In the early days of GPS, when the system accuracy for civilian users was purposefully degraded via the technique known as Selective Availability (SA), the Coast Guard set up a differential GPS (DGPS) system for improving accuracy for maritime users, and for its own buoy tenders, called the Nationwide Differential GPS (NDGPS) network. The NDGPS uses marine radio beacons for broadcasting the differential corrections. Soon after the radio beacon stations became operational, however, the U.S. Government shut down SA, making civilian receivers more accurate at the flip of a switch. Then the FAA developed a satellite-based DGPS called Wide Area Augmentation System (WAAS). These and a few other developments have made the radio beacon-based Coast Guard DGPS broadcasts less necessary. The result is that the Coast Guard and Department of Transportation are currently taking comments from users on the prospect of shutting down 62 NGDPS sites (see below).
If you'd like to weigh in, you can comment here online.
The sites slated for shutdown:
Appleton, WA
Biorka, AK
Bobo, MS
Brunswick, ME
Cape Hinchinbrook, AK
Cheboygan, MI
Cold Bay, AK
Driver, VA
Eglin, FL
Gustavus, AK
Isabela, PR
Key West, FL
Kodiak, AK
Kokole Point, HI
Level Island, AK
Lompoc, CA
Mequon, MI
New Bern, NC
Penobscot, ME
Pigeon Point, CA
Robinson Pt, WA
Saginaw, MI
Sandy Hook, NJ
Sturgeon Bay, WI
Upper Keweenaw, MI
Wisconsin Point, WI
Youngstown, NY