U.S. May Reduce Non-Military GPS Accuracy

ward99 writes "The U.S. government may be degrading GPS satellite signals, to cripple Iraqi forces' ability to use those systems during the war. This could potentially reduce accuracy from ~3 meters to over ~100 meters. Users depending on GPS systems may want to do sanity checks on any data returned by those systems during the war. The U.S. will do this by increasing the inaccuracies on the civilian C/A code, turning back on S/A (Selective Availability), by having the satellites deliberately and randomly return inaccurate information on where they are. S/A degrades GPS accuracy to only 100 meters 95 percent of the time and 300 meters the other 5 percent of the time. This will not effect the military P code."

It is worth noting that this is a localised effect

[James_Duncan8181]

As the GPS network can be degraded or upgraded region by region. I used to be in military service and one of our tips for civilians was that they could always tell when the shit was really about to hit the fan because the GPS accuracy will change massively when compared to a know coordinate point.

Interestingly we were also told that it is not usually done before 24h from action. Anyone want to go a $10 bet with me on that? ;)

Re:Army's stuff

[Gordonjcp]

Or use differential GPS, and get accuracy to a few tens of millimeters.

What about Gallileo (if it was operative)

[pork_spies]

Would be interesting to know what the EU would do with Gallileo at this moment in time. I dare say they would follow the US lead, I suppose...

Wow

[koh]

...by having the satellites deliberately and randomly return inaccurate information on where they are.

Isn't that supposed to be terrorism ? ;)

doubt if it will make any real difference

[guybarr]

My guess is that for high-precision locations, the Iraqis already measured them with high accuracy, while for, say, infantry navigation all you really need is 100m accuracy. (Even less for armored forces, of cource)

And given the air threat, I also doubt their forces will change their localtions too much; if it's camouflaged enough to survive the initial attacks, it will probably stay put.

What about planes??

[borgdows]

Civilian planes use GPS, don't they?
What about other critical systems like police, ambulance, fire brigades and so on??

Thats one reason why europe should build own GPS

[Neuronerd]

There are plans for building a similar system to GPS in Europe so that we are not too much depending on the american empire. The following page [satcoms.org.uk] nicely explains the concept. More is available here [eu.int]. This is technically very interesting and should open up new possibilities for navigation. Furthermore being constructed jointly by many partners and nations we can be reasonably sure that it can not be compromised by one weak leader.

Re:Sanity checks..

[James_Duncan8181]

For your 2 questions:

a) A sane person would rely on GPS because they may not be very good with compass and map, or they may have cordinates for something not marked on a map. When driving at speed the margin of error is negligible, and it enables you to navigate through featureless terrain such as desert playa which are impossible to use a map in.

v)Well...I would walk to a point which I knew the exact location of and then do 10 or 15 GPS location checks to see what the margin of error was.

Did you really not know these answers or am I just feeding a troll?

STDMA

[G3ckoG33k]

There is a better alternative to GPS named STDMA (Self-organizing Time Division Multiple Access). It is patented with U.S. Patent No. 5,506,587, which you may find HERE [uspto.gov].

It is in use in marine navigation. See also HERE [marinelog.com] and for a tech overview HERE [transpondertech.se].

Apparently, the US has tried to suppress the system as it may well replace GPS because of better performance and other reasons; one can imagine wartime control may be of importance here.

Re:What about last time?

[Nogami_Saeko]

There was a big discussion on one of the GPS newsgroups about this very fact - at the time of the last gulf war, civillian GPS units were cheaper, more plentiful, and had more features that the troops wanted/required than the more cumbersome military GPS units.

One of the soldiers was talking about it in the group and basically said the military units were limited to showing long/lat and doing goto-waypoint distance/direction operations. At the same time, civillian units had mapping capabilities, easy to use graphic displays, and were about 1/2 the size.

As other posters have said, it's possible to adjust the SA signal geographically, so they could degrade the signal in the middle east without changing anything in north america. This is the first step that seems logical.

Alternately, they could leave SA off alltogether, and just jam the GPS signal in the area that they are performing operations - the GPS signal is relatively weak and an ECM aircraft could easily block hundreds of miles of GPS reception while flying out of range of ground-based weaponry.

N.

Re:This was *exactly* why we here in Europe...

[Amroarer]

Even if it was, it would still remain under the control of the Russian military, just as GPS is under the control of the Pentagon.

