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.
Plain English
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.
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.