The application relates to motion tracking system (10) for tracking a movement of an object (P) in a three-dimensional space, the system comprising orientation measurement units (S1,S3,...SN) for measuring data related to at least orientation of the object portions, wherein the orientation measurement units are arranged in positional and orientational relationships with respective object portions and having at least orientational parameters a processor (3,5) for receiving data from the orientation measurement units, the said processor comprising a module for deriving orientation and/or position information of the object portions using the received data and a calibration unit (7) arranged to calculate calibration values based on received data and pre-determined constraints for determining at least the mutual proportions of the object portions and orientational parameters of the orientation measurement units. The application further relates to a method for tracking a movement of an object, a medical rehabilitation system and an animation system.
