Wide Area Augmentation System (WAAS)
What is WAAS
Wide Area Augmentation System
WAAS is part of the FAA's plan to retire the existing use of VOR, NDB, ILS, and LOCALIZER aviation navigational systems. WAAS is designed to improve the accuracy and ensure the integrity of information coming from GPS satellites. WAAS will provide accuracy performance of 1 – 2 meters horizontal and 2 –3 meters vertical throughout the majority of the continental U.S. and large parts of Canada and Alaska.
How it works
WAAS works by providing a series of ground stations that receive GPS signals and transmit corrective information back to another satellite that then provides that information to your GPS receiver. This correction is needed to correct timing errors caused by signal propagation thru the atmosphere and other facts that change the timing of the GPS signal.
Other systems
There is another augmentation system called LAAS . Which like WAAS provides a corrective signal but this is done over a much more local area via a line of sight radio link VHF. This is a short range system just for use around the airport environment.
This system is designed to provide ILS like capabilities to aircraft.
External Links
FAA WAAS
FAA LAAS