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    Re: Position from crossing two circles : was [NAV-L] Reality check
    From: George Huxtable
    Date: 2006 Jun 9, 11:42 +0100

    Replying to my posting stating-
    |
    | >The locus of an observer who was somewhere unknown on that circle
    becomes,
    | >after that displacement, not a circle at all. It's distorted, and
    the
    | >greatest distortion occurs in directions at 45 degrees (and 135,
    225,
    | >315 degrees) to the direction of travel.
    
    Herbert Prinz replied-
    
    | I don't understand this. Shifting the circles in an east-westerly
    | direction does not distort them at all. Therefore shifting them
    | north-south must distort them the most. No?
    
    Not so, Herbert. If you shift every point on a circle (or any other
    geometrical figure) in an East-West direction by a certain number of
    DEGREES, then its shape and size remain quite unaltered; that's true.
    But it's not what we are doing here. We are shifting by a certain
    number of MILES, East or West, so points that are in higher latitudes
    get shifted more, in longitude, than those near the equator, and a
    similar eggy distortion is the inevitable result. However, the
    situation is a bit more complex that I first thought when I wrote
    those words at the top of this posting, and although I am quite
    confident that they are true for directions of travel due N, S, E, or
    W, I am less sure whether they apply just as well to courses in
    between them. That needs a bit more pondering.
    
    Here, I wish to record a first. This is, as far as I can recall, the
    first time on this list that Herbert Prinz has EVER been caught out in
    getting something wrong. And I doubt if it will ever happen again.
    
    | >I haven't come across the A'Hearn and Rossano paper, but it
    certainly
    | >seems worth looking up.
    | >
    | I will send you a copy. It may take a few days.
    
    Thank you, Herbert; that is kind.
    
    George.
    
    
    

       
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