DGPS is a navigation enhancement that improves GPS accuracy by using ground-based reference stations to provide differential corrections.

• A. It uses only GPS satellites without corrections
• B. It relies on inertial navigation to improve accuracy
• C. It provides improved accuracy through atmospheric models
• D. It uses ground-based reference stations to provide differential corrections

Answer: (D)

DGPS improves GPS accuracy by using ground-based reference stations at precisely known locations to determine the errors in GPS measurements and then broadcast those corrections to nearby receivers. Each reference station compares its measured satellite ranges to its true position, revealing errors caused by satellite clock and orbit inaccuracies as well as signal path delays. Those error values—differential corrections—are sent to users, who apply them to their own GPS measurements. By removing the common errors that affect all receivers in the area, the corrected positions are much more accurate than standard GPS. This approach relies on ground stations providing corrections, rather than relying on inertial navigation systems or solely on atmospheric models, which is why the description of using ground-based reference stations to provide differential corrections best fits.