GPS Jamming Trials in UK - GASIL
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Disgusted of Tunbridge
Disgusted of Tunbridge
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Can someone who understands better than me what the disadvantages of GPS accuracy are? I can understand if you can throw a nuke off target by a mile or so, you might have a totally razed airbase rather than a completely obliterated one, but who are the 'bad guys' using GPS for devious means? Are we trying to throw their road navigation off course? Why else bother with SA? We have perhaps one of the greatest facilities ever invented being allowed to the world for free, and people are putting an intentional spoiler in. Maybe I'm naive, but I really don't understand.
Per Ardua ad Astraeus
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We are not talking 'nukes' here - the problem arises if you try and lay down weapons using GPS when both sides are just a few hundred feet apart, as in 'Close Air Support'. As you say, a few 100mtrs for a nuke is not a big issue.
And also, why on earth do you need satellites for agriculture?? Surely when ploughing/harvesting you get to the end of the field you turn around and start heading back on a parallel course?
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Rainboe, the problem is terrorists. A primitive gps guided cruise missile can be put together for very little money using off the shelf components. It's not that difficult either.
Gps jamming is one way to stop it.
Gps jamming is one way to stop it.
And also, why on earth do you need satellites for agriculture?? Surely when ploughing/harvesting you get to the end of the field you turn around and start heading back on a parallel course?
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Angels, there are some quite sophisticated uses of GPS in farming now.
For one example, found after a quick Google , see FarmerGPS - Welcome! (or .com). Or do a search of your own if that interested.
I am not an expert. But while doing a survey on fertiliser usage with some local farmers, I encountered one who described his system (not the one in the reference above).
He used a company which sent an ATV over every field, taking soil samples at every 10 metre point, showing soil composition and characteristics. The system then plotted a “contour” map of the field, showing which parts were chalky, which not, which low on (e.g.) nitrogen etc. If you know nothing about farming, you would be amazed at how much it varies over a field, let alone from one to the next. Certainly true in East Anglia UK, and probably lots of other UK places, where the geology and microclimate changes a lot from one place to another.
The fertiliser typically comes in 3 parts, N, P and K. Instead of spreading a mixture with averaged proportions, each was spread by different spreaders on a GPS-controlled machine, using the survey data. The farmer told me it was fascinating to see one spreader wheel slowing down and another speeding up as it reached a bit low on P and high in K etc. Overall, it reduced the total usage and net cost of fertilising.
Other uses of GPS include semi-automatic combine harvester operation.
These and other things require reasonably high positional accuracy from the GPS.
If GPS were stopped, going back to old methods would be challenging, I suspect.
Chris N.
PS – At Precision Farming Tools: Global Positioning System (GPS) - Virginia Cooperative Extension there is what seems an excellent article on GPS, accuracy, etc. – intended for farming but the general descriptions look good to me.
For one example, found after a quick Google , see FarmerGPS - Welcome! (or .com). Or do a search of your own if that interested.
I am not an expert. But while doing a survey on fertiliser usage with some local farmers, I encountered one who described his system (not the one in the reference above).
He used a company which sent an ATV over every field, taking soil samples at every 10 metre point, showing soil composition and characteristics. The system then plotted a “contour” map of the field, showing which parts were chalky, which not, which low on (e.g.) nitrogen etc. If you know nothing about farming, you would be amazed at how much it varies over a field, let alone from one to the next. Certainly true in East Anglia UK, and probably lots of other UK places, where the geology and microclimate changes a lot from one place to another.
The fertiliser typically comes in 3 parts, N, P and K. Instead of spreading a mixture with averaged proportions, each was spread by different spreaders on a GPS-controlled machine, using the survey data. The farmer told me it was fascinating to see one spreader wheel slowing down and another speeding up as it reached a bit low on P and high in K etc. Overall, it reduced the total usage and net cost of fertilising.
Other uses of GPS include semi-automatic combine harvester operation.
These and other things require reasonably high positional accuracy from the GPS.
If GPS were stopped, going back to old methods would be challenging, I suspect.
Chris N.
PS – At Precision Farming Tools: Global Positioning System (GPS) - Virginia Cooperative Extension there is what seems an excellent article on GPS, accuracy, etc. – intended for farming but the general descriptions look good to me.
FX Guru
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Blimey, all I wanted to know and more! Thanks.
I still get the feeling that we are becoming slaves to technology though.
