Abstract: An apparatus for identifying surfaces, comprising a point digitizing apparatus for obtaining data points of a surface to be located and an apparatus, such as a memory device, for storing a mathematical model of a model surface. A microprocessor control unit registers the mathematical model and the obtained data points, wherein the microprocessor control unit accomplishes the registration by (i) determining a data point set comprising various points from the obtained data points, (ii) finding a set of closest points comprising, for each point of the data point set, a closest point on the first mathematical model, (iii) registering the data point set to the set of closest points to obtain a registered point set, (iv) computing a mean square distance of points of the registered point set to the closest point set, (v) comparing the mean square distance to a predetermined threshold and (vi) if the mean square distance is above a threshold, (vi.i) redefining the data point set as the registered point set and (vi.