Drift circle radius
Alternative term: Watch circle radius
Radius of the drift circle (watch circle) of a vessel or buoy.
The term scope is applied to the length of mooring line of a vessel or buoy paid out (from tail chain to anchor or sinker). In shallow waters it may approximate to the drift circle radius.
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM