Abstract: A data processing system and method obtains a three dimensional representation of an object with complex and unique geometry, using a sampling probe having a tip for tracing the surface of the object. Electrical signals are received which are indicative of the position of the tip of the probe. An origin is determined with reference to the object. A plurality of distances, each distance corresponding to a given direction from the origin, is stored in a device addressable by the given direction to store and to retrieve a corresponding distance. The direction and distance of the probe tip with reference to the origin in response to a received signal. The determined distance is compared to any stored distance corresponding to the determined direction. The determined distance is stored when it is less than any stored distance. The probe tip position may be displayed as a projection on a reference surface which surrounds the origin.