PUNITS

1. metres: Positional accuracy is specified in metres (SI units of positional accuracy).
2. degrees of arc: Positional accuracy is specified in degrees of arc.
3. millimeters: Positional accuracy is specified in millimeters.
4. feet: Positional accuracy is specified in feet (imperial units of positional accuracy).
5. cables: a unit of distance originally equal to the lenght of a ship's anchor cable, but now generally considered to be about 600 feet. In the British Navy it is 608 feet, or exactly one tenth of a nautical mile. In the United States Navy it is 720 feet but is infrequently used. Sometimes called cable length