Definition
A system that improves the accuracy, integrity, and availability of GPS signals by using a network of ground reference stations to monitor satellite errors and broadcasting correction data through geostationary satellites to suitably equipped aircraft receivers. In the United States, the SBAS implementation is the Wide Area Augmentation System (WAAS), which enables GPS to be used for precision-like approaches such as LPV.
Plain English
A helper system that makes GPS more accurate and trustworthy for flying. It watches the GPS satellites from the ground, figures out the small errors, and beams corrections back up to the aircraft through another satellite, so the pilot's GPS position is good enough to fly approaches with.
Context Anchor
Seen in instrument procedure and aircraft navigation equipment discussions, especially when a procedure depends on approved satellite navigation performance.
Derivation
Satellite-Based Augmentation System. 'Augment' comes from Latin augmentare, meaning 'to increase' or 'add to.' The system does exactly that — it adds correction information to the basic GPS signal to make it more reliable.
Why Pilots Care
Enables LPV approaches with lower decision altitudes and improves navigation reliability without relying on ground-based navaids.
Intuition Check
SBAS is not the same thing as GPS. GPS provides the basic satellite position signal; SBAS checks and improves the signal information used by the aircraft receiver.
Example Sentence 1
The aircraft's SBAS-capable GPS receiver allowed the crew to fly the LPV approach down to 250 feet above the runway.
Example Sentence 2
With SBAS available, the pilot can fly a more precise initial climb segment using GPS guidance.