Abstract: A method and apparatus is disclosed for measuring the volumetric accuracy during machine operation of a machine having machine members. The method follows the steps of measuring the machine prior to machine operation using traditional methods, mounting sensors on the machine members and calibrating the sensors to a zero position. Each sensor location is correlated to a physical location of a measured geometry point on the machine member. The angular change of the machine members is measured continuously at each sensor location during machine operation. The machine measurements taken by traditional methods prior to machine operation are compared with sensor measurements taken at all times including during machine operation to determine any changes in machine geometry and to calculate tool path error.