最近几年来，地理信息系统无论是在理论上还是应用上都处在一个飞速发展的阶段。 GIS被应用于多个领域的建模和决策支持，如城市管理、区划、环境整治等等，地理信息成为信息时代重要的组成部分之一； “数字地球”概念的提出，更进一步推动了作为其技术支撑的GIS的发展。 与此同时，一些学者致力于相关的理论研究，如空间感知、空间数据误差、空间关系的形式化等等。 这恰好说明了地理信息系统作为应用技术和学科的两个方面，并且这两个方面构成了相互促进的发展过程。
The SVG filter is used to add special effects to SVG graphics. In this tutorial, we will show only one special effect that may be used. After the presentation of the basics, you have learned to use special effects, and you should be able to apply them elsewhere. The key here is to give you an idea of how to do SVG, rather than repeating the entire specification. The filters available for SVG are: FeBlend-filter combined with image FeColorMatrix-for color filter conversion FeComponentTransfer FeComposite FeConvolveMatrix FeDiffuseLighting FeDisplacementMap FeFlood FeGaussianBlur FeImage FeMerge FeMorphology FeOffset-filter Shadow FeSpecularLighting FeTile FeTurbulence FeDistantLight-for lighting filtering FePointLight-for lighting filtering FeSpotLight-for lighting filtering In addition, you can use multiple filters on each SVG element! 1.14.1. SVG filter ¶