Abstract: An algorithm for improved tracking of Air Traffic Control Radar Beacon System transponders is disclosed. The algorithm can be combined with a system that includes an interrogator which transmits an interrogation signal to an associated vehicle transponder at a first frequency, preferably 1030 MHZ in accordance with FAA regulations, and a receiver array which receives the transponder reply signal transmitted by the transponder at a second frequency, preferably 1090 MHZ in accordance with FAA regulations. An angle of arrival processor calculates an angle of the received reply signal, and a position processor calculates the vehicle position based on at least the received angle data.