| In recent years,with the rapid economic development,the urban construction and the scale of cities continues to increase,and the workload of topographic mapping,building 3D modeling,and power line monitoring also increases.However,the traditional manual measurement methods can no longer meet the demand for the detection.As a non-contact 3D measurement method,UAV lidar technology has combined laser 3D scanning,global positioning system and inertial navigation.The detection system can quickly and efficiently acquire high-resolution 3D coordinate data of each target in the measured area with the applihigh-speed laser scanning measurement method.At present,various of research on the UAV lidar systems has made great achievements in the domestic and abroad.Lidar systems mostly adopt spot scanning mode.This detection method has concentrating laser energy and long detection distance,but the scanning structure is relatively complex with higher cost.In contrast,a line scanning imaging lidar based on laser triangulation method combined with UAV is applied to perform low-altitude 3D imaging with the advantages of low cost,high precision and high imaging speed.However,due to the mechanical performance during flight,UAV shake may lead to many issues such as bending,deformation and translation in 3D imaging results.Aiming at these issues,this paper obtains the positioning and attitude information of the UAV laser line scanning unit through the Global Positioning System(GPS)and Inertial Measurement Unit(IMU).In addition,the results of UAV laser line scanning 3D imaging are corrected based on the above information.After the3D imaging experiment by using the UAV laser line scanning system,the effectiveness of the correction algorithm was verified experimentally,the image stitching of multi-route correction data was completed and the 3D scene was reproduced.The main research contents of the paper are as follows:(1)The imaging method of UAV line laser scanning system and the principle of coordinate transformation of image correction were introduced.Then the image correction and splicing method of laser line scanning were analyzed.Several coordinate systems were established and the 3D data were calculated.(2)The UAV laser line scanning system was designed.Firstly,the system of hardware composition was analyzed and constructed in four parts:laser ranging unit,DGPS positioning unit,inertial measurement unit and wireless transmission unit.Secondly,the software system was designed from data acquisition and data processing.Finally,the 3D data of correction were analyzed,processed and displayed,with Geomagic and ENVI LiDAR point cloud data processing software.(3)By using the UAV line scanning imaging system,the disparate experimental research targets was carried out and the issues exist in the cloud image were analyzed.Through the correction algorithm,the imaging error caused by UAV flight was reduced,and the effectiveness of the correction algorithm was verified.The data of multiple routes were spliced with correction data,and the Mosaic area was over 2500m~2.The 3D scene reconstruction was realized in high resolution terrain with the lateral resolution of3.75cm,the vertical resolution of 1cm and the range resolution 1.3cm.The experimental results verified the superiority of the laser line scanning imaging system for the UAV,meanwhile,the efficiency of GPS/IMU based image rectification algorithm was also proved. |
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