基于Silverlight的WebGIS客户端技术与应用试验

WebGIS Client Based upon Silverlight

RIA(丰富型互联网应用程序)技术越来越多的应用于WebGIS,满足了人们对高交互性和丰富表现力的需求,现存的WebGIS客户端解决方案主要是Ajax和Flex,其中Ajax交互能力和表现力不够强大,而对Flex的研究多集中在体系结构、功能模块上。本文在对Silverlight分析的基础上,提出将Silverlight应用在WebGIS客户端的技术可行性,特别是研究了利用Silverlight技术来表达地理空间信息的方式,分析了如何在Silverligt中模拟和改进DeepZoom技术,进行地理空间信息的多尺度高细节展现,运用XAML(可扩展应用程序标记语言)、动画技术等,实现地理信息的矢量栅格一体化表达等功能,并集成视频、图片等多媒体信息,提高了地理空间信息的表现力。同时,对进行大数量表达的算法设计和实现处理等性能提升方面也做了研究。最后,由试验验证了在WebGIS客户端应用Silverlight技术的可行性与性能上的优越性。

The WebGIS development represents a natural answer to the growing requests for dissemination and use of geographical information data. WebGIS originates from a combination of web technology and Geographic Information System. The new technology, RIA （Rich Internet Application）, is more frequently used to enrich WebGIS in meeting the demand of high interactivity and rich expression in some extent. There were papers introducing the solution of RIA applied in WebGIS such as Flex, but they mainly discussed the architecture, the function model and so on. Base on the research of Silverlight, the combination between Silverlight and WebGIS is presented in this paper. Especially, the authors discussed how to represent geographic information in multi-scale by simulating and improving DeepZoom, which enables smooth loading and panning by serving up multi-resolution images and using spring animation. And then we integrated vector and raster geographical data by making use of XAML （ eXtensible Application Markup Language）. It would be much more appealing if taking advantage of animation. The algorithm for displaying huge amount of data was also designed, and it improved the performance efficiently. In addition, the key issue of geospatial web services aggregation and web cache was also mentioned. Finally, to evaluate and present results obtained by this work, this paper includes case studies concerning implementation of the idea. The authors believe that WebGIS based upon Silverlight will play a great role in representing geographic information and aggregating geospatial web services in future, and also, it is more effective.