Definition
A satellite navigation enhancement system that uses a ground station at or near an airport to correct GPS signal errors and broadcast those corrections to aircraft via VHF data link, enabling highly accurate approach, landing, and departure guidance within the local area.
Plain English
A small ground station at the airport that listens to GPS signals, works out how far off they are, and sends the correction to nearby aircraft so their GPS position is far more accurate for approaches and departures.
Context Anchor
Seen on instrument procedure charts and in procedure notes when a departure or approach may use ground-based satellite navigation correction service.
Derivation
"Augmentation" comes from the Latin augmentare, meaning to increase or enlarge. Here it means adding to GPS — making the basic satellite signal more accurate. "Ground-based" distinguishes it from space-based augmentation (SBAS/WAAS), which uses satellites instead of a local ground station.
Why Pilots Care
GBAS supplies the accuracy and integrity needed for lower decision altitudes on certain approaches, improving access to airports when visibility is limited.
Grounding Statement
Picture a fixed receiver at the airport comparing satellite signals to its exact known position, then sending nearby aircraft corrections based on that comparison.
Intuition Check
GBAS is not a separate satellite system. It is ground equipment that improves the satellite navigation signal an aircraft is already receiving.
Example Sentence 1
The crew briefed a GLS approach, which relies on the airport's GBAS to provide precision guidance to the runway.
Example Sentence 2
Before takeoff the crew verified that GBAS coverage was available at the destination for the expected approach.