Definition
A ground-based system that improves the accuracy, integrity, and availability of GPS signals within the local area of an airport, enabling precision approach and landing guidance comparable to or better than an Instrument Landing System (ILS). A GBAS ground station receives signals from GPS satellites, calculates correction data, and broadcasts that data via a VHF datalink to suitably equipped aircraft on approach.
Plain English
Equipment installed at an airport that fixes small errors in GPS signals and sends the corrections to nearby aircraft, so they can fly very precise approaches to the runway using GPS instead of a traditional ILS.
Context Anchor
Seen in instrument approach information, airport navigation discussions, and avionics that can receive GBAS landing guidance.
Derivation
"Augmentation" comes from the Latin augmentare, meaning "to increase" or "add to." GPS on its own is accurate enough for general navigation, but not precise enough for low-visibility landings. GBAS "adds to" the basic GPS signal by supplying local correction data, boosting it to approach-grade precision.
Why Pilots Care
It supports safer, lower-visibility landings at equipped airports by giving reliable vertical and horizontal guidance without requiring heavy onboard equipment.
Analogy
Think of GPS as giving the aircraft a general position, and GBAS as a local airport helper that checks and fine-tunes that information before sending it to the aircraft.
Intuition Check
GBAS is not a separate replacement for GPS. It is a ground-based system that improves and monitors satellite navigation information near an airport.
Example Sentence 1
The crew briefed the GBAS approach to Runway 28, noting that the corrections would be received from the airport's ground station once they were within range.
Example Sentence 2
Pilots can use GBAS to follow a precise glide path to the runway using enhanced satellite signals.