Geo URI scheme
The geo URI scheme is a Uniform Resource Identifier (URI) scheme defined by the Internet Engineering Task Force's RFC 5870 (published 8 June 2010)[1] as:
a Uniform Resource Identifier (URI) for geographic locations using the 'geo' scheme name. A 'geo' URI identifies a physical location in a two- or three-dimensional coordinate reference system in a compact, simple, human-readable, and protocol-independent way.[1]
The current revision of the vCard specification[2] supports geo URIs in a vCard's "GEO" property, and the GeoSMS standard uses geo URIs for geotagging SMS messages. Android based devices support geo URIs,[3] although that implementation is based on a draft revision of the specification, and supports a different set of URI parameters and query strings.
A geo URI is not to be confused with the site GeoUrl[4] (which implements ICBM address).
Example
A simple geo URI might look like:
where the two numerical values represent latitude and longitude respectively,[1] and are separated by a comma.[1] If a third comma-separated value is present, it represents altitude.[1] Coordinates in the Southern and Western hemispheres as well as altitudes below the coordinate reference system (depths) are signed negative with a leading dash.[1] The geo URI also allows for an optional "uncertainty" value, separated by a semicolon, representing the uncertainty of the location in meters, and is described using the "u" URI parameter.[1] A geo URI with an uncertainty parameter looks as follows:
A geo URI may, for example, be included on a web page, as HTML:
<a href="geo:37.786971,-122.399677;u=35">Wikimedia Headquarters</a>
so that a geo URI-aware user agent such as a web browser could launch the user's chosen mapping service; or it could be used in an Atom feed or other XML file.
Coordinate reference systems
The default coordinate reference system (CRS) used is the World Geodetic System 1984 (WGS-84),[1] for planet Earth although other CRS, once defined, may be specified, using the "crs" URI parameter,[5] also separated by a semicolon. Such CRSs may include both other terrestrial systems and those for non-terrestrial coordinates such as those on the Moon or Mars.
A geo URI for a hypothetical lunar CRS created in 2011 might be:
The order in which the semicolon-separated parameters occur is partially significant.[1] Whilst the labeltext parameter and future parameters may be given in any order, the 'crs' and the 'u' parameters must come first. If both are used, the 'crs' must precede the 'u'.[1] All parameters are case-insensitive,[1] so the above example is exactly equivalent to:
References
- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ RFC 5870, section 8.3
