Navigation using GNSS
For the use of a satellite navigation system in aviation, the following requirements have to be met: availability, signal continuity, accuracy, and reliability [source: Mensen, Moderne Flugsicherung]. So far, these requirements have been complied with by on-board systems. Satellite navigation is used in support of area navigation.
The military responsibility of the US and Russia for GPS and GLONASS is still to this day an uncertainty factor in aviation. For this reason, many airlines use a satellite navigation system for secondary positioning only.
Area navigation using GNSS
GNSS allows a much finer determination of flight routes as well as a shift away from rigid routes between navaids. The accuracy of modern GNSS systems is sufficient for this.
Precision approaches using GNSS
Today’s WAAS concepts for satellite navigation for the ICAO landing categories II and III are not accurate enough either [Mensen, Moderne Flugsicherung]
There are current research attempts to improve this by means of GBAS technology. For CAT I precision approaches, GBAS systems are already in use [Mensen, Moderne Flugsicherung]. Evaluations and qualifications for GNSS-based CAT II and III approaches are being carried out. Europe’s first airport fit for EGNOS approaches is Pau-Pyrénées in Southern France [source: ESA News, May 12, 2011]. More airports are in planning.