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US Coast Guard Intends To Kill LORAN-C
adaviel writes "LORAN (Long Range Aids to Navigation) is an electronic navigation system using low-frequency radio, used by many boaters (including me) before GPS. It has an approximately 200m accuracy and is a functional replacement in case GPS fails or the US implements selective availability in time of war. The US Coast Guard, part of the Department of Homeland Security, intends to turn it off starting February 8." This is in spite of $160M spent on modernizing LORAN stations over the past 10 years.
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"This is especially idiotic considering GPS satellites that are currently in orbit are beginning to fail, and no country wants the responsibility of modernizing them, or repairing them."
Okay...
1. The DOD depends on GPS and matains the network. So what are you talking about countries wanting to take responsibility for the GPS network? The US DOD does.
2. You do not repair or modernize GPS satellites... You replace them.
3. GPS is going to keep working until it is replaced with something else or the US stops being a nation.
"Further, what if a GPS receiver goes offline on a ship?"
You use the backup? You don't really think that a ship would only have one do you?
The reason to keep both was that many operators spent a lot of money on Loran and GPS was expensive. Now GPS is cheaper and more reliable than Loran.
Your arguments are along the lines of "We should keep paying for hitching posts on our streets so we can keep horses as a back up for cars."
See my blog http://ilovecookes.blogspot.com/ for light hearted technical information.
200m is the absolute accuracy (and is a bit pessimistic). The repeatable accuracy is much better.
That is, if you sail into a port's harbour channel and save that as a LORAN-C waypoint you will typically be able to get back to that same spot within 20m or so easily.
SA made GPS accurate to 10m.. With the "SA" feature disabled, you're down to 2m... And with Satelite enhancements, it's more like 20cm !
But that's irrelevant.. Because SA was intended to disable any enemy force from using GPS for accurate positioning - until they realized D-GPS (Differential GPS) made the whole point moot (you take a reference point - you send the signal to the receiver - And therefore - the receiver can deduce the SA introduced clock error - because now you have a ref point .. And believe it or not - it is a United Stated Uniform service - the US Coast Gard - that came up with it to overcome the artificially introduced uncertainty).
However, the military still keep exclusive use of the 1Mhz band (with the 10Mhz being public) - for the only purpose of being able to make real time measurements on tropospheric distortions - so - what happens - is that the military can make 1m accurate reading WITHOUT sat aids.
Actually, yes. When I was commercial fishing on a troller in Alaska we used Loran grid coordinates, spoken in Danish, to tell our brothers where the fish were. No one else could understand us. If we said "Over and out" the conversation was finished, but if we said "I'm off," that meant to change frequencies, tell how many King's you'd caught, and give the coordinates. Without the Loran our sneaky ways will have to be changed.
How about a moderation of -1 pedantic.
At least my recollection is that while the absolute accuracy of LORAN isn't nearly as good as GPS, it actually had better repeatability (i.e. the ability to return tomorrow to that fishing spot you found today) than at least pre-DGPS/WAAS GPS did.
Today's modern GPS systems and supplemental accuracy aids probably make this moot, but it's a major reason why LORAN has survived as long into the GPS era as it did.
G.
Frankly, I'm surprised this is still around. Everyone I know has switched over from LORAN-C to GPS or other systems at least a decade ago. Even aside from the cost of maintaining the system to the government, the system is clearly inferior to GPS. For one, since the towers are much lower compared to satelites, it is much easier to have your signal blocked. The system isn't nearly as accurate (as mentioned in the summary) and is also in many contexts much more likely to simply fail. The system also doesn't work if one is far away from land. This is an extremely reasonable cost-saving measure.
500m accuracy for sextants seems unrealistically good to me. My experience is approximately 2km in good conditions and with an accurate clock available. But even that is good enough for navigation.
I've been a sailor most of my life. We haven't used Loran C seriously for almost two decades. Most boats don't even have Loran receivers any more. It's GPS all the way whether you are a casual sailor or a commercial ship captain. In fact, large commercial ships are required to use GPS and special transceivers these days (the boater's equivalent of GPS-based aircraft systems). If backup matters one could pack a RDF or maybe even a sextant, but frankly GPS has not failed even once from the day it became available to boaters. Besides, Loran C pretty much only works near the coastline of major industrialized nations (or did)... it wouldn't be all that helpful if you were lost at sea.
