
NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Bowditch 1995 Table 18
From: Doug Royer
Date: 2005 Feb 2, 16:43 -0800
From: Doug Royer
Date: 2005 Feb 2, 16:43 -0800
"... but is sometimes measured from 0? at the heading either clockwise or counterclockwise through 180?, when it is designated right or left." Jim, I don't know where you got this.Relative bearings are ALWAYS taken from the head in a counterclockwise(right to left,0 - 360)manner. There is a reason for this.One ship takeing clockwise bearings and another takeing c-clockwise bearings is a recipe for disaster. RBs are always taken/given in the above prescribed format. Here's a visual aid: RB + MH = MB RB + TH = TB MB - MH = RB TB - TH = RB Example navigating a vessel and talking to another over the VHF; vessel # 1 I'm in position approximate XYZ on a heading of 210 degrees true,14 kts.I have you relative at 67 degrees,range 9 miles.. Now the 2nd vessel only has to take the recipical of that 67 * relative bearing and that range and run the bearing line and range on the chart from it's pos to plot vessel 1's pos. Kind of dangerous takeing/giving relative bearings any other way due to misunderstandings. I worked your question this way: Course = 002 T. Bearing 1 = 295 T, so RB = 293, or 067 to port. Bearing 2 = 245 T, so RB = 243, or 117 to port.