| After years of development,the vehicle mobile measurement technology has been quite mature.The system includes GNSS/INS positioning and positioning,3D laser scanning,close-up image and other technical means to acquire the point cloud of surrounding objects in real time during rapid movement.However,such systems can only scan the outer layers of buildings or streets,and the system cannot penetrate deep into the interior of the building to perform detailed scanning on special environments such as indoors and underground.The piggyback mobile measurement technology has gradually become a research hotspot in surveying and mapping disciplines,and its core is position determination and attitude determination technology.GNSS/INS can provide high-precision navigation information,and the backpack mobile measurement system achieves high-precision mapping through pos and laser radar data fusion.However,in the indoor or GNSS signal long-term loss of lock observation environment,the positioning accuracy of the GNSS/INS integrated navigation system is restricted,and high-precision mapping cannot be satisfied.Simultaneous Localization and Mapping(SLAM)is a relative positioning method.The core idea of SLAM is to calculate the POS by point cloud feature abstract and matching,thereby achieving relative positioning.In recent years,with the development of the laser SLAM technology,a piggyback mobile measurement system based on laser SLAM has emerged.Aiming at the problem of high-precision positioning of the backpack mobile measurement system in the weak GNSS signal region,this paper is based on the laser SLAM indoor and outdoor backpack mobile measurement system.The system related multi-sensor time synchronization technology,multi-sensor spatial position calibration technology,laser SLAM technology and other content have been extensively studied.The main contents are as follows:(1)Multi-sensor time synchronization technology for backpacks.Time synchronization technology is an important technology for multi-sensor data fusion.Accurate time synchronization is the premise of high-precision mapping for backpack mobile measurement systems.This paper describes the time synchronization method of the core sensor on the backpack mobile measurement system.By introducing the GPS time system during the operation,high-precision time synchronization of multi-sensor can be realized.(2)Calibration technology for multi-sensor backpacks.The calibration of the backpack movement measurement system includes the relative spatial relationship between the carrier and the laser scanner and the relative spatial relationship between the two laser scanners.In this paper,the spatial positional relationship between the carrier and the laser scanner is calibrated based on the surface constraint model,and the accuracy of the calibration is analyzed.The error in the residual after calibration is 0.051m.The relative spatial relationship between two lidars(VLP-16)is obtained by the external parameter calibration method based on the plane conversion model,and the calibration accuracy is evaluated.The root mean square error from point to plane after conversion is less than 2cm,and the experimental results are accurate.(3)Laser SLAM technology.The laser SLAM technology is combined with backpack mobile measurement technology,and the theory of laser SLAM based on graph optimization is expounded.Combined with the characteristics of the sensor and the actual project requirements,the 3D laser SLAM backpack mobile measurement system was independently developed.Through the system,experiments in indoor and outdoor scenes have obtained 3D point cloud data and maps that are consistent with the actual scene.Finally,through the precision experiment analysis,the relative accuracy of the system in the room reaches 0.027m,and the relative accuracy of the outdoor reaches 0.037m,which satisfies the task of large project measurement. |
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