Malcolm, Deepak,
5 points are the minimum required to uniquely define an ellipse (see
http link below)
A few years ago I tested various ellipse fitting algorithms (written up
in JSG somewhere). The 3 point analytical method I tested (DePaor 1988)
is the least accurate with large axial ratios and the most susceptible
to noise in the data. However, it is simple and fast and will work fine
with good quality data and low axial ratios (<6).
Regards
Tim Wynn
http://users.cs.cf.ac.uk/Paul.Rosin/resources/papers/ellipse3.pdf
DePaor, D.G., 1988. Strain determination from three known stretches-an
exact solution. Journal of Structural Geology 10, 639-642
-----Original Message-----
From: Tectonics & structural geology discussion list
[mailto:[log in to unmask]] On Behalf Of Malcolm McClure
Sent: 07 July 2009 16:43
To: [log in to unmask]
Subject: Re: Free Data Graphing, Animation, and Analysis Software
Deepak:
ACD systems Canvas 9.0.4 has a 3 point circle fitting option. 3
points may not be enough to define an unique ellipse.
Regards
Malcolm.
|