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The Axe is Falling
January 6, 2010 1:53 PM   Subscribe

Loran C will cease operation in 2010. Loran C is "a terrestrial radio navigation system using low frequency radio transmitters that uses multiple transmitters (multilateration) to determine the location and speed of the receiver." It is currently used as a backup to GPS for navigational and timing purposes.
posted by vansly (54 comments total) 4 users marked this as a favorite

 
That sucks.
posted by exogenous at 1:54 PM on January 6, 2010


There's been some protest against the shutdown in GNSS circles, but it was to no avail. It will be interesting to see what happens when/if GPS is ever compromised.
posted by vansly at 1:57 PM on January 6, 2010


Huh. Still, satellites in orbit are pretty safe and GPS devices are pretty ubiquitous.

I wonder what's happening to the spectrum allocation?
posted by GuyZero at 1:57 PM on January 6, 2010


Satellites in orbit are safe, but the signal is pretty small. It would be pretty easy to deny GPS service to a large area with minimal cash outlay.
posted by vansly at 2:00 PM on January 6, 2010


Yeah, let rot something like a ground based backup system which is cheap to fix, cheap to maintain and cheap to secure

and instead, have your sole source

a satellite system whch has to transmit through atmosphere, could be disabled by space junk, and will take much longer to fix.

God i love forward-thinking infrastructure decisions.
posted by lalochezia at 2:01 PM on January 6, 2010 [5 favorites]


Lots of old, reliable networks being shut down recently. I was sad to see AMPS cellular traffic go dark out in rural North Dakota.

Wonder if any of the receivers or transmitters are good for anything else... I remember playing with Ricochet modems with a friend of mine after that network died. Oh, star mode.
posted by fake at 2:04 PM on January 6, 2010


Wonder if any of the receivers or transmitters are good for anything else

I know the transmitting stations have some pretty nifty gear in them. Femto-second accurate clocks and the like. We also have on tube technology transmitter running in Canada, complete with 200kV plate voltage.
posted by vansly at 2:08 PM on January 6, 2010


My understanding is that GPS signals are quite weak and therefore susceptible to jamming. This is troubling in view of the plan to rely in GPS to keep aircraft separated. For a while it looked like eLORAN would be the back up to GPS.

Right now there are lots of ground-based navigation aids apart from Loran (VORs and NDBs) that could act as backups, but they have been reduced in number lately (especially NDBs, not so much VORs) as expensive to maintain (using old and arguably obsolete technology) and less accurate than GPS.
posted by exogenous at 2:10 PM on January 6, 2010


(VORs and NDBs)

Neither of which give you a velocity vector. A single VOR with Distance Measuring Equipment or two standard VORs (RNAV) can give you a location. NDBs can give you a cardinal direction from the transmitter only - and no one carries two direction finders on their aircraft, so no using it for pinpointing location.

You could probably get something close to LORAN (albeit not nearly as accurate as GPS) by using two VORs and a computer set up to track previous locations - much like your car's GPS determines your speed down the highway.

The chief economic driver here is that no one makes this stuff anymore, so replacement parts are increasingly one-offs or short runs that are expensive to produce. In addition, the knowledge base is shrinking as the folks who developed this stuff get old and retire.
posted by backseatpilot at 2:52 PM on January 6, 2010


In addition, the knowledge base is shrinking as the folks who developed this stuff get old and retire.

An unmaintained, unused backup isn't much of a backup.

