MCCT: A Multidimensional Geomorphic Change Detection Strategy for Complex Terrain Areas Using Satellite Remote Sensing Data

Abstract

Accurate monitoring of soil erosion over large areas with complex terrain has faced challenges, which primarily stem from an insufficient capacity of existing satellite remote sensing techniques for monitoring multidimensional geomorphic change in complex terrains. In this study, a framework combining synthetic aperture radar (SAR) and optical satellite imagery was proposed to overcome the above challenges. A multimodal high-resolution satellite image registration method was proposed to mitigate the geometric distortions of high-resolution optical images induced by terrain undulations within small areas in the complex terrain. The registered optical images were employed to derive horizontal geomorphic changes using the optical pixel offset tracking (POT) method, while the surface displacement projected onto the radar line of sight (LOS) was retrieved using multitemporal interferometric SAR (MT-InSAR). The quantification of soil erosion/deposition was then achieved by integrating horizontal geomorphic changes with interferometric SAR (InSAR)-derived LOS deformation using a weighted least-squares inversion, while the corresponding uncertainty was quantified using the covariance matrix. The proposed image registration method was evaluated using registration errors and deformation uncertainty on stable areas, while the detected soil erosion and deposition were verified based on erosion pin measurements, laser scanning, and manually digitized terrain feature line change directions. The results showed that the proposed registration method achieved subpixel registration accuracy, with a root-mean-square error (RMSE) <5 cm. The derived erosion and deposition were generally comparable with the results obtained by laser scanning and erosion pin monitoring (R ${}^{2}{\,}\gt {\,}~0.6$ , p < 0.01, Nash–Sutcliffe efficiency (NSE) > 0.5), with an RMSE of 3.28 cm according to erosion pin measurements. In addition, the migration of terrain feature lines was found to be generally opposite to the direction of surface horizontal deformation, particularly pronounced at gully heads. This further demonstrated the feasibility of our monitoring results. Overall, this study provided a promising framework for soil erosion monitoring over complex terrain areas based on satellite remote sensing, while further work is still required to improve the accuracy of the method, particularly to improve the capacity of InSAR for monitoring large and rapid changes.