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    Sextant Positions versus Map Datums?
    From: Jared Sherman
    Date: 2002 Jan 15, 11:05 AM

    Okay, a sextant position is based on the almanac which is based 
    on...ergh...How exactly does that match up to a map datum? Should a sextant 
    position line up with a WGS84 chart position? An NAD27? A what-ever-is-most 
    recent datum? Or can it be expected to be off by...What distance actually?
    
    If NAD27 and WGS84 disagree by a mile, then wouldn't the "most accurate" 
    sextant position still either be off by a mile, or have been off by a mile? 
    Or maybe still be off wherever the map datum doesn't match a "spherical 
    earth" model?
    
    How exactly does one accomodate the "no datum here" from a sextant position? 
    Aside from the fact that the difference may be meaningless out at sea, where 
    the maps all agree that "you are here" in the big empty spaces and a mile or 
    two doesn't always matter.
    

       
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