Physics-informed decomposition of LOS displacement for infrastructure monitoring

In recent years, the use of Synthetic Aperture Radar (SAR) satellites for infrastructure monitoring has gained significant attention due to their wide observation range and elimination of on-site sensor installation needs. However, the displacement obtained from Interferometric SAR represents only the line-of-sight (LOS) displacement, which is challenging to interpret. Previous studies have proposed methods using LOS data from multiple angles, Multiple Aperture Interferometry (MAI), offset tracking, and ground measurements. Nevertheless, MAI and offset tracking lack sufficient accuracy, while the multi-angle LOS method has limitations in its application range. Methods using ground measurements face issues with sensor installation costs and durability. To address these challenges, this research aims to establish a method for decomposing LOS displacement using data from a single satellite, focusing on bridges as critical infrastructure to monitor. While previous studies use multiple LOS displacements or ground measurements as constraints for decomposition, this study enables decomposition using a single satellite by employing constraints based on physical laws. We estimate the vertical and longitudinal displacements that satisfy these physical constraint conditions. To examine how different constraints affect the results, two types of constraints are used and compared. The proposed method is validated by comparison with conventional methods using two satellites. Our investigation demonstrates that the estimated vertical and longitudinal displacements closely match the values obtained from the conventional method. Additionally, the results provide insights into the influence of the constraints on the outcome.