(see: StackOverflow)
posted by GuyZero at 2:56 PM on January 6, 2010 [1 favorite]


.
posted by dibblda at 2:57 PM on January 6, 2010


There's a solar activity maximum in 2011, and we're disabling a GPS backup now?
posted by Zalzidrax at 3:06 PM on January 6, 2010 [1 favorite]


None of the pilot nerds I know are too sad to see LORAN go. It was a neat system, my partner's Cardinal used to have a LORAN for position and it was fairly useful. But GPS just works so much better. Global, way more accurate, and with the benefit of lots of consumer development to get very cheap receiver chipsets, moving map displays, etc. LORAN never got to the point where you could use it for instrument approaches in an airplane, so it's never been a primary navigation instrment.

backseatpilot, I have in the back of my head someone actually built a moving map type display that worked off multiple VORs. But I can't lay my hands on a reference now. I was surprised that the RNAV approaches are simply being re-branded as GPS approaches, I guess the tolerances are about the same?
posted by Nelson at 3:21 PM on January 6, 2010


Here's the Federal Register notice (PDF).

(VORs and NDBs) Neither of which give you a velocity vector. A single VOR with Distance Measuring Equipment or two standard VORs (RNAV) can give you a location.

A single VOR/DME area navigation (RNAV) receiver (like my KNS-80) plus a timer will give velocity. But yes, it is relatively inaccurate, requires line of sight to the transmitter for VOR (NDBs don't, but are quite inaccurate), and old technology. My first KNS-80 had a minor problem and was written off as uneconomical to repair, but at least I could pick up a good replacement relatively cheaply. Undoubtedly it came from someone who had replaced it with a GPS.

Perhaps inertial guidance will increase in popularity, now that solid-state attitude and heading reference devices are becoming cheaper.
posted by exogenous at 3:37 PM on January 6, 2010


Another argument for eLoran was that GPS reception in cities (with all these obstacles and potential interference sources) could be unvoluntarily compromised (not jammed).
posted by Monday, stony Monday at 3:38 PM on January 6, 2010


Acutally, now that I think of it, the KNS-80 must have a built in timer, since it provides groundspeed (velocity). Shows you how much I use it.
posted by exogenous at 3:39 PM on January 6, 2010


Yeah, let rot something like a ground based backup system which is cheap to fix, cheap to maintain and cheap to secure

Depends on whether $36 million per year is cheap for a backup that no one is using.
posted by smackfu at 3:44 PM on January 6, 2010


Depends on whether $36 million per year is cheap for a backup that no one is using.

I know absolutely nothing about this subject, but the phrase "a backup no one is using" makes me shudder. Every backup is a backup no one is using. Until it's not.
posted by The Bellman at 4:21 PM on January 6, 2010 [2 favorites]


No, it's not. A backup must be used on a regular basis otherwise you have no idea whether it will function when you need it. The notion of a static offline backup is a pretty outdated concept. Increasing evidence shows that when you suddenly need such backups that either they don't work or you can't interface to them.

For example:

- what if there are no functional Loran receivers? Not much point in transmitting.
- what if the Loran transmitters have become mis-calibrated? (I have no idea how Loran works, this is theoretical)

The StackOverflow reference was to popular site StackOverflow.com, a website for professional software developers. They had a total site crash. And then they discovered that their backup had been silently failing for months. They literally had nothing. A backup that never gets restored and tested is not a backup.

The other classic WTF story is when the IT guys managed to reassemble the hardware and restore a backup image of a 10 year-old system to get some super-essential piece of financial data. They booted it up after days of work and when they got to the login prompt they realized no one had the password to get in.

Anyway, before GPS existed, Loran was used by itself with no backup systems (other than compasses and dead reckoning, etc). I don't think that particularly upset anyone.
posted by GuyZero at 4:31 PM on January 6, 2010 [1 favorite]


GuyZero: That sounds like a backup no one is testing or maintaining -- which certainly does sound like a pretty bad investment of $36 mil.
posted by The Bellman at 4:37 PM on January 6, 2010


The backup for GPS is VOR navigation... which they'd better not shutdown anytime soon. GPS availability is carefully tracked for GNSS approaches. Usually, this is due to interference from ground stations ( cough ) with big antennas doing mysterious things in the middle of the night.

For instance:

http://s533.photobucket.com/albums/ee339/valkyrie21_photo/?action=view&current=outage.png
posted by sea at 4:48 PM on January 6, 2010


It was Coding Horror -- Stack Overflow co-owner Jeff Atwood's blog -- that crashed without backup; not Stack Overflow itself.

