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    Re: Sextant Positions versus Map Datums?
    From: Brian Whatcott
    Date: 2002 Jan 18, 5:37 PM

    At 04:50 PM 1/18/02, you wrote:
    >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?).
    >...
    >Bill Murdoch
    
    For what it's worth, here is the correspondence between
    WGS72, NAD27 for CONUS (one of numerous NAD27 bases)
    and NAD83 for that general area, as given by the waypoint
    depicted in these datums by the Garmin GPS40:
    
    NAD27 CONUS  N30 16 28.2 W097 44 24.1
    WGS72               N30 16 28.8 W097 44 25.2
    NAD83                N30 16 28.9  W097 44 25.2
    
    
    
    Brian Whatcott
       Altus OK                      Eureka!
    

       
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