GPS satellites have been freely accessible to the world through the "public good" policy of the United States Air Force and their NAVSTAR Global Position System (GPS). It is a system of satellites that broadcast a specific radio signal to connect to a receiver like this one. If three or more of the NAVSTAR satellites are in transmission range of the GPS unit, through simple mathematical calculations based on the distances between each orbiting satellite and the receiver, a position is determined. This in turn translates into latitude, longitude and altitude co-ordinates on a GPS receiver.
Geotagging has become an important part of digital photographic organization, classification and notation. The process involves obtaining coordinates through GPS triangulation, and embedding them in a way that allows a photographer to store the location to which the photograph was taken within the digital image file itself. In order to generate these coordinates, a GPS receiver like the Jobo photoGPS is required.
The Jobo photoGPS datalogger is a lightweight and compact device, intended to be mounted in the hotshoe of a digital SLR and is activated by the electrical pulse that normally would trigger a shoe-mounted flash. The photoGPS has its own USB-rechargeable internal battery, so it need not drain the camera's battery. As such, a fully-charged photoGPS can be used for several weeks without a recharge as the device will "sleep" in-between exposures. The photoGPS only operates in full power mode at the time of the synchronized exposure.
When the photoGPS is triggered, it saves the current location data to its own internal memory. So through a multi-stage geotagging method, the geospatial data is collected and embedded in an image's metadata only after the photoGPS is connected to a PC or Macintosh computer and the included software is run.
Ultimately, JPEG, RAW and XMP sidecar files can be updated with 'where' data" to supplement the 'who,' 'what,' and 'when' information normally recorded on digital images. This data is very helpful when organizing or identifying photos and for the purposes of online sharing and viewing.