| The construction of three dimensional digital city is a hotspot of Smart City research at present. It develops with higher precision, macroscale, integration.3D digital model is an important part of 3D city geospatial framework development. It is widely used in City Planning, and requires high precision and good visualization.3D city models require visualization of high fining geometry and texture, up and down the ground integration when assisting City Planning. Present 3D city models cannot completely meet the demands of City Planning in model precision, efficiency, effect and so on. And this affects its further applications in City Planning and Management.For the demands of precise spatial relations, realistic visualization and up and down the ground integration of 3D city models, this paper does some deep analysis on the construction theory and methods of each kind of 3D city object, and takes full advantage of the existing spatial geographic data of digital city. The theory of high precision 3D city integration modeling towards City Planning is studied, solving the serial problems during the fast, precise and realistic integration modeling process. And also, a set of overall solution is put forward. The key contents and results are as follows:1. High precision 3D city integration modeling system towards city planning is studied. This paper analyzes the requirement of 3D digital city towards city planning and the characteristics of integration modeling and existing data resources in detail. Based on these, Data classification and organization of 3D digital city are divided and discussed. And integration modeling system is researched from a global viewpoint, including source data collection and utilization, geometric modeling, texture mapping and so on.2. Most of 3D city models cannot reflect topographic fluctuation changes, low geometry precision and bad texture simulation effect of road modeling. Besides, purely outdoor labor to collect texture and height information is of low efficiency. Those existing problems can be well solved by Mobile Mapping System (MMS). However, traditional commercial MMS is of high cost. Thus a kind of easy and practical mobile image acquisition system is proposed. CORS service enhanced by Beidou satellite navigation system is in use in the mobile mapping system. It takes less time to get the fixed solution by using DGPS. This system integrates digital camera and panoramic camera together to accomplish the fast collection of road elevation and refined texture.3. High precision and fast modeling method of building texture towards city planning is proposed. Based on the basic theory of typical texture mapping, a texture mapping method based on planar mapping is studied and implemented. This method is perfectly suitable for texture mapping of building facade. Another method on a rapid generation of synthetic textures of building's roof towards city planning is proposed to improve the resolution of 3D model textures4. Key technologies of 3D road and ancillary facilities modeling based on terrain features are analyzed. A new method and theory of 3D city facility components rapid construction is proposed in this paper. It combines images, DEM,2D vector diagram to create urban road traffic signs, markings and landscape automatically. It achieves fast and precise modeling of 3D road and ancillary facilities through two algorithms:one is height and orientation matching algorithm with the road reference line which is captured by mobile image acquisition system, and the other is city components census data being associated with 3D road ancillary facilities model library algorithm.5. Aseamless modeling method of underground pipelines and ancillary facilities integration is studied. It solves the problems of elbow joint, tube point sets, smooth transition of different diameter of the well chamber model in detail. Meanwhile, it solves the mount and combination of underground pipeline and ground ancillary facilities. In the underground space modeling, an underground 3D parametric modeling method based on planning verification is proposed, it develop a corresponding collection and 3D pre-processing software, and solving the 3D modeling problem of underground building.This paper develops a series of 3D data manufacturing softwares by using those key technologies described above. And they are tested well in actual production process in Changzhou, Shenyang and Fuzhou. Byconstruction of practical data and application system, high precision 3D city integration modeling system towards city planning has been proved to be correct and effective, which meets the demands of high precision, high efficiency, realistic visualization of 3D digital city towards City Planning. |
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