Research On Uav Laser Line Scanning Radar System For Near Shoal 3D Imaging

In recent years,the development of marine exploration has been promoted by the exploitation of marine resources.With the attention to the exploitation of marine resources,three-dimensional imaging has gradually become more popular in the field of marine exploration.Near shoal,as the interface area between ocean and land,is the focus of marine resources development.It has always been a popular research area for ocean exploration.Lidar detection is one of the most important methods of human detection.Linear structured light scanning technology,which is non-contact,fast and accurate,plays an important role in three-dimensional imaging of ocean exploration.At present,the research of linear scanning method in the air has formed a relatively perfect theoretical system and application model.However,due to the wave on the surface of sea water,suspended particles in sea water,absorption and scattering of light by sea water,light refraction and other factors,the theory in the air does not work,so the underwater measurement technology of linear structured light still has great problems.Aiming at the above problems,this paper proposes a method to distinguish and extract underwater laser fringes for shoal scanning,and establishes an underwater laser measurement model with refraction compensation.Based on Global Positioning System(GPS)and Attitude Acquisition Unit(IMU),a set of UAV-borne laser line scanning radar system is designed and three-dimensional imaging of shoal is realized.The main contents of this paper are as follows:Firstly,the imaging principle of UAV line scan radar system is introduced.This paper introduces the theory of triangulation ranging,three-dimensional coordinate transformation and GPS coordinate transformation,and the common algorithm for extracting laser fringe centers.A more accurate projection-light surface model is established and camera distortion model is introduced.An underwater refraction compensation model is established for underwater target imaging,and the principle and process of point cloud splicing are presented.The method of laser fringe extraction and resolution in underwater imaging are also proposed.Secondly,a laser line scanning radar system for UAV is designed.The hardware is analyzed and designed from four parts: laser imaging unit,RTK-GPS positioning unit,IMU attitude acquisition unit and data transmission unit.The platform and library are selected according to the requirements of airborne and ground software respectively.The airborne software is designed based on Lab VIEW platform to realize data acquisition pre-processing and data preservation.The ground software is based on VS,QT,PCL and OPen CV realizes data download,laser stripe center extraction,point cloud resolution,point cloud display and preservation functions.Finally,the experiment of near shoal scanning is carried out by using the designed UAV laser line scanning radar system.The effect of water surface reflection and backscattering on stripe extraction is reduced by using the water imaging laser stripe center extraction algorithm,which verifies the effectiveness of the stripe extraction algorithm.Three-dimensional imaging of high-resolution shoals has been achieved by three-dimensional scanning in the estuary near shoal and trestle shoal.The experimental results verify the correctness of the projection-light surface model and the point cloud solution,splicing of refraction compensation,and the superiority of the UAV laser line scanning radar system in near shoal detection.