Definition
A method of improving GPS position accuracy by using ground-based reference stations at precisely known locations. These stations compare their actual surveyed position to the position reported by GPS satellites, calculate the error, and broadcast a correction signal to nearby GPS receivers. The receiver applies the correction to produce a much more accurate position fix than standard GPS alone.
Plain English
A way of making GPS more accurate by using a fixed station on the ground that already knows exactly where it is. The station works out how wrong the GPS signal is at that moment and sends a correction to your aircraft, so your GPS position becomes more precise.
Context Anchor
Seen in navigation equipment descriptions, instrument flying discussions, and procedures where improved GPS position accuracy matters.
Derivation
‘Differential’ comes from Latin differre, meaning ‘to carry apart’ or ‘to differ.’ Here it points to the difference between the GPS-reported position and the true surveyed position of the ground station. That difference is the correction.
Why Pilots Care
Delivers the sub-meter accuracy required for certain GPS approaches and reduces the chance of being slightly off course in low-visibility conditions.
Intuition Check
DGPS does not mean a separate set of satellites. It means GPS position information corrected by comparing GPS error at a known fixed location.
Example Sentence 1
The approach relied on DGPS corrections to deliver the accuracy required for the lower landing minimums.
Example Sentence 2
DGPS corrections allowed the aircraft to track the final approach course with greater precision than unaugmented GPS.