time difference of arrival (TDOA)
A group of equipment configured to provide position derived from the secondary surveillance radar (SSR) transponder signals (replies or squitters) primarily using time difference of arrival (TDOA) techniques. Additional information, including identification, can be extracted from the received signals.
ICAO (2010), ANNEX 10/IV Aeronautical Telecommunications — Surveillance Radar and Collision Avoidance Systems 2010, Amdt. 85