Plain English Meaning
A ground antenna site that beams WAAS correction signals up to a satellite, which then sends those corrections down to aircraft so their GPS position is more accurate.
Full Definition
A ground facility within the Wide Area Augmentation System (WAAS) that transmits the WAAS correction message to a geostationary satellite, which then rebroadcasts it to GPS receivers in aircraft. The GUS receives processed correction data from a WAAS Master Station and uplinks it on the appropriate frequency to the WAAS geostationary satellite for distribution to users.
Context Anchor
Seen in discussions of how WAAS works, especially the ground-to-satellite part of the system that supports WAAS-capable GPS navigation and approaches.
Derivation
The name describes its job directly: it uplinks (sends signals up) to a satellite, and those signals are GPS correction data. 'Uplink' is the standard term for a ground-to-satellite transmission, the opposite of 'downlink' (satellite-to-ground).
Why Pilots Care
It forms the uplink path that delivers real-time corrections, enabling GPS-based precision approaches with the required accuracy and integrity.
Grounding Statement
Picture the GUS as a ground transmitter that sends the corrected GPS information up to a satellite, which then sends it back down to aircraft.
Intuition Check
A GUS is not equipment in the aircraft. It is a ground station that helps deliver WAAS information to aircraft through satellites.
Example Sentence 1
The GPS Uplink Station sends the WAAS correction message to the geostationary satellite, which rebroadcasts it to aircraft below.
Example Sentence 2
During an instrument approach the pilot relies on data that originated at the GUS minutes earlier.