Reconstructing3D Model Of Ancient Tower Based On Terrestrial Laser Scanning

The terrestrial three-dimensional laser scanning is a new measurement technology. The advantages of high measurement precision, high speed, all-weather have changed the traditional ancient building measurement and has been used more and more widely. Ancient towers, as labor crystallization created by ancient Chinese people, has important historical value, scientific value, artistic value, social value and economic value, which is the study of politics, economy and culture during the different period of our country, religion, science and technology development of important physical resources. However, due to natural and man-made factors, the survival condition of the tower is precarious, while keep ancient architecture in digital achieves, protect culture relic and layout modern architecture through the means of modern information technology has necessity and economic significance.Based on reconstructing3D model by terrestrial LiDAR point cloud of Guangxiao Tower as the goal, the paper in accordance with the " the point cloud registration-3D reconstruction-quality evaluation" as the main line to discuss. In view of the practical problems encountered in the process of3D reconstruction, a set of design which is easy operation, high speed efficiency of terrestrial LiDAR point cloud3D reconstruction technology solutions has been proposed, which has a certain reference and practical value.Firstly, the paper put forward a multi-view point cloud registration algorithm based on central axis which aim to registered point cloud without corresponding target matching and less overlap area between the tower body and roof data. Aflcr data processing of denoising, vacations and segmentation, fit the point clouds into round shape or regular polygon by layers according to the outline of building. Make the number of point cloud data each layer, the topological relations, symmetry and the point cloud fitting participation as four indicators for fitting the midpoint coordinates to filter, so as to gain the tower body and the roof central axis equation. Turn the point cloud registration to the problem of three-dimensional linear feature matching in the three-dimensional space. Through the geometrical characteristics of the axial finished the Guangxiao Tower point cloud registration. The algorithm is suitable for the building with whole or partial symmetrical structure, which has the advantages of fast. convenient and simple.Then, on the basis of Guangxiao Tower3D point cloud model, combining with the characteristics of Chinese ancient buildings with a modular system and standard, puts forward the mode! objedification3D reconstruction technology. With basic elements and common component elements constitute a3D model library. Parametric design3D model objects in the library, including the shape parameters, scale parameters and attitude parameters. Match the ground LiDAR point cloud and model library objects through parameters adjustment and rapid replication the model according to the building structure of the repeated positioning. In addition, on the basis of3D model, through the projection cutting quickly get the plan/clcvation/scction mapping of Guangxiao Tower. In terms of Guanxiao Tower digitized achievement, formed a datasct including the LiDAR point cloud model, the3D model and a scries of two-dimensional linear plan maps.Finally, the3D model quality evaluation method is studied and discussed. According to the different purposes and requirements divided the quality of the model into two aspects of visual and geometry. Apply the entropy weight and fuzzy comprehensive evaluation method to put forward the three dimensional model visual quality index. Then the spatial location accuracy, space constraints criterion and the spatial geometric accuracy evaluate the overall and partial three dimensional model respectively. Make the Guangxiao Tower as the evaluation object and further analyzed the structure complexity, data accuracy and human factors which may impact on the geometry precision of3D model. Hxperiments show that the quality evaluation system has certain scientific and effectiveness.