Research On Discontinuities Imaging And Its Application In Optical Bathymetry System

The 21st century is the century of the ocean.With the increasing population of the world,the shortage of resources and other problems are becoming more and more serious.Countries all over the world are competing to turn their attention to the ocean and speed up the research of the ocean and the development and utilization of marine resources.China is a big marine country,and the development of marine economy is promising.In order to implement the national marine strategy and build a powerful marine country,it is necessary to go deeper.Understanding the oceans,managing the oceans and speeding up the field of the oceans.The pace of scientific and technological innovation.The research in the field of marine surveying and mapping is the basis of the development of the ocean,and the bathymetry survey is the basis of the mapping of seafloor topography and geomorphology.In particular,it is of great scientific significance and application value for coastal water depth and underwater topographic and geomorphological survey.Airborne laser bathymetry(Airborne Laser Bathymetry,ALB)technology is widely used in the exploration and development of shallow water area,which is the focus of research in the field of marine surveying and mapping.In terms of hardware,there are already more mature systems in foreign countries,but our country is still in the stage of laboratory research and experimental analysis.In the aspect of data processing,scholars at home and abroad put forward a variety of processing methods,to varying degrees have significant results.However,the problems of low measurement accuracy,large calculation error and difficult to identify the received target signal are still the difficulties and key points of the current research.Therefore,combined with the basic advantages of laboratory research in the field of mathematics and marine information,this study focuses on the methods and technologies of airborne laser bathymetry system,especially the optical bathymetry system model,algorithm and data processing.The main contents and innovations of the study are as follows:(1)Combined with the transmission characteristics and system parameters of laser,the mathematical relationship of 532 nm laser echo signal model is established,and the simulation experiment is carried out with MATLAB.According to the data characteristics of airborne laser bathymetry echo signal and the data filtering algorithm,a signal processing method based on multi-physical field is proposed.Specifically,the received echo signal is regarded as the permeability of porous media,starting from the echo signal itself,the diffusion is slow in the place with small velocity mode value,the diffusion speed is large in the place with large velocity mode value,and the adaptive smoothing processing is carried out.Based on the simulation data,the traditional filtering methods,such as median filtering and mean filtering,are used to process the multi-physical field signal processing method respectively.The results show that the multi-physical field processing method can better filter the airborne laser echo signal.(2)The parameter inversion and seafloor intermittent imaging of optical bathymetry system are studied.The Fresnel-Kirchhoff diffraction formula is obtained by selecting the Green's function in the form of spherical wave under the Kirchhoff boundary condition.Based on the scalar diffraction theory and the theory of parameter discontinuity inversion of wave equation,the mathematical theory of seafloor discontinuity imaging and parameter inversion of optical bathymetry system is given.The seafloor reflection coefficient of the received echo signal are inversed(calculated)by numerical simulation,and the position of seafloor water depth(Intersection)is finally obtained.(3)Oval scanning modeling and simulation analysis of scanning trajectory of UAV Laser bathymetry system.Based on the principle that the spatial straight line intersects with the plane,the scanning trajectory of the laser foot point of the sea surface and the seafloor is deduced,and the three-dimensional point cloud of the laser foot point of the bottom of the sea is established,which provides the basic data support for the calibration of the measurement data.