On Monday at 2000 GMT, the U.S. Coast Guard terminated the transmission of the LORAN-C radionavigation signal, marking the end of a system which has been an important factor in maritime navigation (and, to a lesser extent, air navigation) for more than half a century. The termination of LORAN was based on budget considerations and on the conclusion that LORAN’s functions have been supplanted by GPS. I’m not totally sure that this was a good decision.
LORAN (LOng RAnge Navigation) was developed for military purposes during WWII, with first operational use in 1942. The system was retained after the war because of its usefulness to shipping, commercial fishing, and long-distance air transportation. LORAN worked by transmitting pulses from various high-powered stations scattered around the globe: the receiver measured the time differences in the reception of the pulses from different sources, from which the position of the vessel or aircraft could be calculated. In the late 1970s, the original version of the system, LORAN-A, was replaced with LORAN-C, which operated on a lower frequency, with more highly-automated receivers and with significantly increased positional accuracy.
Most LORAN users have now converted to GPS: however, there are signficant concerns about the increasing level of navigational dependency on this satellite-based system. For one thing, GPS signals are necessarily weak and can be jammed relatively easily. This was much less of a threat for LORAN because of the very high power (up to 4 megawatts) of its terrestrial transmitters.
Various proposals have been advanced for GPS backup systems, one of which involves radio signals transmitted from blimps. An alternative that was on the table was e-LORAN, involving the upgrade of the system’s accuracy to about 8 meters: indeed, significant money has already been invested in e-LORAN development. I’ve seen estimates that the cost of completing e-LORAN deployment would have been about $250MM, which is roughly the same amount of money being spent to dismantle the existing LORAN infrastructure. (LORAN operating costs were quite reasonable, about $35MM/yr.) I wouldn’t be surprised if whatever we wind up doing for GPS backup turns out to cost a lot more.
Anyhow–thanks, LORAN, for 68 years of reliable service. Mariners and pilots may want to raise a glass in appreciation of the scientists and engineers who developed this sytem and the Coast Guardsmen who maintained it.