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Subject: Re: Still on LOP's
From: Michael Wescott (wescott_mike@XXX.XXX)
Date: Mon May 06 2002 - 11:44:02 EDT
Bill Murdoch wrote:
> I am still having a hard time with the 25% of the time you are inside
> the cocked hat rule. It just does not 'feel right'. I have played
> around with the Excel spreadsheet map that I mentioned a week or so
> ago, and I can not get the calculations to work like I think they
> should.
> We have been discussing LOPs in two-dimensional (surface) navigation.
> I have what may be a simpler question. What rule applies in
> one-dimensional navigation? Let's say you are a tightrope walker,
> getting nervous, and want to know exactly where you are on the rope.
> You whip out your sextant and with a little skill and calculation plot
> two POPs (points of position). The two POPs are not in the same spot
> (naturally). What is the chance that you are between the two POPs?
> What is the chance that you are to one side of both? What is the
> chance that you are on the other side of both?
Answers: .5, .25, .25
Usual assumptions apply: no "systemic errors", equally probable that error
is + or -. If both are plus, they're both on one side of you. If both are -
then they're both on the other side of you. If #1 is + and #2 is - then
one is one each side. Likewise, if #1 is - and #2 is +. Four equiprobable
possibilities and 2 of the four have you between the POPs: 50% and 1 in
four (25%) for each of the other two possiblities.
--
Mike Wescott
Wescott_Mike@XXX.XXX
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