What is differential GNSS (DGPS) and its typical accuracy improvement?

• A. DGPS uses a reference station to broadcast corrections to rovers, improving accuracy from meters to tens of centimeters or better depending on corrections and geometry.
• B. DGPS uses two receivers at the rover to average measurements.
• C. DGPS reduces accuracy to protect privacy.
• D. DGPS uses only carrier-phase corrections.

Answer: (A)

Differential GNSS works by using a reference station with a precisely known position to track the same satellites as a rover. The reference station computes the errors the satellites are introducing—clock errors and atmospheric delays—by comparing its observed signals to what those signals should be at its known location. It then broadcasts these corrections to rovers, which apply them to their own measurements. This process removes many of the common errors, so the rover’s position becomes much more accurate.

Typically, the improvement is from meter-level accuracy in a standalone GNSS solution to tens of centimeters or better with DGPS, though the exact result depends on the quality of the corrections and the geometry of satellites in view. More favorable geometry and higher-quality corrections yield tighter accuracy.

A simple averaging of two rover receivers doesn’t provide the differential corrections that DGPS delivers. Privacy or data-restrictive aims don’t drive GNSS accuracy, and DGPS is not limited to carrier-phase corrections alone; it uses corrections to both code and carrier measurements, with the specifics varying by system.