Next message: Jim Thompson: "Re: Navigational computers"
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
www.jimthompson.net
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