See Differential GPS.
Differential GPS - a form of corrected GPS giving enhanced accuracy in the few decimetre range (better than stand alone GPS, not as good as RTK).
differential data is received from external DGPS Receiver
Differential GPS (DGPS) is used to correct a GPS signal to achieve higher position accuracy.
Differential GPS. Enhanced performance GPS using locally provided clock and position information from a fixed transmitter. One of the options for LCS (location services) for mobiles.
Differential Global Positioning System
Differential Global Positioning Satellite (System)