Research And Realization Of The Technology Of Rapid Reconstruct 3D Model On Large Scale Data

Digital city is one of the applications of GIS. It is a reality visual expression of the city. As the development of communication technology, in the city's management and scene display, the three-dimensional digital city has played an important role. Currently, a large number of two-dimensional data need 3D visualization expanded to provide more visual and accurate analysis information. At the same time, this expansion is also facing a series of problems, such as the 3D models' data sources and the Model generation methods, the management of the three-dimensional database and the updating of the database. All of these systems are constraining the popularization of 3D applications.Aim at these problems, for target of rapid construct the 3D model based on the 2d data without the 3d database, the author defines a technology of rapid reconstruct three-dimensional on large scale data. The implemental part includes the data source, model and scene.After compare and analyze the existing data, we take the two-dimensional large scale maps, the attribute data and the three-dimensional CAD model data as the data source. Two-dimensional digital maps and attribute data are used to build the dynamic model and the 3D CAD model as the external models. Compared with especial 3D model data, the use of this data sources with low-cost, efficient features can make full use of existing resources and reduce the creation investment of 3D models and shorten the project cycle.Different from other three-dimensional modeling systems, this technology does not contain the 3D database, and bring it to the 3D model library. The models include surface, buildings, pipelines and point features of the abstract models. Obtains the spatial information of the model from two-dimensional database, with the corresponding model generation algorithms, models pf the actual elements can be build dynamic in a city. Even two-dimensional data changed, the 3D system can be updated real-time, avoiding the additional expenses of the huge three-dimensional database, reduced the application's complexity.Another key point is that technology about models and attributes of the relationship between the algorithm and its' attributes, is the three-tier management methods. In this way, the ID is the only relationship between attributes and the model, all the operating are depend on it. The middle layer relates the models and the scenes, not only to control the dynamics reconstruct, but also enquiries, analysis operation, and feed back the operation results to all users.Accordmg to the actual data and the attributes of two-dimensional data, reference to the design ideas, the author has completed a test three-dimensional reconstruct model system. The system based on the ArcGIS environment, the Oracle 9i and the ArcSDE, accord with the current mainstream application environment. In this system, without the three-dimensional database, dynamic construct the surface model, the building model and the pipeline model. Establish the three-tier scenes management linked by ID.Compared to the other methods, in this modeling process reduces the investment, reduces the manual operations and improves the efficiency, reduce the project cycle, and reach the earlier expected goal.