Abstract: A system and method for measuring the absolute position of one body which is constrained to move with respect to another body includes a plurality of magnetic identification units, which are adapted to be mounted in a predetermined absolute position on a first body. Each of the magnetic identification units has an identity characteristic that is associated therewith. A Sensor having a transducer is adapted to be fixed to a second body. The transducer is adapted to sense (a) the relative distance of at least one of the magnetic identification units with respect to a benchmark location which is fixed relative to the transducer and the second body. It is also equipped to sense the identity characteristic of the sensed unit. A controller is provided to receive data representing the relative distance and identity characteristic of the sensed unit from the sensor.