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Andres has quoted the relevant page from the AstronavPC manual, that I
referred to in my own posting. Was that from the same edition as mine,
2000-2005, or a later edition? I'm interested to discover whether the text
has changed since, or not.

Andres has produced some nice illustrative plots of fits to position lines,
and the resulting confidence-ellipses..

He ends by showing a series of LOPs, taken at intervals from a single body,
stating-

"An example of a rapid fix, the algorithm is very robust.

 See [NavList 5168] Series of Sun sights in relatively rapid succession"

=================

His posting [5168] was in response to posting [5129] from Frank in May 08,
which asked-

"By the way, have you ever considered the general problem of taking a series
of Sun sights in relatively rapid succession (at an arbitrary time of day,
not necessarily around noon)? For example, suppose it's 1500 local time. If
I take ten sights over half an hour, what kind of position fix can I get?
This is a generalization of the "sights around noon" problem. There's no
easy graphical solution but it's similar in other respects.

================

Somehow, I doubt whether that plot from Andres, which appears to have been
of observations taken at intervals of half-an-hour over a period of 4 or 5
hours, was what Frank had in mind when he made that proposal. It would be
interesting if Andres would repeat that exercise, showing the group of LOPs
that results if Frank's proposal is followed, of ten sights over half an
hour, around 1500 hours. Frank doesn't provide all necessary details, but we
could just choose representative values such as 0 degrees dec, and 45
degrees latitude.

I wonder if the algorithm would look quite so robust then, in providing a
"fix".

George.

contact George Huxtable, at  george@hux.me.uk
or at +44 1865 820222 (from UK, 01865 820222)
or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.

   

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