Fish Radio

GPS signal set to be shut down

November 5, 2015

Differential GPS  Credit:

Differential GPS

This is Fish Radio. I’m Laine Welch – A mariner GPS signal is set to shut down. There’s still time to comment. More after this —

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Mariners have until November 16 to comment on plans to pull the plug on a GPS signal still counted on by many tugs, barges, ferries and fishing boats. Claiming declining usage across the country, the federal government intends to shut down 62 Differential Global Positioning System  sites, or DGPS, next January 15, leaving 22 sites available to users in coastal areas.  Alaska currently has 15 DGPS sites; six are scheduled to close.

The DGPS was brought on line in 1999 to supplement satellite-based GPS. The augmented signal provided better accuracy using land-based reference stations to transmit correction messages over radio beacon frequencies. Many believe it has outlived its usefulness.

 What we’ve discovered is that the technology for GPS satellites and receivers has increased so much, the need to have so many signals really isn’t there anymore. A Federal Aviation Administration study in 2014 showed that GPS without the Differential antenna signal achieved accuracy of position of less than one meter, in most cases.

Petty Officer John Gallagher serves aboard the USCG Cutter Spar based in Kodiak. He says the 22 stations left on line will cover the nation’s most critical waterways in the most challenging navigational transits. Spar captain, Lt. Commander Dough Jannusch, agrees that the differential signal is no longer needed.

 We’re out there in the Aleutians with our ship positioning buoys to very high accuracy and not using differential antennas. If it’s good enough for us, it’s also sufficient for people to safely navigate waterways.

Others argue that’s fine for open seas, but operating in harbors, fjords and other tight spots prevent a line of sight. Nearly all of the 43 comments posted so far on the Dept. of Transportation website expressed concerns about decommissioning the DGPS.

Wayne Carnes is captain of the high speed craft Fairweather which travels at 36kts while carrying 250 passengers and 40 vehicles. Carnes wrote that the DGPS signal is needed

in the narrow waterways of Southeast Alaska, and that it is especially important during times of bad weather when standard piloting methods and RADAR become limited.

Comments on pulling the plug on the DGPS signal are accepted through Nov. 16.

Fish Radio is also brought to you by Ocean Beauty Seafoods – who salutes and says thanks to the men and women fishing across Alaska for their hard work and dedication. ( In Kodiak, I’m Laine Welch.