Sweet Loran

The global positioning System (GPS), whose history was recounted in our last issue, is so cheap, reliable, and easy to use that it is making older, radio-based navigation systems obsolete. loran (LOng Range Aids to Navigation), which dates from 1942, is one of the oldest, so it might seem a prime candidate for dismantling. Yet when the U.S. government announced plans to do just that, the ensuing uproar showed that there are still plenty of loran lovers out there.

In the loran system, ground-based stations transmit precise time signals. By comparing how long it takes a signal to arrive from two different stations, users can calculate how much farther they are from one station than from the other. In loran’s original form, as used by Navy and Coast Guard vessels, this difference yielded a hyperbolic line on a map. Repeating the process with a different pair of stations yielded a second line, and the ship’s position was where the two intersected.

During World War II, getting a fix with loran was a painstaking, time-consuming process done on paper with drafting equipment. Nowadays it’s all electronic. Still, the system has its shortcomings. At least three stations must be within range (typically a few hundred miles) for loran to work. This requires a far-flung network of outposts, many of which are in foreign countries (which now run the stations themselves) or geographically inhospitable places. Even so, large portions of the globe, including most of the Pacific Ocean (in particular, Hawaii) and the entire Southern Hemisphere, are not covered. On land, terrain features can interfere with the signal. Atmospheric and weather effects are also a problem.

Nonetheless, loran has many fierce supporters. The captain of a recreational fishing boat told the Asbury Park (N.J.) Press that after decades spent scouting for promising places to fish, “I’ve got numbers for over 6,000 spots. About half of them are GPS and the other half are loran.” The Massachusetts Lobstermen’s Association points out that “for pinpointing where [our] traps are located, the GPS system is not as exact [as loran]. By exact we mean to within a few yards. If our lobster buoys are gone for whatever reason, we are forced to grapple for our lobster pot trawls that are strung out in a line on the bottom… .”

Other users stress loran’s sturdiness, including its “robust, low-frequency, penetrating signal,” as a Department of Transportation official put it. (Stations typically broadcast at power levels in the hundreds of kilowatts.) Telecommunications providers rely on its precise time readings as a supplement to GPS, or a backup when GPS is unavailable. With its weak signals, GPS is vulnerable to satellite failure, jamming, “spoofing” (malicious broadcast of a fake signal), natural interference (from the ionosphere, sunspots, or solar flares), and disruption through sabotage or accident. Television antennas, improperly shielded military communications equipment, paging transmitters, and even wireless toll-collection devices have knocked out GPS service. Since loran and GPS use different frequency bands and work in different ways, something that interferes with one is unlikely to be a problem for the other.

Best of all, the current system, known as loran-C, is being replaced with enhanced loran, or eloran. The upgrade will improve timing precision and signal stability and increase accuracy to levels comparable with GPS. Combining GPS and eloran will yield even more accurate results.

Still, there is considerable anti-loran sentiment, and it is not new. As long ago as 1995 President Bill Clinton proposed shutting down loran. Congress said no and allocated funds to keep it running through 2008. The debate shifted in 2001, when a report highlighting the vulnerability of GPS to sabotage was released on September 10. The next day’s events made such an attack seem much less remote and much more fearsome. Even so, budget cutters continue to see loran as a tempting target. In February 2006 the Coast Guard, which administers loran under the overall control of the Federal Aviation Administration (FAA), announced plans to phase the system out over four years.

The Departments of Transportation and Homeland Security responded in time-honored Washington fashion by appointing a panel. Its chairman was Bradford Parkinson, who decades ago played a major role in the development of GPS. After Parkinson’s group recommended continuing loran, the two departments published an official notice inviting public comments. By the time the comment period expired, at the end of March 2007, nearly 1,000 comments had been received, the great majority pro-loran.

It cannot be denied that for navigation there are many other alternatives to GPS. Michael Sollosi, head of the Coast Guard’s Office of Navigation Systems, describes his office’s role as “aid mix”—deciding “what is the appropriate combination of satellites, radio signals, lights, day marks, horns, bells, whistles, buoys, rules, regulations, oversight.” Among the electronic systems in the mix are “DECCA, OMEGA, CHICA, DPS, GPS, Galileo, AIS, VTS, LRIT, the list goes on and on.” With GPS so ubiquitous, Sollosi says, underwriting loran “at a cost of $34 million annually using 350 people at 24 stations around the country” cannot be justified as part of the Coast Guard’s mission.

At this point it remains unclear who will maintain and pay for loran in the future, and for how long. Yet enough groups want to keep it in service that its dismantling anytime soon appears unlikely. As loran shows, sometimes an old technology can remain useful in ways that were never envisioned when it was introduced.