NavList:

Bill,

When working with true and magnetic bearings to be plotted on a chart you will be using the pelorus 0° clockwise to 360°.  If doubling the angle on the bow or using Bowditch table 7 (1981)/table 18 (2002) then work port and statboard off the bow or stern. There is also the radian rule which is worked port and starboard off the bow. see link:

https://www.youtube.com/watch?v=Q8sJcePmziM

Greg Rudzinski

From: Bill B
Date: 2015 Apr 14, 14:34 -0700

Recently viewed a page at the URL below and it struck me as vague and misleading regarding "relative bearing" and pelorus use:

http://www.gosailing.info/Navigation%20-%20Relative%20Bearings.htm

I've always regarded relative bearing (RB) as a 0-360d measurement with the bow-end of the lubber line being O. The above article seems to suggest it is always measured 0-180 CW on the starboard side and 0-180 CCW on the starboard side. Also that a pelorus card is always set to 0.

I consider RB starboard and RB port to be a subset of RB. Borrowing from submariner terminology it makes communications/notations easier for me to use "Angle of the bow" or "AOB" noting port or starboard when necessary.

My calculations use the following (True bearing = TB, compass = C)

AOB or RB starboard = RB

AOB or RB port = 360 - RB

RB = TB + C

TB = RB-C

C = RB - TB

Add or subtract 360 if less than 0 or greater than 360 respectively.

Any opinions on standard usage of RB and AOB?