differential GPS

The system of establishing position by getting the fix from a constellation of navigational satellites, in which the errors caused by the atmosphere or the ionosphere and those induced by selective availability are corrected. The system has a much higher accuracy than the conventional GPS. It uses two receivers, a rover at an unknown location (aircraft’s GPS receiver), and a base station at a known fixed location. The base station computes corrections based on the differences between its actual and observed ranges to the tracked satellites and sends the correction to the rover receiver.