A method of building up a measurement data set for a surface of an object using an analog measurement probe mounted on a machine tool apparatus which obtains scanned measurement data of the surface over a plurality of offset traverses. Subsequent traverses are offset from previous traverses such that over a series of traverses the analog probe's surface detecting region progresses i) laterally across the object, and/or ii) away from or towards the object. The course of relative motion for at least one subsequent traverse is generated and/or updated based on data obtained during at least one previous traverse.