This schema defines the Garmin track movie offset extension to be used with the GPX 1.1 schema. The root element defined by this schema is intended to be used as a child element of the "extensions" element in the trk element in the GPX 1.1 schema. The GPX 1.1 schema is available at http://www.topografix.com/GPX/1/1/gpx.xsd. Offset (in seconds) from the beginning of this track's linked movie to the first point in the track.