摘要:This study is devoted to comparing the most popular circle fits (the geometric fit, Pratt’s, Taubin’s, Kåsa’s) and the most recently developed algebraic circle fits: hyperaccurate fit and HyperLS fit. Even though hyperaccurate fit has zero essential bias and HyperLS fit is unbiased up to order $\sigma^{4}$, the geometric fit still outperforms them in some circumstances. Since the first-order leading term of the MSE for all fits are equal, we go one step further and derive all terms of order $\sigma^{4}$, which come from essential bias, as well as all terms of order $\sigma^{4}/n$, which come from two sources: the variance and the outer product of the essential bias and the nonessential bias.