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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Systematic Error (LOPs revisited)
From: Peter Fogg
Date: 2003 May 29, 10:27 +1000
From: Peter Fogg
Date: 2003 May 29, 10:27 +1000
Bill's on the money! It seems to me that this is the key to understanding the whole process. Any number of intersecting LOPs are a succession of intersections involving 2 lines. With a triangle there are 3 bisectors of these 3 intersections, when extended they meet at a point. Keep going ... Sorry about the "quadrant" error. My understanding was that this means an area divided into 4 parts but it seems that it only refers to 4 equal parts. You live and (hopefully) learn ... George Bennett has flown the coop, flying out today. By co-incidence, I shall soon be following in the same general direction, off to France for most of June to visit family, although I am also looking forward to renewing my aquaintance with the northern celestial sphere. My extended family, if you will ... I don't think this is altogether a bad thing. Anybody interested in this technique needs time to draw his own diagrams and think about them. I know only too well from experience that learning new and unfamiliar ideas can be a painful, slow, and frustrating process. Just as well its worth it, apart from anything else it keeps our brains young. ----- Original Message ----- From: "Noyce, Bill"To: Sent: Thursday, May 29, 2003 1:23 AM Subject: Re: Systematic Error (LOPs revisited) > Peter Fogg: > > >Lets start with those 2 intersecting LOPs. If there is a systematic error > > >then it will be either towards the direction of the 2 azimuths or away. > > George Huxtable: > > Sorry, but I'm lost already. Presumably Peter is discussing here LOPs from > > compass bearings of landmarks. > > I think the later discussion makes clear that Peter is discussing > LOP's from celestial observations. In that case, if you draw > an arrow from each LOP, toward the body observed, then one "quadrant" > has both arrows pointing to it, one has both arrows pointing away, > and two "quadrants" have a mismatch. If the errors in the two > observations have the same sign, then the true position must be > in one of the two matching quadrants; if the errors are equal, > the true position must be on the angle bisector that passes through > these two quadrants. > > Of course, in the two-observation case, there's no information to > estimate whether systematic errors are likely. > > -- Bill >