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A method of measuring an artifact using a machine on which a measuring probe is mounted. The method has the following steps: determining the approximate position of one or more points on the surface of the artifact; using this approximate position to drive at least one of the probe and artifact to o

A method of measuring an artifact using a machine on which a measuring probe is mounted. The method has the following steps: determining the approximate position of one or more points on the surface of the artifact; using this approximate position to drive at least one of the probe and artifact to one or more desired relative positions of the probe and the surface and taking one or more surface measurements of said point on the surface of the artifact at said location, wherein there is no relative movement between the probe and the artifact whilst the one or more surface measurements are taken; and using data from the measurements to determine a position of the one or more points on the surface in which dynamic error is substantially reduced.

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The invention claimed is: 1. A method of measuring an artefact using a machine on which a measuring probe is mounted for relative movement with respect to the artefact, said machine having at least one measuring device for providing an output indicative of the relative position of the probe, the pr

The invention claimed is: 1. A method of measuring an artefact using a machine on which a measuring probe is mounted for relative movement with respect to the artefact, said machine having at least one measuring device for providing an output indicative of the relative position of the probe, the probe having at least one measuring device to provide one or more probe outputs which in combination with the machine output are indicative of the position of a point on the surface of the artefact, the method having the following steps in any suitable order: (a) determining the approximate position of one or more points on the surface of the artefact; (b) using the approximate position determined in step (a) to drive at least one of the probe and artefact to one or more desired relative positions of the probe and the surface and taking one or more surface measurements of said one or more points on the surface of the artefact at said position, wherein there is no relative movement between the probe and the artefact whilst the one or more surface measurements are taken; and (c) using data from step (b) to determine a position of the one or more points on the surface in which dynamic error is substantially reduced. 2. A method according to claim 1 wherein the approximate position of a point on the surface is determined by taking one or more readings with a measurement probe. 3. A method according to claim 2 wherein the one or more readings is taken whilst there is relative movement between the probe and the surface. 4. A method according to claim 2 wherein the one or more readings is taken whilst the probe is stationary relative to the surface. 5. A method according to claim 2 wherein the measurement in step (b) is taken with the probe at a position closer to the surface than the measurement in step (a). 6. A method according to claim 2 wherein the approximate position of a point on the surface is determined by taking two or more readings with a measurement probe, said readings being taken at different stylus deflections, probe forces or probe stand-offs and the data relating to said two or more readings is extrapolated to determine the approximate position. 7. A method according to claim 6, wherein the probe is a linear probe and measurement data is obtained from two or more positions. 8. A method according to claim 6 wherein the probe is a non linear probe and wherein the measurement data is obtained from three or more positions. 9. A method according to claim 1 wherein the probe has a deflectable stylus, and wherein the surface measurement in step (b) is taken at a low stylus deflection. 10. A method according to claim 1 wherein the probe has a deflectable stylus, and wherein the surface measurement in step (b) is taken at a low probe force. 11. A method according to claim 1 wherein the probe comprises a non-contact probe, and wherein the surface measurement in step (b) is taken at a favorable stand-off. 12. A method according to claim 1 wherein the step of taking one or more surface measurements whilst there is no relative movement between the probe and the artefact comprises recording a plurality of surface measurements and taking an average of the surface measurements. 13. A method according to claim 1 wherein step c) comprises extrapolating data from two or more surface measurements, said two or more surface positions having different stylus deflections, probe forces or probe stand-offs. 14. A method according to claim 13 wherein at least one of said two or more surface measurements is obtained from step a). 15. A method according to claim 1 wherein the step of determining the approximate position of a point on the surface of the artefact in step (a) is done by taking one or more surface measurements of the point on the surface of the artefact, wherein the one or more surface measurements of step (a) are taken whilst there is relative motion between the probe and artefact at constant speed; and wherein the one or more measurements in step a) and step b) have the same probe deflection, probe force or stand-off and wherein the difference in the measurements in steps a) and b) enables the dynamic error to be determined. 16. A method according to claim 15 wherein the method includes the further step (d) of taking one or more surface measurements, wherein the one or more surface measurements are taken when there is relative motion between the probe and artefact at constant speed and wherein the probe deflection or force is lower than in steps a) and b) and wherein the one or more surface measurements taken in the step (d) at the lower probe deflection or force are corrected for dynamic error. 17. A method of measuring an artefact using a machine on which a measuring probe is mounted for relative movement with respect to the artefact, said machine having at least one measuring device for producing an output indicative of the relative position of the probe, the probe having at least one measuring device to provide one or more probe outputs which in combination with the machine output are indicative of the position of a point on the surface of the artefact, the method having the following steps in any suitable order: (a) taking two or more surface measurements of a point on the surface of the artefact, wherein the measurements are taken whilst there is no relative movement between the probe and the artefact, the two or more surface measurements being collected at different probe forces, stylus deflections or probe stand-off, (b) determining the position of said point on the surface of the artefact by extrapolating said two or more surface measurements. 