A means developed in the British Navy during the First World War (1914–18) for providing an accurate measurement of the distance over the ground run by a ship, as opposed to through the water where the ship was affected by such factors as wind, tide, current, etc. As the ship moved forward a thin wire was pulled off a reel on the ship's stern. A dial on the reel then recorded the amount run out which equated with the distance the ship had travelled over the ground. It had a particular value in such naval operations as minelaying, which needed exact measurements when laying a minefield. It was also useful for hydrographic surveys.
Subjects: Maritime History.