Assessing POT Methods for Large-Displacement Landslide Measurement with Multi-Source Imagery: A Case Study of the Zhenba Landslide

A large landslide struck the Zhenba Dahekou area of Shaanxi Province, China, on 9 September 2021. To accurately extract landslide displacement in emergency situations, in this study, we explore the feasibility and effectiveness of using satellite images and post-failure emergency UAV images to investigate the large displacement of the landslide through the pixel offset tracking (POT) method and evaluate four different POT methods, including NCC operated in the spatial domain (NCC), the orientation correlation method in ImGRAFT software (ImGRAFT), the multi-pass method in GIV software (GIV), and the frequency method in COSI-Corr software (COSI-Corr). It is found that the Zhenba landslide has moved southwest by about 74.3 m~96.4 m with the sliding direction between 231°~258°. The southward displacement of the landslide gradually decreases from southeast to northwest, and the westward displacement on the west side is greater than that on the east side. The relative matching precision of the POT methods in stable areas reached 0.8 m, superimposed on an image registration RMSE of 1.2 m. Under the experimental conditions of this study, ImGRAFT demonstrated robust overall performance. In terms of matching ability, ImGRAFT and NCC outperform GIV and COSI-Corr. In terms of displacement gradients expression ability, ImGRAFT and COSI-Corr outperform NCC and GIV; in terms of matching efficiency, COSI-Corr, GIV, and ImGRAFT are far superior to NCC. This study expands the application of multi-source optical data to investigate landslides and provides suggestions for the displacement extraction of large-displacement landslides, which will be helpful for the emergency investigation and research of landslides in the future.