High precision deformation monitoring of landslide via corner reflector-, persistent scatterer-, and distributed scatterer-synthetic aperture radar interferometry three-scale robust combination

Synthetic aperture radar interferometry (InSAR) has been successful in detecting and monitoring landslides over the last decade. However, its accuracy encounters challenges such as spatial and temporal decorrelation, unwrapping errors, and atmospheric delays. These issues are particularly pronounced in steep, intricate, and densely vegetated mountainous areas prone to landslides, which will complicate the processing of InSAR data and impact the reliability of landslide detection and monitoring. We introduce a approach that combines corner reflectors (CRs), persistent scatterers (PSs), and distributed scatterers (DSs) using a three-scale robust fusion method. The goal of this method is to utilize CR as consistent reference points, PSs as constraint factors, and DSs as variables to be estimated for improving the precision and dependability of deformation inversion. Moreover, maximum likelihood estimation is utilized to mitigate the influence of gross errors, enhancing the robustness of results derived from InSAR data processing. The three-scale robust fusion method demonstrated superior performance to the DS-InSAR method using both advanced synthetic aperture radar (ASAR) and phased array type L-band synthetic aperture radar (PALSAR) datasets, as evidenced by increased measurement points and enhanced monitoring accuracy compared with global positioning system (GPS) measurements. This robust fusion method is particularly suited for known landslides outfitted with CRs, which have garnered substantial research interest and have established various ground-based deformation monitoring systems including leveling, global navigation satellite system (GNSS), and CRs. In scenarios where CRs are absent, alternative methods such as GNSS or leveling can be deployed to function as reference points, effectively serving a constraining role. Moreover, for concealed and unidentified landslides that lack pre-installed monitoring infrastructure, the robust fusion method remains applicable to integrate PSs and DSs and facilitates the selection of several highly coherent and stable ground objects to act as reference points, thereby achieving similar outcomes to those in sites with established CRs. The proposed method is appropriate for most landslide disaster monitoring scenarios in complex mountainous regions.