Definition
An enhancement to standard GPS that improves position accuracy by using ground-based reference stations at precisely surveyed locations. These stations compare their known position with the position calculated from GPS satellites, then broadcast the difference (the correction) to nearby aircraft receivers. The receiver applies the correction to its own GPS solution, reducing position errors from several meters down to roughly a meter or less.
Plain English
A way of making GPS more accurate. A ground station at a known spot checks how far off the GPS reading is, then tells nearby aircraft how much to adjust so their position is sharper.
Context Anchor
Seen in navigation equipment descriptions, position accuracy discussions, and older GPS-related aviation material.
Derivation
Differential here means 'based on a difference.' The system works by measuring the difference between a known true position and the position GPS reports, then sharing that difference as a correction. Knowing this makes the name self-explanatory rather than mysterious.
Why Pilots Care
Delivers meter-level accuracy needed for many instrument approaches and reliable navigation when visual references are unavailable.
Analogy
It is like checking a watch against a clock you know is correct, then using the difference to adjust your own time.
Intuition Check
DGPS does not mean a separate kind of satellite system. It means GPS position information corrected by comparing it with a known fixed location.
Example Sentence 1
DGPS corrections allowed the receiver to display position accurate to within a meter.
Example Sentence 2
DGPS corrections allowed the aircraft to track the final approach course with greater precision.