Ship’s length (Bridge GPS antenna to fwd) + (How many shackles x 27.5m)
FOR Example :
= 6 shackle on deck and (bridge GPS antenna to fwd) is indicated by L = 100m
= 6 shackle +L
= 6×27.5m +100
= (265/ 1854 ) nm
= (0.1431×10) cable @ one NM is equal to 10 cable
= 1.431 cable
Centre of swinging circle is the point where anchor fluke touches SEABED.
Alternatively, The following is the formula used to calculate Swing Radius of a boat at anchor.:
Swing Radius = LOA + [ ( RODE ) 2 – ( DEPTH + FREEBOARD)2 ] 1/2
LOA: Overall length of the boat, including any additions or extensions from the stern
RODE: The length (line to the anchor) of the rode from the bow pulpit to the anchor.
DEPTH: The water depth over the anchor.
FREEBOARD: The distance from the deck at the bow pulpit to the water.
Note all measurements of length and distance must be in the same units.