Definition
A navigation system that improves the accuracy of standard GPS position fixes by using a network of fixed ground reference stations. Each reference station knows its own exact location, compares it to the position reported by the satellites, calculates the error, and broadcasts a correction signal to nearby receivers. A DGPS-equipped receiver applies that correction to its own position, producing accuracy typically within a few meters instead of the larger error margin of unaided GPS.
Plain English
Regular GPS is accurate, but not perfectly. DGPS adds ground stations that measure how far off the satellite signals are right now and send a correction. Your receiver uses that correction to fix its position more precisely.
Context Anchor
Seen in instrument navigation discussions where GPS accuracy, position fixing, and navigation-system reliability are being explained.
Derivation
Differential here means "based on the difference" — the system works by measuring the difference between the GPS-reported position and the known true position of a reference station, then passing that difference along as a correction.
Why Pilots Care
It delivers the higher position accuracy needed for certain instrument procedures and reduces the risk of navigation error in low-visibility conditions.
Intuition Check
DGPS is not a separate set of GPS satellites. The “differential” part means GPS errors are found by comparison with a known ground position, then corrected.
Example Sentence 1
DGPS corrections allowed the receiver to display position accuracy within a few meters during the approach.
Example Sentence 2
DGPS corrections allowed the aircraft to meet the tighter tolerances of the GPS-based procedure.