Forget eyeballs and radar! Brits tackle GPS jammers with WWII technology Navigation technology developed during World War Two has been deployed to run a network of longwave transmitters as a GPS backup in parts of England and Scotland. As of Friday, the eLoran system had been switched on along the east coast at seven ports. It is expected to cover all of the British Isles by 2020. Quangocrats who …
First off, a Ring Laser Gyro only gives you rotation, not translation information. Navigation grade RLG's typically have an integration error of about 1 degree per hour. The other component of an inertial measurement unit (IMU) is the accelerometers to give you translation information, with a typical navigation grade accuracy of about 1mg (milli gee). Three gyros and three accelerometers are normally combined in an IMU. The combination of an IMU and a computer running navigation equations is called an Inertial Navigation System (INS). A typical navigation grade INS has a total integration error of about 1 nautical mile per hour. Believe me, you don't want to sail around relying on an INS to tell you where you are. You only want it to see if your GPS is being spoofed or for very short term navigation when you GPS has dropped out. A "military grade" INS has an integration error of about 1 nautical mile per 24 hours, a tactical grade (like on a JDAM) has a total integration error of about 10 nautical miles per hour, which again is why the INS is used for short term when the GPS is screwy.
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> My understanding is that SINS grade navigation units are much better than that
That's correct. While the previous poster's general description is a generally accurate description of an IMU (Inertial Motion Unit), there is no such thing as a "typical" INS. As you can imagine, the requirements are rather different for an ICBM, an orbiting satellite, an airliner, a jet fighter, a surface vessel, an ROV, and a submarine, to mention just a few examples.
The ballpark figure of 1 nm / hr can be loosely associated with the electromechanical IMUs of pre-2000s airliners, and possibly other applications as well, though I have none in mind right now.
Actually it's DED reckoning. It means to take a previously known position, adjust for time, speed, heading, wind, tide and the accuracy of the helm in holding the planned course, in order to DEDUCE your current position.
Involves a lot of assumptions, and is thus increasingly unreliable over time.
> What, exactly, was unplugged?
The Beeb's journo's brain.
He probably misunderstood (perhaps intentionally, for sensationalism's sake?) someone's explanation.
On a merchant (i.e., large) ship, the gyrocompass is almost universally fed an NMEA string containing latitude in order to correct for Earth rate drift. If you lose the feed, the effect might go from nil (if navigating East-West) to not particularly serious, plus the correction can be set manually anyway.
As for the radar, a CMG (Course Made Good) input is usually fed into it, typically from GPS (the gyro tells you which way the bow is pointing, which is not usually the way you are going). In the absence of it, it will just not give you the option to go CMG up. Actually, position is also fed into radars, which is then used to augment the information it is able to give you, such as derive a lat/lon for any targets being tracked.
The one thing that has not been mentioned is AIS. Without a GPS (or some other system) feed, your own position will not be broadcast, although you will still receive data for all other targets.
A complete GPS loss is not a common occurrence (loss of differential corrections is more frequent) but I've experienced it two or three times. In practice it's more of a minor annoyance than anything else--mind, if it stayed out for more than a few hours that'll be a different story.
Absolutely worthless on a dark night.
The accuracy of a sextant, even in the hands of a skilled user, is often measured in miles, even in calm water. In a gale......
They are fine for crossing oceans, just don't get anywhere near your landfall in the dark, particularly an uninhabited island.
These days, what with quartz wristwatches, they ought to be able to make at least a guess at their longitude, and at night even the passengers should be able to tell the latitude. No doubt old-fashioned navigation has been largely taken out of the curriculum for navigators due to the ubiquity of GPS, but I would think that some of the basics are still taught and practised. Never mind GPS jammers; what if these systems are shut down in the event of war?
> No doubt old-fashioned navigation has been largely taken out of the curriculum for navigators due to the ubiquity of GPS,
No it hasn't.
> but I would think that some of the basics are still taught and practised.
