A geotagged photograph is a photograph which is associated with a geographical
location by geotagging. Usually this is done by assigning at least a latitude
and longitude to the image, and optionally altitude, compass bearing and
other fields may also be included. In theory, every part of a picture can
be tied to a geographic location, but in the most typical application, only the
position of the photographer is associated with the entire digital
image. This has implications for search and retrieval. For example, photos of a
mountain summit can be taken from different positions miles apart. To find
all images of a particular summit in an image database, all photos taken within
a reasonable distance must be considered. The point position of the
photographer can in some cases include the bearing, the direction the camera
was pointing, as well as the elevation and the DOP.
Methods of geotagging photographs There are a few methods of geotagging
photographs, either automatic or manual. Automatic methods provide the easiest
and most precise method of geotagging an image, providing that a good signal has
been acquired at the time of taking the photo.
= Automatic using a built-in GPS = Several manufacturers offer cameras with
a built-in GPS receiver, but most cameras with this capability are camera
phones as camera manufacturers after initial experience in the market came to
treat GPS cameras as a niche market. The 2008 Nikon P6000, for example, an early
geotagging camera, was replaced in 2010 by the P7000 which lacked that feature.
Some models also include a compass to indicate the direction the camera was
facing when the picture was taken. Canon EOS 6D
Canon Powershot SX280HS Panasonic Lumix DMC-TZ10
Sony Alpha 55V Sony Alpha 65V
Nikon Coolpix P6000 Some mobile phones with assisted GPS use
the cell phone network to speed GPS acquisition times.
= Automatic using a connected GPS = The D1X and D1H that Nikon introduced in
2002 included a GPS interface. In 2006 the first special GPS receiver for Nikon
was produced by Dawntech. Since 2009 Nikon has sold its own Geotagger GP-1.
Canon uses the USB socket on the wireless file transmitter unit as the
GPS interface. Some digital cameras and camera phones
support an external GPS receiver connected by cable, or inserted into the
memory card slot or flash shoe. The Samsung SH100 can connect using Wi-Fi to
get position data from a GPS-enabled smartphone. Generally the relevant GPS
data is automatically stored in the photo's Exif information when the photo
is taken. A connected GPS will generally remain switched on continuously,
requiring power, and will then have location information available
immediately when the camera is switched on.
Many GPS-ready cameras are currently available, made by manufacturers such as
Nikon, Fujifilm, Sony and Panasonic. Automatic geotagging combined with
real-time transfer and publishing results in real-time geotagging.
= Synchronizing with a separate GPS = Most cameras sold today do not contain a
built-in GPS receiver; however, an external location-aware device, such as
a hand-held GPS logger, can still be used with a non-GPS digital camera for
geotagging. The photo is taken without geographical information and is
processed later using software in conjunction with the GPS data.
Timestamps made by the camera can be compared with timestamps in the recorded
GPS information, provided that the clocks in the separate devices can be
synchronized. The resulting coordinates can then be added to the Exif
information of the photo. = Manual geotagging =
Location information can also be added to photos, for example via its Exif
specification that has fields for longitude/latitude, even if no GPS
device was present when the photo was taken.
The information can be entered by directly giving the coordinates or by
selecting a location from a map using software tools. Some tools allow entry
of tags such as city, postal code or a street address. Geocoding and reverse
geocoding can be used to convert between locations and addresses.
Manual geotagging also introduces possibilities of error, where a
photograph's location is incorrectly represented by wrong coordinates. An
advanced comparative analysis of such photos with the total collection set of
all photos available from the surrounding coordinates, needs to be
done to single out and flag such photos, but such a software's value, need and
purpose could be limited in today's environment where almost every
smartphone and camera have geotagging built-in and users do not need to
manually enter this information. = Remote standoff capture =
Some manufacturers of military and professional mapping-grade GPS
instruments have integrated a GPS receiver with a laser rangefinder and
digital camera. These multi-functional tools are able to determine a remote
subject's GPS position by calculating the subject's geographic location
relative to the camera's GPS position. These instruments are commonly used in
military applications when an aircraft or operator is targeting an area, the
position is inaccessible, there are personal health & safety concerns, or
the user wants to quickly capture multiple targets from a single, safe
position. Civilian integrated GPS cameras with
rangefinders and remote standoff capability are currently available made
by manufacturers such as Ricoh and Surveylab.
Uses When geotagged photos are uploaded to
online sharing communities such as Flickr, Panoramio or Moblog, the photo
can be placed onto a map to view the location the photo was taken. In this
way, users can browse photos from a map, search for photos from a given area, and
find related photos of the same place from other users.
Many smartphones automatically geotag their photos by default. Photographers
who prefer not to reveal their location can turn this feature off. Additionally
smartphones can use their GPS to geotag photos taken with an external camera.
Geotagged photos may be visually stamped with their GPS location information
using software tools. A stamped photo affords universal and cross-platform
viewing of the photo's location, and offers the security of retaining that
location information in the event of metadata corruption, or if file metadata
is stripped from a photo, e.g. when uploading to various online photo
sharing communities. Geotagging is also being used to
determine social patterns. For example, Now app uses geotagged Instagram photos
to find nearby events happening now. See also
Geotagging Point of Interest
GPS tracking Geocoding
Geocoding on Commons References
External links GIS Directories at DMOZ
GIS Maps at DMOZ Assigning Textual Names to Sets of
Geographic Coordinates