His mea culpa.
posted by We had a deal, Kyle at 4:54 PM on January 6, 2010


Hm, perhaps just wishful thinking on my part. Mea culpa for me as well.
posted by GuyZero at 5:07 PM on January 6, 2010


1. For starters, there is more than one GPS out there, right? Dependence on the US-managed NAVSAT is why GLONASS and Galileo are being built.

2. There are other non-US based LORAN and other terrestial navigation systems in place, of varying effectiveness. Where there many ships or planes that were relying on LORAN or other deprecated systems as backup at this point?

3. A good sextant and almanac is accurate to like a quarter of a nautical mile. We'll be fine- no one's jamming celestial bodies out of existence! :)
posted by hincandenza at 5:32 PM on January 6, 2010


Correct me if I'm wrong, but aren't the internal nav systems (that are secondary to GPS) on newer generation airliners almost as accurate as relying on LORAN?
posted by Burhanistan at 5:33 PM on January 6, 2010


I know absolutely nothing about this subject, but the phrase "a backup no one is using" makes me shudder.

I could have phrased that better. I meant a system that no one is using anymore that will only be used as a backup.
posted by smackfu at 5:45 PM on January 6, 2010


I could have phrased that better. I meant a system that no one is using anymore that will only be used as a backup.

Vestigial is the word you might have been looking for (not that I think LORAN is vestigial, but that word has a simple but effective power to make people not like something).
posted by Burhanistan at 5:47 PM on January 6, 2010 [1 favorite]


My partner and I were given a guided tour of our local LORAN station some years ago and it was quite an eye opener. The station, quite a ways inland, was run exactly like a ship. All the equipment was meticulously maintained and looked as if it was completely from the 1940's including enormous custom made tubes ("valves" in UK) which were replaced at regular intervals and considerable expense. Even then funding was on a year to year basis (more or less) based on the perceived fragility of the satellite systems.

It struck us that commanding this station must be one of the loneliest posts in California.
posted by speug at 6:09 PM on January 6, 2010


Burhanistan, you probably mean INS == Inertial navigation system. Yes, airliners have these. Smaller corporate & private airplanes probably don't. INS is as good or better than GPS, and is required for high precision (zero or very low visibility) instrument approaches.
posted by sea at 6:11 PM on January 6, 2010


My father worked on LORAN-C systems back in the late 60's (the Greenland, Bø in Norway and Jan Mayen stations). I have a large number of beautiful 6x7 Kodachrome slides from these sites and will probably scan and publish them before the shutoff because I think it's worthwhile as a historical document. Here are two fun ones, which are neither 6x7 nor Kodachrome, but it shows how different things were back then.

After GPS started becoming ubiquitous he would always mention the benefits of keeping the LORAN-C system running as a backup, especially because of the low cost and extreme reliability and range of the transmitters. GPS jamming is a serious potential problem that is not being attended sufficiently, although reception has improved a lot as receivers have become more sensitive and accurate.

Like some others have mentioned, a backup is often forgotten until it's really needed in an emergency. Unfortunately this entire decision came under control of the Department of Homeland Security, and I think we all know their track record for brilliance. It's funny how the article mentions there are "sufficient alternatives" but fails to actually mention any, especially since several independent studies have screamed very loudly about this.

All of this is quite sad because of the development of eLORAN, which considerably improves accuracy and provides for more functionality and actually approaches simple GPS for accuracy (± 8 meters). This is really a decision that is worth lamenting, and hopefully our dependence on GPS will not turn out to be a disaster in an emergency.

It is true, however, that the low penetration of LORAN-C/eLORAN receivers is a problem and probably the real reason for this decision, but it would be preferable for commercial vessels to have mandatory receivers precisely for this reason. It's also incredibly sad because the cost of running this system compared to the ridiculous way the DHS are spending billions of dollars is really nothing, especially since they've already spent some money upgrading.
posted by rune at 6:20 PM on January 6, 2010 [1 favorite]


The backup for GPS is inertial navigation.

