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    Re: Sextant Positions versus Map Datums?
    From: Rodney Myrvaagnes
    Date: 2002 Jan 16, 8:48 AM

    On Wed, 16 Jan 2002 00:27:05 -0500, Jared Sherman wrote:
    >Yes, I found a USGS topo and a nuatical chart both on the Maptech mapserver, 
    and "the same" place--a landmark on the maps--was
    located 1.1 miles apart when I plotted the position shown on the topo map 
    against the position shown on the chart. The topo may have
    been NAD27 because it was older, the nautical chart should be NAD84 or something similarly recent.
    It couldn't be NAD27. I have used nautical charts in New York Harbor of both 
    datums and they are too close to notice a difference in
    this area. What was the landmark? I would go to a map store and buy the topo 
    map immediately if it really has such a discrepancy, for
    use as a cautionary item in auxiliary navigation courses.
    I keep a pre QE2 grounding copy of chart 13218 (on which the "Queen's bottom" 
    reef does not appear) for comparison with the
    current resurveyed chart, for the same purpose.
    Rodney Myrvaagnes                   J36 Gjo/a
    "Religious wisdom is to wisdom as military music is to music."
    "What contemptible scoundrel stole the cork from my lunch?"  --  W. C Fields

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