Definition
An enhancement to the standard Global Positioning System (GPS) in which a network of fixed ground-based reference stations, whose precise locations are known, compares the position they calculate from GPS satellite signals to their actual surveyed position. The difference between the two is the satellite signal error. This correction is then broadcast to nearby GPS receivers, which apply it to their own readings to produce a much more accurate position fix than standard GPS alone can deliver.
Plain English
A more accurate version of GPS. Ground stations sitting at known locations check how wrong the GPS signal is at that moment, then send out a correction so nearby receivers can fix their own readings.
Context Anchor
Seen in GPS navigation, avionics descriptions, and discussions of position accuracy.
Derivation
Differential here means 'based on the difference between two values.' The system works by measuring the difference between a known true position and the position GPS reports, then passing that difference along as a correction.
Why Pilots Care
Provides the accuracy needed for safe instrument approaches and reliable navigation when visual references are limited.
Grounding Statement
Picture a fixed GPS receiver sitting on a precisely known point on the ground; when GPS shows it slightly off that point, the system turns that error into a correction for nearby users.
Intuition Check
Differential does not mean a different kind of GPS satellite system. Here it means using the measured difference between a known true position and a GPS-calculated position to improve accuracy.
Example Sentence 1
The airport's instrument approach relies on a differential global positioning system to deliver the accuracy required for the lower minimums.
Example Sentence 2
Maintenance confirmed the Differential Global Positioning System receiver was receiving corrections from the nearest ground station.