DGPs

DGPS, or Differential Global Positioning System, is an enhancement to the Global Positioning System that improves positioning accuracy by using ground-based reference stations at known coordinates to compute and transmit correction data to nearby users. A DGPS receiver applies these corrections to the satellite measurements, yielding more accurate position estimates than standalone GPS.

Operation involves a network of fixed reference stations that monitor GPS satellite signals. Because the stations’ locations are precisely known, they can compare observed pseudorange values to true values and generate differential corrections that account for common errors such as satellite or clock biases and atmospheric delays. The corrections are broadcast to users through local radio beacons on VHF/UHF bands or via satellite augmentation systems and internet-delivered messages. Receivers with DGPS capability apply the corrections to their measurements, producing improved solutions.

Accuracy and scope: DGPS can reduce typical horizontal errors from several meters to about 1–3 meters in open sky, with vertical accuracy improving correspondingly. Coverage is limited to the service area of the reference network and depends on signal integrity, satellite geometry, and propagation conditions. It is widely used in maritime navigation, land surveying, construction, and precision agriculture.

Variations: DGPS is part of a broader family of augmentation techniques. Satellite-based augmentation systems (SBAS) such as WAAS and EGNOS provide DGPS-like corrections from space, while conventional terrestrial DGPS networks rely on fixed ground beacons and radio transmissions.