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Subject: Re: Relative plotting vs Geographical plotting
From: Brian Whatcott (inet@XXX.XXX)
Date: Fri Jan 11 2002 - 21:05:04 EST
At 03:43 PM 1/11/02, you wrote:
>George Huxtable [mailto:george@XXX.XXX] 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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