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Herbert,

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
MPP?

Joel Jacobs


----- Original Message -----
From: "Herbert Prinz" 
To: 
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
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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