Which statement best describes a differential GPS solution?

Which statement best describes a differential GPS solution?

• A. It relies on a single measurement to estimate positions.
• B. It uses the difference by comparing measurements from two satellites at the same receiver to remove common errors.
• C. It uses differential corrections by comparing measurements from a base station to a rover to remove common errors.
• D. It does not rely on any reference station.

Answer: (C)

Differential GPS fixes rely on using a known, fixed reference to remove the errors that affect all GPS signals at once. A base station with precisely known coordinates watches the same satellites as the rover and compares its measured ranges to the true ranges. The difference between the measured and true ranges reveals the GPS errors at that moment—errors that are common to both receivers. That set of corrections is then sent to the rover, which applies them to its own measurements. Because the rover uses corrections derived from the base station, the shared satellite clock, orbit, and atmospheric errors cancel out, giving a much more accurate position than a standalone GPS solution. Relying on a single measurement wouldn’t provide enough information to determine a precise position. Not using a reference station means there are no differential corrections to remove those common errors. And basing the method on comparing measurements from two satellites at the same receiver describes a different, non-standard approach that doesn’t implement the typical differential correction mechanism with a base-rover pair.

Differential GPS fixes rely on using a known, fixed reference to remove the errors that affect all GPS signals at once. A base station with precisely known coordinates watches the same satellites as the rover and compares its measured ranges to the true ranges. The difference between the measured and true ranges reveals the GPS errors at that moment—errors that are common to both receivers. That set of corrections is then sent to the rover, which applies them to its own measurements. Because the rover uses corrections derived from the base station, the shared satellite clock, orbit, and atmospheric errors cancel out, giving a much more accurate position than a standalone GPS solution.

Relying on a single measurement wouldn’t provide enough information to determine a precise position. Not using a reference station means there are no differential corrections to remove those common errors. And basing the method on comparing measurements from two satellites at the same receiver describes a different, non-standard approach that doesn’t implement the typical differential correction mechanism with a base-rover pair.