The geometric least squares circle through points pᵢ is the centre c and radius r that minimise S(c, r) = ∑(|pᵢ − c| − r)², the total area of the squares on the radial residuals. Setting ∂S/∂r = 0 makes r the mean distance |pᵢ − c|, and ∂S/∂c = 0 balances the