Geotagging

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Geotagging, sometimes referred to as Geocoding, is the process of adding geographical identification metadata to various media such as websites, RSS feeds, or images and is a form of geospatial metadata. This data usually consists of latitude and longitude coordinates, though it can also include altitude, bearing, and place names.

Geocoding also refers to the process of taking non-coordinate based geographical identifiers, such as a postal address, and assigning geographic coordinates to them (or vice versa).

Geotagging can help users find a wide variety of location-specific information. For instance, one can find images taken near a given location by entering latitude and longitude coordinates into a Geotagging-enabled image search engine. Geotagging-enabled information services can also potentially be used to find location-based news, websites, or other resources.[1]

Web sites

Geotagging HTML web pages is done with meta tags. The GeoURL standard requires the ICBM tag: 

<meta name="ICBM" content="50.167958, -97.133185">

The similar Geo Tag format allows the addition of placename and region tags: 

<meta name="geo.position" content="50.167958;-97.133185">
<meta name="geo.placename" content="Rockwood Rural Municipality, Manitoba, Canada">
<meta name="geo.region" content="ca-mb">

Microformat

The Geo microformat allows co-ordinates within web pages to be marked up in such a way that they can be "discovered" by software tools. Example: 

<span class='geo'>
<span class='latitude'>50.167958</span>; 
<span class='longitude'>-97.133185</span>
</span>

which might display as:

50.167958; -97.133185

(and gives a live Geo microformat on this page).

A proposal has been developed[2] to extend Geo to cover other bodies, such as Mars and The Moon.

An example is the Flickr photo-sharing web site, which provides geographic data for any geocoded photo in all of the above-mentioned formats.

Geotagging in tag based systems

No industry standards exist, however there are a variety of techniques for adding geographical identification metadata to an information resource. One convention established by the website called GeoBloggers, encourages users to add tags to their Flickr images and del.icio.us bookmarks, enabling them to be found via a location search. Both Flickr and del.icio.us allow users to add metadata to an information resource via a set of tags, see folksonomy.

The convention established by GeoBloggers uses three tags to geotag an information resource:

where latitude and longitude are the geographic coordinates of a particular location. These are expressed in decimal degrees in the WGS84 datum, which has become something of a default datum with the advent of GPS.[citation needed]

Using three tags works within the constraint of having tags that can only be single 'words'. Identifying geotagged information resources on sites like Flickr and del.icio.us is done by searching for the 'geotagged' tag, since the tags beginning 'geo:lat=' and 'geo:lon=' are necessarily very variable.

A further convention proposed by FlickrFly adds tags to specify the suggested viewing angle and range when the geotagged location is viewed in Google Earth:

  • ge:head=xxxx e.g. ge:head=127.00, where xxxx is the view heading in decimal degrees (0-360) where zero is looking North.
  • ge:tilt=yyyy e.g. ge:tilt=60.00, where yyyy is the view tilt angle in decimal degrees, where 0 is looking straight down and 90 is looking horizontally from ground level.
  • ge:range=zzzz e.g. ge:range=560.00, where zzzz is the range of the viewpoint in metres from the marker location.

GeoTagging in Specific Systems

Adding geographic metadata to media is often a non trivial process, thus geotagging is often perceived as a burden[3], however, some systems are beginning to address the issue such as MapWith.Us. MapWith.Us automatically geotags photos taken with cell phones, this is sometimes referred to as mobile geotagging. The MapWith.Us mobile application automatically inserts location metadata into photographs, uploads the photographs to an online map, and publishes the photos based on the acquisition location. Since the process is automated, privacy is a concern, however, it has been addressed in recent version of their product.


In August 2006 Flickr introduced support for geographic information in the picture properties and its interface[4], deprecating the Geobloggers method.

On Wikipedia the {{coor title dms}} template is used for geotagged. Another template {{coord}} adds geo microformats automatically.

Geoblogging

Geoblogging attaches specific geographic location information to blog entries via geotags. Searching a list of blogs and pictures tagged using geotag technology allows users to select areas of specific interest to them on interactive maps.[citation needed]

The progression of GPS technology, along with the development of various online applications such as Flickr, has fuelled the popularity of such tagged blogging.[citation needed]

See also

References

  1. ^ GPS adds dimension to online photos Anick Jesdanun, AP, 2008-01-19
  2. ^ "Geo Extansion Straw-Man Proposal". Retrieved 2007-12-28.
  3. ^ Stephen, Shankland (2007-09-5). "Geotagging links photos to locales". cnet. {{cite news}}: Check date values in: |date= (help)
  4. ^ [1] broken link 2008-01-19

External links

Encoding for web pages, RSS, etc.

Articles and documents

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