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Hi
Just joined into this topic
IF I understand your question ,the term is called "Equal  Altitudes at
Noon". This is NOT a fix per se but an E.P. (estimated position).

Haste make  waste and I just hope that I've properly grasped your question.

himself

-----Original Message-----
From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf
Of frankreed@HistoricalAtlas.net
Sent: June 3, 2008 8:42 AM
To: NavList@fer3.com
Subject: [NavList 5255] longitude around noon (a twist)


I made one last try at convincing George Kaplan (a name some of you know) to
join us in Mystic this week, but alas, it's not in the cards.

While I was at it, I chatted in my email a bit about longitude around noon
and asked him this:
 "Which leads to a question: is there an established name in the literature,
or even in your own jargon, for a fix resulting from a series of ten or
twelve sights taken over a relatively short period of time? I've been
calling it a "rapid-fire fix". Do you know another name?"

His reply:
 "I don't know of a special name.  You're correct, of course, if you can get
a bunch of sights on either side of noon, you can get good enough geometry
to get a 2-D position.  It works with the LOPs, too, in that they provide a
good spread of azimuth around then.  There is a slight catch, however, and
that is, the higher the Sun is in the sky (and therefore the more rapid the
altitude and azimuth change near noon) the more you have to worry about the
curvature of the LOPs.  In some near-degenerate cases (sun within several
degrees of the zenith), the usual straight-line plotting -- or math that
assumes straight-line LOPs -- may not provide the right fix."

That's a good point about sights very close to the zenith. I had mentioned
previously on the list that there may be a special case when the Sun is
close to the zenith. I still haven't thought through whether it really
screws up the graphical technique or merely requires more stringent rules
for its application.

 -FER







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