Much like the more widely used Wide Area Augmentation System (WAAS), the Differential GPS (DGPS) system was designed to help give GPS signals a boost in accuracy and integrity through the use of correction messages. DGPS has been used especially on the coasts, but is technically a nationwide system which spans the whole of the United States.
However, that might not be the case for much longer. Yesterday, a notice was posted in the Federal Register which requested public comment on the idea of shutting down more than half of the DGPS sites in the country.
What is DGPS?
Developed on the coasts of the USA in the late 1980s and expanded inland in 1998, the DGPS system consists of a series of ground-based systems which compare the GPS signal to their known locations. The two locations are then compared and a correction signal is generated and sent over radiobeacon frequencies to GPS devices capable of receiving the signals.
Shut down proposal
According to the brief, the DGPS system is no longer experiencing widespread use due to “a number of factors” including:
- US Coast Guard changes in policy to allow Receiver Autonomous Integrity monitoring to assess the integrity of a GPS signal independently
- Increased adoption of the WAAS system
- Limited availability of consumer-grade DGPS units
- No mandatory requirement of DGPS within US waters
- Discontinuance of Selective Availability
- GPs modernization and advancements
The proposed shutdown will include a total of 62 Differential GPS stations, leaving 22 operational around coastal areas. The termination is expected to take place on January 15, 2016 and the government is interested in collecting public comments on the issue.
How to comment
The request for comment was posted by Coast Guard, the Transportation and the Engineer Corps, and those governmental bodies are looking for comments on how you use DGPS, the impact if the system was shut down, possible alternatives to DGPS and possible alternate uses for the DGPS infrastructure.
If you’re interested in commenting on the use of DGPS, there are any number of ways to submit a comment including:
- Visiting this website and searching for the docket number DOT-OST-2015-0105
- Faxing written or typed comments to 202-493-2251
- Mailing written or typed comments to: Docket Management Facility (M-30), U.S. Department of Transportation, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE., Washington, DC 20590-0001.
All comments, in order to be received and reviews, must be sent by no later than November 16, 2015. The comments will be posted and searchable in the Federal Register, and just to be on the safe side I recommend including the docket number (DOT-OST-2015-0105) somewhere on your comment to be sure it gets filed properly.
For more information or to read the call for comments yourself, click here.
