The development of a prototype aircraft-height monitoring unit utilising an SSR-based difference in time of arrival technique

The authors describe a method of monitoring the geometric height of aircraft using an SSR-based radar technique. A research and development project is currently being carried out by Roke Manor Research and the UK National Air Traffic Services on behalf of Eurocontrol. Knowledge of the true target height of aircraft will assist in the establishment and maintenance of reduced vertical separation margin (RVSM) airspace for aircraft flying at FL290 (29000 ft) and above, providing more efficient use of airspace