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Nationwide Differential GPS (NDGPS)
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Maritime Information

Since March 15th, 1999, the U.S. Coast Guard Navigation Center has operated the Nationwide Differential GPS (DGPS) Service, consisting of one control center and 84 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, greatly enhancing harbor entrance and approach navigation. 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.

Coverage Plots

NDGPS provides service for coastal coverage of the continental U.S., the Great Lakes, Puerto Rico, 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.

NDGPS Partnerships

The US Coast Guard operates the Nationwide DGPS System for surface users.  The primary users of this GPS augmentation system are mariners, surveyors, and agricultural users.  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.