Yes they are. Though perhaps not as much as I would like. :)
Plus a good navigator never relies on a single piece of data. Even a quick naked eye glance at Polaris¹ can tell an experienced navigator if he's in the right bit of ocean.
¹ E.g., if I can't see it and I'm supposed to be in the Barents, I get worried. If I do see it and I was expecting to make landfall in Australia shortly, I get worried too. :)
When I learned to fly a few years back, we were taught NOT to go near the GPS. We couldn't even use a calculator, we used a 'whizz wheel' circular slide rule for all calculations, pencil and rulers on paper maps.
Modern browser encryption is basically symmetrical one-time-pad encoding, with the one-time-pad created and exchanged on-the-fly with difficult to solve prime factorisation problems, but you can do the whole one-time-pad stuff by hand (it's actually pretty fun if you like puzzles)
I think it's important to know this stuff, because it works, solidly, no matter if there's a massive EMF pulse, power failure, whatever.
> When I learned to fly a few years back, we were taught NOT to go near the GPS.
Mostly because the instructors had no idea how to use it. Either they were a bunch of old farts or they had been taught by one.
That has caused a number of GA accidents, either with pilots getting lost when a GPS could have got them out of trouble easily, or with pilots getting lost because they relied on a GPS without knowing how to use it.
Learn to operate and use everything at your disposal, and cross-check your info.
A lot of WW-II bombers had a special dome on top so the navigator could take sextant sightings. B-17, B24, Lancaster, etc. Sextants do work in aircraft.
And no, I'd guess 85% of just about any ship or aircraft personnel have no clue how to use a sextant today. Maybe some midshipmen fresh out of the academy...
"A lot of WW-II bombers had a special dome on top so the navigator could take sextant sightings. B-17, B24, Lancaster, etc. Sextants do work in aircraft."
They do work, just not very well. Y-Gerat, X-Gerat, OBOE, GEE, LORAN all got developed by both sides in WW2 because it was realised that navigating by the stars was a sure way to missing a bombing target.
The Germans knew this from the outset, and it took a long time for R.V. Jones (one of the best brains Britain had in WW2) to be given the resources to find out how the Germans were doing it. Typically the RAF insisted that its crews could achieve good accuracy by navigating by the stars, and it took them a long time to acknowledge that they were missing their targets by many, many miles.
Detective Emil said: “The US Coast Guard is busy decommissioning the existing eLoran infrastructure.
Wrong. The USCG spent millions refurbishing key parts of the old LORAN system, and tested the proposed replacement eLORAN system. Congress, in its infinite "eat the seed corn" wisdom, ordered the LORAN system decommissioned, thereby wasting the LORAN millions already spent. The US never implemented an eLORAN network. Europe has decided for reasons of marine safety at sea to implement the eLORAN technology. The US did not.
Why, you say? Well ... a $15 piece of jamming kit can bring down the GPS coverage in a wide area; being mobile, the jammers can easily evade tracking. One should recall that GPS satellite signals are extremely hi-frequency/low power and ridiculously easy to jam.
The new eLORAN system is extremely low frequency/high power, and near-impossible to jam. Accuracy of the system for marine navigation is quite good, approaching GPS standards.
The US has bet that we are impregnable from attack by nasty system jammers; Europe is not quite so confident and is investing in redundancy. 'Nuff said.
Coastwise navigation is infinitely safer with electronic positioning systems; those who think the sextant is sufficient should try getting a position during a storm on a small craft. The best backup for an electrical system or GPS equipment failure is a handheld GPS with fresh batteries. Problem solved. Redundancy is easy. Arguments to the contrary are the realm of armchair admirals.
@Gray,
Quite right.
WW2 Technology? Bloody Lazy Journalists (inc The Register)
I'm slightly irritated by the description as being "WW 2 Technology" that seems to have attached itself to eLORAN. It's anything but WW2 technology. Such a description is similar to saying that digital TV is based on the technology of Logie Baird.