I was held up at Dover for over two hours recently because the P&O booking computer crashed. They couldn't get anyone onto the ferries. The traffic was queuing up the hill out of Dover and because of that traffic people sailing with other companies couldn't leave either.
I was near the front of the traffic and on talking with various port employees it turned out P&O don't really have a Plan B for when their computer goes TU.
In the future, if we become over-reliant on GPS and it is suddenly turned off, how would the airline industry cope? Easily? With difficulty?
Not panicking, just wondering.
I still get the feeling that we are becoming slaves to technology though.
I was held up at Dover for over two hours recently because the P&O booking computer crashed. They couldn't get anyone onto the ferries. The traffic was queuing up the hill out of Dover and because of that traffic people sailing with other companies couldn't leave either.
I was near the front of the traffic and on talking with various port employees it turned out P&O don't really have a Plan B for when their computer goes TU.
In the future, if we become over-reliant on GPS and it is suddenly turned off, how would the airline industry cope? Easily? With difficulty?
Not panicking, just wondering.
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The accuracy of GPS isn't really a disadvantage, except for people in the military who are paranoid by profession and spend lots of time imagining ways in which their own technologies could be used against them. The military philosophy is to keep every technology classified forever so that the bad guys can never use it (and if civilians must suffer from not having it, so be it).
Fortunately, cooler heads prevailed with GPS, which is why the military was ordered to make it available to the civilian world.
The overreliance on GPS is a concern, and there is no obvious back-up. Galileo will not be a back-up, since it's just another version of the same technology. The problem is that there may be no back-up for satellite navigation in general, especially as government authorities foolishly decide to retire other forms of navigation to save money. If you have VORs or NDBs, you can still find your way home in bad weather. If you have only GPS, and GPS stops working, you're lost.
There are some circumstances in which GPS accuracy can lead to problems. One problem, already adumbrated here, is that GPS normally is used in conjunction with a database, and the overall accuracy of GPS in practice depends not only on the satellite longitude and latitude, but also on the accuracy of the database that tells equipment what lies at that latitude and longitude. This is why GPS might put you a mile north of an airport: chances are that the GPS was right on the mark, but the database was substantially in error.
Another drawback to accuracy is that it can put two aircraft in exactly the same place at the same time, which is bad. Two aircraft flying towards Big Mountain might still be thousands of feet from each other, but two aircraft flying towards the BGRSK waypoint might well blend together when they reach it, if they happen to coincide in altitude and time.
Still another drawback is excessive reliance on and trust in the technology by pilots who don't really understand how GPS works and what the potential problems with it might be. They come to believe that GPS is always perfectly accurate, and they might find out too late that it isn't. Some pilots talk as though they trust GPS altitude more than altimeter altitude, for example, when in fact the altimeter is orders of magnitude more accurate than GPS for altitude.
There's also too much willingness to trust GPS for approaches (in theory or in practice), as a substitute for ILS. But ordinary GPS cannot come close to ILS for accuracy, especially for precision approaches. Using GPS in place of ILS requires LAAS (which is not GPS at all, but merely a supplementary technology), and even that is delicate. And no, things like WAAS or RAIM do not make GPS anywhere close to foolproof.
As always, the smart aviator will use every available tool to maintain maximum safety in the air. GPS is all well and good, but it's still extremely important to have a Plan B. Airliners have this built in to some extent, with flight management systems that can combine information from multiple sources (GPS, IRS, VORs) to arrive at highly reliable conclusions; but private pilots in small aircraft who have got into the habit of navigating solely by GPS can get into deep trouble (as multiple NTSB accident reports demonstrate).
Fortunately, cooler heads prevailed with GPS, which is why the military was ordered to make it available to the civilian world.
The overreliance on GPS is a concern, and there is no obvious back-up. Galileo will not be a back-up, since it's just another version of the same technology. The problem is that there may be no back-up for satellite navigation in general, especially as government authorities foolishly decide to retire other forms of navigation to save money. If you have VORs or NDBs, you can still find your way home in bad weather. If you have only GPS, and GPS stops working, you're lost.
There are some circumstances in which GPS accuracy can lead to problems. One problem, already adumbrated here, is that GPS normally is used in conjunction with a database, and the overall accuracy of GPS in practice depends not only on the satellite longitude and latitude, but also on the accuracy of the database that tells equipment what lies at that latitude and longitude. This is why GPS might put you a mile north of an airport: chances are that the GPS was right on the mark, but the database was substantially in error.