The whole point (well, one of the major ones, anyway) of Galileo was to create a network which wouldn't be under military control, and so could be relied upon not to be switched off at inconvenient moments.

Exactly why GPS can't be trusted

[Anonymous Coward]

If this isn't the best (and only needed) reason anyone would NOT use GPS for critical applications, such as airplane collision avoidance systems, I don't think I'll ever see one.

Then they ask why Europe don't want to use GPS for exactly this application. Duh!

Re:It is worth noting that this is a localised eff

[jkrise]

"the GPS network can be degraded or upgraded region by region"

Who holds the keys to this action? Does it mean all GPS systems are at the mercy of a single entity in the US which can degrade or upgrade accuracy as it may please?

Worse than terrorism, it seems to me. I've seen GPS based land-use data systems. Wonder what'd happen if they're built using degraded data.

Re:What about Gallileo (if it was operative)

[jeremyp]

I doubt it since a lot of the European countries are not enthusiastic about a war and France in particular is dead against it. France is the main driver behind the European space effort.

Re:What about Gallileo (if it was operative)

[slashtom.org]

Not a chance! Does it look like France and Germany are doing what the US tell them.

But what chance has the EU got of getting Gallileo working in the next decade. Their current military project, the Eurofighter is years behind and billions over budget.

Re:it *is* our stuff

[LazySlacker]

Isn't that a bit like saying. It isn't your car - the money used to buy it was given to you by your employer.

I rather like to idea of getting a bunch of people together - going round to military HQ and saying - "can we have our bomb back?"

Re:What about Gallileo (if it was operative)

[LazySlacker]

Isn't 'military project' and 'over budget and late' a tautology?

Re:What about Gallileo (if it was operative)

[the_2nd_coming]

a lot of euopean countries? name them. I can show you a map that has France, Gremany, Belgum, denmark, norway, sewden,greece, and finland as being anti-this war. the rest of europe is on our side. more than 2 times the amount against the war are for the war.

Re:doubt if it will make any real difference

[sql*kitten]

My guess is that for high-precision locations, the Iraqis already measured them with high accuracy, while for, say, infantry navigation all you really need is 100m accuracy. (Even less for armored forces, of cource)

That's an awfully big assumption. Consider the terrain in southern Iraq. A few tens of metres (or less) is the difference between fording a river with your tank, and getting bogged down in marshland and having to sit and wait for a recovery vehicle, and all the while vulnerable to air attack. Iraq isn't all desert as many people think; a lot of it is quite wet because of the Tigris and Euphrates rivers. The inhabitants of southern Iraq are often known as the "Marsh Arabs" for this reason. Even worse, few metres can mean the difference between a clear lane through a minefield, and straying into an uncleared area. Tanks may look clumsy, but they still require precision handling.

Re:Army's stuff

[Anonymous Coward]

You know..if there was a medal for ignorance, I think you just would have won the gold.

A lot of countries don't have the technology to build satellites, or the money to research said technology..thus, they rely on the existing infrastructure. And some people rely -extensively- on accurate GPS measurements..sea-faring vessels, civilian aircraft, the list goes on. Think of how they might be affected if they weren't even aware this change was taking place; particularly if they were conducting research in a remote location, and relied upon GPS to..well..figure out where the hell they are.

Send up your own satellites indeed. I'm suprised an American can actually speak those words, yet still be amazed why they're so hated outside their own country.

Re:It is worth noting that this is a localised eff

[Chanc_Gorkon]

Yep. GPS is pretty old hat now and the military can totally jam it to others in some instances (so I have heard). I think that this is a stupid idiot spouting off. of course I could be an idiot for spouting off about totally jamming GPS in Iraq(what makes you think they could not? I mean I have no proof either way). GPS has a far reaching effect now. Much more now then it did even 2 years ago. Surveyors use it now as well as Amateur Radio operators with APRS and lots of other people use it. Buses use it in my town. Besides, GPS is not needed necessarily to guide a missile. What did they do before? Same thing that's been already done. Having a GPS just increases your chances of hitting the target you want. You could still hit it without GPS.

Re:It is worth noting that this is a localised eff

[James_Duncan8181]

The nice thing about conrolling it is that you can offset it at will. So you could have a (stupidly designed) nuke in the air and offset GPS by 20 miles and watch your command bunker avoid a direct strike. Also you could completely ruin the GPS in this way system for desert use. This is why is is good to suddenly kill it, since you have got the tank crews used to using it.

