Contribution of GNSS to ADS

Automatic dependent surveillance (ADS) is part of the Future Air Navigation System (FANS) and will provide improved air traffic management (ATM). In particular ADS provides better surveillance of aircraft by air traffic control (ATC) thus allowing reduced aircraft separation. The perceived use of GNSS is for finding position. Clearly GNSS can offer greater navigation accuracy, but it is not needed for ADS. Use of GNSS for both ADS position reporting and navigation is initially (particularly for air transport aircraft) likely to be on a supplemental basis. Thus GNSS may be of some benefit in determining the position of an aircraft, but GNSS is not essential for ADS since the accuracy requirements for the navigation data are not demanding, and can easily be met by modern inertial navigation systems