Definition
In GPS operation, the interruption or weakening of satellite signals reaching the receiver to the point that the receiver can no longer compute a reliable position. Signal loss can be caused by terrain or building obstructions, aircraft attitude that blocks the antenna's view of satellites, interference, jamming, or insufficient satellite geometry.
Plain English
The GPS receiver stops getting a good enough signal from the satellites to tell you where you are.
Context Anchor
Seen in GPS navigation discussions, cockpit GPS messages, and situations where terrain, aircraft structure, antenna problems, or interference can keep satellite signals from reaching the GPS unit.
Why Pilots Care
Signal loss removes reliable GPS position data and may require immediate switch to alternate navigation sources.
Analogy
It is like a phone losing service in a dead spot: the device may still work, but it is not receiving enough outside signal to keep giving current information.
Grounding Statement
In flight, signal loss means the GPS unit may still be powered on, but the satellite information it needs is not reaching it well enough to guide you reliably.
Intuition Check
Do not assume signal loss means the GPS unit has failed completely. It usually means the unit is not receiving enough usable satellite signals at that moment.
Example Sentence 1
During the steep turn, the pilot noticed a brief signal loss on the GPS as the wing blocked the antenna's view of the satellites.
Example Sentence 2
Flying low through mountainous terrain caused brief signal loss until the aircraft climbed clear of the obstruction.