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With the development of GIS, digital city has been developing day by day from initial birth to mature. Digital city is based on technology of computer, multimedia and storage for huge amount of data, leveraging wide-band network, 3S technology and virtual reality technology, which implements three-dimensional description of multi-resolution, multi-scale, multi-dimensional space-time. It is necessary for success of digital city to have three-dimensional city model, for the reason that comparing to two-dimensional model, three-dimensional city model gains more reality in user experience and more straightforward manner in user interaction. By three-dimensional city model, users could avoid suffering from abstract two-dimensional map, instead they could get a bird’s-eye view or far view or near view, walk in a virtual reality environment. In addition, by three-dimensional city model, that three-dimensional analysis, like sun-shine analysis, can be implemented.With worldwide surging development of Internet, Web has become an efficient information publishing platform. If we combined digital city and Web technology, it will be very convenient for users to get information of digital city everywhere. In addition, some on-line analysis can be available for people, making digital city be applied in larger area. If users can experience and manipulate three-dimensional city model in Web browser, it will bring better user experience.Therefore, establishment of a three-dimensional city model with reality-sense, equipping with different level of details, covering large extent, along with effective visualization on Web browser, bring convenient service, real user experience, powerful functions, as well as straightforward user interaction. Such features also bring the GIS product more competition advantage. Obviously, the study around it is very interesting.The LandXplorer provided by Autodesk, Inc. is a kind of digital city product for urban plan. The author study related problems based on LandXplorer development and finally gain plentiful achievements.The thesis consists of items as following:(1) Elaborate history and current state of digital city, point out that the three-dimensional city model is an important part of digital city. (2) Introduce the architectural level design of LandXplorer as preparation for succeeding work.(3) Study on how to establish three-dimensional city model and implement visualization on Web browser, coming up with solutions for certain important problems:a. Come up with a solution for integrate GIS data from different data sources into one data model by leveraging FDO facility.b. Implement low-cost and fast generation of three-dimensional city model by generating terrain surface, buildings, roads, trees, utilities models from two dimensional GIS data.c. Store model data and implement level of details (LOD) with quad-tree approach.d. Implement web-based rendering of three-dimensional scene based on Java OpenGL.(4) Illustrate the design and implementation of web-based Viewer subsystem as a practice of visualization of three-dimensional city model on Web browser.(5) Finally, summarize the work I have done and look forward to the future.
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