Definition
The collection of inaccuracies that can affect a Global Positioning System position solution, including satellite clock and orbit errors, ionospheric and tropospheric signal delays, receiver noise, multipath reflections (signals bouncing off surfaces before reaching the antenna), and geometric weakness when too few satellites are visible or they are poorly distributed across the sky.
Plain English
The various small mistakes that can creep into a GPS-calculated position. They come from the satellites themselves, from the atmosphere bending the signal, from signals bouncing off nearby surfaces, and from poor satellite arrangement overhead.
Context Anchor
Seen in instrument flying, GPS navigation, approach planning, and any situation where the pilot is relying on GPS guidance instead of outside visual references.
Derivation
GPS stands for Global Positioning System. Error comes from a Latin word meaning “to wander” or “go astray.” That fits the aviation meaning: the displayed GPS information has wandered away from the aircraft’s true position or true movement.
Why Pilots Care
Unaccounted GPS errors can produce position deviations large enough to affect instrument approach safety and situational awareness.
Grounding Statement
A GPS position is a calculated estimate, not a direct measurement of where the airplane is sitting in space.
Intuition Check
GPS errors are not just mistakes made by the pilot. Here, “errors” means inaccuracies in the GPS information itself or in how the receiver calculates and displays it.
Example Sentence 1
The instructor explained the main GPS errors so the student would understand why the receiver sometimes shows a slight position shift on the ground.
Example Sentence 2
Cross-checking the GPS position against the VOR helped the crew detect any GPS errors before reaching the final approach fix.