| With the rapid development of digital city and the constant expansion of city3D space model application fields, demand in the3D model of city buildings grows day by day. Nevertheless, facing city buildings with large spatial scale, huge data volume and quick data update demand, traditional buildings3D reconstruction method has some disadvantage in terms of efficiency, precision, cost, scale, technical threshold, etc. Hence, this essay attempted to introduce target recognition and parameterization technology, and presented a popular3D reconstruction solution with low cost, low threshold and high efficiency that adapt to city buildings, thus met the urgent demand for digital cities and related fields.The main content of this essay is as follows. First, it summarized and reviewed three main fields including building3D reconstruction, target recognition and parametric modeling, and pointed out the existing problems of the above fields. Second, three major technology systems were deconstructed in depth and causes of "dual parallel framework" were pointed out as well. It also offered a practical way of the cross."Ternary cross framework" of3D reconstruction in city buildings was constructed through system reconfiguration. Third, aiming at remote sensing image segmentation, it also presents an object oriented multi-scale region merging method and a fast region merging method based on the classified merging cost. Fourth, aiming at vector graphics optimization, it presented a single-level optimization method for vector graphics based on deleting cost, a multi-level optimization method for remote sensing image vector graphics as well as a rectangle fitting optimization method for the building groups. Fifth, aiming at3D information extraction, it presents building height extraction method based on extended statistical model and three models to retrieve building storey information. A geometry correction method for building footprints aiming at lateral satellite images was also put forward. Sixth, a "parameter-modeling separation" system framework was presented. Aiming at parameter management module of this framework, the method of parameter association, organization and management as well as recovery and management of attribute block of CAD were designed. Composed of style library management and project library management sub-module, web site service module was designed. Aiming at automatic modeling module, DXF-SHP conversion, the design of the CGA syntax rules, rule library frame, rule library calling and parameter transmission as well as automatic modeling script were put forward. Seventh, through integrating key technology and methods, it also developed city buildings3D reconstruction software prototype system (3DRS) as well as its subsystem CBRS and CityUp. Meanwhile, empirical research was developed based on the example of the West Lake district in Hangzhou city. Also, the feasibility of the whole solutions was evaluated from the following aspects like precision, efficiency, cost, technical threshold, data presentalism, etc.Research showed that, first, building target recognition and parametric modeling technology could exactly solve two difficult points of building3D reconstruction."Ternary cross framework" made three technology systems form a closely connected, procedure clear, division identified and target consistent unit, which offers theory support and method guidance for relevant research. Second, object oriented multi-scale region merging method made multi-scale segmentation in consideration of terrain features possible. By reducing the queue length to a large extent, segmentation precision and implementation speed was improved. Not only does the fast region merging method based on classified merging cost guarantee segmentation precision but also merging speed advantage becomes notable with the increase of the initial segmented region number. Third, compared with classical DP method, the single-level optimization method for vector graphics based on deleting cost was of higher precision and lower time complexity. Also, it outperformed the former in terms of processing capability per unit node and processing speed at the same compression ratio. Compared with the traditional single-level optimization method, multi-level optimization method for remote sensing image vector graphics had stronger adaptability to image segmentation scale and spatial resolution, which can better restore multilevel character of ground feature. Rectangle fitting optimization method for building groups could effectively reduce computation time of the minimum area bounding rectangle, ensured rectangles be parallel on opposite side and be perpendicular on adjacent side. The shape and area precision of the optimization result were both relatively ideal. Fourth, three methods including the building height extraction method based on extended statistical model, the building storey information retrieval method and the building footprint geometry correction method, respectively reached higher precision level and could meet corresponding application demand. Fifth, the "parameter-modeling separation" system framework and the series of innovation methods aiming at the three modules largely reduced technical threshold and marginal cost of parametric modeling platform and increased modeling efficiency, thus offering a brand-new strategy for the quick and widespread popularity of parameter technology. Sixth, methods and system proposed in this essay met the experiment’s preseted target in terms of precision, efficiency, cost, threshold, data presentalism, etc. It showed comprehensive advantages with public orientation. The whole solutions are feasible. Seventh, it is very likely the research results will push forward the construction of3D digital city spatial data infrastructure, making it more widely used in urban planning and management, architecture and landscape design, national defense and military, emergency relief, environmental protection, virtual tourism, transportation navigation, etc. |
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