| 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. While SVG provides a great convenience to view the electronic map, and it's also the orientation of electronic map development in the future.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, The source of topic, background of this research and the structure of paper are introduced. It analyses the computation schema and main technology and its advantage and disadvantage of WebGIS. It also elaborates the tendency of WebGIS development in the future and emphysizes the GML format of network transportation and distributed computation WebGIS technology. The second chapter analyses the storage method of map data, particularly, it analyses the map data storage method with object-relation database oracle 9i and with MIF files and makes a efficiency comparison between them. On the basis of front theory analysis, the author constructs frame structure of the whole WebGIS application system, puts forward a kind of WebGIS scheme which has four layers of Browser and Sever(B/S) structure, transports and stores map data in the form of GML files, views map data atbrowser side by SVG format, in this chapter, it realizes MIF files reading in environment of C#. The third chapter discuss the XML technology and its application in WebGIS, points that GML is a application of XML in geography which can describe geography information and coincidence relation of spatial object between MIF files and GML files, so it develops a middleware based on OGC spatial data modules in server-side and realizes the function of visiting heterogeneous data and obtaining spatial data and converting to GML, and it also validating the GML which generated at present by GML Schema. In chapter four, in the basis of elaborating SVG technology, It analyzes data modules and its implementation code based on SVG technology, designs XSLT Stylesheet which converts GML to SVG, accomplishes SVG generating in client-side, then it realizes a kind of client-side scheme which is the middle-level client-side based on SVG Plug-in, and it is showed by practice research. The conclusion and prospect of the work what to do on this research in the last chapter.The objective of this thesis not only researches the theory about WebGIS based on GML butalso studies how to realize the theory. Many technologies are applied to this research, including XML, GML, SVG, C#. |
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