As a very rough rule of thumb, a good ring laser inertial measurement unit drifts by 1 mile/hr -- that is, on a 5 hour flight, it might be off by 5 miles. So it's not good enough to do automatic landings like GPS can, but we're not talking about airliners getting lost over the ocean or anything.

And no one can interfere with an inertial navigation system from outside the plane.
posted by miyabo at 6:25 PM on January 6, 2010


Correct me if I am wrong, but no one has mentioned INS (Inertial Navigation Systems) or IRS (inertial reference systems). I retired from flying in 1985 when at that time my B727 had two INS installed. Do today's aircraft not have these devices as backups to GPS?
posted by lungtaworld at 6:26 PM on January 6, 2010


[speug]
It struck us that commanding this station must be one of the loneliest posts in California.

The LORAN-C station on Jan Mayen is terrifyingly far away from civilization. The station website is fascinating.

As for the equipment itself, it certainly used to look the way you describe, but for example here are the receivers and here are the timer equipments used at the Bø station in Norway.
posted by rune at 6:29 PM on January 6, 2010 [3 favorites]


Correct me if I am wrong, but no one has mentioned INS (Inertial Navigation Systems) or IRS (inertial reference systems).

They've been mentioned twice (although I didn't use the proper nomenclature). I brought them up because I read something about the latest generation of Boeing and Airbus INS being remarkably accurate.
posted by Burhanistan at 6:30 PM on January 6, 2010


Some of our 727s had OMEGA but Wikipedia says" the use of Omega declined during the 1990s, to a point where the cost of operating Omega could no longer be justified. Omega was permanently terminated on September 30, 1997 and all stations ceased operation."

So that's gone too.
posted by lungtaworld at 6:32 PM on January 6, 2010


Inertial navigation systems in airliners are very cool and require no external communications at all to function, over the short term. Their position accuracy drifts over time, though, so they do need regular position updates from external sources. A drift rate of a few miles per hour of operation isn't unusual.

The source of INS position updates can be a GPS receiver these days. Prior to that, they used ground-based DME (distance measuring equipment) stations to update their positions. The navigation system has a database of these and knows their locations, and can tune in the nearest ones and measure its own distance from each DME station. By doing this it can figure out where it is.

I think many airliners have not been upgraded to use GPS for INS position updates, so they still use the network of terrestrial DME stations. And I'd be surprised if this capability had been removed even from airliners that do use GPS.

You can't use the INS to fly a precision approach to a runway, but we have the ground-based instrument landing system (ILS) equipment for that still. And while it wouldn't be ideal to spend a lot of time in the air with just the INS and no GPS or DME updates, this was commonly done for hours at a time for trans-oceanic flights.
posted by FishBike at 6:37 PM on January 6, 2010


Rune:

I have done some installation work at Canadian Loran C stations. Some of the equipment in the linked photo looks like some of the equipment that is still in service.
posted by vansly at 7:23 PM on January 6, 2010


Also, thank you for posting the historical picture. My wife was blown away by how similar I look to the man in glasses.
posted by vansly at 7:28 PM on January 6, 2010


3. A good sextant and almanac is accurate to like a quarter of a nautical mile. We'll be fine- no one's jamming celestial bodies out of existence! :)

except, you know, the sun and clouds.
posted by ArgentCorvid at 7:47 PM on January 6, 2010 [1 favorite]


Is this the time for a Canadian navigation anecdote? I think it is.

This happened in the 1970s to someone who gave me a course. They were flying an old DC-4 in the North West Territories (I believe it was from Pond Inlet to Iqaluit; it would be in Nunavut today). We in the Canadians are proud to be hosts to the Magnetic North Pole, but this can present some navigational challenges. Because of this, they were relying on a non-directional beacon.

