Global Positioning System Reference
In-Depth Information
artifacts and thus extend the world. This raises an interesting point about the
extension of maps and positioning systems from the real world into virtual worlds.
Linden Labs has spawned a real monetary economy (starting with a virtual one
based on Linden Dollars) where participants trade their artifacts. Maps of virtual
worlds may become interesting commercially (at least to the gaming aficionados).
Virtual reality maps of the real world are also growing, which are used for
“serious gaming” (e.g., scenario, mission, and contingency planning) and by
planners and architects to showcase future built environments to prospective
stakeholders.
8.5
Geotagging, Geoindexing, and Searching
8.5.1
Geotagging
In the context of the WWW and its information protocols, a tag is a reference
embedded within the script that accompanies each Web page. It might become a
visible entity such as a displayed image or remain invisible and form part of a
logical address to something important. In the context of the Geoweb, a geotag is
a reference to a geographical entity, for example a point of interest (PoI), and is
associated with a pair of geographical coordinates. Automatic geotagging can be
achieved with a GPS receiver that would perhaps store a waypoint that could then
be converted into a geotag and included on a Web map. Web 2.0 mapping actively
encourages people to add their own tags and enhance the usefulness of the content
(particularly if shared). An example of a geotagged mashup would be to place
geotags on a Web 2.0 map or aerial image in the place where holiday photographs
were taken. The actual photographs might be stored within a Web 2.0 photograph
sharing site (e.g., Flickr) but the URL for each photo along with other information
such as time, subject, and direction would be associated with the tag.
8.5.2
Geoindexing and Searching
Using a less structured approach, WWW content may be automatically searched
with the aim of recognizing geographical information (and indeed other
information that is in a structured format). For example, a simple postal code or a
more complex set of latitude and longitude coordinates could be extracted if they
were always associated with addresses. So it is possible to take general-purpose
textual content (that is scripted behind each Web page) and set an indexing engine
to “crawl” through the pages and extract the georeferences, and then to build them
into a database that can be then rapidly interrogated by various location-based
services. This bottom-up approach is less predictable but can greatly improve the
access to random information. For example, along with postal codes or
coordinates, it would be possible to extract times (perhaps opening times) so that
