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July2004 |
Present realities and the future of Internet gis
Three kinds of Internet GIS
Internet GIS has many difference faces and alternative names, such as "internet mapping", "distributed GIS", "web-based GIS", "networked GIS", "on-line GIS" etc. To simplify the variety of Internet GIS, we identify three kinds of Internet GIS: Internet GIS for data sharing, Internet GIS for information sharing, and Internet GIS for knowledge sharing (Fig 1).
The first type of Internet GIS is for data sharing. Data sharing combines with the functions of on-line data archive and data search services. Two typical applications are on-line data warehouses (or data archive centers) and on-line data clearinghouse. An online data warehouse is for archiving, accessing and downloading both GIS databases and/or remotely sensed imagery. For example, the USGS National Map Seamless Data Distribution System is an example of an on-line GIS data discovery service (http://seamless.usgs.gov/). A web-based data clearinghouse can help users to search and index the contents of metadata, and then access the actual data through the descriptions of metadata. Clearinghouses may access dataset or inventory detail. The premier dataset clearinghouse portal for Federally acquired data is the Federal Geographic Data Committee (FGDC)'s data clearinghouse ( http://clearinghouse3.fgdc.gov). Clients can access descriptions of datasets, and may be redirected to the dataset holder to access individual dataset granules. NASA's Earth Science Data Information System (ESDIS) Project's new ECHO system is an example of an inventory clearinghouse. Clients of an inventory clearinghouse can access descriptions of individual dataset granules and can broker data orders to providers on behalf of users (Pfister et. al., 2001).
The second type is for information sharing. Multiple interactive map servers and mobile navigation services are the typical applications. Web-based mapping functions include the display, zoom-in/out, query of spatial information. The major requirement of information sharing services is to provide effective web-based display mechanisms and client/server communication protocols (Tsou, 2004). One on-line mapping example can be found at the US Census Bureau American Factfinder (http://factfinder.census.gov/servlet/ReferenceMapFramesetServlet?_lang=en). The reference and thematic maps provided by the Factfinder are built on the OGC standards and use data represented in the GML standard.
The third kind of Internet GIS focuses on the sharing of knowledge. This is the most challenging task for the development of Internet GIS and only few applications are available today. The goal is to provide on-line GIS modeling and spatial analysis functions without running GIS engines or software packages locally. Some Internet GIS applications utilize Java language or other distributed component technologies, (like .NET or web services) to develop on-line GIS functions. The implementation of these web-based software components can provide ubiquitous access for all different types of GIS applications, from environmental monitoring, emergency response, urban planning, spatial decision support systems, media press, etc. One example can be found at the web site of San Diego State University, Geography Department, which created a on-line Java-based analysis toolbox for remotely sensed imagery (http://map.sdsu.edu/arc/Analytical_tools.htm).
Internet GIS allows easy access to GIS functions using a standard Internet web browser. These interfaces provide a flexible way to access both spatial information and powerful, geospatial analytical tools. Today, almost everyone has experienced the advantages of Internet GIS, such as using MapQuest.Com or Yahoo!Map. The next section will review the recent development history of Internet GIS and give a reality check of today's Internet GIS technologies.
 Fig 2 The architecture of three-tier Internet Map Server
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