Car Overall Three-dimensional Laser Mobile Modeling System Calibration

With the flourishing development of the concept of digital and information city, people's demand for three-dimensional spatial information of city is growing increasingly. As a result, quick acquisition and automatic processing technology of three-dimensional spatial information become the core and future trends of geospatial information acquisition. As a new laser ranging technology, laser scanning technology can quickly access three-dimensional information of the target with high-resolution and large areas through high-speed laser scanning. Meanwhile, as the GPS, inertial navigation and CCD technology boom, these techniques have become propellant for the rapid development of high accuracy integrated mobile mapping technology. A high-precision vehicle-borne three-dimensional laser mobile mapping system which is fusion of position and posture determination technology, the laser scanning and CCD digital image technology has been developed at Capital Normal University in Beijing to serves for fast and direct acquisition of three-dimensional information of the measured objects. The accuracy of three-dimensional spatial information acquired by vehicle-borne laser mobile mapping system largely depends on the overall accuracy of the system calibration and verification. The accuracy of the system also affects the accuracy and authenticity of three-dimensional information in the city.Based on above this paper focused on the research and implementation on the calibration method of the vehicle-borne laser mobile mapping system. In previous work, the system overall calibration used the principles and experimental method of control points calibration which requires laying a large number of control points. However, to find out the control points precisely in the laser points cloud is a very difficult task. Therefore, we tried a new calibration method by using surface features of building referring to the calibration ideas based on roads and walls in the TerraMatch. At this point it needs lying only three control points on the wall to determine plane equation which greatly reduces the workload. This paper also gave a detailed description of the principle and the experimental method of this method and also verified the effectiveness of the algorithm by comparing the experimental results with the control point calibration results. Under the background of the research on vehicle-borne three-dimensional laser mobile mapping system, the paper based on the contents, principles, algorithm realization, experiment design and experiment results analysis of vehicle-borne system overall calibration. The layout of the paper is introduced as follows. First it introduces the importance on overall calibration of the vehicle-borne system and research situation at home and abroad. The second chapter outlines the entire vehicle system and introduces details of the various sensors modules which compose the vehicle system and work flow of obtaining data. To understand the work flow of the system is benefit for establishing mathematical model of relations between the various sensors which is crucial for the system overall calibration. This paper also demonstrates contents and principles of the two calibration methods of vehicle-borne system from the perspective of coordinate system definition, coordinate system transformation, calibration mathematical model, error equation establishment and least squares including algorithm analysis theory and calibration process design. From layout calibration field and fulfill calibration experiments, the paper elaborates the two system calibration steps in detail and makes accuracy analysis. Finally, it summarizes our current progress and achievements on this work and pointes out deficiencies and further research direction of the paper.