Definition
The way the Global Positioning System determines an aircraft's position by receiving timed signals from a network of orbiting satellites and calculating the distance to each one. The receiver compares signals from at least four satellites to compute a three-dimensional position (latitude, longitude, altitude) and precise time, which it then uses to provide navigation guidance such as track, groundspeed, distance, and bearing to a chosen waypoint.
Plain English
How GPS works: the receiver listens to several satellites, works out how far away each one is, and uses that to figure out exactly where the aircraft is and where it's going.
Context Anchor
Seen in instrument flying discussions when learning how GPS-based navigation equipment determines aircraft position and provides guidance.
Derivation
‘Function’ comes from the Latin functio, meaning ‘performance’ or ‘how something works.’ So ‘function of GPS’ simply means ‘how GPS does its job.’
Why Pilots Care
Reliable GPS function supports direct routing, instrument approaches, and continuous situational awareness regardless of ground-based navigation coverage.
Analogy
GPS is like figuring out your position by knowing how far you are from several fixed points at the same time. The GPS receiver does this very quickly using satellite signals instead of visible landmarks.
Grounding Statement
In the aircraft, GPS position comes from received satellite signals, not from the airplane sensing the ground directly.
Intuition Check
Do not read “function” here as a menu choice or button on the GPS unit. Here it means the basic job of GPS: using satellite signals to determine position and support navigation.
Example Sentence 1
The instructor explained the function of GPS by showing how the receiver uses signals from four satellites to fix the aircraft's position in three dimensions.
Example Sentence 2
Before starting an approach the pilot verified the function of GPS was providing valid position data.