Deployment and design of bi-directional corner reflectors for optimal ground motion monitoring using InSAR

SAR interferometry (InSAR) requires coherent radar reflections to measure ground displacements. However, natural coherent reflectors are not always available due to changes in the scattering properties of the ground, e.g., growing vegetation. Furthermore, the opportunistic nature of InSAR measurements can limit its use for infrastructure monitoring. The scattering properties of infrastructure may not be optimal to monitor it, because some parts may appear invisible to radar for a particular observing direction. This is especially problematic for satellite InSAR. To overcome these problems, corner reflectors are usually employed. They are installed in areas where the radar does not detect coherent reflections with their orientation pointing at the required observing angle. However, corner reflectors also have some limitations. To provide with high signal-to-clutter ratio (SCR) and avoid decorrelation noise, their size is required to be large, which can complicate their deployment and maintenance. In addition to that, traditional corner reflectors are unidirectional and cannot provide with reflections at orthogonal directions as required for a vector decomposition of the displacement. We demonstrate that with a predefined deployment formation the size of reflectors can be reduced while maintaining the overall SCR. We also provided a new design of a small, bidirectional reflector tile, which can reflect at required multiple angles for ascending and descending satellite passes.