Every measurement of dimensions such as size, angle, radius, form and position on workpieces is subject to a certain measuring uncertainty. The entire measuring process including the machine technology, the attributes of the part, the geometry of the features measured, the environment and the operator all influence the magnitude of this measuring uncertainty.The geometry of the features has an especially strong influence on the results of real measurements. Thus, using identical machine technology, the radius of a sector, for example, can be measured much less accurately than that of a full circle. When measuring angles or axis directions, the length of the sides are calculated directly into the measuring uncertainty (Fig. 54).