DGPS reference station anenna

The (US) Nationwide Differential Global Positioning System (NDGPS) service augments GPS by providing increased accuracy and integrity using land-based reference stations to transmit correction messages over radiobeacon frequencies.

It is understood that a number of factors have contributed to declining use of NDGPS and, based on an assessment by the Department of Homeland Security (DHS), DOT, and USACE, DHS, DOT, and USACE are proposing to shutdown and decommission 62 DGPS sites, which will leave 22 operational sites available to users in coastal areas. A notice inviting public comment on the shutdown and decommissioning of these DGPS sites has been published and termination of the NDGPS broadcasts at these sites is planned to occur on 15 January 2016.

NDGPS coverage