Geometrical Product Specifications (GPS) — Acceptance and reverification tests for coordinate measuring machines (CMM) — Part 6: Estimation of errors in computing Gaussian associated features

This part of ISO 10360 is a geometrical product specification (GPS) standard and is to be regarded as a general GPS standard (see ISO/TR 14638). It influences link 5 of the chains of standards on size, distance, radius, angle, form, orientation, location, run-out and datums. For more detailed information of the relation of this part of ISO 10360 to other standards and the GPS matrix model see annex B. Coordinate measurement technology is widely used in industrial metrology to assess features of a workpiece. A common requirement is to fit an associated feature to a data set consisting of coordinate measurements of a real feature. This fitting is carried out by software. Software for calculating an associated feature provides values of parameters of the associated feature that are descriptive of the size, shape, location and orientation of the feature. These parameters are useful — for the purpose of carrying out calculations involving the feature, often in conjunction with other associated features and other information, and — in determining the extent to which a workpiece satisfies dimensional and positional specifications. The reliability of information about features that is determined from associated features is influenced by the quality of the software for computing these features. The tests defined in this part of ISO 10360 are concerned with assessing the correctness of the parameters of computed associated features as measured by a coordinate measuring machine (CMM) or other coordinate measuring system. Although different criteria may be used to compute associated features, for example, by minimizing the Euclidean or Chebyshev norm of residuals, this test is applicable for software designed for unconstrained Gaussian (least-squares) features. In the case of reverification tests of CMMs, the software test of this part of ISO 10360 usually does not provide new or different information in comparison with that obtained by an acceptance test, since software is supposed to be stable over time. However, a reverification test of the software may be useful following possible corruption or alteration of the software under test. For software already in existence, the evaluation of the performance may not be obtained only by fulfilling the requirements of this part of ISO 10360. However, such cases do not necessarily exclude the ability of the software to perform correct computation of measurements. This part of ISO 10360 is applicable to software submitted for test in respect of the values it provides for the parameters of an associated feature. The test procedure is based on applying the software under test to reference data sets, and comparing the results obtained with reference results.