They were carrying cargo, and one Inuit man.

Along the way, an engine failed. Luckily, the DC-4 has three more.

Then, someone at the village decided simply turned off the beacon. Apparently, someone tought no flights were coming in that day.

This put the plane in quite a dire situation: the DC-4 had no INS, the magnetic compass was useless, as was the radionavigation system, and they were hundreds of miles from any inhabited place. They had to try to keep flying straight while trying to match terrain features with what was on their maps (but their maps were mostly limited to showing coastlines). The pilot and copilot tried to keep calm.

After a while (after the time they should have reached their destination, had the flight gone well), the Inuit man stood up.

He pointed in a direction perpendicular to the direction of the plane and said "$village, there!".

And so they turned that way, and were able to land.
posted by Monday, stony Monday at 8:05 PM on January 6, 2010 [3 favorites]


I remember going boating with some friends who had a Loran system, which usually indicated that we were sailing about 20 miles inland. I wasn't impressed.

As has been mentioned by hincandenza, there are three GPS type system either in orbit, or soon to be in orbit: GPS, GLONASS, and Galileo. There are already receivers around that can use both GPS and GLONASS, and there will be systems that also receive Galileo.

Also, GPS doesn't have to come from a satellite. It is possible to send GPS signals from the ground, just like Loran.

And lastly, GPS can be upgraded over time. The last GPS satellite launched was GPS-II, and the next will be GPS-III. They add things like improved anti-jamming with extra signals on different frequencies.
posted by eye of newt at 9:10 PM on January 6, 2010


Hm, perhaps just wishful thinking on my part.

WTF? What an asshole thing to say.
posted by Space Coyote at 9:30 PM on January 6, 2010


correction--they are still launching GPS-IIs. The IIIs won't launch for a few years.
posted by eye of newt at 9:44 PM on January 6, 2010


I'm totally against this, not that it really matters.

LORAN (especially eLORAN) is a decent backup to GPS for giving a body a general position. It's also as repeatable, if not more so, than GPS, which is great for marking an unknown location and returning to it later.

Unassisted GPS is often rather inaccurate, although our GPS devices are pretty good at hiding that fact.
posted by wierdo at 10:00 PM on January 6, 2010


Curiosity got me Googling, and I found out that India has their own little GPS type system called IRNSS, with three geostationary and four orbiting satellites, and China launched the first? of their own system called Compass.

And Japan launched their own Quasi-Zenith Satellite that works with GPS and provides consistent coverage over Japan.

So there are no shortage of Loran replacements around the world. Crafty GPS receiver companies will find ways of using as many of these as possible to plot your position.
posted by eye of newt at 10:01 PM on January 6, 2010


[rune]
Nice shots and a great website - thank you! The LORAN-C station on Jan Mayen does indeed define isolation - but at least they have state-of-the-art artillery to play with and there's a really neat volcano nearby...
posted by speug at 11:15 PM on January 6, 2010


rune:
"Here are two fun ones, which are neither 6x7 nor Kodachrome, but it shows how different things were back then."
Both links went to the same picture. I think this is the second one intended to be linked (with bonus cat).
Because I care.
posted by vapidave at 12:39 AM on January 7, 2010


It seems like the crux of this issue is that DHS is claiming there are sufficient alternatives in the case of emergency, but doesn't say what they are. I'd rather we have demonstrated alternatives BEFORE shutting off a demonstrated working system. If that's GPS "satellites on a stick" (ground-based GPS) or ">VOR/DME/ILS or whatever, they should say so. Oh wait, they (the Federal DOT and Defense Dept. anyway) did, here.