Another drawback to accuracy is that it can put two aircraft in exactly the same place at the same time, which is bad. Two aircraft flying towards Big Mountain might still be thousands of feet from each other, but two aircraft flying towards the BGRSK waypoint might well blend together when they reach it, if they happen to coincide in altitude and time.
Still another drawback is excessive reliance on and trust in the technology by pilots who don't really understand how GPS works and what the potential problems with it might be. They come to believe that GPS is always perfectly accurate, and they might find out too late that it isn't. Some pilots talk as though they trust GPS altitude more than altimeter altitude, for example, when in fact the altimeter is orders of magnitude more accurate than GPS for altitude.
There's also too much willingness to trust GPS for approaches (in theory or in practice), as a substitute for ILS. But ordinary GPS cannot come close to ILS for accuracy, especially for precision approaches. Using GPS in place of ILS requires LAAS (which is not GPS at all, but merely a supplementary technology), and even that is delicate. And no, things like WAAS or RAIM do not make GPS anywhere close to foolproof.
As always, the smart aviator will use every available tool to maintain maximum safety in the air. GPS is all well and good, but it's still extremely important to have a Plan B. Airliners have this built in to some extent, with flight management systems that can combine information from multiple sources (GPS, IRS, VORs) to arrive at highly reliable conclusions; but private pilots in small aircraft who have got into the habit of navigating solely by GPS can get into deep trouble (as multiple NTSB accident reports demonstrate).
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Anthony, it's not like that with military. GPS is for delivery (guidance) and fusing (detonation) but never used alone as it is jammable. Cartography is the big issue with GPS, as you say. Cartography can be a long way out -- in my personal experience hundreds of metres, quite far enough to kill you. The real danger is that it seems to be so accurate while it is miles out. If only GPS could shrug and say "not sure", but that isn't built into the system.
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For those who worry about SA or any other way of 'switching it off': be assured that the largest usergroup of GPS has been proven in recent months to be quite supported by government and does not even move/navigate.
Banks nowadays use GPS to time transactions as a microsecond delay on a volatile stock/currency market can cost/bring in (dependend on the party) serious money.
As for Galileo/all others: the 28 (or maximum of 30 +2) satelites that the US can put up (a 5 bit ID seemed sufficient in the 70's) are often insufficient (try living above 60 lat). As the optimal RF spectrum for sending time-sensitive signals through the atmosphere is not to wide, it only takes some simple programming to include multiple pseudo-range sources (be it NAVSTAR/Galileo/Glonass/Some Geostationary stations)
i.e. Don't see Galileo as a competitor/the future (depending on view) see it as addition: 20+ satelites in view and you have continued navigation between high buildings. (in aviation, that would probably be combined with a prospect of having a chat on the merits of keeping above MSA in relation to keeping your licence)
Banks nowadays use GPS to time transactions as a microsecond delay on a volatile stock/currency market can cost/bring in (dependend on the party) serious money.
As for Galileo/all others: the 28 (or maximum of 30 +2) satelites that the US can put up (a 5 bit ID seemed sufficient in the 70's) are often insufficient (try living above 60 lat). As the optimal RF spectrum for sending time-sensitive signals through the atmosphere is not to wide, it only takes some simple programming to include multiple pseudo-range sources (be it NAVSTAR/Galileo/Glonass/Some Geostationary stations)
i.e. Don't see Galileo as a competitor/the future (depending on view) see it as addition: 20+ satelites in view and you have continued navigation between high buildings. (in aviation, that would probably be combined with a prospect of having a chat on the merits of keeping above MSA in relation to keeping your licence)
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On the subject of back ups ... I let the GPS & AP talk to each other, they seem to get on just fine. I am busy monitoring all the other navaids, or even looking at the map!
Just in case the lights go out permanently, I've still got a slide rule ...
Just in case the lights go out permanently, I've still got a slide rule ...
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How much use will Galileo’s extra satellites be to our present GPS receivers? Are they compatible? Or will only new receivers that have both GPS and new Galileo capability be able to use both sets of satellites?
Chris N.
Chris N.
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In the future, if we become over-reliant on GPS and it is suddenly turned off, how would the airline industry cope? Easily? With difficulty?
Having been personally using INS for enroute navigation since the very late nineteen sixties/early nineteen seventies on 707 aircraft, it can be very accurate, for the enroute case.
The Litton units were/are more robust, the Carousel units more accurate, in my experience.
Plus/minus one nautical mile enroute navigation (over long enroute sectors)accuracy is possible, IF the specific units are maintained properly.
