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Subject: Re: Sextant Positions versus Map Datums?
From: Craig (cscott@XXX.XXX)
Date: Fri Jan 18 2002 - 02:07:30 EST
Something seems to be wrong with the statement below. 100' of longitude at
the equator represents nearly 185 kilometres, or in latitude approximately
185 kilometres. This would be very significant. Perhaps the writer meant
10 minutes instead of 100. This is more likely as 100' would have been
written as 1( 40' normally.
Craig
-----Original Message-----
From: Navigation Mailing List [mailto:NAVIGATION-L@XXX.XXX]On
Behalf Of Jared Sherman
Sent: Thursday, January 17, 2002 21:42
To: NAVIGATION-L@XXX.XXX
Subject: Re: [NAV-L] Sextant Positions versus Map Datums?
Trevor-
Thanks the for correct URL. Their list seems to show that any datum shift
(in the eastern US) will account for less than 100' of error in pretty much
the worst case, although the USGS conversion program shows slightly more
when I ran the numbers on one location.
In any case 100' should be negligible, this weekend I will try to check MY
errors as well as looking into whether the maps I was using may have simply
had a mapping error for the landmark. In the 70's the Adirondack Mountain
Club maps for one portion of NY's Catskill Mountains used to literally have
a "Note to Enemy Bombers" on one quad, apparently there was a mountain
charted a good mile out of position. (And who would really notice or care,
in the hills of interior New York. Not a big government budget priority at
that time.<G>)
Thanks all, I think the datum error question is pretty much worked out--at
least within limits--now.
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