Estimating Relative Surface Deformation via Pixel-Based InSAR Phase Differencing

Surface deformation monitoring is a critical component of natural hazard management. While Interferometric Synthetic Aperture Radar (InSAR) provides high-resolution observations, the traditional spatial phase unwrapping process remains a potential source of measurement bias and error. To circumvent the complexities of the process, this study presents an alternative workflow for estimating relative surface deformation by differencing the phase of a target area from a reference area on a pixel-by-pixel basis. Building on a preliminary experiment using a single corner reflector (CR) installed on top of a building, we designed an experiment site in an area characterized by low SAR backscatter to minimize background interference. A dual CR setup was deployed: one with manual height adjustments to simulate vertical displacement, while the other was maintained at a constant elevation to serve as a high-stability reference. By utilizing Sentinel-1 imagery with a 6-day revisit cycle, we evaluated the ability of the proposed workflow to detect relative movement between the two reflectors. Whereas the previous experiment using natural adjacent pixels as a reference yielded a standard deviation of approximately 0.6 cm, the current dual CR setup allows for more precise signal localization and stricter control over the stability of the reference point. Our findings suggest that this method is capable of detecting localized deformations and provides a pathway toward more automated and error-resistant disaster management tools.