Svg, Technology Research And Application In Webgis

WebGIS is a kind of computer system under the environment of Web, which has the function of compatible with, storing, dealing with, analyzing and revealing and employing geographical information. It is the combination of Web technology and GIS technology,which utilize Internet to share geographical information, and let customer through browser obtain data and function service of geographical information system.Newest network technology XML (Extensible Markup Language) is profoundly affecting the WebGIS development. SVG (Scalable Vector Graphics) based on XML, is the Web vector graphic solution of W3C recommendation.SVG is a opening standard of vector graphics describes languages having text attribute. Based on the SVG Web cartographic representation, has the merit which GTF or the JPEG map is unable to compare: the small document size; the high image quality; the rich visual performance effect; the accurate color description; searchable text, the interactive support. Therefore OGC (Open Geospatial Consortium) already take SVG as the recommendation standard. Of the Web cartographic representation, therefore this dissertation chooses SVG as the carrier which issued the Web map.First, this dissertation discussed systematically some technical questions about WebGIS system such as concept, characteristic, system classifying, structure, etc. and analyzed some present problem of WebGIS deeply. Point out Web popular vector graphics solution at present—Scalable Vector Graphics remarkable behavior in mutual control and map denote,and will play an important role in the construction of WebGIS.Second, the writer analyzed deeply and introduced the development, characteristic, and rule of grammar of SVG. at the same time introduced some prevail SVG software at present.And discussed the geographical spatial data of SVG code from realization foundation to geographical spatial data organization and designment of code scheme. After introducing the script language of SVG—JavaScript, has analyzed the principle of SVG DOM and parsing course, this dissertation realized GIS interactive function of SVG map: scaling map and zooming map; map visibility control;highlighting map, labeling dynamically, attribute inquirement and so on.Third, this dissertation discussed the algorighm of shortcut and the problem of blurry query's theory and realistion.Finally, the writer released Tianjin software corporation WebGIS system based on SVG, regarded this as example to expound the scheme of constructs WebGIS based on SVG Explained system's requirement, structure, interface design, recommended the systematic function realization emphatically, and explained the advantage of developing WebGIS system based on SVG finally.The research proved that, applies SVG in the WebGIS development, enable WebGIS the function, the usability to obtain the very big enhancement, and will enormously promote the WebGIS development.