This part of ISO 15530 specifies the evaluation of measurement uncertainty for results of measurements obtained by a CMM and by using calibrated workpieces. It provides an experimental technique for simplifying the uncertainty evaluation of CMM measurements, whose approach (substitution measurements) leads to measurements being carried out in the same way as actual measurements, but with calibrated workpieces of similar dimension and geometry instead of the unknown workpieces to be measured. Non-substitution measurements on CMMs are also covered, as are the requirements of the uncertainty evaluation procedure, the measurement equipment needed, and the reverification and the interim check of the measurement uncertainty. NOTE The evaluation of measurement uncertainty is always related to a specific measuring task.