On March 12, Professor Michael Goodchild was the featured speaker at the weekly Colloquium held on the ESRI campus.  His topic, "Citizens as Sensors: Web 2.0 and the World of Volunteered Geography," discussed the growing phenomena of contributions to cooperative georeferenced databases by members of the community.  Referenced was the wiki-genre site, Wikimapia.  There, participants can post comments about georeferenced locations.  Other sites mentioned were Flickr where users upload photos to lat/long locations and OpenStreetMap, an international effort to create a free source of map data through the efforts of volunteers.

Goodchild described the results of Volunteered Geographic Information (VGI) as "assertive" information as opposed to the "authoritative" information collected by government agencies and the various data collection efforts by private industry.

Goodchild also discussed the implied authority ascribed to some sites because computerization can imply authority per se.  He cited georeferencing errors by Google Earth in the city of Santa Barbara and explained how subsequent use of those incorrect positions creates, in essence, a new datum or horizontal reference system that is substantially different from the current North American datum, but which is widely accepted because of the perceived authority of Google.

Asserting that citizen science has made a significant contribution to the knowledge-base of our world, Goodchild indicated that VGI can have a positive impact on the collection of geographic information, particularly at the local level.

Well known citizen science efforts include Frogwatch, a volunteer amphibian study sponsored by the National Wildlife Federation and the US Geological Survey; the Search for Extra-Terrestrial Intelligence (SETI), a distributed computing project hosted by the Space Sciences Laboratory at the University of California, Berkeley; and the many bird watching surveys that require volunteer participation.