Study And Implementation Of Vector WebGIS Based On SVG

W3C has put forward a vector graphics data SVG which integrate vector graphics grid graphics and plain text, SVG is used for transmission and display vector graphics. SVG As a kind of language based on XML, SVG able to work much more well on data exchanging and transmission. SVG technologies use in WebGIS, the spatial data can be described in SVG files, the speed of network transmission can be obviously improve, performance well in data exchage. SVG technologic also do well in some GIS project, it can provide more methods for developer to resolve the same problem.Through introducing SVG specification and analyzing the possibility of using in Web/GIS. Author tries to set up SVG based on \WebGIS system structure and explain its workflow and design . As the mian purpose of w3c design SVG is to show vector data,but geospatial data is a very complex data,it include graphical data,geometric data,attribute data,grid data and topology data.The current SVG standards do not support topological relations.But SVG can be expand,SVG can be space geographic data encoding,according to geospatial data on the characteristics of the necessary expansion of SVG,so that SVG can be more effective in describing the geographical data.SVG integrated vector graphics,bitmap image and pure text is a good map form of expression.SVG is a WebGIS the development of a new development direction and ideas.With Google introduced Google Maps, GMail and a series of services so that people feel a new Web experience. This experience notable feature is no need to download, install,fast response, has a good interactive. This gratifying experience from service in the methods adopted by Ajax. For WebGIS, this is a good user experience but its application has been lack.Researchers and developers always have difficults in the performance and experience to find a suitable balance. For this issue the article explores the ways in WebGIS Ajax client to achieve the application and improve the user experience. Ajax model with the traditional model of the difference is the induction of response services. Ajax engine will strip the pages of client for data layer, control layer and performance layer. Use of JavaScript and the DOM data based on XHTML and CSS standard interface for the drawing.WebGIS has the Basic characteristics in using Ajax.The key point of paper is to analyze the realization technologies of WebGIS based on SVG, including spatial information visualization,spatial data information coding with SVG, realization dynamic interaction with SVG files basede on AJAX and Java Servlet technologics. Author develop with SuperMap Object Java , conver superMap data to SVG files,realization zoom function, span function , measure distance function, query information so on, the key technologic in the paper.