What is Geo-Tagging?

Geotagging is the process of adding geographical identification metadata to various media such as photographs, video, websites, or RSS feeds and is a form of geospatial metadata. These data usually consist of latitude and longitude coordinates, though they can also include altitude, bearing, accuracy data, and place names.

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]

Less commonly, this process has been called geocoding (ie. a geocoded photograph), a term that more often refers to the process of taking non-coordinate based geographical identifiers, such as a street address, and finding associated geographic coordinates (or vice versa for reverse geocoding).

Photos

With photos stored in various file format, the geotag information is typically embedded in the metadata (stored in Exchangeable image file format (EXIF) or Extensible Metadata Platform (XMP) format). These data are not visible in the picture itself but are read and written by special programs and most digital cameras and modern scanners. Latitude and longitude are stored in units of degrees with decimals[2]. This geotag information can be read by many programs and photo services, such as Google Earth, FlickR, Smugmug, and others.  If you upload your photos to a photo sharing site, ask them if they support geo-tagged images.

How its done

Each photographer from Lavallee Photo has a GPS device on them that saves time & location information -- called a track.  Each camera’s internal clock is synchronized to within 1 second of real time before the shoot.  As we shoot the pictures, the camera automatically saves the exact time it was taken.  When we go back to the office and do the offsite processing, we have specialized software that combines the GPS “track” information and the time that each picture was taken, and writes the exact location (latitude, longitude and altitude) each picture was taken into the files.

More technical information for technical

Our program uses EXIF+XMP+IPTC tags allow for geocoding information to be stored invisibly right within the image files. It supports JPEG photos as well as a wide variety of other formats. Metadata is written without altering the image quality.