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    Re: "100 Problems in Celestial Navigation"
    From: Joel Jacobs
    Date: 2004 Apr 2, 05:07 -0500

    Since you indicate an error may be the result of estimating the MPP within a
    cocked hat, I am interested in what method you recommend to determine the
    Joel Jacobs
    ----- Original Message -----
    From: "Herbert Prinz" 
    Sent: Friday, April 02, 2004 1:30 AM
    Subject: Re: "100 Problems in Celestial Navigation"
    > 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.
    > Renee,
    > 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
    > 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
    > 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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