| In recent decades,mobile mapping systems have received significant attention due to the widespread use of low-cost sensors,advancements in computational resources,maturing surveying algorithms,and the increasing demand for geographic information system data.While many mobile mapping systems integrate multiple sensors to provide larger and more robust measurement solutions,the improvement in performance and positioning accuracy has also led to increased sensor diversity and costs,as well as increased data processing difficulties,which can even result in data redundancy in certain application scenarios.Therefore,it is necessary to research low-cost,user-friendly,and accurate vehicle-mounted mobile mapping systems.This thesis proposes a light and compact vehicle-mounted mobile mapping system capable of acquiring digital imagery,laser point clouds,and pose data for collecting and updating road information for highway inspection and maintenance.The establishment of a vehicle-mounted mobile mapping system requires addressing two problems: firstly,how to eliminate errors in the integration of a multi-sensor system,specifically the system calibration problem;secondly,how to achieve the coordinate mapping from two-dimensional image points to threedimensional ground points,namely the system measurement problem.The main contributions of this thesis are as follows:This thesis provides a systematic overview of the coordinate systems and coordinate transformations related to the vehicle-mounted mobile mapping system.A mathematical model for vehicle-mounted mobile measurement is established,and the sources of errors in system integration are analyzed,including positioning errors of the POS system,pixel errors caused by distortion,and placement errors of the digital camera.To address the eccentricity error between the digital camera and IMU sensor in the vehiclemounted mobile mapping system,a two-step method for eccentricity calibration is proposed.The calibration of system eccentricity error is completed using this method.Experiments are conducted to validate the necessity of eccentricity error correction,and the results indicate that the correction of eccentricity error eliminates systematic errors present in the measurement system.To address the issue of depth deficiency in single-image measurements of the vehiclemounted mobile measurement system,a laser point cloud-assisted single-image measurement method is proposed based on the pinhole imaging model.The accuracy of this method is compared with that of stereoscopic measurement using two images.Experimental results demonstrate that utilizing laser point cloud assistance in single-image measurement yields high accuracy and stable measurement results.This thesis constructs a light and compact vehicle-mounted mobile mapping system integrating a digital camera,laser scanner,GNSS receiver,and IMU sensor,and completes the calibration of system errors and the development of the software system.The feasibility of the system is verified through specific measurement examples,with results showing absolute measurement accuracy of 0.104 meters for the horizontal plane and 0.140 meters for the elevation,and relative measurement accuracy of 0.059 meters,meeting the requirements for collecting three-dimensional information on road objects. |
