Differential Global Positioning Systems (DGPS) are enhancements to the Global Positioning System (GPS) which provide improved location accuracy, in the range of operations of each system.
DGPS refers to using a combination of receivers and satellites to reduce / eliminate common receiver based and satellite based errors reduce orbit errors reduce ionosphere and tropospheric errors reduce effects of SA eliminate satellite and receiver clock errors improve accuracy significantly 100’s of Kilometres to metres to centimetres to millimetres DGPS uses one or several (network) fixed ground based reference stations (in known locations).
The base station compares its own known location, to that computed from a GPS receiver. Any difference is then broadcast as a correction to the user. Correction signals can be broadcast either from ground stations, or via additional satellites. These services are privately owned and usually require a user subscription.