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    Re: Problems with AstronavPC
    From: Joel Jacobs
    Date: 2004 Feb 16, 16:29 -0500

    I may be plain dumb, but how would you know in advance that the AP is within
    or without 30NM from the intercept if you hadn't first reduced the sight
    which requires the selection of an AP. Or is this a misunderstanding of
    terms? Isn't it that the AP should be within 30 NM of the DR?
    Joel Jacobs
    ----- Original Message -----
    From: "Jim Thompson" 
    Sent: Monday, February 16, 2004 3:32 PM
    Subject: Re: Problems with AstronavPC
    > I'm new to CN, but isn't the only reason that we try to keep the AP within
    > 30 NM of the intercept for convenience in plotting?  In theory we don't
    > need an AP: with the right tools (electronic would be the only practical
    > way) we just need the GP of the Body, Azimuth to the GP, and co-altitude
    > (distance to the LOP from the GP).  In that special case, the intercept is
    > the co-altitude, which of course tends to be many hundreds or even
    > of miles away from where we are on the celestial LOP.  All a computer
    > have to do is produce data that we need to plot a short segment of the LOP
    > and the intercept on a large-scale plotting sheet; specificaly a reference
    > point on the plotting sheet, a bearing line to draw toward or away from
    > point, and the distance from that point to the LOP along the bearing line.
    > I know -- that "reference point" is the same concept as an AP.  But is
    > any other reason why we need to select an AP relatively close to our real
    > position?
    > Jim Thompson
    > jim2@jimthompson.net
    > www.jimthompson.net
    > Outgoing mail scanned by Norton Antivirus
    > -----------------------------------------
    > > -----Original Message-----
    > > From: Navigation Mailing List
    > > [mailto:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM]On Behalf Of Aubrey
    > > O'Callaghan
    > >
    > > I then placed my initial position nowhere near where I was. After about
    > > iterations it converged to my actual position. I was quite surprised as
    > > had thought that one's initial guess should be approximately where one
    > > (at least within a few degrees).

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