The measurement round the vessel. The girth is generally measured at a station 0.55 from the fore end of the L.W.L. It is taken in two separate ways--i.e., by skin or by chain. The skin girth is taken by following the skin surface of the plank or body right round under the keel, from gunwale to gun. wale. The chain girth is taken at the same place and between the same points with the string, tape, or chain pulled taut. The difference between the two girths is called the "d" measurement.