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    Re: Sextant Positions versus Map Datums
    From: Rodney Myrvaagnes
    Date: 2002 Jan 21, 5:20 AM

    Did you locate the water tower by bearings on the other landmarks? If you 
    describe exactly what you did, someone on the list might
    be able to locate some of the other 90%. As we saw both on converted charts 
    near NYC and the Corpscan program you used,, the
    datum difference hardly accounts for any of it.
    You don't need a pre-WAIS GPS. You can just turn off the WAIS feature if you 
    don't want to use it. Then you will have all 12
    channels working normally. Turning it off will increase the area in which the 
    fix wanders but won't change its center as long as SA
    remains off, so I am not sure what the point would be.
    On Sun, 20 Jan 2002 23:21:52 -0500, Jared Sherman wrote:
    >Incidentally--carefully locating the Jones Beach Water Tower on my 1985 NAD27 
    1:20,000 chart shows it to be located 0.3nm
    away from the current position of the tower that is given in the 
    http://www.ngs.noaa.gov/cgi-bin/ds_mm.prl reference list.
    >So infosofar as that particular area, more than 1/10th of my position error 
    appears to come from the landmarks being shown in the
    wrong place. 1/10th down, 9/10th's more to go. It will be interesting to 
    take a (pre-WAAS) GPS to the three area benchmarks
    that are accessible and see how well it compares.
    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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