The lightweight “Midori” web browser supports “geo:” URIs natively since version 0.3.6. Here’s the respective release announcement (from May 2011, only discovered now):

http://mail.xfce.org/pipermail/xfce/2011-May/028718.html

The browser extracts latitude and longitude from a geo: URI entered or clicked on, and redirects the user to the respective location on OpenStreetMap.

Very cool.

An initiative called “GeoSMS” proposes the use of “geo:” URIs in text messages (mobile short messages – SMS). This was actually a use case that i discussed with several IETF fellows during the development of the geo: URI specification – i’m happy that someone took the effort to write a formal specification.

The proposal got an amazing amount of press coverage, including articles on  New York Times, der Standard (german), Times of India, intomobile and various other news sites in the mobile and tech industry.

It’s nice to see how the design properties of the “geo:” URI (short, simple, human-readable) are the base for another simple and straightforward standard proposal. Let’s hope that mobile phone developers implement GeoSMS (and, hence “geo:” URIs) in their future products. The GeoSMS developers themselves have already created an Android application called “I am Here”. More details and the actual specification are available here:

GeoSMS – “geo:” URIs in text messages

RFC5870 – the “geo:” URI specification

“geo:” is getting more attention in other areas of the Internet Engineering Task Force. After the VCARDDAV working group has included “geo:” URIs in their revision of the vCard scheme, the SIPCORE working group is now discussing the use of “geo:” in their “Location Conveyance” draft.

SIP is the IETF’s protocol for establishing Realtime Application Sessions, and is very commonly used for Voice over IP. It has gained massive popularity in recent years, and is not just be used in VoIP-Software, but also in Public Branch Exchanges from various vendors, open source products such as Asterisk, Kamailio and a wide range of carrier products. SIP is the base for telephoney in the upcoming Next Generation networks such as LTE, and a major component of IMS systems. A good percentage of phone calls being routed between carriers as of today already uses SIP.

For those reasons, the IETF is looking into ways to embed location information into SIP messages. This is important for services such as Emergency Services, but can of course be used for any other realtime application that needs to transmit location information in its session setup. An example of that could be location conveyance between contacts in a social network, or applications for “checking in”, such as Gowalla and Foursquare.

The current version of the SIP Location Conveyance Specification uses “Content ID” URIs (besides “sip”/”sips”/”pres”) to refer from the new “Geolocation:” header to a MIME body part, which then contains the location embedded in a PIDF-LO Presence/Location document. Such a geolocation header (and respective body part) would look like this:

Geolocation: <cid:[email protected]>
     ;inserted-by="[email protected]"

   --boundary1

   <?xml version="1.0" encoding="UTF-8"?>
      <presence xmlns="urn:ietf:params:xml:ns:pidf"
          xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
          xmlns:cl="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"
          xmlns:gml="http://www.opengis.net/gml"
          entity="pres:[email protected]">
        <dm:device id="point2d">
         <timestamp>2007-12-02T14:00:00Z</timestamp>

         <status>
          <gp:geopriv>
            <gp:location-info>
              <gml:location>
                <gml:Point srsName="urn:ogc:def:crs:EPSG::4326">
                  <gml:pos>33.001111 -96.68142</gml:pos>
                </gml:Point>
               </gml:location>
            </gp:location-info>
            <gp:usage-rules>
              <gp:retransmission-allowed>no</gp:retransmission-allowed>
              <gp:retention-expiry>2007-12-07T18:00:00Z</gp:retention-
                            expiry>
            </gp:usage-rules>
            <gp:method>DHCP</gp:method>
            <gp:provided-by>www.example.com</gp:provided-by>
          </gp:geopriv>
         </status>
        </dm:device>
      </presence>
   --boundary1--

PIDF-LO allows for great flexibility of location types, can contain civic addresses, and extensive privacy rules. However, conveyance of a simple “point” type location could also be achieved by using the “geo:” URI in the Geolocation header directly as follows:
Geolocation: <geo:33.001111,-96.68142>

Which, obviously, would be much more compact, probably easier to parse, and not in the need of a seperate MIME body part.
However, the “geo:” URI specifically lacks privacy rules, because an URI itself does not identify a Target, but rather reflects just a physical location in space. In SIP Location Conveyance as a “GEOPRIV Using Protocol”, privacy is required.
There is currently a discussion going on the SIPCORE mailing list, and the proposal is that a “geo:” URI (when used in an “Geolocation” SIP header) would come with implicit default rules (currently under discussion whether those default rules would be GEOPRIV’s general default rules, or defaults specific to the use of “geo:” in the context of the “Geolocation:” header).
We’ll keep watching the discussion.
				

vCard – the first spec to use “geo:”?

The first specification that is using the “geo:” scheme seems to be the revision of the vCard format. vCards are “virtual business cards”, and contain a multitude of contact information about a person or an organization.

vCard GEO property

The geographic location of a person’s office is of course one of those properties – even the original specification of vCard (RFC 2426) contained an “GEO” property (defined in Section 3.4.2). That property has a range of shortcomings:

• There’s no way to specify altitude
• the Coordinate Reference System is not defined (see here [PDF] why you should care)
• Recommends to always use six decimal places (roughly one meter) rather than allowing for uncertainty values

New revision of vCard includes “geo:” URI

The current revision of the vCard specification (currently worked on in the IETF’s VCARDDAV working group) has changed the format of the “GEO” property. The new definition requires a URI rather than the lat/lon tupel as value, and notes in an example that the “geo:” URI scheme is “particularly well-suited”, although other URI schemes are allowed too. A example vCard using the “geo:” URI looks like this (edited for brevity):

BEGIN:VCARD
VERSION:4.0
FN:Simon Perreault
...
GEO;TYPE=work:geo:46.772673,-71.282945
...
CLASS:PUBLIC
END:VCARD

As outlined above, the structure of vCards allows to supply parameters for properties – in the example above, the GEO property is specified for the “work” location of the contact.

vCard applications become geo: aware

The integration of the URI scheme into the very popular vCard format means that very likely future revisions of vCard applications will be able to parse and use “geo:” URIs. Looking at the list of applications that support vCards, it looks like a bright future for our newly-born URI scheme.

Andy Armstrong of hexten has created yet another implementation of the “geo” URI scheme – this time it’s CPAN module for all the Perl fans out there: URI::geo provides a class to create and parse “geo” URIs from within Perl scripts – a simple example to create a URI from latitude and longitude information looks like this:

use URI::geo;

my $guri = URI::geo->new( { lat => 55, lon => -1 } );

The current module version 0.0.4 is available from CPAN here, API documentation can be found here.

Andy, thanks for implementing and getting the module into CPAN!