Defense Media Network

Newest Defense Media Network Promotion

U.S. Coast Guard Ensures Mariner Safety

An enduring mission undergoing significant changes




One of the founding missions of the U.S. Coast Guard is safeguarding mariners. New technologies slowly advanced their capabilities through the last century, but the rapid evolution of technology in recent years has led to significant changes that will be continuing for decades to come.

“Regardless of the budget, our demands have increased, our navigation requirements have changed. We provide, from an ATON [aids to navigation] mission perspective, a mitigation of the transit risk throughout the marine transportation system, as well as notifying mariners of safety issues. And we have not really adjusted for increased demand, especially in the last three years. So we are looking to improve our delivery of the services we provide,” Cmdr. John M. Stone, chief of the Navigation Technology and Risk Management Division, told Coast Guard Outlook.

From paper notices to radio voice messages to LORAN to GPS to DGPS to GPS III to eLORAN, the goal has always been the same – to provide mariners with the best possible information, as quickly as possible, to improve the safety of marine transportation and recreational boating.

“With these increased demands, we need to modernize the delivery of these services to provide cost-effective efforts based on developments in new navigation technologies and acceptance of those by the maritime community. We’ve grown from GPS to electronic chart systems, Automatic Identification Systems [AIS] that help with collision avoidance and to get the message out to mariners on our ATON and marine safety information.”

In the late 1950s, the Coast Guard began building a series of 24 LORAN-C (Long Range Navigation) stations across the lower 48 states, working in partnership with Canada and Russia to also provide coverage in Canadian waters and the Bering Sea. With an accuracy of better than 0.25 nautical miles for equipped users, it provided navigation, location, and timing services for both civil and military air, land, and marine users and as an en route supplemental air navigation system for both Instrument Flight Rule and Visual Flight Rule operations.

When the Global Positioning System constellation of 24 satellites became operational in 1995, GPS grew into the dominant timing and navigation system for all users. Because the U.S. military, which owns GPS, put an intentional deviation into the system called selective availability – reducing position accuracy from 10 meters to 100 meters – the Coast Guard implemented a Differential GPS (DGPS) capability, using a nationwide system of 84 sites to restore its accuracy.

When the military removed selective availability in 2000, DGPS was no longer needed as a broad-range ATON. In addition, a new constellation of GPS III satellites, delivering signals three times more accurate than the current generation, are scheduled for launch in the next few years. However, the Coast Guard found some users wanted to retain the old system – mostly maritime pilots who use the differential signal to make their close quarters and docking evolutions safer.

Automatic Identification System

An on-screen illustration of the Automatic Identification System (AIS). The AIS is a shipboard collision-avoidance broadcast system that acts like a transponder, operating in the VHF maritime band, and is capable of handling well over 4,500 reports per minute and updates as often as every two seconds.

“So in consultation with DOT [Depart of Transportation] and the Army Corps of Engineers, which have eight DGPS sites, we came up with a plan to continue to cover the maritime sector with 21 sites, although I expect that to grow by three or four as additional comments come in,” Capt. Scott Smith, chief of the Coast Guard Office of Navigation Systems, said.

In February 2010, the Coast Guard terminated all U.S. LORAN-C transmissions, and ceased Russian/American LORAN-CHAYKA signals and Canadian coast LORAN-C signals the following August. At that same time, the secretary of Homeland Security gave the Coast Guard permission to start demolishing its legacy LORAN sites and research new technologies, including something to ensure safe maritime movement should GPS signals become lost or compromised.

Congress later ordered demolition of the last eight towers halted so they could be used in that research. Four of those – Wildwood, New Jersey (the first Coast Guard LORAN site); Dana, Indiana; Boise City, Idaho; and Fallon, Nevada – are now being used by the Department of Homeland Security (DHS) Science & Technology Directorate and Harris Corp. to test an Enhanced LORAN system.

Prev Page 1 2 3 4 Next Page


J.R. Wilson has been a full-time freelance writer, focusing primarily on aerospace, defense and high...