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Discontinuance of the Nationwide Differential Global Positioning System (NDGPS)

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Coast Guard, DHS.




The U.S. Coast Guard (USCG) announces the discontinuance of its remaining 38 maritime Differential Global Positioning System (DGPS) sites. The USCG will implement the closures through a phased reduction in service, which will commence in September of 2018, and conclude by September of 2020. These closures will culminate in the complete cessation of the Nationwide Differential Global Positioning System (NDGPS) service. This notice provides the general schedule for the discontinuance of the remaining maritime DGPS sites. Specific site broadcast termination dates will be published via local notices to mariners (LNMs).

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If you have questions on this notice, contact CAPT Mary Ellen Durley, Coast Guard, telephone (202) 372-1605 or email

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Background and Purpose

The Maritime Differential GPS system was established in the late 1980s to augment the existing GPS signal with accuracy corrections and integrity monitoring. This augmentation signal was broadcast over Medium Frequency from terrestrial broadcast sites. At the time, the publicly available GPS signal was intentionally degraded through Selective Availability (SA), and thus augmentation was necessary to meet minimum requirements for maritime positioning and navigation. Selective Availability was permanently discontinued in 2000, and as system technology has improved, observed positional accuracy for un-augmented GPS consistently meets requirements for harbor/harbor-approach navigation on modern GPS receivers.

On July 5, 2016, the USCG, the U.S. Department of Transportation (DOT), and the U.S. Army Corps of Engineers (USACE) published a notice in the Federal Register (81 FR 43613), which announced that the Nationwide Differential Global Positioning System (NDGPS) would remain operational with a total of 46 USCG and USACE sites available to users in the maritime and coastal regions. Since 2016, the USACE has discontinued 7 sites, and the USCG has discontinued 1 site in Aransas, TX due to storm damage from Hurricane Harvey. Currently, there are only 38 remaining NDGPS sites, all of which are maritime sites.


The USCG has continued assessments and outreach affirming that the positional accuracy provided by un-augmented GPS and GPS augmented by the U.S. Wide Area Augmentation System (WAAS) is sufficient to meet its mission requirements and navigational safety requirements for harbor approaches. Because there is no regulatory requirement for the carriage of Differential Global Positioning System (DGPS) equipment, and other GPS augmentation systems such as WAAS are already in prevalent use by marine navigation equipment, the USCG cannot justify further investment to upgrade and maintain the NDGPS system. Additionally, the Coast Guard no longer has a mission requirement for DGPS to position Maritime Aids to Navigation because current Coast Guard policy allows the placement of aids to navigation with un-augmented GPS or GPS augmented by WAAS. Finally, other government and commercial augmentation systems (e.g. WAAS) are readily available to provide GPS accuracy corrections. For these reasons, Start Printed Page 12403the NDGPS system was reduced from the 2015 constellation of 84 sites, to the current constellation of 38 maritime sites. Pursuant to this announcement, the USCG's remaining 38 maritime sites will be discontinued in stages, beginning in September of 2018 and ending in September of 2020.

Timeline of Maritime Sites To Be Discontinued

Termination of the NDGPS broadcast during Fiscal Year 2018 is planned to occur at the following sites. Specific broadcast discontinuance dates for each site will be announced via Local Notices to Mariners (LNMs) 60 days in advance of the termination of the NDGPS broadcast.

  • Annapolis, MD
  • New Bern, NC
  • Robinson Point, WA
  • Pigeon Point, CA
  • Bobo, MS

Termination of the NDGPS broadcast at the following sites is planned to occur in Fiscal Year 2019.

  • Whidbey Island, WA
  • Appleton, WA
  • Fort Stevens, OR
  • Cape Mendocino, CA
  • Lincoln, CA
  • Point Loma, CA
  • Kokole Point, HI
  • Upolu Point, HI
  • Driver, VA
  • Kensington, SC
  • Cape Canaveral, FL
  • Card Sound, FL
  • Tampa, FL
  • Wisconsin Point, WI
  • Mequon, WI
  • Upper Keweenaw, MI
  • Cheboygan, MI
  • Detroit, MI
  • Youngstown, NY

Termination of the NDGPS broadcast at the following sites is planned to occur in Fiscal Year 2020.

  • Penobscot, ME
  • Acushnet, MA
  • Hudson Falls, NY
  • Moriches, NY
  • Sandy Hook, NJ
  • English Turn, LA
  • Angleton, TX
  • Annette Island, AK
  • Biorka, AK
  • Kenai, AK
  • Kodiak, AK
  • Gustavus, AK
  • Potato Point, AK
  • Level Island, AK

General information regarding the NDGPS Service and graphics depicting the proposed changes to NDGPS coverage are available at the USCG's NDGPS General Information website at:​?pageName=​dgpsMain.

For more information on the NDGPS outages and broadcast termination dates, visit the USCG's website at​?pageName=​dgpsSiteInfo&​currentOutages.

Additional information on GPS, NDGPS, and other GPS augmentation systems is also available in the 2017 Federal Radionavigation Plan, which is published by the Department of Defense, Department of Homeland Security, and U.S. DOT, and is also available at the USCG's website at​?pageName=​pubsMain.

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Authority: This notice is issued under the authority of 5 U.S.C. 552(a) and 14 U.S.C. 81.

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Issued in Washington, DC, on March 14, 2018.

Michael D. Emerson,

Director of Marine Transportation Systems, U.S. Coast Guard.

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[FR Doc. 2018-05684 Filed 3-20-18; 8:45 am]