Geotagging
Recording the latitude, longitude and sometimes altitude of an image's capture point in its metadata.
Measured in
degrees
In depth
Geotags come from an in-camera receiver, a phone connection or a separate GPS logger matched by timestamp. They make an archive searchable by map and are invaluable for returning to a location. They also carry real privacy risk, which is why coordinates should be stripped before publishing images made at home or with vulnerable subjects.
Examples in practice
A landscape photographer returns to an exact viewpoint three years later using the geotag from the original frame.