&ltTangential Personal Anecdote&gt The avionics shop that installed my shiny new WAAS-capable GPS also took out and kept my old LORAN-C + GPS receiver, which kind of pissed me off because there was no good reason to remove it, but after waiting 5 months for them to finish a 2 week job, I just wanted my plane back. My old LORAN would, in certain fairly predictable areas, like south of Mount Rainier and over San Diego, decide that its internal consistency checks were failing and tell me that the LORAN position + accuracy said we were in one place, while the GPS said we were 5 miles away, plus there was that whole mid-continent gap in LORAN coverage, but I sure found it more convenient as a backup than retuning and triangulating VOR receivers every 15 minutes.&lt/TPA>

I'd also like it if the military would stop occasionally jamming GPS "in the vicinity of China Lake" by which they mean a 200 nautical mile radius. China Lake may be in the middle of the Mojave Desert, but the GPS signals can be messed up over Los Angeles, Las Vegas, Fresno, etc. I did one flight from the Bay Area to Tucson in which the GPS was pretty wrong for a hundred miles of the trip over the Mojave. Not a huge deal for safety, but I did want to stay out of the restricted Edwards AFB airspace and I wouldn't have wanted to rely on GPS for that. (The old VOR/DME/KNS-80, ADF/NDB, and Mark I Eyeballs worked fine, which further undermines my first point.)

Finally, if you figure out your airspeed, stick to a compass heading, and keep track of the time you've been flying, dead reckoning is surprisingly accurate, especially if you can get even occasional fixes from any kind of radio navaid or even a visual landmark. This is easier if you're not also trying to fly the plane at the same time, which I suppose is why they used to have navigators (people, not electronic boxes).

posted by Hello Dad, I'm in Jail at 3:30 AM on January 7, 2010


Hey, live preview lied about the &gt and &lt. Sorry about that.
posted by Hello Dad, I'm in Jail at 3:31 AM on January 7, 2010


In the very late 1970s, when GPS was being bid out by the DoD, a few of us at Texas Instruments invented the electronic charting system, the precursor of today's electronic navigators (it used real-time geographical information and digitized maps to present a continuous "you are here" map — it could also tell you how you got there, but it couldn't tell you how to get somewhere else). Although GPS was its inspiration, we used LORAN for the prototype, and most of the commercial justification. We weren't really sure that this GPS stuff would catch on.

.
posted by ubiquity at 5:18 AM on January 7, 2010 [1 favorite]


[vapidave] Both links went to the same picture. I think this is the second one intended to be linked (with bonus cat).

Thanks! Sorry about that! I'll revisit this thread or start a new one once I have some high quality scans done, and once the shutdown is more imminent.
posted by rune at 10:01 AM on January 7, 2010


By the way I forgot that the official slogan for the Jan Mayen station is:

Theory is when you understand everything, but nothing works.
Practice is when everything works, but nobody know why.
At this station we combine theory and practice,
so nothing works and nobody know why.

posted by rune at 10:08 AM on January 7, 2010


3. A good sextant and almanac is accurate to like a quarter of a nautical mile. We'll be fine- no one's jamming celestial bodies out of existence! :)

except, you know, the sun and clouds.


The SR-71 had an astro-inertial navigation system... like a regular INS but with automated star sightings to correct for INS drift. It even worked during the day, though clouds were indeed a problem. But once you get up to 80,000 feet, there aren't many clouds. Just the thing for accurate navigation in the pre-GPS days, over territory without ground-based radio navigation aids, or where people may be actively messing with those to try to disrupt your mission!
posted by FishBike at 10:43 AM on January 7, 2010


Just last night I was watching Wonderful World of Flying and the 1987-era video had an awesome demo of EvenTide's Argus 5000 moving map display. A really great looking vector display connected to an aviation database and LORAN for navigation inputs. The database updates came in the form of a replaced circuitboard and the 3" square tiny map view was like looking through a porthole, but there was a little airplane on a map and you could fly all the way to the airport! The UI was surprisingly sophisticated, actually, not too much different from contemporary GPS moving maps. Anyway, the video never once uttered the term "GPS", it was all LORAN, and the device looked really cool.
posted by Nelson at 12:04 PM on January 10, 2010


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