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From: Paul Werner (no email)
Date: Tue Oct 14 2003 - 05:06:23 EDT
----- Original Message -----
From: Federico Rossi
To:
Sent: Friday, October 10, 2003 1:39 PM
Subject: least squares method for determining a fix
Hi,
does anybody know the formulas to calculate the error ellipse around the fix obtained with the least squares method?
I've got some formulas that I found on a Spanish site, but they don't explain what is sigma (I suppose a variance) and most of all how to compute it.
The formulas are (a probability of 0.95 is generally considered):
k=sqrt(-2*log(1-probability)
theta=arctan(2*B/(A-C)
a=sigma*k/sqrt(nObs/2+B/sin(theta))
b=sigma*k/sqrt(nObs/2-B/sin(theta))
where: a and b are the axis of the ellipse
nObs is the number of sights
A, B and C are parameters calculated with the least squares method as found in the Nautical Almanac
These formulas only give a and b, what about the orientation of the two axis?
Thanks.
Federico
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