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Re: Bowditch 1995 Table 18

From: Royer, Doug (no email)
Date: Wed Feb 02 2005 - 19:43:21 EST

  • Next message: Jim Thompson: "Re: Bowditch 1995 Table 18"

    "... 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.


  • Next message: Jim Thompson: "Re: Bowditch 1995 Table 18"



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