NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Sextant Positions versus Map Datums?
From: Craig Scott
Date: 2002 Jan 18, 12:08 AM
From: Craig Scott
Date: 2002 Jan 18, 12:08 AM
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@LISTSERV.WEBKAHUNA.COM]On Behalf Of Jared Sherman Sent: Thursday, January 17, 2002 21:42 To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM 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.) Thanks all, I think the datum error question is pretty much worked out--at least within limits--now.