Find Ellipse Centre with three points and radius known

Hi,

I am doing a measurement of a cylindral object with might be standing veticle or tilted. A device shoots a laser and takes measurement of (HA,VA,and length from device to the point) by this process three points are measure along top cylindrical object and so on for bottom. The radius of pile is known, now i want to find center for ellipse with measurements of three points as (x1,y1),(x2,y2),(x3,y3) and radius. how can i achieve that?

Re: Find Ellipse Centre with three points and radius known