Of Webgis Based On Svg And Ajax Technology, Research And Design

Restricted by specific support environment, limited network bandwidth for data transfer, difficult data sharing, lack of rich data expression, the traditional WebGIS technology faces severe challenges. At the same time because grid maps are transmissed on network for the graphics, map zooming, roaming, selecting are not available locally. They must be sent to the server, new grid maps are generated on the server and are transferred back to the client to display, resulting excessive burden on the server, network congestion and so on. And the traditional technology in WebGIS does not support animation and other multimedia message, which makes it difficult to realize dynamic effects and embed other multimedia information.SVG is an open standard text-style vector graphics description language. SVG can be used on the page to show a variety of high-quality vector graphics, including image processings such as graphics, text, animation, color, filter effects. The key is: SVG is fully described in plain text. In other words, this is a specifically designed for network, and text-based image format. And SVG is based on XML, therefore, is highly scalable and can describe any complex images.Ajax is an integrated multi-technology. Based on XHTML and CSS, it uses DOM to achieve dynamic display and interaction; uses XSTL and XML to exchange and process data; uses XMLHttpRequest objects to read data asynchronously; uses JavaScript to handle data binding. Ajax can provide asynchronous communication with the server so as to free end-users out of the request-response cycle.This article designs amd developes multimedia WebGIS by SVG and Ajax. The system uses SVG as map file format and uses Ajax to communicate between the client and server. The WebGIS has thus achieved the high image quality, transmission speed, etc.The article mainly solves: 1 the organization of spatial database. We Combine the features of SVG with the features of map to design and realize the storage of spatial data in the relational databases; 2 the organization of map data and the basic map symbol design in SVG; 3 the middle tier dynamically accesses the spatial data in the database and sends them to the client in XML format; 4 after the client gets middle-tier data the maps can be dynamically loaded; 5 achievement of the basic functions in the client, such as: roaming, zooming, etc; 6 digital implementation of grid maps in SVG; 7 implementation of the basic analyzing functions of GIS, such as: query, web search; 8 the implementation of other multimedia features, such as: animation, sound and so on.