OZ,
That is not correct, the GBAS system has the 3 to 4 ref antennae at the airport. , which gather the sat GPS signal, and correct algorithm for the actual location. That correction, along with the final approach path, is sent to the aircraft. GBAS can also be used for dpartures, and a runway can be used for arrival and departures from the same end. Cant do that with ILS or VOR.
All WAAS does is correct the GPS signal. While the claim is lower minima, to 200', I doubt if you will ever see anything less than 250' in use, as that glass basement is the FAA mantra. You may see it on the charts, but permission to use...well.
As far as costs, if you have more than 2 runway ends, the GBAS cost is even with the VOR. More than that, and the $2 million to put in the GBAS is amortized very quickly.
For the airlines, the equipment on the both Boeing and Airbus new aircraft are GBAS capable, and doesnt cost anymore for you to tell them to flip that switch.
I have not seen a WAAS certified commercial system avilable or installed on a commercial aircraft.
As far as I know, there are aircraft using the GBAS at Sydney, with no extra cost.
I just dont see very much in the way of advantages of WAAS, its just a more accurate GPS system, with all of the same issues as GPS.
Last edited by FlightPathOBN; 13th Jun 2012 at 14:44.