关键词: 万维网地理信息系统, 地学研究, 空间数据共享

Abstract: This paper introduces the concepts, basic principle, implementing technology, present situation and developing trend of WebGIS, and discusses the applicability of this new technique to geosciences. WebGIS is an Internet-based network GIS, which changes the running and serving modes of traditional GIS. The usage of traditional GIS was restricted to a community of trained experts, whereas WebGIS can make GIS technology accessible for many people through the application of GIS available on World Wide Web. The greatest advantage of WebGIS is its On-line feature; it not only can move the general GIS functionality, such as zoom, pan, point query on internet, but also has some statistical and spatial analysis capabilities. Moreover, it provides spatial operating functions such as buffer, overlay etc. Users can make their inquiries in spatial way and customize thematic maps in browser just like to query their spatial database in a local computer. They can also download the needed data to their local machines for use in their locally installed GIS software. There are several possible classifications of WebGIS. They mostly adopt the popular three-layer Browser/Server architecture consisting of browser, WebGIS application-server and GIS map-server. The browser sends GIS requests and displays maps with the interactive user-interface on client computer. The WebGIS application-server receives the requests and dispatches them to a proper map-server. The GIS map-server processes user's requests using available GIS applications and delivers the results to clients. The technical methods to implement WebGIS include Plug-ins, ActiveX, JAVA and ASP. The applications of existing WebGIS represent a wide variety of quality, aims and technical solutions. Most of the WebGIS are still in prototypes. At present, most of the WebGIS are still Online Retrieval Systems. This is mainly because that they are easy to operate and real spatial analysis is not necessary for many issues. The development directions of WebGIS, however, maybe involve interoperability and integration with RDBMS and Mobile. JAVA-based concepts also seem to became more popular. The disadvantages like long transmission times and non-uniform user interfaces can be overcome by more efficient code and a better bandwidth of the Internet. Professional JAVA classes that are developed by software vendors for WebGIS purposes can help to provide the needed performance. Geosciences require a vast amount of spatially referenced data. The distribution nature of capture, process, storage and utilization of the spatial data needs a high efficient mechanism of data sharing and interoperability. The upgrading of GIS to networking environment allows remote access to distributed data and analytical functions, and hence may supply good solutions for spatial data sharing and work collaboration in geosciences. It enables the users to bring the power of GIS and Web to studies in geosciences.

Key words: WebGIS, Geosciences study, Spatital Data Share