groups started to investigate the use of remote sensing for damage detection in civil infrastructures. This technique presents in principle several advantages, not least the possibility to monitor a network of structures using the same sensor. However, its implementation for civil engineering projects is still at its infancy and a limited number of applications can be found in literature. The goal of this paper is to investigate the feasibility of using InSAR data for structural health monitoring of bridges with reference to a number of case studies. Data measured by radar satellites with different spatial and temporal resolutions and different frequency bands are processed to extract bridge displacement data and analyzed to identify possible structural damages. The SqueeSAR technique is used to extract displacement time histories from SAR images acquired by radar sensors with different spatial and temporal resolution (TerraSAR-X and RADARSAT 1–2). Displacements are then processed to identify anomalies possibly related to damage. Results show that high-resolution radar data enable the detection of very small structural displacements due to environmental changes, such as temperature variation.