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    Re: How accurate are fixes in practice?
    From: Frank Reed
    Date: 2008 Jul 13, 14:34 -0400

    Jeremy, you wrote:
    "My normal Celnav fixes are usually within 3 nm and I am disappointed by
    worse results.  Sunlines are usually within 1 nm when I use the GPS fix as
    the AP, as are LAN observations."
     From anecdotal evidence consisting of conversations with ocean navigators,
    this appears to be about normal for observations under "good conditions"
    with a good metal sextant and no shortcuts in sight reductions. The standard
    deviation error in individual sights (judging from the offset of LOPs from a
    GPS position) appears to be roughly 1 minute of arc, implying that about
    two-thirds of LOPs are within 1 nautical mile. The distribution appears to
    have some "kurtosis" meaning that there's more likelihood of larger errors
    than a plain normal (Gaussian) distribution would imply, but it's
    So what are "good conditions"?
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