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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 23, 04:52 -0300
From: Jim Thompson
Date: 2004 Oct 23, 04:52 -0300
Alex, thanks for the review. I found it hard to follow all the many messages in this thread, so obviously I missed some consensus-making. Please see questions below. > -----Original Message----- > From: Alexandre Eremenko > On Fri, 22 Oct 2004, Jim Thompson wrote: > > 2. Use either the raw sextant observations, > > or reduce each observation and > > use the reduced set. > > If you reduce each observation, there is no point > in averaging them. > And there is no point in taking them in a short time > interval. Is that not true only if the navigator plots all the acceptable-looking sights and then uses a plotting method to find the center of the sights? Alternatively, why not average themm arthmetically, and then plot that single average, as the single best estimate? Seems to me that saves plotting 3-5 separate LOP's. > > 1. The body is very likely to be changing > > altitude in a nonlinear fashion. > > Just vice versa: very UNLIKELY. > Namely: ONLY when near the meridian on high altitude. > In all other cases it is linear for all practical purposes. I thought that, strictly speaking, the bodies all move in a non-linear fashion, however our ability to detect that non-linearity throughout most of the celestial "window" with a sextant is very limited, so to all intents and purposes their movement can be considered linear over short time durations of observation. Jim Thompson jim2@jimthompson.net www.jimthompson.net Outgoing mail scanned by Norton Antivirus -----------------------------------------