NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Latitude by Lunar Distance
From: George Huxtable
Date: 2006 Nov 13, 15:52 -0000
From: George Huxtable
Date: 2006 Nov 13, 15:52 -0000
In reply to my explanation, that it was unjustified to claim that averaging 4 observations resulted in a halved error, except when those observations were statistically independent, Frank Reed replied- | It is no "assumption", George. It works in practice, again and again. Or I | should say, it works 'for me' again and again, and that's why I recommend it. | Also, in the log books of vessels from the early 19th century, you frequently | find references to averaging four or more observations. This was standard | historical practice. Averaging four such observations will certainly do no harm, and I did not, and do not, criticise such a practice. It will reduce, to some extent, the resultant error, depending on what part of the error was random, and what part of the error repeats each time. However, unless any systematic component is entirely lacking, Frank's claim that the error will be halved remains invalid. And we have seen, by examining the origins of such errors, that much of the overall error is systematic, and will repeat, exactly the same, from one shot to the next. That part of any overall error is not reduced by averaging successive observations. Frank is not immune from the laws of statistics. George. contact George Huxtable at george@huxtable.u-net.com or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---