The optimization on the performance of vector WebGIS based on SVG

SVG is a sort of markup languages based on XML,it is used to describe two dimension vector graphics and vector/raster mixed graphics,the spatial data of GIS can be realized with the graphic object of it,SVG can support JavaScript by itself,and SVG can be mapped into the tree structure in the memory through DOM,so the client can operate DOM by JavaScript to realize the scale,the roam,the inquire,the control for the map layers,etc.thus the vector WebGIS can be realized.Because SVG describes the vector spatial data of GIS with the simple text,the data amount are relatively small,and SVG supports GZIP compression,the data amount can reduce 75%~80% from SVG to SVGZ after compressing,so the transmission load of network can be lightened and the display pace of map can be accelerated.If we can cooperate using the cache technology of the server and client,using those methods that can optimize DOM parsing and promote the performance of image render,the performance of vector WebGIS based on SVG can be further improved.