METHOD OF AND APPARATUS FOR DETERMINING THE POSITION OF A BODY WITHIN THE CROSS-SECTION N ELECTROMAGNETIC BEAM

摘要

The position of a body is determined using a beam of electro-magnetic waves directed along a sight line generally towards the body. The cross-section of the beam is changed and a sensor mounted on the body senses these changes in cross-section and from the time periods in which electro-magnetic waves are received by the sensor two signals are produced in sequence, a first signal representative of a first co-ordinate position of the body within the cross-section of the beam and a second signal representative of a second co-ordinate position of the body within the cross-section of the beam.