Geotagging, orGeoTagging, is the process of adding geographical identificationmetadata to various media such as ageotagged photograph or video, websites, SMS messages, QR Codes orRgSSfeeds and is a form ofgeospatial metadata. This data usually consists oflatitude and longitude coordinates, though they can also includealtitude,bearing, distance, accuracy data, and place names, and perhaps atime stamp.
Geotagging can help users find a wide variety of location-specific information from a device. For instance, someone can find images taken near a given location by entering latitude and longitude coordinates into a suitable imagesearch engine. Geotagging-enabled information services can also potentially be used to findlocation-based news, websites, or other resources.[1] Geotagging can tell users the location of the content of a given picture or other media or thepoint of view, and conversely on some media platforms show media relevant to a given location.
The geographical location data used in geotagging can, in almost every case, be derived from theglobal positioning system, and based on alatitude/longitude-coordinate system that presents each location on the earth from 180° west through 180° east along theEquator and 90° north through 90° south along theprime meridian.[citation needed]
The related termgeocoding refers to the process of taking non-coordinate-based geographical identifiers, such as a street address, and finding associatedgeographic coordinates (or vice versa forreverse geocoding). Such techniques can be used together with geotagging to provide alternative search techniques.[citation needed]
Geotagging is a popular feature on several social media platforms, such as Facebook and Instagram.
Facebook users can geotag photos that can be added to the page of the location they are tagging. Users may also use a feature that allows them to find nearby Facebook friends by generating a list of people according to the location tracker in their mobile devices.[2]
Instagram uses a map feature that allows users to geotag photos. The map layout pin points specific photos that the user has taken on a world map.
Two main options can be used to geotag photos: capturing GPS information at the time the photo is taken or "attaching" geocoordinates to the photograph after the picture is taken.
In order to capture GPS data at the time the photograph is captured, the user must have a camera with built in GPS or a standalone GPS along with a digital camera. Because of the requirement for wireless service providers in United States to supply more precise location information for 911 calls by September 11, 2012,[3] more and more cell phones have built-in GPS chips. Most smart phones already use a GPS chip along with built-in cameras to allow users to automatically geotag photos. Others may have the GPS chip and camera but do not have internal software needed to embed the GPS information within the picture. A few digital cameras also have built-on or built-in GPS that allow for automatic geotagging.[4]
Devices use GPS, A-GPS or both.A-GPS can be faster getting an initial fix if within range of a cell phone tower, and may work better inside buildings. Traditional GPS does not need cell phone towers and uses standard GPS signals outside of urban areas. Traditional GPS tends to use more battery power. Almost any digital camera can be coupled with a stand-alone GPS and post processed with photo mapping software, to write the location information to the image'sexif header.
In the field ofremote sensing the geotagging goal is to store coordinates of every pixel in the image. One approach is used with theorthophotos where we store coordinates of four corners and all the other pixels can be georeferenced byinterpolation. The four corners are stored usingGeoTIFF orWorld file standards.Hyperspectral images take a different approach defining a separate file of the same spatial dimensions as the image wherelatitude andlongitude of each pixel are stored as two 2D layers in so calledInput geometry data (IGM) files,[5] also known as GEO files.
Audio/video files can be geotagged via: metadata, audio encoding, overlay, or with companion files. Metadata records the geospatial data in the encoded video file to be decoded for later analysis. One of the standards used withunmanned aerial vehicle isMISB Standard 0601 which allows geocoding of corner points and horizon lines in individual video frames.[6] Audio encoding involves a process of converting gps data into audio data such as modem squawk. Overlay involves overlaying GPS data as text on the recorded video. Companion files are separate data files which correspond to respective audio/video files. Companion files are typically found in the .KML and .GPX data formats.[7] For audio and video files which use thevorbiscomment metadata format (includingOpus,Ogg Vorbis,FLAC,Speex, andOgg Theora), there is a proposed GEO LOCATION[8] field which can be used. Like all vorbis comments, it is plain text, and it takes the form:
GEO_LOCATION=(decimal latitude);(decimal longitude);([optional]elevation in meters)
for example:
GEO_LOCATION=35.1592;-98.4422;410
TheGeoSMS standard works by embedding one or more'geo' URIs in the body of an SMS, for example:
I'm at the pubgeo:-37.801631,144.980294;u=16RFC 1876 defines a means for expressing location information in theDomain Name System. LOC resources records can specify the latitude, longitude, altitude, precision of the location, and the physical size of on entity attached to an IP address. However, in practice not all IP addresses have such a record, so it is more common to usegeolocation services to find the physical location of an IP address.
The GeoURL[9] method requires theICBM tag[10] (plus optionalDublin Core metadata), which is used to geotag standard web pages inHTML format:
<metaname="ICBM"content="50.167958, -97.133185">
The similar Geotag format allows the addition of place name and region tags:
<metaname="geo.position"content="50.167958;-97.133185"><metaname="geo.placename"content="Rockwood Rural Municipality, Manitoba, Canada"><metaname="geo.region"content="ca-mb">
TheRDF method is defined by W3 Group and presents the information in RDF tags:[11]
<rdf:RDFxmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#"><geo:Point><geo:lat>55.701</geo:lat><geo:long>12.552</geo:long></geo:Point></rdf:RDF>
TheGeo microformat allows coordinates within HyperText Markup Language pages to be marked up in such a way that they can be "discovered" by software tools. Example:
<spanclass="geo"><spanclass="latitude">50.167958</span>;<spanclass="longitude">-97.133185</span></span>
A proposal has been developed[12] to extend Geo to cover other bodies, such asMars and theMoon.
