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    Re: Relative plotting vs Geographical plotting
    From: Trevor Kenchington
    Date: 2002 Jan 12, 4:21 AM

    Geoffrey Kolbe wrote:
    
    > I am a little confused. George says that the target ship is overtaking the
    > "own" ship, Peter thinks that the target ship is the one being overtaken.
    > But the relative bearing is constant at 322 degrees, so (as George says)
    > the two ships are in fact on collision courses. In this context, what does
    > "overtaking" mean, as neither ship is "pulling ahead" of the other?
    
    The relative bearing of "own ship" from "target ship" is 137 [reciprocal
    of the relative bearing from "own ship", less the 5 degrees difference
    in headings], meaning that "own ship" is more than two points abaft the
    beam of "target ship". Under the Collision Regulations, "own ship" is
    therefore the overtaking vessel and (assuming that they are within sight
    of each other and not operating by radar alone in thick fog) is obliged
    to keep clear.
    
    
    Trevor Kenchington
    
    
    --
    Trevor J. Kenchington PhD                         Gadus{at}iStar.ca
    Gadus Associates,                                 Office(902) 889-9250
    R.R.#1, Musquodoboit Harbour,                     Fax   (902) 889-9251
    Nova Scotia  B0J 2L0, CANADA                      Home  (902) 889-3555
    
                        Science Serving the Fisheries
                         http://home.istar.ca/~gadus
    

       
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