If it comes to that, GPS can also be described as having been based on WW2 technology; it's just yet another way of determining position by measuring distances USING A RADIO SIGNAL from transmitters whose positions are known. That's a perfect description of eLORAN, LORAN-C, GEE, X-GERAT, Y-GERAT, OBOE, JAY, or any other radio based navigation system. With GPS the only conceptual difference is that the transmitters are in space. Even the idea of putting up a satellite to broadcast a radio signal also originated in WW2 in the mind of an RAF officer call Arthur C. Clarke. [Okay, so he thought about geo-stationary satellites, but he set the theme for all the ideas that followed.]
Drop the Bias, El Reg, and Think
The Register, no doubt spurred on by that retired and possibly out-of-date navigator Lewis Page, seems to be biased against eLORAN. That may be because LP thinks that it is inaccuracte.
However it seems to have had no difficulty in achieving 5m accuracy in limited trials (see this). Without differential corrections it seems to get to 6.8m (see this presentation, page 37. Also the nature of eLORAN is such that the more tranmitters you build the more accurate it becomes (unlike LORAN-C), lessening the need for differential eLORAN. A widespread deployment would be useful for almost all purposes, with differential eLORAN put in only where it mattered.
Incidently, LORAN-C is almost certainly something that Lewis Page has used and been irritated by. It would certainly irritate me. However I wonder if he's ever actually ever used an eLORAN receiver? By all accounts it's no different to using plain old vanilla GPS. In fact the whole essence of eLORAN is to make it as simple to use as GPS.
I find that lack of imagination inside El Reg surprising. As Gray says above it is cheap and effective, and it uses is a digital radio system (for its data channel) of a sort that normally gets a bunch of technologists like The Register excited. They like GPS, WiFi, Freeview, DVB-S, Bluetooth: what's not to like about eLORAN?
(They'd also like Digital Radio Mondiale [DRM - an unfortunate acronym] too if they'd ever heard of it. DRM is what DAB should have been).
I think the reason why they don't like it is because they have no imagination as to what eLORAN could become. So how about they try this on for size? It would be pretty simple to build a chip scale eLORAN receiver in the same way we currently build chip scale GPS receivers. If we had one of those, you could put on in every mobile phone, sat nav, train, mobile phone base station. That is, everything that uses GPS could be capable of also using eLORAN with a minimum of additional hardware. Also a chip scale eLORAN receiver would probably use a lot less power than a GPS receiver (there's less maths to do). Surely that's something to like?
Come on El Reg, Give it Some Backing
I think that it's quite interesting that it's the authorities in the maritime world that are pushing eLORAN. No doubt that's why Lewis Page gets hot under the collar about it. However the likes of the GLA, US Coast Guard, Trinity House, etc. all have centuries long cultures of ensuring that the navigational aids they provide to mariners are there, are working, and are working well. It's no surprise that they feel that GPS dependency is a dangerous thing.
I'm sure that Lewis Page (I don't know him) was an able and dutiful navigator, but that's a rarity in the maritime world these days; some ships can't even miss a wreck despite radio warning, guard ships, bouys and lights. If the commercial maritime world is hell bent on being automated all the way to the harbour entrance then the maritime authorities will ineviablty make sure that the technology behind it is backed up.
However there's plenty of other users of GPS who would be mortified if their GPS stopped working, not least every single smartphone user. The Register should be expressing an air of gratitude towards the likes of the GLA for giving us all the prospect of a decent backup that we could all use in a way wholly compatible with today's technology.
Disclaimer: I have no connection to any organisation with an interest in eLORAN or navigation.
Well bloody well wreck yourself if you can't navigate without GPS.
Navigation by dead reackoning/chart/compass/log/sextant/stars/eyeball/fluke or whatever has worked for millenia. Ocasionally it has failed: most of the coast of Britain is a graveyard to the unfortunates who got it wrong, but it has still got many a boat or ship from A->B.
