The direction is simple, there will be WAAS and GBAS in the future.
WAAS is sat based, hence the SBAS designation. The WAAS signal contains 2 parts, the sat correction factor, and a local ionospheric delay correction factor. The LPV-200 has very specific requirements, and unless there is a ground station at the airport location, you wont likely get a good enough correction factor for the 200' minima.
The WAAS will replace CAT I ILS, and will be the vertical guidance for smaller airports where GBAS infrastructure doesnt make sense. WAAS is a little more complicated, (and expensive) than people believe. Ground stations feed master stations, and master stations feed sats, which the ac receives, and must have a WAAS MMR. (2 systems, just like GPS are required)
Since WAAS is also based on GPS, all of the same issues with RAIM, prediction, outages, etc still have to be accounted for.
The GBAS will be the approach guidance for commercial aircraft, down to CAT III autoland, for all the major airports. All new Boeing and Airbus aircraft, as well as the 787 are GBAS equipped.
Last edited by FlightPathOBN; 17th Jun 2012 at 18:26.