A geotagged photograph is a

photograph A photograph (also known as a photo, or more generically referred to as an ''image'' or ''picture'') is an image created by light falling on a photosensitivity, photosensitive surface, usually photographic film or an electronic image sensor. Th ...

which is associated with a geographic position by

geotagging Geotagging, or GeoTagging, is the process of adding geographical identification metadata to various media such as a geotagged photograph or video, websites, SMS messages, QR Codes or RgSSfeeds and is a form of geospatial metadata. This data ...

. Usually this is done by assigning at least a

latitude In geography, latitude is a geographic coordinate system, geographic coordinate that specifies the north-south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from −90° at t ...

and

longitude Longitude (, ) is a geographic coordinate that specifies the east- west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek lett ...

to the image, and optionally

elevation The elevation of a geographic location (geography), ''location'' is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational equipotenti ...

, 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 dilution of precision (DOP).

Methods

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 phone A camera phone is a mobile phone that is able to capture photographs and often record video using one or more built-in digital cameras. It can also send the resulting image wirelessly and conveniently. The first commercial phone with a color c ...

s, as camera manufacturers after initial experience in the market came to treat GPS cameras as a

niche market A niche market is the subset of the market on which a product is appealed to a small group of consumers. The market niche defines the product features aimed at satisfying specific market needs, as well as the price range, production quality and the ...

. 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 A compass is a device that shows the cardinal directions used for navigation and geographic orientation. It commonly consists of a magnetized needle or other element, such as a compass card or compass rose, which can pivot to align itself with No ...

to indicate the direction the camera was facing when the picture was taken. *

Canon EOS 6D The Canon EOS 6D is a 20.2-megapixel full-frame CMOS digital single-lens reflex camera made by Canon. The EOS 6D was publicly announced on 17 September 2012, one day before the start of the Photokina 2012 trade show. It was released in late ...

* Canon PowerShot SX280HS * Canon PowerShot S100 * Fujifilm FinePix F550EXR * Fujifilm FinePix F770EXR * Nikon COOLPIX P330 * Nikon COOLPIX P6000 * Panasonic Lumix DMC-TZ10 * Panasonic Lumix DMC-TZ40 * Sony Alpha 55V (

DSLR A digital single-lens reflex camera (digital SLR or DSLR) is a digital camera that combines the optics and mechanisms of a single-lens reflex camera with a solid-state image sensor and digitally records the images from the sensor. The reflex des ...

) * Some mobile phones with

assisted GPS Assisted GNSS (A-GNSS) is a GNSS augmentation system that often significantly improves the startup performance—i.e., time to first fix, time-to-first-fix (TTFF)—of a global navigation satellite system (GNSS). A-GNSS works by providing the nece ...

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 (WFT) as the GPS interface. Some

digital camera A digital camera, also called a digicam, is a camera that captures photographs in Digital data storage, digital memory. Most cameras produced today are digital, largely replacing those that capture images on photographic film or film stock. Dig ...

s and

s 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 Wi-Fi () is a family of wireless network protocols based on the IEEE 802.11 family of standards, which are commonly used for Wireless LAN, local area networking of devices and Internet access, allowing nearby digital devices to exchange data by ...

to get position data from a GPS-enabled

smartphone A smartphone is a mobile phone with advanced computing capabilities. It typically has a touchscreen interface, allowing users to access a wide range of applications and services, such as web browsing, email, and social media, as well as multi ...

. Generally the relevant GPS data is automatically stored in the photo's

Exif Exchangeable image file format (officially Exif, according to JEIDA/JEITA/CIPA specifications) is a standard that specifies formats for images, sound, and ancillary tags used by digital cameras (including smartphones), scanners and other system ...

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 (, ; ) is a Japanese optics and photographic equipment manufacturer. Nikon's products include cameras, camera lenses, binoculars, microscopes, ophthalmic lenses, measurement instruments, rifle scopes, spotting scopes, and equipment related to S ...

Fujifilm , trading as , or simply Fuji, is a Japanese Multinational corporation, multinational Conglomerate (company), conglomerate headquartered in Tokyo, Japan, operating in the areas of photography, optics, Office supplies, office and Biomedical engine ...

Sony is a Japanese multinational conglomerate (company), conglomerate headquartered at Sony City in Minato, Tokyo, Japan. The Sony Group encompasses various businesses, including Sony Corporation (electronics), Sony Semiconductor Solutions (i ...

and

Panasonic is a Japanese multinational electronics manufacturer, headquartered in Kadoma, Osaka, Kadoma, Japan. It was founded in 1918 as in Fukushima-ku, Osaka, Fukushima by Kōnosuke Matsushita. The company was incorporated in 1935 and renamed and c ...

. Automatic geotagging combined with real-time transfer and publishing results in real-time tagging.

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.

Timestamp A timestamp is a sequence of characters or encoded information identifying when a certain event occurred, usually giving date and time of day, sometimes accurate to a small fraction of a second. Timestamps do not have to be based on some absolu ...

s 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

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 A postal code (also known locally in various English-speaking countries throughout the world as a postcode, post code, PIN or ZIP Code) is a series of letters or numerical digit, digits or both, sometimes including spaces or punctuation, inclu ...

or a street address.

