Research And Implementation Of WebGIS Based On Silverlight

WebGIS is the result of combination of Internet technology and GIS.Although its history is very short, as an effective means to spread GIS, WebGIS has been quickly accepted and popularized and has become a hot point in GIS field. However, because of constraint of application technologies of first generation Internet,it can't make full use of calculation resources of the client.Moreover,it has poor expressiveness and poor interactivity.All these three factors constrain the further development of WebGIS.With the birth of application technology of second generation,namely,Rich Internet Application,it will cause revolutionary change to status.RIA is an important direction of the current Web technology development,and is a kind of technology innovation of expression layer ,and is a client technology with rich technical ability.It brings new opportunity for the development of WebGIS.Silverlight is a kind of RIA client implementation technology.So the research put emphasis on how to apply Silverlight technology to the development of WebGIS to improve expressiveness and interactivity of WebGIS,and promote WebGIS to develop more deep-rooted.First,the overall structure of the system is designed, based on service-oriented manner,according to the hierarchy theory,the server has been designed.According to Silverlight technical characteristics, MVVM pattern is introduced into the Silverlight client design and implementation.The raster date engine which has been desigined and developed realizes multi-source raster data loading.System achieves the vector data rendering,animation and multimedia integration,with vector graphics ability,visual effects and multimedia technology.Experimental reaults show that Silverlight has rich data model and rich interface expression ability,which can improve WebGIS expressiveness and interacitity.In order to improve WebGIS loading speed,paper puts forward ondemand dynamic loading mode,which further strengthens users'experience.Example system realizes raster data and vector data overlay, animation, multimedia integration, transparency control, map perspective and so on , the system runs smoothly, without refreshing page.Compared with WebGIS based on the HTML, it has the greater advantage, and the system can integrate different data sources. The results show that Silverlight has broad application prospect in WebGIS. Key Words:Silverlight;WebGIS;DeepZoom ;XAML;MVVM...