WebGIS Research And Practice Based On GML

The WebGIS (Web Geography Information System) is a result of combining GIS with computer application technique, which is an important developmental way in the future. WebGIS has provided a way for different system to share and publish the data, but in the data interoperability fields, there are also many problems to be resolved. XML (extensible Markup Language) is proposed by W3C (World Wide Web Consortium), it's widely supported in the Internet. GML (Geography Markup Language) is proposed by OGC (OpenGIS Consortium), it's a geospatial data-coding standard based on XML. GML makes the data interoperability possible and it will brings new changes for the WebGIS development.First, this dissertation introduces the advantages and disadvantages of technology of WebGIS, points the problems the WebGIS faced, that is data interoperability; second, discusses XML and GML knowledge, especially the schema of GML and the advantages of using GML describing geospatial data; and then, raises a structure model of WebGIS system based on GML; finally introduces the realization techniques. The WebGIS system uses GML describing geospatial data, adopts Java Applet displaying the map, and adopts ASP realizing Web-Site foundation and giving off responses to the requests from client. During the project practice, an application GML schema is created, and a functional modular for transforming data from MapInfo to GML format is developed. This system uses compressed datas to improve the transmission rate. The data transform are accomplished in the server-side. In the client-side, there are many functions: map-display, layer-control, zoom in, zoom out, move and map-search.The system which is based on GML and without commercial software, can solve the data interoperability effectively. It is a rewarding practice in the data interoperability field of WebGIS, and it provides practicability and reference to independent WebGIS.