Comprehensive geological survey and research on Wuzhizhou Island of Sanya City based on UAV tilt photography technology

It is extremely difficult to carry out comprehensive geological surveys on uninhabited island due to factors such as inconvenient transportation, lush vegetation coverage, and steep terrain. To overcome the shortage in in-situ investigational staff, reduce safety risks, and improve the working efficiency, the UAV (manned aerial vehicle) tilt photography technology was applied and tested in the Wuzhizhou Island, Hainan Province. A FEIMA D20 UAV carries a D-OP3000 module that equipped with 5 lens with which low-altitude (190m), multi-angle, and high-precision image data could be obtained quickly. The average ground resolution of the image was finer than 0.03m. In addition, Smart3D software was used to generate digital orthophoto maps (DOM) and to build a real-scene 3D model of the island. Therefore, the island could be observed in an omnidirectional way, and the overall understanding of the island was enhanced. Combined with a comprehensive study of digital orthophoto maps, the real-scene 3D model and field investigation, and the linear fracture characteristics of Wuzhizhou Island were obtained, and its origination was explored. The information of current status of land development and utilization of the island was extracted and 15 hidden risk points of geological disasters were spotted, including costal bluff collapse, fault activity, and beach erosion, to which countermeasures were proposed. This study provided a scientific basis for island development and utilization, ecological protection and restoration, geological disaster management, and comprehensive management of the islands alike.