How to find center and radius of hand-drawn circle? You are given a set of points {(X1,Y1), (X2,Y2),...}  which represent a hand-drawn circle, so it's not perfect. You are asked to find the center and radius of this circle.
My intuition tells me this involves minimization, and I need to find the coefficients in a non-linear generalized least squares model. Am I not thinking of a simpler or more "proper" approach?

You can use a trick to make this a regular least-squares optimization, in an extension of the method for finding the center of a circle through three points. Draw a perpendicular bisector for every pair of points. If the points are all on a circle, they will all intersect at a common point; since it is an approximate circle, they will slightly miss each other. The squared distance to each line is a quadratic form, so the sum of the squared distances is also a quadratic form, and minimizing this is a least-squares problem. That's the center of the circle.
Given this, you can just find the radius as the mean of the distances of each point to the center.
