Incremental Hierachical Partitioned Organization And High-Performance Network Transimission Of Vector Data Considering Feature Characteristics

With the development of the hardware and software, the Internet has gradually become the platform of data releasing, date sharing, and distributed computing. Because of it's inherently distributed features. By means of the Internet and driven by the network technology, multimedia technology and spatial information technology, WebGIS has broad development and applications.In GIS applications, there are two main types of data:vector data and raster data. Vector data has the features of compact data structure, low redundancy, good graphical display quality, and high precision. So vector data are conductive to networking and search analysis. The raster data has the features of simple data structure, easy to surface modeling and spatial analysis, etc. Raster data has played an important role in land monitoring, hazard analysis, environmental monitoring, and so on.At present, because of the extensive and practical applications of vector data, it has become the cornerstone of spatial information construction. In order to meet the different application requirements, a variety of GIS software have their different data structures and business models to make the vector data structure to demonstrate the diversity and complexity. However, above all the data models can not solve the issues of rapid vector data transmission and display in the clients of WebGIS.With the development of Web2.0, the high-performance network transmission of raster data has been solved by the block model. The WebGIS technology based on the raster image formats has become matured and applied in the fields of national information construction. But because of raster data's inherent deficiencies, WebGIS based on the raster image technology has the restrictions of its function applications. Therefore, the exploration of WebGIS based on vector data has become one of the current hot topics of concern.This paper firstly describes WebGIS implement mechanism in detail from the aspects of its basic features, technical model and architecture, And WebGIS construction methods from the applications. What's more, combined with current mature WebGIS technology based on map image, the author analyzes not only the data organization model, interactive data transmission, data presentation, but also data organization thinking, characteristics and problems of the current progressive transmission of vector data through the experiments.Secondly, this paper discusses how to apply the cache technology to the WebGIS based on vector data in order to reduce the repeatability of data transmission. Then, the author analyzes quadtree data structure, proposes a linear quadtree construction method based on file storage and discusses the topological relations of the same level and different levels. Combined with progressive transmission model of vector data, WebGIS theory and idea of space for time, the author proposes vector data organization model based on block-level incremental vector model in the server, the corresponding methods of cutting vector blocks and file storage, and the methods of data fusion in the client.Thirdly, this paper describes the essence of the vector data compression and five lossy compression algorithms from the local compression and the overall compression. Taking into account the loss of data compression, this paper analyzes the Huffman coding, arithmetic coding, dictionary coding, Combined with vector date features, network transmission and data compression, the author analyzes the establishment of a suitable vector data model, compression vector data before data transmission, the geometric compression of vector data coordinates, and idea of network compression and transmission based on Gzip coding to reduce the amount of vector data transmission. Meanwhile I propose a new strategy to enhance transmission efficiency of vector data through a combination of vector data organization at server side, reducing update data volumes, interactive transmission based on feature characteristics, as well as interactive as asynchronous transmission methods. By means of these methods, we finally achieve the goal of promoting user experience.Finally, the author verifies the described data compression, cache application, transmission strategy, and data fusion, by the experiments from the amount of network data transmission, transmission time, data display and editing in the client. Furthermore, the author points out the problems as above.