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Joel,  I think maybe you misunderstood me, which means that I did not
explain myself well.

My thinking is that in standard CN we pick an AP (either our DR position or
a rounded AP position) close to where we think we are, and then reduce the
sight relative to that AP.

In the special case I described, the navigator does not need an AP nearby,
if they have a way to plot a 2,000 mile co-altitude (distance to GP).

Does that make more sense?

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 Joel Jacobs
>
> 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?
>
> ----- Original Message -----
> From: "Jim Thompson" 
> > 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
> even
> > 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
> thousands
> > of miles away from where we are on the celestial LOP.  All a computer
> would
> > 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
> that
> > 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
> there
> > any other reason why we need to select an AP relatively close
> to our real
> > position?
> >
> > > -----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
> 3
> > > iterations it converged to my actual position. I was quite
> surprised as
> I
> > > had thought that one's initial guess should be approximately where one
> is
> > > (at least within a few degrees).

   

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