| A GIS (Geographical Information System) is an information system that deals with geographical spatial information. It is capable of inputting/outputting, storing, displaying spatial data and their attribute, inquiring, synthetically analyzing geographical spatial information and making decision based on it. Traditional GIS develops into Web GIS with information sharing, along with the development of distributing network techniques and the proposal of digital earth. Web GIS is a combination of GIS and WWW. It expands the application field of GIS, and makes GIS a very popular information management tool.XML is a makeup language simplified from SGML standards by W3C. SVG, which is a subset of XML, is an open text-based vector graphics standard developed by W3C. After wholly analyzing SVG criterion based on XML, XML/SVG and Web GIS technology are combined. A model of distributing real-time Web GIS based on B/S(Browser/Server)multilayer-mode is presented, and the key points of database server, web server and browser and their resolution methods are discussed respectively.Two very important points in data dynamic issue are how to get data and how to exhibit dynamic effect. SVG itself is a static document though it is based on data. So real-time data cannot be obtained by SVG documents. And we must seek other techniques. SVG and data issuing technology are combined: the hidden page method is devised. This is a very good solution for Web GIS to issue real-time information. The most important trait of the hidden page method is that it gives a vivid effect and a high respondent speed.In the end, an example on national gold mine Web GIS is implemented. It attests that the traits on this model, such as high respondent speed, good commonality, low request on the client, convenient for systems' maintenance and updating, are better than any other traditional model. It expands the application field of XML. and develops an advanced system model for Web GIS. |
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