Definition
Airborne avionics units that determine the aircraft's position, altitude, ground speed, and time by receiving signals from a constellation of navigation satellites. GPS refers specifically to the U.S. satellite system, while GNSS is the broader term covering GPS together with other satellite systems such as GLONASS (Russia), Galileo (Europe), and BeiDou (China). In IFR operations, only receivers certified to the appropriate TSO standard may be used for navigation, approach guidance, and required position reporting.
Plain English
Cockpit units that figure out where the aircraft is by listening to navigation satellites overhead. They give the pilot position, speed, and time, and on certified units they also provide approach guidance and route navigation.
Context Anchor
Seen in instrument flying, route planning, and approach discussions when satellite-based navigation is used.
Derivation
GNSS is the umbrella term; GPS is one specific system within it. The distinction matters because newer receivers use signals from multiple satellite systems, not just GPS, even though pilots and charts often still say 'GPS' out of habit.
Why Pilots Care
They deliver the precise position data required to follow published instrument routes and approaches safely.
Intuition Check
Do not think of GPS and GNSS as exactly the same thing. GPS is one specific satellite navigation system; GNSS is the larger family of satellite navigation systems that can include GPS.
Example Sentence 1
After losing VOR reception, the pilot used the IFR-certified GPS/GNSS receiver to continue navigating the airway and make the required position report.
Example Sentence 2
During the flight, the GPS/GNSS receiver provided continuous updates that kept the aircraft on the assigned course.