Hell, even I know how to find Polaris. Can't find the sun? a polarizing filter will sort that out. Funky sunglasses or a lump of cordierite will do the trick - make sure you have some on the bridge.
This is what I do:
https://groups.google.com/forum/#!topic/sci.geo.earthquakes/ufOlD22r9DE
The thing is, one of the first things I noticed is that in some long lasting weather setups, the RF interference is breathtaking. And all the while in all my amateur research I never realised the Bomber Command exploits of WW2 were the blokes behind the boys in that particular back room.
Well done them. Lets have an outing can we?
The only bod I am aware of is the not then yet Professor Jones.
What about the power loss?
Navigating without port lights is a real pain, these should have backup batteries IMHO.
I did wonder about whether the GPS problem could be avoided if jamming detectors were installed, it is not that hard to use simple triangulation using multiple Rx units to distinguish a genuine-but-weak signal from intentional jamming.
One Arduino + GPS Rx would make for a great project and have real world implications.
Tried Decca inn the 1960's on east coast USA... map accuracy was 1/4 mile zone of uncertancy, as it was a hyperbolic ststem, accuracy changed by location, could be factored out "if you knew where you were in the first place" 3 axis GPS can locate all 4 legs of a mountain top microwave tower...Decca can't be effectively jammed...gps goes away w/brute power jamming... this means unsymmetrical warefare= a cheap device will disable all shipping in a limited area... a terrorist dream or a chapter out of the Art of War.
REF= a free on line book by the US GOV, Bodich - the American Practical Navigator... or HO-5 from Annapolis press, single volume, large size.
IMHO= no one who is in charge of navigaqting any marine vessel should be without it and understand all of it... in the middle of the night with power out and the only remaing RDF taped to the chart table w/a candle burning in the center of the loop antenna and...you still made port... tied up, coffee break, bed, GN.
Much better to develop VORTAC sites at each harbor and former lighthouse sites... the current ground and onboard kit is cheap, solid state, and relatively free of brute force jamming possabilities...best part= no additional charts needed, only note the facilities...RS.
I was about to mention Decca, till I saw that you had already done so. I evaluated it as one of the backups in a very important system for locating certain road vehicles as long ago as 1988, and found that within mainland UK, as well as at sea, its performance was sufficient for that purpose. It also occupied almost zero bandwidth (unlike Loran, which is a nuisance to other spectrum users) and would be very hard to jam (again unlike Loran). The receiver technology eventually became very cheap, and nowadays could be integrated into a phone or tablet, if the demand was there. Sadly a very fine, low-budget British invention is gone, because no-one wanted to pay for its upkeep, believing that GPS was the ultimate answer!
But you CAN emulate and improve on the better aspects of Decca, and give Loran a sound thrashing, by using combinations of broadcast transmitters. A university research group demonstrated it 20 or maybe 30 years ago. Fixed monitoring stations, maybe 10 to 20 to cover the UK, measure the relative phase of the modulation on all transmitters carrying, say, Radio 4. You need to do that to cover for arbitrary delays in transmission links etc. Given that information, and a means to broadcast it, a mobile that can pick up 3 or more Radio 4 transmitters on different frequencies can do a simple phase comparison, much like the Decca coarse pattern used for lane ident. Then it can compare carrier phase, and get down to as good acuracy as Decca. If FM signals are available, you can get down to feet quite easily. It is in theory possible to use stations carrying different programs, but the computation gets to be rather complex! But 2 of one program and 2 of another gives you two simple locus lines, and one intersection, without fancy stuff.
I think that the phase information could be done relatively easily to the Coastguard monitoring stations which provide the correction data for differential GPS, and included in their broadcast data. There, problem solved, in the UK, and apart from anything that may already be patented by others, I hereby release this idea into the public domain. If open source hardware and software hackers want to knock up something that works, that would be very good....
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