Definition
The airport-based equipment portion of a Ground-Based Augmentation System (GBAS), consisting of multiple precisely surveyed GPS reference receivers, a central processing unit, and a VHF data broadcast transmitter. The facility receives GPS signals, calculates corrections and integrity data based on the known surveyed positions, and broadcasts that information to aircraft on approach so they can fly precision approaches to runways at that airport.
Plain English
The equipment installed at an airport that listens to GPS satellites, works out how much the GPS signals are off, and broadcasts a correction to arriving aircraft so they can fly very accurate approaches to the runway.
Context Anchor
Seen in instrument procedure and NextGen discussions about satellite-based approach guidance near an airport.
Derivation
GBAS stands for Ground-Based Augmentation System. 'Augmentation' comes from Latin 'augmentare,' meaning 'to increase or add to.' The ground facility 'augments' raw GPS by adding the corrections that make satellite navigation accurate enough for landing.
Why Pilots Care
Enables lower landing minima and reliable GPS-guided approaches at equipped airports.
Analogy
Think of it like a local correction station. It knows exactly where it is, compares that known position with what the satellites appear to show, then sends the needed correction to nearby aircraft.
Grounding Statement
Picture fixed antennas and equipment on the airport continuously checking satellite signals and sending corrected approach guidance to aircraft nearby.
Intuition Check
Do not assume “facility” means a building the pilot visits. Here, it means the installed ground equipment that supports GBAS guidance.
Example Sentence 1
The GBAS ground facility was reported out of service, so the crew briefed the ILS approach instead of the GLS.
Example Sentence 2
Approach charts list the GBAS ground facility frequency so the aircraft can receive the correction signals.