We report a preliminary survey and analysis of community GIS (Geographical Information Systems) over the Web. The Internet and the Web have enabled unprecedent development in online communities, such as popular auction sites, virtual forums, and syndicated blogging, just to name a few. Web technologies are making an impact to GIS as well, as evidenced by the various web-based GIS and new standards like GML (Geography Markup Language) and SVG (Scalable Vector Graphics).When the Web, community, and GIS are put together, however, we are less assured of their combined potential, and, indeed, do not witness many success stories. This presentation will make an effort to categorize web-based community GIS by the following four dimensions

o People and community

o Spatial data sources

o Web technologies

o Sustainability

and hope to make clear the opportunities offered by web-based community GIS.