Definition
An enhancement to standard GPS that improves position accuracy by using a network of fixed ground-based reference stations at precisely known locations. Each reference station compares its known position to the position calculated from GPS satellite signals, then broadcasts the difference (the error correction) to nearby GPS receivers. The receiver applies these corrections in real time, reducing typical GPS positional error from several meters to roughly one meter or better.
Plain English
DGPS is regular GPS made more accurate by using ground stations that already know exactly where they are. Those stations measure how wrong the satellite signal is at that moment and send a correction to your receiver, so your position shows up much closer to the truth.
Context Anchor
Seen in instrument navigation discussions where GPS accuracy, position correction, and approved navigation equipment are being explained.
Derivation
‘Differential’ comes from the Latin differentia, meaning ‘a difference.’ In DGPS, the system works by measuring the difference between a known true position and the position GPS reports, then sharing that difference as a correction.
Why Pilots Care
Provides the higher accuracy and integrity needed for certain GPS-based instrument approaches and reduces the chance of large position errors during flight.
Analogy
It is like checking a clock against a trusted time source. Once you know your clock is 2 minutes slow, you can correct the time you read from it.
Intuition Check
Differential does not mean a completely separate kind of GPS. Here it means GPS corrected by comparing the GPS reading with a precisely known location.
Example Sentence 1
The approach was supported by a DGPS-based augmentation system, giving the crew the accuracy needed to fly to lower minimums.
Example Sentence 2
With DGPS corrections active, the GPS position remained stable even when flying through areas of minor signal interference.