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Rainboe, the problem is terrorists. A primitive gps guided cruise missile can be put together for very little money using off the shelf components. It's not that difficult either.
Gps jamming is one way to stop it.
Gps jamming is one way to stop it.
Rumor 1:
I think I've read somewhere that commercial GPS chip sets like http://www.sirf.com/products/GSC3LPProductInsert.pdf have inbuilt max speed and max altitude just for that reason (60Kft, 1000knts in the link). It may not stop from using it on short range missiles, but longer range wont work.
Rumor 2:
One of the reasons Selective Availability (SA) was switched off is that during some 'recent' US deployment (Desert Storm? Balkans?), troops on the ground were using (on their own) commercial devices as navigation aid, which obviously where affected by the SA. Switching off SA made life of the troops on the ground easier.
Rumor 3:
UK is kind of against the militarization of Gallileo (using it to guide weapons), France and Germany want it. Could be because of better relationships with the USA, or maybe that the UK has suffered losses from European built guided weapons (Falklands, Exocet ASM), that with a military Gallileo signal will just get better.
Non rumor:
Gallileo when finished (2014+) wont be better in accuracy than the latest block of GPS satellites (Block III?). GPS will be superior by then. Gallileo is better than the current GPS satellites, but not the GPS of 2014+. The military signal of GPS may be even better by then (beam focusing etc).
Its the strategic independence in navigation that makes EC fund it fully after the failure of the PPP (Private-Public Partnership).
China is also chipping in some 300-400 million euros, they have their own local positioning system, and looking for a global one in the future.
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GPS/Galileo "competition"
1.I know of no reason why Galileo should be superior to GPS,and anyrate it doesn't exist yet (just two demonstrators, the cheaper of which was from a UK university and saved the dayfrom losing frquency allocation to comms industry)
2. The benefit comes from combination of both systems(both sides have sworn that they will be mutually compatible).Doubling of number of satelliteswill inprove RNP considerably.
3.FAA have dilly-dallied over back-up. Among candidates are E-Loran (no timing for dreaded bankers), residualATC radar.INS would probably require
calibration, but not everyone has got it.(Litton have done it experimentally)
4.I am not sure Europe can produce thegoods. They havn't yet certified EGNOS, which is little more than a copy ofWAAS,which now is certified for hundreds of runway ends.
Keith
2. The benefit comes from combination of both systems(both sides have sworn that they will be mutually compatible).Doubling of number of satelliteswill inprove RNP considerably.
3.FAA have dilly-dallied over back-up. Among candidates are E-Loran (no timing for dreaded bankers), residualATC radar.INS would probably require
calibration, but not everyone has got it.(Litton have done it experimentally)
4.I am not sure Europe can produce thegoods. They havn't yet certified EGNOS, which is little more than a copy ofWAAS,which now is certified for hundreds of runway ends.
Keith
Dual GPS and Galileo receivers will be required. They are already on sale now (for marine and land use at least, I don't think aviaiton sets are available yet).
Galileo is more accurate. It's a new system whereas GPS dates from the 80s. The system can't develope much when the original satellites are still in use. Although GPS Block 2 satellites are flying and Block 3 are coming soon, they are still hampered by the limitations of the original system. Galileo achieves 1m accuracy in it's basic mode. It's also much faster to aquire and compute a position.
GPS has a problem in that the programme of replacing satelites is behind schedule. Recently, the US Government accountability office warned that full coverage may be lost in the near future due to this.
Galileo is more accurate. It's a new system whereas GPS dates from the 80s. The system can't develope much when the original satellites are still in use. Although GPS Block 2 satellites are flying and Block 3 are coming soon, they are still hampered by the limitations of the original system. Galileo achieves 1m accuracy in it's basic mode. It's also much faster to aquire and compute a position.
GPS has a problem in that the programme of replacing satelites is behind schedule. Recently, the US Government accountability office warned that full coverage may be lost in the near future due to this.
Galileo is far more advanced and will give far better accuracy. And it is in operation now
16 June 2009 Yesterday at the Paris Air Show in Le Bourget, ESA and Arianespace signed a contract for the launch of the first four operational Galileo satellites on two Soyuz launch vehicles from Europe’s Spaceport in French Guiana.
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I too used a sextant when I was doing the RYA yacht-masters course, never used it in anger though as I've always been able to use radio aids to roughly locate my position. This was in the 60's when Consol was still operating and radio beacons were thick on the ground.