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    Re: Sextant Positions versus Map Datums?
    From: Bill Murdoch
    Date: 2002 Jan 18, 3:51 PM

    In a message dated 1/18/02 2:23:55 PM Eastern Standard Time,
    jared.sherman{at}VERIZON.NET writes:
    
    
    > Bill-
    > NAD 83 --  30:16:28.82N, 97:44:25.19W --or-- 30d16m28.77992N,
    > 97d44m25.10907s
    > NAD-27 --  30:16:28.03N, 97:44:24.09W
    > WGS-72 --  30:16:28.68N, 97:44:25.75W
    >
    > Interesting because using the USGS "Corpscon" conversion tool, I entered
    > the NAD27 position and asked for the NAD83 position, which as you can see
    > differs from the ones that the Texans found. Question being, did they read
    > a map and measure from it? Or convert datums, using a formula different
    > from the one the USPS supplied?
    >
    
    I do not know.  That star in Liberty's hand must be one of the most unique
    benchmarks in the United States.  If you go to:
    
    http://www.ngs.noaa.gov/cgi-bin/ds_mm.prl
    
    and bracket the location one minute each way, it will give you a data sheet
    with all the information that the NGS has on the control point including its
    location on a couple of different datums (sp?).
    
    Still, the star has different locations on different datums (sp?), but what
    is its location with respect to (projected from the center of the earth onto)
    a sphere located by a plane in the heavens formed by the earth's equator and
    a similar perpendicular plane passing through both the center of the earth
    and a certain telescope mount in Greenwich England ?  And, what is the
    largest difference exists between that celestial coordinate system and a
    modern chart datum.
    
    Does your conversion program make that conversion ?
    
    Bill Murdoch
    
    
    

       
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