Principle of operation differential GPS DGPS

Differential GPS (DGPS) works by placing a GPS receiver that is a reference station at a known location.
The station measures the ranges to each satellite.
Then it uses the measured ranges and the actual ranges calculated from its known position.
Measured ranges can contain errors such as ephemeris data errors or internal receiver noise.
The difference between measured and calculated ranges becomes a “differential correction”.
The differential correction is then transmitted to the DGPS receivers.