基于SVG的矢量WebGIS实现技术研究

Research on the vector WebGIS realization based on SVG

SVG是一种基于XML的用来描述二维矢量图形和矢量/栅格混合图形的标记语言,虽然SVG不是为了面向地理空间数据发布而制定的标准,但它的许多特性都能被广泛地应用到WebGIS中,从而实现矢量WebGIS。由于SVG通过简单的文本语句描述矢量图像,所以SVG通常数据量很小,并且SVG支持GZIP压缩,所以基于SVG构建WebGIS能减轻网络传输负载,加快地图显示速度。SVG内置了对JavaScript的支持,且SVG可通过DOM解析映像成内存中的树型结构,所以客户层可通过JavaScript对DOM的操作实现对地图的缩放、漫游、查询、图层控制等交互操作。

SVG is a sort of markuplanguages based on XML, it is used to describe two dimensional vector graphics and vector/raster mixed graphics. Though SVG is not a standard to release spatial data of geography, but it can be widely applied to WebGIS, thus the vector WebGIS can be realized. Because SVG describes vector picture by the format of simple text, there is a small amount of SVG data, and SVG can be compressed through GZIP, so the WebGIS that be constructed based on SVG can reduce transmission load of the network and accelerate the display speed. SVG can support JavaScript by itself, and SVG can be mapped into the tree structure in the memory through DOM, so the client can realize the zoom, the roaming, the querying, and the control for map layers with operating DOM by JavaScript.