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    Re: "100 Problems in Celestial Navigation"
    From: Herbert Prinz
    Date: 2004 Apr 2, 01:30 -0500

    Renee Mattie wrote:
    > I'm having problems with "100 Problems"
    > [...] after working the first 6 problems, I am finding myself 5-10 miles
    > away from the
    > author most of the time.
    I reduced problem 1-6 with a computer program and obtained a fix at N 40
    09.6 W 046 5.2 where Gray gets N 40 09 W 46 04.
    A difference of 1 mile in each coordinate is too high to blame it on
    different sight reduction methods. More likely, the difference comes from a
    bad estimate or an arbitrary choice of the MPP (most probable position)
    within the cocked hat. Since the cocked hat consists of 6 lines it is
    difficult to guess the MPP from the geometry of the LOPs.
    However, 5 miles difference indicates an error. I notice that Gray
    specifies index correction, not index error. Did you get this right? A
    confusion of this kind can easily throw you off by 5 miles.
    Post your results for problem 1-6 (DR, intercepts and azimuths of
    individual LOPs), then we can discuss them. Those who think that particular
    sight reduction methods can lead to a result 5 miles off are invited to
    demonstrate them to us so that we can avoid these methods in the future.
    Herbert Prinz

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