NavList:

   

Reply

Hewitt Schlereth wrote-

| George, it looks like I may have misunderstood the document I got the
| (nearly) equal AM/PM altitudes from. I thought it was your spreadsheet
| and cited it's designation - LONG AROUND NOON.XLS (SS) - in the
| worksheet I attached to my e-mail. The numbers I used were from that
| document - which I took to be yours. They looked mighty like sextant
| altitudes; so, certainly not random numbers generated by me.
|
| Maybe my worksheet didn't come through to the List?  Here it is again.

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

Hewitt and I have got ourselves at cross-purposes, it seems.

I had produced 20 simulated sets of "perturbed" sextant altitudes, each of
13 observations taken at regular intervals around noon. These were offered
so that list-members could analyse them in any way they chose, to try to
discover the original latitudes and longitudes on which they were based,
information which I withheld. The table was attached to [7940] as
noon1a.rtf, or (the same data), attached to [7959], as noon1a.doc .

In case anyone wanted to see how that data had been generated, I also added
the Excel spreadsheet, that generated those data sets.. Each time that
spreadsheet is run, (or when button F9 is pressed), a new set of random
numbers is generated, which creates a new, unique set of perturbed
altitudes. I hadn't intended anyone to use that spreadsheet itself to
generate those sets of altitudes, but there's nothing wrong with doing so;
indeed, that's what Dave Walden did, generating 1000 such sets to look for
the scatter.

Hewitt has done the same, but has generated only one such data-set, which
has given an answer which Hewitt tells is is within 1' of the intial value.
To which I suggest that if that is the case, it's only so as the result of a
fluke, and will not be repeatable.

If Hewitt will kindly load and run that Excel program again, it will invent,
this time, a completely new set of 13 altitudes, showing a similar general
shape but differing in every detail. And if he analyses the new set as he
did before, he will, I suggest, get a very different answer. Every time he
presses F9, it will change again.

However, having satisfied himself on that score, he could usefully apply
whatever technique he chooses, to one or more of the data sets attached to
those messages cited above, also attached here. The first two sets, only,
provide that original data. For the other 18, only I know the original lat
and long from which the data set has been constructed.

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.

--~--~---------~--~----~------------~-------~--~----~
Navigation List archive: www.fer3.com/arc
To post, email NavList@fer3.com
To , email NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---

   

Reply