Status and development of UAV remote sensing technology in mining surface subsidence and fracture measuring

The development and utilization of underground coal resources can cause the mining area surface subsidence and fractures and other hazards, which is not conducive to the protection of ecological environment and the sustainable and stable supply of energy and minerals in mining areas. Comprehensive and efficient measuring of surface subsidence and fractures in mining areas can improve the awareness level of mining damage and scientifically prevent secondary disasters. At present, the mainstream measure methods, such as manual measure of ground observation points and satellite remote sensing, have problems such as high operation intensity and expensive cost, and InSAR is difficult to obtain large-scale deformation due to wavelength limitation. As a new method of geographic information acquisition, Unmanned Aerial Vehicle Remote Sensing (UAVRS) technology has the advantages of flexibility, efficiency, accuracy, repeatability, and comprehensive coverage, and has become a research hotspot in mining area surface subsidence and fractures measuring. Systematic review of domestic and abroad literatures and analysis of frontier progress and development trend are conducive to technological innovation and application in this field. Firstly, the main points of UAVRS and the technical process of measuring surface subsidence and fractures in mining areas are introduced briefly. The UAV is equipped with visible light camera, LiDAR, infrared thermal imaging camera and other sensors, generate remote sensing results such as Digital Elevation Model (DEM) and Digital Orthophoto Map (DOM); Then, in terms of surface subsidence measuring, the research progress, technical difficulties and prospects of terrain acquisition, differential DEM subsidence model, subsidence parameters acquisition and horizontal displacement measuring are analyzed by citing literature cases. In the field of surface fractures measuring, the research progress and problems of image processing, machine learning and infrared thermal imaging are introduced. Finally, the future development direction is forecasted from the advantages of UAVRS technology in subsidence measuring, fractures background noise, fractures prediction and identification accuracy, and data processing speed. Research shows that: (1) UAVRS technology is competent for surface topography acquisition and subsidence measuring in mining areas, and fusion with InSAR data can improve the measuring accuracy of subsidence parameters; (2) Based on DEM acquired by UAVRS, image processing and machine learning methods can realize intelligent recognition of surface fractures, and deep learning is studied to eliminate environmental interference and improve the accuracy of fractures recognition; (3) The research of surface horizontal displacement and subsidence law, the improvement of fracture identification rate and its distribution prediction, the rapid and automatic processing of aerial survey data, and the fusion of multi-source remote sensing data are the main development directions of technology application and research in this field. UAVRS technology has broad prospects in the field of mining surface subsidence and fractures measuring, can drive the transformation of green and intelligent development of mines from the technical level.