This is a system of denoting impromptu relative bearing widely used in practical navigation to give the position of an observed object readily and comprehensibly. "Relative" means that it does not state or imply any compass directions whatsoever. The vessel can be pointed in any direction. The clock numbers are relative to the direction in which the vessel points. The angular distance between adjacent clock numbers is 30 degrees, a round unit that simplifies mathematical juggling. A quick clock number can be shouted by a lookout, whereas after a calculation and comparison of compass points, which might be unknown anyway, it might be too late for the vessel to avoid danger.
