Method for scanning the surface of a workpiece

A measuring system for measuring a surface, the system comprising:

• a coordinate positioning apparatus;
• a probe head mounted on the coordinate positioning apparatus;
• and
• a surface sensing device, including a portion mounted to the probe head, the surface sensing device measuring the position of the portion relative to the surface, the probe head including at least one drive for rotating the surface sensing device about at least one axis, wherein
• the coordinate positioning apparatus is configured to move the probe head relative to the surface,
• the probe head is configured to be driven to rotate the surface sensing device about the at least one axis in order to control a deflection or offset vector of the surface sensing device along a vector relative to the surface to within a predetermined range in real time while scanning along the surface,
• the surface sensing device is configured to be scanned along the surface by driving it with at least the probe head in at least one rotational axis along a drive vector, and
• the drive vector is in a direction in which the surface sensing device is driven along the surface, the drive vector being generally tangent to the surface at an instantaneous position of said portion of the surface sensing device, and the drive vector being controlled by at least one drive that drives only the probe head, the at least one drive adjusting the drive vector based on real-time feedback which is determined from the deflection or offset vector.