Differential GPS (DGPS)

Differential GPS (DGPS) improves position accuracy by applying corrections from a reference station at a known location to a roving receiver, canceling common-mode satellite-clock, orbit, and atmospheric errors. Code-based DGPS gives meter-level horizontal accuracy, typically 1 to 3 m, against the 5 to 10 m of stand-alone GPS. Maritime DGPS broadcast on marine radiobeacons in the 285 to 325 kHz band long served coastal navigation and survey positioning. It differs from RTK, which uses carrier phase for centimeter accuracy. DGPS positioning supports the horizontal-uncertainty limits of the lower IHO S-44 orders.