Théorie de l'erreur de circularité

This report gives the theory of the circularity error, as defined by ISO-norms, that is, the minimum of the radius difference between two concentric circles that enclose the measured curve. The common center of the optimal pair of circles being called the best center, the question of its existence is fully discussed. It is then proved that this problem is equivalent to the research of a circle which is the best approximation of the given curve by respect of a uniform norm. A characterization of the best center is developed, from which the unicity of the best center is proved.