Nothing that complex. Calibration takes care of reference frame translations and rotations. Error mapping is a recorded error data table.

Put the tool at a known XYZ location (known either by cmm or calibration tooling) and compare the results given by the mechanism encoders after inverse kinematics. You know it is at point A, but the mechanism says it thinks its at point A PLUS some error in X,Y,Z. If you do this enough times all throughout the workspace you will find error patterns (not necessarily linear).

Now with software, you can error correct by calculating (interpolating from the error mapping results) how much error the robot would probably have at that position and then adding in error correcting offsets.

Very crude, painful procedure, but needs to be done only once per machine.

Jamison