Re: [OpenMap Users] How to calculate focal points of an OMEllipse?

Hi Jeoff,

I think those points are in the algorithm in OMEllipse, but they are
pretty obscured by the algorithm. Looking at the algorithm on the page
you provided, it looks pretty simple to implement that alorithm.
You'll have to use the GreatCircle class and work in lat/lon space, but
the idea is the same as on the page. The OMEllipse already has the
parameters.

- Don

On Mar 31, 2004, at 9:40 AM, Wilks wrote:

> OMEllipse is constructed using a LatLonPoint, major/minor axes, and
> rotation
> angle.
>
> Once constructed, does anyone know how I can get the coordinates
> (LatLonPoint, Geo, etc.) of the two Focal points?
>
> I'm looking for the foci F and F' as represented in the diagrams here:
> http://www.geocities.com/thesciencefiles/ellipse/facts.html
>
> The above web page explains how to get the focal points for a simple
> ellipse
> centered over a Cartesian origin, but I am getting tripped up by the
> intricacies of the real-world ellipse's properties such as rotation
> angle,
> and the fact that it's on a spherical surface.
>
> Any help would be appreciated. Even if someone can walk me through an
> algorithm, that I could implement by extending OMEllipse, that would
> be very
> helpful.
>
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