Variety of applications. The need of fitting circles or circular arcs to observed points arises in many areas. In medicine, one estimates the diameter of a human iris on a photograph [141] or designs a dental arch from an X-ray [21]. Archaeologists examine the circular shape of ancient Greek stadia [157] and mysterious megalithic sites (stone rings) in Britain [65, 177]; in other studies they determine the size of ancient pottery by analyzing potsherds found in field expeditions [44, 80, 81, 190]. In industry, quality control requires estimation of the radius and the center of manufactured mechanical parts [119] (other interesting applications involve microwave engineering [54, 169] and the lumber industry [13]).