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    Re: Sextant Positions versus Map Datums?
    From: UNK
    Date: 2002 Jan 16, 7:51 AM

    On Tue 15 Jan 2002 7:51 PM in Navigation-L,
    Jared Sherman [mailto:jared.sherman{at}VERIZON.NET] said:
    > Peter-
    > 
    >
    > Nope. Go from NAD27 to WGS84 and the world can move a mile
    > instantly. How much it moves, and which way it moves, depends
    > on the datum change and also on your position on the chart,
    > i.e. some places "move" less than others.
    
    Between datums, yes. The "horizontal difference" I was referring to
    was between the ellipsoids that underlie the various datums. When you
    project celestial LOP's onto either a sphere or one of these
    ellipsoids, you get pretty much the same result. It's the landmarks
    that appear to move when you compare charts built on different
    datums, such as the Texas Capitol Dome in the example John Kabel
    pointed out.
    
     -- Peter
    

       
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