Geocoding Address geocoding, or simply geocoding, is the process of taking a text-based description of a location, such as an address or the name of a place, and returning geographic coordinates, frequently latitude/longitude pair, to identify a locati ...

and

reverse geocoding Reverse geocoding is the process of converting a location as described by geographic coordinates (latitude, longitude) to a human-readable address or place name. It is the opposite of forward geocoding (often referred to as address geocoding or ...

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 A laser rangefinder, also known as a laser telemeter or laser distance meter, is a rangefinder that uses a laser beam to determine the distance to an object. The most common form of laser rangefinder operates on the time of flight principle by ...

and

. 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 (for example over a valley or wetland), there are personal health & safety concerns (motorway traffic), or the user wants to quickly capture multiple targets from a single, safe position (trees, street signage and furniture). 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 Flickr ( ) is an image hosting service, image and Online video platform, video hosting service, as well as an online community, founded in Canada and headquartered in the United States. It was created by Ludicorp in 2004 and was previously a co ...

, Panoramio or

Moblog Mobile blogging (also known as mobloggingIto, M. (2002) 'Mobiles and the appropriation of place', receiver magazine, 8, www.receiver.vodafone.com) is a method of publishing to a website or blog from a mobile phone or other handheld device. A 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

s 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.

Formats

With photos stored in

JPEG JPEG ( , short for Joint Photographic Experts Group and sometimes retroactively referred to as JPEG 1) is a commonly used method of lossy compression for digital images, particularly for those images produced by digital photography. The degr ...

TIFF Tag Image File Format or Tagged Image File Format, commonly known by the abbreviations TIFF or TIF, is an image file format for storing raster graphics images, popular among graphic artists, the publishing industry, and photographers. TIFF is w ...

and many other file formats, the geotag information, storing camera location and sometimes heading, is typically embedded in the

metadata Metadata (or metainformation) is "data that provides information about other data", but not the content of the data itself, such as the text of a message or the image itself. There are many distinct types of metadata, including: * Descriptive ...

, stored in

Exchangeable image file format Exchangeable image file format (officially Exif, according to JEIDA/JEITA/CIPA specifications) is a standard that specifies formats for images, sound, and ancillary tags used by digital cameras (including smartphones), scanners and other system ...

(Exif) or

Extensible Metadata Platform The Extensible Metadata Platform (XMP) is an ISO standard, originally created by Adobe Systems Inc., for the creation, processing and interchange of standardized and custom metadata for digital documents and data sets. XMP standardizes a data ...

(XMP) format. These data are not visible in the picture itself but are read and written by special programs and most

s and modern

scanners ''Scanners'' is a 1981 Canadian science fiction horror film written and directed by David Cronenberg and starring Stephen Lack, Jennifer O'Neill, Michael Ironside, and Patrick McGoohan. In the film, "scanners" are psychics with unusual telep ...

. Latitude and longitude are stored in units of degrees with decimals.In this format, a positively signed coordinate indicates Northern or Eastern hemisphere, while negative sign indicates Southern or Western hemisphere. This geotag information can be read by many programs, such as the

cross-platform Within computing, cross-platform software (also called multi-platform software, platform-agnostic software, or platform-independent software) is computer software that is designed to work in several Computing platform, computing platforms. Some ...

open source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use and view the source code, design documents, or content of the product. The open source model is a decentrali ...

ExifTool. An example readout for a photo might look like: GPS Latitude : 57 deg 38' 56.83" N GPS Longitude : 10 deg 24' 26.79" E GPS Position : 57 deg 38' 56.83" N, 10 deg 24' 26.79" E or the same coordinates could also be presented as decimal degrees: GPS Latitude : 57.64911 GPS Longitude : 10.40744 GPS Position : 57.64911 10.40744 When stored in Exif, the coordinates are represented as a series of rational numbers in the GPS sub-IFD. Here is a hexadecimal dump of the relevant section of the Exif metadata (with

big-endian '' Jonathan_Swift.html" ;"title="Gulliver's Travels'' by Jonathan Swift">Gulliver's Travels'' by Jonathan Swift, the novel from which the term was coined In computing, endianness is the order in which bytes within a word (data type), word of d ...

byte order): + PS directory with 5 entries , 0) GPSVersionID = 2 2 0 0 , - Tag 0x0000 (4 bytes, int8u : , dump: 02 02 00 00 , 1) GPSLatitudeRef = N , - Tag 0x0001 (2 bytes, string : , dump: 4e 00 SCII "N\0" , 2) GPSLatitude = 57 38 56.83 (57/1 38/1 5683/100) , - Tag 0x0002 (24 bytes, rational64u : , dump: 00 00 00 39 00 00 00 01 00 00 00 26 00 00 00 01 , dump: 00 00 16 33 00 00 00 64 , 3) GPSLongitudeRef = W , - Tag 0x0003 (2 bytes, string : , dump: 57 00 SCII "W\0" , 4) GPS Longitude = 10 24 26.79 (10/1 24/1 2679/100) , - Tag 0x0004 (24 bytes, rational64u : , dump: 00 00 00 0a 00 00 00 01 00 00 00 18 00 00 00 01 , dump: 00 00 0a 77 00 00 00 64

References

External links

Assigning Textual Names to Sets of Geographic Coordinates (pdf)

Open source photo kml generator for Google Earth
Digital photography GIS file formats Metadata Geographic data and information