Researching The Theory And Practice Of WebGIS Based On Geography Markup Language

WebGIS is the production of Internet technology applying to GIS. WebGIS is a good tool to get GIS data and Geographic information service for us. But WebGIS meets some problems for the further development, such as absence of interaction and limitation of visiting heterogeneous database. So WebGIS needs some new technologies to resolve these problems. XML is a new technology, which promotes the development of Web. Geography Markup Language (GML) specification is defined by OGC. This specification is intended to enable the transport and storage of geographic information in XML, which will make an important role in the development of WebGIS.This paper studies how to resolve the two problems. The client-side of the WebGIS is designed based on GML/SVG vector data to guarantee the interaction. All the heterogeneous data are converted into GML data based on OGC geometry data model in order that the WebGIS can operate these data. In the first chapter, Map-Services Implementation Specification, principle of WebGIS, advantages and disadvantages of technology of WebGIS are introduced. The second chapter points that GML is a application of XML in geography, which can describe geography including features, coordinate reference systems, geometry, topology, etc. GML can be converted into SVG that can be drawn in Web browser. A structure model of WebGIS application based on GML is constructed and the modules in server-side are accomplished in chapter three. There are two methods to implement the client-side in chapter four. One uses JavaApplet program, the other uses SVG plug-in. Each method has its own example. In the last chapter, what I have learned is concluded, and the tendency of the future development of GML and distributed WebGIS is analyzed.The objective of this thesis not only researches the theory about WebGIS based on GML but also studies how to realize the theory. Many technologies are applied to this research, including XML, GML.SVG, Java ,etc.