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Subject: Accuracy of Altitude sighting at Sea
From: Dr. Geoffrey Kolbe (geof@XXX.XXX)
Date: Sat Oct 23 1999 - 04:37:24 EDT
Thankyou to everyone who replied to this question.
The consensus seems to be that the standard deviation of an altitude
sighting at sea is, at best, about two minutes. Put another way, when a
line of position is drawn on a chart as a result of a sighting, the
experienced navigator will actually treat this as a "band of position"
about 4 miles wide, and would expect his vessel to be somewhere on that band.
I have to say, I was a little surprised at this. It means that one is
hardly justified in buying a C.Plath Navistar sextant, when for a 50th of
the price one can buy a Davis Mk 3 plastic sextant and not really be
compromised by its comparative crudeness and simplicity!
I read recently that the US Naval Academy has now stopped teaching
Celestial Navigation, much to the relief of the cadets who found this to be
the hardest subject, along with electrical engineering! However I was
surprised when reading the piece that when they had done Celestial
Navigation, the acceptance level of skill was that the cadet should be able
to find his position to within 3 miles. However, this seems to be quite in
accord with the consensus of this list.
Thanks again,
Geoffrey Kolbe.
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