NOTE: Assessing Error of Fit Functions for Ellipses

j51 ej . A variety of error of fit (EOF) functions have been proposed for use in the least-square fitting of ellipses. We describe four measures for assessing the suitability of such EOFs, quantifying Thus, many different ellipse estimation techniques detheir linearity, curvature bias, asymmetry, and overall goodpend on a suitable error term, although there has been ness. These measures enable a better understanding to be gained little comparison between them (but see [3, 4, 8]). The of the individual merits of the EOF functions.  1996 Academic Euclidean distance from Xj to the ellipse boundary would Press, Inc. be a good choice for ej , but requires solving a quartic equation which may have up to four solutions, requiring the one with the minimum distance to be determined [10].