Nationwide Differential GPS Shutdown Proposed, Comments Sought

August 18, 2015  - By
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Twenty-two NDGPS sites that serve coastal areas would remain operational under the proposal.

An Aug. 18 Federal Register notice proposes shutting down the Nationwide Differential Global Positioning System (NDGPS) in January 2016 because of a decline in its use, except for sites in coastal areas.

The notice, issued by the U.S. Coast Guard (USCG), Transportation Department (DOT) and Corps of Engineers (USACE), reads:

The 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. The service was implemented through agreements between multiple federal agencies including the  USCG, DOT, and Army Corps of Engineers, as well as several states and scientific organizations, all cooperating to provide the combined national DGPS utility.

However, a number of factors have contributed to declining use of NDGPS and, based on an assessment by the Department of Homeland Security, DOT and USACE. DHS, DOT and USACE are proposing to shut down and decommission 62 DGPS sites, which will leave 22 operational sites available to users in coastal areas.

A DGPS reference station antenna.

A DGPS reference station antenna.

Contributing factors cited in the decision are:

  • USCG changes in policy to allow aids to navigation (ATON) to be positioned with a GPS receiver using Receiver Autonomous Integrity Monitoring (RAIM), which assesses the integrity of a GPS signal within the receiver;
  • increased use of Wide Area Augmentation System (WAAS) in commercial maritime applications, which uses ground-based reference stations and satellite communications to improve accuracy;
  • limited availability of consumer-grade NDGPS receivers;
  • no NDGPS mandatory carriage requirement on any vessel within U.S. territorial waters;
  • the May 1, 2000 Presidential Directive discontinuing GPS Selective Availability
  • continuing GPS modernization; and
  • the DOT Federal Railroad Administration’s determination that NDGPS is not a requirement for the successful implementation of Positive Train Control (PTC), which provides the railway system the capability to positively enforce movement authorities along railroad systems.

US_NDGPS_Coverage_APR29_SmIn April 2013, announced that DHS and DOT were in the process of analyzing the need for NDGPS. “The response to the 2013 notice was limited, but the responses received were well informed on the NDGPS system, its use, and current and potential applications,” the notice reads. “While a limited number of responders found the broadcast of corrections to be beneficial, no respondents reported the discontinuance of DGPS broadcast to be detrimental or harmful. Ship pilots in particular noted that DGPS can be critical in confined waterways for precise ship-handling maneuvers.”

Public comments on the proposed shutdown and decommissioning of 62 DGPS sites are being accepted until Nov. 16. Termination of the NDGPS broadcast at these sites is planned to occur on Jan. 15, 2016.

Full details on how to submit public comments can be found on the Federal Register page.

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3 Comments on "Nationwide Differential GPS Shutdown Proposed, Comments Sought"

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  1. JJM says:

    “Limited availability of consumer-grade NDGPS receivers”. Unfortunately a very RARE beast indeed. If it’s Brand A vs Brand B with very similar characteristics, my selection is the one with the most DGPS capabilities even at a higher cost. Remember that when failures occur 1 = None and 2 = 1.

  2. LanceAndre says:

    With companies like goDigiFarm and HPRTK offering nationwide RTK and DGPS service via the internet for around a $1000 a year I think there are very good alternatives available in the private sector to pick up the slack. Do you want this service from your government or private sector?

  3. Dan Abbott says:

    Too many programs continue on their own momentum beyond their usefulness. Since there are alternatives, and the coastal areas are still covered, this seems like an eminently reasonable step to me.

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