The coast guard should have abandoned Loran C years ago.
-Matt
Loran A that I was using around 1970. In mid-Atlantic you couldn't get signals during the day and accuracy was around 1 nm, but it certainly was nice to have.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
It has better *resolution* than that, although I can't speak for the accuracy (meaning repeatability).
Back in the day, I actually rigged up a Loran system and a surplus Compaq Plus luggable computer in my car, and wrote a program in QuickBASIC to log lat/long data points while driving back to college from vacation. Just to see what it would look like, I drove completely around a cloverleaf interchange (four 270-degree turns), and continued on. When I got where I was going and ran the data through a really cheapo plotting program I wrote, I could clearly see all four loops (some a little flattened, probably more due to the 1-second time resolution than anything.)
Granted, this was in the middle of nowhere (low noise), at night (nice propagation), with a long whip antenna on the top of the car -- but it was still impressive for Loran-C. (And yeah, I know it would be a piece of cake for any half-decent GPS receiver.)
As for selective availability, I think this could be implemented over Loran -- although Loran's repeatability without modifications is probably no better than the ~50m accuracy of GPS+SA...
Paleotechnologist and connoisseur of pretty shiny things.
"Without the Loran our sneaky ways will have to be changed"
Come up with a list of 100 words. Danish, Esperanto, Klingon, or whatever. Assign numbers from 00 to 99. Read off your GPS coordinates using one word for every two digits. Save time by pre-defining large grids with special names to avoid having to read off more digits than necessary.
I've got notes around here somewhere on a more sophisticated version of that I was playing with for search and rescue use - not to conceal anything, but to be more efficient and accurate than reading strings of numbers. The words were simple, of a consistent number of syllables, phonetically distinct (long Hamming distance) and with multiple lists you can make it tolerant of transposition of words. The idea was for the encoding to be done on a GPS receiver - you wouldn't need to do it manually.
The "new" version of DGPS is called WAAS (wide area augmentation system), which is where airports in the US will have local DGPS stations send their correction data to the WAAS satellite, and these corrections will be distributed to aircraft flying over the US for use as precision approaches (instead of the use of radio equipment at the end of runways).
Knew a lobsterman who told me he'd steam for two hours, come up on his Loran set point - cut the throttle, stick his gaff out the port side of the boat and grab his trawl, without fail. In the dark. Sounds a bit better than 200 m. He had the lobsters to prove it!
There are also examples of quite amazing navigation done using sextants, particularly the voyage of the James Caird http://en.wikipedia.org/wiki/Voyage_of_the_James_Caird
Well they can simply turn GPS off (entirely or over certain areas) or introduce large-scale errors; since they don't control Galileo that's not an option and jamming is the only solution. And since jamming is not a precision tool it would be nice if jamming operations didn't interfere with the more selective control available for GPS.
They're probably also worried about unintentional interference from Galileo. Or jamming from third parties -- if someone starts jamming radionav systems it would be useful to know if they're targeting the EU or the US.
On the contrary. The GPS constellation consists of fast-orbiting spacecraft. Period is about 11 hours. So all that must happen is an event that lasts 11 hours and has sufficient energy to do the job. The reserve sats (block IIR) orbit at the same rate; they'd be just as fried as the block II and block IIA sats.
For GPS to work, you need a minimum of three working sats within LOS of the antenna; the position fix is determined from the downward intercept of three spheres centered on the sats. Anyone who is depending on this, and suddenly loses it, may be in serious trouble. And it's not all that easy to whip out a sextant in the cockpit of an aircraft, or in your SUV (I'm really not sure how many expeditions actually carry a sextant, for that matter. I don't own one, and I do know how to use one.)
Here, take a look at this charmer, happened only 2 years ago: X-class flare. Pay particular attention to the duration.
I've fallen off your lawn, and I can't get up.