NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Averaging
From: Jim Thompson
Date: 2004 Oct 20, 16:52 -0300
From: Jim Thompson
Date: 2004 Oct 20, 16:52 -0300
Fred's observer sextant altitude curves look a heck of a lot prettier what I get from the deck of our boat at anchor on a lunch hook. My R-values certainly are not 0.9999 for a straight line fit! Obviously I need more practice. I think I agree with Bill -- in real life on a small boat I would be happy with averaging 4-5 sights over 5 minutes. My random observational errors are more likely to be much higher than any systematic error owing to nonlinearity in a body's motion, with the exceptions he noted. Jim Thompson jim2@jimthompson.net www.jimthompson.net Outgoing mail scanned by Norton Antivirus ----------------------------------------- > -----Original Message----- > From: Bill > What did this beginner learn from the exercise? > > * Alex and Herbert are correct,the error is more pronounced for high > altitude bodies, and they are unacceptable targets for averaging > except for > all but last-ditch efforts, especially at meridian passage; even if > double-second-differences and problems with the operator holding > the sextant > vertical are discounted. > > * Shy away from averaging a body with a declination within 10d-20d of the > observer's latitude. (If it would have trouble casting a > significant shadow > of the mast on the deck, leave it alone. This is cel nav SOP.
