The Key Technologies Of Metropolis Three Dimensional Geographical Information System

Modern city is the symbol of modern civilization and the center of economy, politics, technology, culture and education. Metropolis, super cities or city agglomeration concentratedly reflect the comprehensive national strength, the government management capacity and international competitiveness of a country. GIS as a management and decision-making tool of the metropolis have been the core of urban spatial information infrastructure. It assumes the functions of the city’s comprehensive information storage, analysis, exchange and service. And it provides the advanced quantitative and scientific technology and methods for the planning and construction and management of metropolis. The three-dimensional geographical information system (3DGIS) of metropolis as an urban spatial information infrastructure framework for the new form has a lot of new content and faces many technical challenges. Firstly the 3DGIS of metropolis is short of the complete system of data production, data management and system application and the cyclic system of continuous data update. Secondly, owing to lacking the data standards of three-dimensional city model, the elements in the established three-dimensional city model is incomplete, untrue and inaccurate,which is difficult to effectively meet the needs of-urban management, in particular, the sharing in city-level. Thirdly, because the industry application and the technology integration is not enough, the 3DGIS of metropolis can not directly support the three-dimensional space decision-making of industry. Fourthly, the services based on the city’s three-dimensional model and other geo-spatial information still remain in spatial reference applications on the department-level, so the 3DGIS of metropolis can not support multi-departments or city-level business applications. Lastly, there are many technical issues in the compact and social services of the three-dimensional city model. In response to these technical challenges, the paper’s main research contents are as follows:1. The advance in GIS technology of metropolis is deeply analyzed in this paper. And the basic pattern of 3D GIS and its main features of metropolis are summarized and raised. The corresponding technical difficulties are also indicated. Furthermore, in these aspects of the geographical spatial cognition, the three-dimensional data acquisition, the three-dimensional space expression and data management, the virtual reality and three-dimensional visualization and so on, the relevant technology trends are briefly reviewed.2. Aiming at the features of the metropolis 3DGIS, the overall scheme of the urban 3DGIS is proposed. The systematic framework, the data system, the functional system, the application system and the programs for running, update and maintenance are designed. The software systematic framework of 3DGIS based on SOA is proposed.3. Aiming at the complex business needs of city planning and management and the problems existing in the multi-scale standardized production of three-dimensional city model, the classification of levels of detail (LOD) for all elements of three-dimensional city models which cover the whole city is defined, and its quantitative specifications are also defined. The quantitative specifications include the geometric precision, texture resolution, model performance and other requirements of various LOD models. The different combined applying methods of macro, meso and micro multi-scale three-dimensional models are raised. The production and checking acceptance methods of main models (the terrain models, the building models, the models of transportation facility, the pipeline models, the vegetation models) are proposed too.4. metropolis 3DGIS have higher requirements in the data integrating management which are the whole elements, the huge data volume, the high requirement in real-time application and so on. Directing at these, the paper presents the integral organizing and managing method of the 3D space data concluding the terrain model, the overground object models (building, transportation, vegetation and other models), the underground pipeline models and so on. And the optimizing strategy of 3DGIS based on server clusters, distributed storage, grading and grid reconstruction model is put forward. These provide practical technical solution for the integrated management of urban ground and underground 3D model data.5. The increasingly complicated space relation and decision is faced in the metropolis construction. Combining with professional requirements about 3D space decision for city-planning, the process and technique of 3D space’s planning evaluation are studied in this paper. And various analysis technics of 3D space and the production methods of city planning models are discussed. Furthermore, a practical 3D decision support system is designed and applied actually, which have obtained good results.6. In view of the achievement in this paper, the super city 3d model database of Wuhan is designed and established. And the multi-scale terrain model of whole district range with 8494 square kilometers area, the whole overground elements 3D model of main city zone with 525 square kilometers area and the underground pipes models with 400 square kilometers area are established. Then, the Wuhan 3D geographic information management platform is studied and built. It is achieved to integratedly manage the whole elements 3D model and the underground utilities models with their related two-dimensional geographic data, thematic data and attribute data in city lever. Furthermore, the common three-dimensional information services of city-level multi-departments sharing also are brought about. These have been practically applied in the city planning, the management of actual populations and actual houses and other significant business work.