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    Re: Systematic Error (LOPs revisited)
    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" 
    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
    > > >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
    > > 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

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