what is Differential GPS (DGPS)? Differential GPS, or DGPS, has been developed to improve GPS accuracy to within a few meters. DGPS was originally initiated by the U.S. Coast Guard to counter the accuracy degradation caused by Selective Availability. Even with S/A now eliminated, DGPS continues to be a key tool for highly precise navigation on land and sea. DGPS technology adds a land-based reference receiver – located at an accurately surveyed site – to the other GPS components. This non-moving DGPS reference station knows where the satellites are located …