Landslide deformation monitoring by three-camera imaging system

Landslide deformation is a critical issue for WuWanZai as it will affect the road safety and cause transportation problem. Since the relief of this area is about 400 meters with an area of tens of hectares, we use an unmanned helicopter equipped with a three-camera imaging system to acquire high spatial resolution images in order to measure detail terrain variation. The unmanned helicopter can fly according to terrain slope to obtain 1–3 cm spatial resolution images. The acquired three-camera images are stitched into one perspective image in advance to construct a large format virtual image with a frame size of 34 mm by 78 mm and a FOV of 53° × 97°. Integrating ground control points that were measure by static GNSS continuous observation, we conduct aerial triangulation and dense point cloud generation by PhotoscanPro. We have acquired six dataset of UAV images since April 20, 2018. Then, we have conducted cloud-to-cloud distance calculation, DSM elevation difference calculation, ortho-image change analysis, photogrammetric points and GNSS stations displacement analysis, etc. In the end, from photogrammetric point displacement analysis, we have detected 1.6 meters displacement around the fourth curve of WuWanZai due to a heavy rainfall occurred at June 20. Based on the cloud-to-cloud distance analysis and DSM elevation difference results, we have observed more than 5 meters of height difference at the landslide area due to another heavy rainfall happened at Oct. 23–24. Experimental results demonstrate that by using the proposed UAV and three-camera imaging system can effectively detect landslide deformation in high accuracy.