ASSOCIATED PRESS PHOTO In this photo made Thursday, Jan. 14, 2010, a GPS unit on a lobster boat displays Loran coordinates, in Portland, Maine. The Loran-C radio navigation system, that for decades had been the preferred choice for millions of mariners, has become obsolete and is being shut down.

PORTLAND, Maine — The plug is being pulled on a radio navigational system that for decades was the preferred choice of mariners in waters off the U.S.

As low-cost GPS has emerged in recent years, the LORAN-C system has become obsolete and is no longer needed for navigation or safety, the Department of Homeland Security says. Over the protests of some U.S. senators and others who say the LORAN network should be maintained as a GPS backup, most of the nation's LORAN transmission towers will be turned off Feb. 8, with the remainder being shut down by Oct. 1.

LORAN marked a quantum technological leap when it first became popular among fishermen more than 25 years ago. Its passing marks the end of an era brought on by further advances in technology.

"It's like changing over from old-fashioned reel-to-reel-tapes to discs and newer technology," said Oscar "Bill" Look, a longtime lobsterman from Beals Island in eastern Maine.

LORAN — short for "long-range navigation" — was developed during World War II for military ships and aircraft. LORAN-C was developed for civilian use in 1957 and uses radio signals from 24 land-based towers operated by the Coast Guard across the U.S. to determine positions at sea or in the air.

For decades, it was the standard-issue navigation system for commercial fishing boats, recreational craft and other vessels, as well as a supplemental navigation aid on many small aircraft. At the peak, an estimated 1.2 million to 1.5 million were in use.

But mariners and pilots began turning to global positioning systems, which use signals from satellites, in the mid-1990s when GPS became widely available.

The time has now come to shut down the entire LORAN system, the government says. The Department of Homeland Security says eliminating LORAN could save $36 million in 2010 and $190 million over five years. It would result in the elimination of 256 jobs, according to the Coast Guard.

Practically speaking, the end of LORAN will have only a small impact.

Relatively small numbers of fishermen, primarily old-timers, and some general aviation pilots use LORAN receivers on their boats and planes. Major manufacturers stopped making them years ago.

Still, the decision to pull the plug has drawn protests, including objections from Sens. Olympia Snowe and Susan Collins of Maine, Sen. Joe Lieberman of Connecticut and Maine Gov. John Baldacci. They say they are troubled by the decision to do away with LORAN without identifying a backup system to GPS.

Erik Johannessen, president of Megapulse Inc. in Billerica, Mass., which manufactures integrated GPS/LORAN equipment, said it makes sense to develop an enhanced LORAN system — known as eLORAN — by building upon the existing LORAN network. It's vital to maintain a viable backup should GPS be disrupted or compromised, potentially negatively affecting maritime navigation, air traffic and even cell phone and power grid networks, he said.

"This isn't about who's using the system now," said Johannessen, who's also an officer with the International Loran Association, a group that promotes LORAN. "We're talking about something future-looking. We want to have a system in the future that will help protect GPS. That's what eLORAN is all about."

In the Federal Register notice announcing the end of LORAN-C, the government says LORAN was never intended to be any sort of backup to GPS and that there are other alternatives available.

In the meantime, the Department of Homeland Security said it plans to continue evaluating whether a single national system to back up GPS is necessary.

Look doesn't own a LORAN receiver any more, but he has memories of when he first bought one decades ago. The unit cost him more than $2,000, but it was like nothing else he had seen before and changed the way lobstermen fished.

"People would ask, 'You went out on a thick-fog day and you were able to haul all your traps? How did you find them?'" Look said. "Well, we plotted them on our LORAN and when you got to the right numbers, you looked over and there was your buoy. That was new technology."