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    Re: Relative plotting vs Geographical plotting
    From: Brian Whatcott
    Date: 2002 Jan 11, 7:05 PM

    At 03:43 PM 1/11/02, you wrote:
    >George Huxtable [mailto:george{at}HUXTABLE.U-NET.COM] said:
    > >
    > > I don't think Peter Smith's solution can possibly be correct: commonsense
    > > tells me so. We have two ships travelling in nearly the same direction,
    >and
    > > the second ship is slowly overtaking the first. In that case, the speed of
    > > the overtaking ship must be greater than that of the ship being overtaken.
    >
    >Hmmm. I'm not sure from the above who's the "second ship" and who's
    >the "first ship". The target is ahead of us and to Port (bearing 322d).
    >The bearing is constant, so we are converging. Since the target is
    >ahead and the range is decreasing, we must be overtaking the target.
    >
    > > ...
    > > If you add the vectors 12 knots at 150 and 1.45 knots at 142, using trig
    >or
    > > drawing, you end up with 13.44 knots at 149.1.
    >
    >But that gives the target a greater speed than our own ship, even
    >though we are overtaking it.
    >
    >Moreover, the target is on our Port bow (bearing 322d). For our
    >courses to converge (constant bearing), the target's course must
    >be a little to starboard (i.e., numerically GREATER) of ours. Thus,
    >if we're making 150d, he should be making a little greater then 150d.
    >If he's making 149.1d, we would be diverging.
    >
    >Can you read an Excel spreadsheet? I have both the geographic and
    >relative vectors problems worked out trigonometrically. I'll send
    >it to you and see what you think.
    >
    >  -- Peter
    
    
    Peter,
    you have already said enough to substantiate your position without
    support from a product of the evil empire. (ugh!).
    
    Brian
    
    Brian Whatcott
       Altus OK                      Eureka!
    

       
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