GA will benefit from GNSS in several different ways:
VFR flying: the complex airspace structures require precise navigation under visual flight rules with GNSS support. Without this assistance, sooner or later airspace infringements will become unavoidable. Similarly, GNSS is an indispensable aid under poor visibility and for night flights.
IFR flying: the aim is to replace the traditional, expensive and maintenance-intensive navigation and landing aids (NDB, VOR, LOC & GP) with augmented GNSS. The same applies for the conventional SSR, which is to be replaced by the GNSS-based ADS-B. This transition is already far advanced in the USA, but in Europe it is still at an early stage.
Today augmented GNSS permits minimum approach altitudes up to CAT I using LPV/APV. Improvements for lower minimum altitudes are under development. Moreover, with suitable instrumentation ADS-B will enable every pilot to view the traffic situation in the vicinity on the cockpit screen. Finally, augmented GNSS will make it possible to initiate low-cost ILS approach procedures without transmitters on the ground, even at small aerodromes.
As well as the high GNSS position accuracy in the order of metres, another benefit is the possibility in conjunction with the digital terrain models available today of providing advance warning that an aircraft is on course to collide with an obstacle or with the terrain (CFIT).
Last but not least, navigation on the ground (taxiing) becomes a lot easier and safer, especially at large airports with complex taxiway and runway structures. Augmented GNSS should largely eliminate runway incursions resulting from disorientation.
To conclude therefore, given the increasing density of air traffic and the rapid rate at which it is growing, the future of air transport is unthinkable without GNSS, especially when one considers that the only way of safely managing the limited resources of airspace is with 4D navigation.
