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Since March 15th, 1999, the U.S. Coast Guard Navigation Center has operated the Nationwide Differential GPS (DGPS) Service, currently consisting of one control center and 46 remote broadcast sites. The DGPS service broadcasts correction signals on marine radiobeacon frequencies to improve the accuracy and integrity to GPS-derived positions.

Users can expect better than 10-meter accuracy throughout all established coverage areas. Typically, the positional error of a DGPS position is 1 to 3 meters. In addition, this maritime service provides 10-meter (2 dRMS) navigation accuracy and integrity alarms for GPS and DGPS out-of-tolerance conditions within ten seconds of detection.

Proposed NDGPS Transition

Over time, a number of factors have contributed to the declining public use of Nationwide Differential Global Positioning System (NDGPS), including lack of a carriage requirement, technological advances in GPS, and limited availability of consumer-grade DGPS receivers. In collaboration with the Department of Transportation and U.S. Army Corps of Engineers, the U.S. Coast Guard has finalized a Federal Register Notice (FRN) that reduces the number of Differential GPS sites throughout the country, while maintaining coverage in major maritime ports and waterways. The FRN is available via the link below.

Coverage Plots

NDGPS provides service for coastal coverage of the continental U.S, the Great Lakes,  portions of Alaska, Hawaii, and a greater part of the Mississippi River Basin. The plots attempt to account for ground conductivity, transmitter output power, and land topography using Millington’s method. To view these coverage areas, simply use the links below.

DGPS Partnerships

The US Coast Guard operates the Nationwide DGPS System for surface users. The primary users of this GPS augmentation system are mariners and surveyors. To provide this free service, the US Coast Guard leverages its partnerships with the US Department of Transportation (DOT) and the US Army Corps of Engineers.

DGPS Partner's Logos - U.S. Coast Guard, U.S. Department of Transportation (DOT), U.S. Army Corps of Engineers