Metadata is "data about data" and is at the heart of geotagging [wikipedia.org]. Digital photographs may use any number of several different standards such as EXIF, IPTC, and XMP for embedding data into a photo's file. Data may include the camera type, the author, the focal length, latitude, longitude and a myriad of other tags. EXIF (exchangeable image file format) is a standard supported by many file types and includes tags for GPS latitude and longitude.
While most digital photo formats use EXIF and IPTC metadata, some photos additionally, or even exclusively use XMP. XMP metadata includes a schema that duplicates the EXIF metadata and also does much more. GPSPhotoLinker handles XMP using two simple rules.
- When reading a file, GPSPhotoLinker favors any metadata recorded in XMP over that recorded in EXIF.
- When writing to a file always writes EXIF metadata when possible, but also writes XMP metadata if there exists any XMP in the photo.
Supported EXIF tags
The following six tags are always written to the metadata:
Elevation tags are only written when elevation data is available.
The GPS time and date stamps are only written when using GPS generated track points. Manually entered track points, most waypoints, and the time-weighted average points do not write a time and date stamp.
Shifting the date and time stamp on the photos shifts the following time tags, when available.
Supported IPTC tags
The administrative location tags are written to the IPTC metadata and the XMP metadata when available. This data is fetched from Microsoft's Terraserver (default) or geonames.org, but can be disabled in "GPSPhotoLinker > Preferences".
The IPTC and XMP location tags are only written when manually inputed by the user.