An example is theFlickr photo-sharing Web site, which provides geographic data for anygeotagged photo in all of the above-mentioned formats.
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 websiteGeobloggers and used by more and more sites, e.g. photo sharing sitesPanoramio andFlickr, and the social bookmarking sitedel.icio.us, enables content to be found via a location search. Such sites allow users to add metadata to an information resource via a set of so-calledmachine tags (seefolksonomy).
geotaggedgeo:lat=57.64911geo:lon=10.40744
This describes the geographic coordinates of a particular location in terms oflatitude (geo:lat) andlongitude (geo:lon). These are expressed in decimal degrees in theWGS84datum, which has become something of a default geodetic datum with the advent ofGPS.[citation needed]
Using three tags works within the constraint of having tags that can only be single 'words'. Identifying geotagged information resources on sites likeFlickr anddel.icio.us is done by searching for the 'geotagged' tag, since the tags beginninggeo:lat= andgeo:lon= are necessarily very variable.
Another option is to tag with aGeohash:
geo:hash=u4pruydqqvjA further convention proposed byFlickrFly adds tags to specify the suggested viewing angle and range when the geotagged location is viewed inGoogle Earth:
ge:head=225.00ge:tilt=45.00ge:range=560.00
These three tags would indicate that the camera is pointed heading 225° (south west), has a 45° tilt and is 560 metres from the subject.
Where the above methods are in use, their coordinates may differ from those specified by the photo's internal Exif data, for example because of a correction or a difference between the camera's location and the subject's.
In order to integrate geotags in social media and enhance text readability or oral use, the concept of 'meetag' or tag-to-meet has been proposed. Differing from hashtag construction, meetag includes the geolocation information after an underscore. A meetag is therefore a word or an unspaced phrase prefixed with an underscore ("_"). Words in messages on microblogging and social networking services may be tagged by putting "_" before them, either as they appear in a sentence, (e.g. "There is a concert going _montreuxjazzfestival", "the world wide web was invented _cern _geneve", ...) or appended to it.[13]
Geoblogging attaches specific geographic location information toblog entries viageotags. Searching a list of blogs and pictures tagged using geotag technology allows users to select areas of specific interest to them on interactive maps.[14]
The progression ofGPS technology, along with the development of various online applications, has fueled the popularity of such tagged blogging,[citation needed] and the combination ofGPS phones andGSM localization, has led to themoblogging, where blog posts are tagged with exact position of the user.Real-time geotagging relays automatically geotagged media such as photos or video to be published and shared immediately.
For better integration and readability of geotags into blog texts, themeetag syntax has been proposed, which transforms any word, sentence, or precise geolocalization coordinates prefixed with an underscore into a 'meetag'. It not only lets one express a precise location but also takes in account dynamically changing geolocations.
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One of the first attempts to initiate the geotagging aspect of searching and locating articles seems to be the now-inoperative site Wikinear.com, launched in 2008, which showed the user Wikipedia pages that are geographically closest to one's current location.[15]
The 2009 appCyclopedia works relatively well showing geotagged Wikipedia articles located within several miles of ones location, integrated with a street-view mode, and 360-degree mode.
The app Respotter Wiki, launched in 2009, claims to feature Wikipedia searching via a map, also allowing users to interact with people around them, via messaging and reviews, etc. The app, in its current function, however, seems to give only geotagged photo results.
As of 2017, theWikipedia-World Project provides a simple map search tool which can display tagged articles near to a particular location, as well as a variety of more sophisticated tools integrated with external mapping services.[16]
Following a scientific study[17] and several demonstrative websites,[18][19] a discussion on the privacy implications of geotagging has raised public attention.[20][21][22][23] In particular, the automatic embedding of geotags in pictures taken with smartphones is often ignored by cell-phone users. As a result, people are often not aware that the photos they publish on the Internet have been geotagged. Many celebrities reportedly gave away their home location without knowing it.[citation needed] According to the study, a significant number of for-sale advertisements onCraigslist, that were otherwise anonymized, contained geotags, thereby revealing the location of high-valued goods—sometimes in combination with clear hints to the absence of the offerer at certain times. Publishing photos and other media tagged with exact geolocation on the Internet allows random people to track an individual's location and correlate it with other information. Therefore, criminals could find out when homes are empty because their inhabitants posted geotagged and timestamped information both about their home address and their vacation residence. These dangers can be avoided by removing geotags with ametadata removal tool for photos before publishing them on theInternet.[citation needed]
In 2007, fourUnited States ArmyApache helicopters were destroyed on the ground by Iraqi insurgent mortar fire; the insurgents had made use of embedded coordinates in web-published photographs (geotagging) taken of the helicopters by soldiers.[24]
Another newly realized danger of geotagging is the location information provided to criminal gangs and poachers on the whereabouts of often endangered animals. This can effectively make tourists scouts for these poachers, so geotagging should be turned off when photographing these animals.According to Chinoitezvi Honour, some phones automatically geotag pictures hence location should be turned off when taking pictures.
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Media related toGeotagging at Wikimedia Commons