Monday, January 25, 2010

Winds of Change - LORAN-C

Port Townsend, today. Overshadowed by the obvious news of the day, the Department of Homeland Security announced the beginning of the end of LORAN C. (I absolutely detest that name, “Homeland Security.” Conjures up visions of ranks and files of flag carrying citizens tramping along to some nationalistic music … circa 1941.)

At any rate, the determination has been made that Global Navigation Satellite System (GPS) is here to stay and Long Range Aid to Navigation (LORAN) system C is redundant, obsolete, and therefore to be terminated, beginning next month.

There are some who think LORAN C should be maintained, in a reduced profile, as a backup system should there be a compromise of GPS.

Indeed, the General Lighthouse Authorities of England have decried total dependence on GPS because of it is “vulnerable to both intentional and un-intentional interference … the GNSS system suffer occasionally from undetected failures.” (Indeed with nations competing to perfect satellite killers … but then, what do we mere mortals know?)

LORAN A was invented during WWII to provide reliable long-range navigation for high-level bombers. It went into service in 1941, and was shut down in 1981. LORAN B was fiddled with from 1959 and abandoned in 1962. LORAN C was finally available in 1974, and will be shut down completely by October of this year.

LORAN operates on the principle of radiating low frequency radio pulses transmitted by a Master station in conjunction with three Slave stations, referred to as a “chain,” to impose predictable radio wave patterns over long distances. Popular Science Magazine gave a detailed explanation of how the system works.

Defense Mapping Agency and National Oceanographic and Atmospheric Administration Navigation (NOAA) charts featured beautiful sweeping lines, showing the radio frequency pattern generated by the Master and Slave transmitters.

A specially calibrated radio receiver on an aircraft or vessel measured the beat of the incoming signals. This was converted to latitude and longitude read outs, showing the navigator his position with a fair amount of accuracy on a navigation chart.

To insure the accuracy of those printed patterns, a room full of sophisticated monitoring and measuring equipment with round the clock operators was required to precisely control the frequency and pulse broadcast from impressive transmission towers.

I remember as a young lad, working on a tug for Alaska Freight Lines, watching the mate plotting fixes on a chart, using readings from our LORAN receiver. (I also worked for the US Coast & Geodetic Survey (USC&GS), now the National Oceanographic & Atmospheric Administration (NOAA) making navigation charts, but that’s another story another time.)

The Gulf of Alaska was covered by two Chains. The Alaska Chain, with it’s Master transmitter at Tok, Alaska, with slaves at Kodiak, Shoal Cove and Port Clarence, Alaska.

We also received signals from the Canadian West Coast Chain, with the Master transmitter at Williams Lake BC, with slaves located at Shoal Cove, George Washington and Port Hardy BC.

“Coasties” had some really choice duty stations, like Attu! I do believe the slogan on the patch reflects the feelings of young Coast Guard personnel manning these stations! [Patch Courtesy Joe Stephens, "Crusty old Joe's" with a ton of memorabilia of lonely military outposts in Alaska!]

I remember the mate showing me how he shot the sun at noon each day with a sextant. Not necessary while in transit on the Inside Passage, to be sure. But to keep those traditional basic navigation skills alive.

3 Comments - Click here:

SDP45 said...

This is pretty interesting, as I can see the lights of the George, Washington (don't forget the comma!) installation. They say you can get tours of the place with advance notice. Suppose I need to get my butt out there to do so.


Anonymous said...

I'm not sure how I feel about shutting down LORAN-C myself. I'm a fan of redundancy when it comes to safety. It's hard to argue that modern technology doesn't have its weaknesses.

I see the point though, we'd probably save a few bucks without the old system around.

Thanks for the post Robert,

SDP45 said...

It would seem they were able to shut the last of them down earlier than expected. The one at George, WA last transmitted on August 3, instead of October. The installation is dormant, though fully intact, as are all of the other Loran stations, save for 2 which have had their towers removed for safety reasons.


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