Method and device for determining the change in an object

A computer program embodied on a machine readable medium for determining a change in a first object, which in an initial state said first object is connected to a second object via a joint, wherein a first reference system is rigidly connected to the second object and a non-invasive coupling device couples a second reference system to the first object, comprising:

• code that ascertains and/or stores, prior to separation of the first object from the second object at the joint, a first location corresponding to a location of the second reference system relative to the first reference system, and a second location corresponding to a location between at least one reference point on the first object relative to the first reference system;
• after the first object has been altered, code that directs the re-assembly of the joint between the altered first object and the second object, wherein the first location is used to align the altered first object to the second object;
• code that after alignment, ascertains or stores a third location corresponding to a location of the at least one reference point relative to the first reference system;
• and
• code that determines the dimensional change in the first object due to the alteration based on a change in location between the second location and the third location of the at least one reference point.

A device for determining a dimensional change of a first object, which in an initial state is connected to a second object via a joint, comprising:

• a first reference system directly couplable to the second object;
• a second reference system non-invasively couplable to the first object;
• a trackable pointer instrument for determining a position of at least one characteristic point;
• and
• a navigation system for detecting positions of the first reference system, the second reference system, and the pointer, wherein said navigation system is configured to compare detected locations in an initial state prior to separation of the first object from the second object with detected locations after the first object has been altered and re-attached to the second object and, based on the comparison, determine the dimensional change of the altered first object.