18. A method according to claim 17 wherein the probe has a deflectable stylus, wherein said two or more surface measurements taken in step (a) are collected with the probe having different stylus deflections, and wherein, in step (b), said two or more surface measurements are extrapolated to correspond with the rest position of the stylus. 19. A method according to claim 17 wherein the probe has a deflectable stylus, wherein said two or more surface measurements taken in step (a) are collected with different probe forces between the stylus and the surface of the artefact; and wherein, in step (b), said two or more surface measurements are extrapolated to correspond with zero probe force. 20. A method according to claim 17 wherein the probe comprises a non-contact probe, wherein said two or more surface measurements taken in step (a) are collected with the probe at different stand-offs from the surface of the artefact, and wherein, in step (b), said two or more surface measurements are extrapolated to determine the surface position. 21. A method according to claim 17 wherein the probe is a linear probe and measurement data is obtained from two or more positions. 22. A method according to claim 17 wherein the probe is a non-linear probe and wherein the measurement data is obtained from three or more positions. 23. A method according to claim 17 wherein the step of taking two or more surface measurements whilst there is no relative movement between the probe and the artefact comprises recording many surface measurements and taking an average of the surface measurements. 24. A method of measuring an artefact using a machine on which a measuring probe is mounted for relative movement with respect to the artefact, said machine having at least one measuring device for providing an output indicative of the relative position of the probe, the probe having at least one measuring device to provide one or more probe outputs which in combination with the machine output are indicative of the position of a point on the surface of the artefact, the method having the following steps in any suitable order: (a) taking two or more surface measurements of a point on the surface of the artefact, wherein said two or more measurements have the same probe deflection or probe force and wherein one or more surface measurement is taken with relative motion between the probe and artefact at constant speed and one or more surface measurement is taken with no relative motion between the probe and artefact; (b) determining the dynamic error from step (a) (c) taking one or more surface measurements of said point on the surface of the artefact, wherein the measurement is taken with a smaller probe deflection or probe force than the measurements in step (a) and wherein the measurement is taken with relative motion between the probe and artefact at constant speed; (d) correcting the one or more surface measurements of step (c) for dynamic error to thereby provide a measurement having reduced static and dynamic errors. 25. Apparatus for measuring an artefact using a machine on which a measuring probe is mounted for relative movement with respect to the artefact, said machine having at least one measuring device for providing an output indicative of the relative position of the probe, the probe having at least one measuring device to provide one or more probe outputs which in combination with the machine output are indicative of the position of a point on the surface of the artefact, the apparatus comprising a controller for carrying out the following steps in any suitable order: (a) determining the approximate position of one or more points on the surface of the artefact; (b) using the approximate position determined in step (a) to drive at least one of the probe and artefact to one or more desired relative positions of the probe and the surface and taking one or more surface measurements of said point on the surface of the artefact at said location, wherein there is no relative movement between the probe and the artefact whilst the one or more surface measurements are taken; and (c) using data from step (b) to determine a position of the one or more points on the surface in which dynamic error is substantially reduced. 26. Apparatus for measuring an artefact using a machine on which a measuring probe is mounted for relative movement with respect to the artefact, said machine having at least one measuring device for producing an output indicative of the relative position of the probe, the probe having at least one measuring device to provide one or more probe outputs which in combination with the machine output are indicative of the position of a point on the surface of the artefact, the apparatus comprising a controller for carrying out the following steps in any suitable order: (a) taking two or more surface measurements of a point on the surface of the artefact, wherein the measurements are taken whilst there is no relative movement between the probe and the artefact, the two or more surface measurements being collected at different probe forces, stylus deflections or probe stand-off, (b) extrapolating the measurement data to that corresponding to the position of said point on the surface of the artefact. 27. Apparatus for measuring an artefact using a machine on which a measuring probe is mounted for relative movement with respect to the artefact, said machine having at least one measuring device for providing an output indicative of the relative position of the probe, the probe having at least one measuring device to provide one or more probe outputs which in combination with the machine output are indicative of the position of a point on the surface of the artefact, the apparatus comprising a controller for carrying out the following steps in any suitable order: (a) taking two or more surface measurements of a point on the surface of the artefact, wherein said two or more measurements have the same probe deflection or probe force and wherein one or more surface measurement is taken with relative motion between the probe and artefact at constant speed and one or more surface measurement is taken with no relative motion between the probe and artefact; (b) determining the dynamic error from step (a) (c) taking one or more surface measurements of said point on the surface of the artefact, wherein the measurement is taken with a smaller probe deflection or probe force than the measurements in step (a) and wherein the measurement is taken with relative motion between the probe and artefact at constant speed; (d) correcting the one or more surface measurements of step (c) for dynamic error to thereby provide a measurement having reduced static and dynamic errors.