Study Of Spatial Data Interoperability In WebGIS Based On GML

WebGIS combined Internet and GIS is a necessary trend of the development of the GIS software. But the difference in stored format, data model and data structure etc. results in the production of multiple sources and different structure data, it makes use of data difficult. How to integrate and publish the existing heterogeneous data including the GIS spatial data in various formats, how to use direct vector map in a browser to create highly interactive maps and how to realize asynchronous transmission of data between browser and server, the key to these questions is spatial data interoperability. It depends on the new Web standard. The advent of XML gives an effective way. The paper deeply studies spatial data interoperability of WebGIS using GML with Web Service, SVG and Ajax.Firstly, the paper analyses the primary implement method and formation model of WebGIS in detail.Secondly, the paper expounds correlative content of XML and analyses several important techniques based on XML including GML, Web Service, SVG and Ajax in detail. And analyses applications of them in WebGIS, especially GML and its application of WebGIS.Thirdly, based on description of these theories, system designed goals and principles, a technologic project for GML-Based WebGIS spatial data interoperability application system under .NET systematic framework is brought forward. And a system model-GWSA (GML-Web Service-SVG-Ajax) is designed using the project. At last, the system is divided into several function modules and a GML database is founded. Finally, the paper realizes the system and proposes a method for each tier. The client (browser) is set up SVG Viewer to display vector maps; MVC design pattern which is very popular at present is used in the behavior tier in order to separate behavior formats from operation logic; the Ajax engine is utilized to realize asynchronous transmission of spatial data in Web server, in WebGIS application server, all kinds of web services are made and for the sake of GML data transformed SVG data, a XSLT transform engine is proposed. Using data warehouse and distributed databases are used to store and manage heterogeneous data, model warehouse and distributed model databases are utilized to store models, in database tier, GML data is transmitted. In realization, arithmetic for transferring spatial data stored in SQL Server database into GML is designed. A storage method for GML in SQL Server database is provided. At last, a case is used to show applications of the system model in spatial data interoperability.At last, concludes the whole paper, expects the future and puts forward the next work.