In a desert with no useful GPS, you have to stick to roads. The bombers know where the roads go. This is how we absoletely hammered the Iraqi army last time (traffic jams for the Iraqis bugging out of Kuwait on the main highway).

Re:GPS jamming

[dachshund]

I suspect the Iraqis have little need of GPS--their military probably knows their country pretty well and they don't have much in the way of smart weapons.

On the contrary. The Iraqis' biggest weakness in the first Gulf War was their inability to navigate through the open desert. There's very little in the way of navigation aids out there, so it doesn't matter how well you know the country.

GPS is their ticket off of the roads, allowing them to do what we did-- go right through the unposted desert. My question is how much this signal will be degraded, and whether it will seriously hinder efforts at desert navigation.

Re:A question

[Sunda666]

Actually, most units have a 12-channel parallell receiver, so it can do a pretty job and narrow your
position within 9 meters. 4-channel GPS units are things of the past (or used sometimes when size
matters more than accuracy).

Also, there are a "new" addition to the GPS system called WAAS (wide-area-augmentation-system) which
uses differente sattelites (this ones being geo-stationary) to send differentials information about
the GPS's sattellites signals. This way, a civilian WAAS-enabled unit like mine (garmin etrex vista)
can have an accuracy of about 3 meters, in theory. I find WAAS pretty dodgy and dont tend to use it
much because of higher battery comsumption and higer CPU usage, for a small improvement in the
accuracy (I mostly use the GPS in the car, so...)

cheers.

Re:Alternatives

[Moridineas]

THanks for the links. Very informative. In their it says that the US military has never degraded civilian service, neither during Gulf War I or during Kosovo. Though there are contigency plans to limit affectiveness for a specific area (from one of the links). Sounds good to me. But the important part is that it's never been done.

The interference sounds like a very serious issue as well.

Also, the US didn't annoucne anything--we still have no idea if the signals will be degraded or not. This all comes on the speculation of a German autoclub--no doubt the first group of people informed of US military policy.

Scott

Where are the GPS+GLONASS receivers?

[raygundan]

A few civil engineers I know who do some survey work use big, expensive receivers that pick up both GPS and GLONASS signals to further increase accuracy. Why aren't there any consumer-level units that pick up both GPS and GLONASS signals? The more satellites you get, the better your fix, and if the unit was smart enough to notice SA being turned on, it could use the GLONASS fix instead.

I'm assuming that somewhere there are cheap civilian GLONASS receivers-- if they cost about the same as cheap 12-channel GPS receivers ($150) you should be able to build a combo unit for less than $300. Cost is reduced by only needing one screen, but increased by needing additional logic or code to combine the two networks' signals into a single position.

Has anybody seen one of these?

Rumor has it...

[Andy Dodd]

that the US turned off SA in the first place to neuter the Galileo project by reducing its perceived need.

Well, the second time the US turned SA off was for that reason.

This article is really amusing because of the fact that the government actually turned SA OFF for the last Gulf War, as there was a shortage of military GPS receivers and soldiers were ordering civilian units mail-order.

Re:This was *exactly* why we here in Europe...

[Anonymous Coward]

Is it really worth the money and the effort to send up an entire system so that coverage can be ensured during the say 2% of time when the GPS signals are distorted for military reasons?

Yes!! I work for a USA company that is working on Gallileo receivers. The higher precision and reliability of the Gallileo system will likely entirely supplant the other two GNSS systems.

They've planned for this

[Dont tempt me]

In the FAA air traffic simulator where I work, we have recently done studies preparing for what would happen if the GPS satellites were disabled (on purpose or jammed from a terrorist). NATCA (the controllers union) has developed procedures for what to do when this happens. Most aircraft would fall back to their backup navigation systems, assuming such systems would work on the route they were currently on. Less than 2% would even need attention, and it would be minor intrusion at that -- just enough to get then to where they can fly on their own. Even in the future, when some of the current systems are removed, it won't be much more of a problem.

So you can feel just as safe flying as you currently do ;)

Re:Using the P code

[gklyber]

There is a nice description of using the P code in the March 2003 NASA Tech Briefs. There is a link to the article on this page [nasatech.com] and this direct link [nasatech.com]. Free registration required.

The method described does some signal conversion to extract useful information from the P code even when the A code (encryption) is not known. It uses an approximation of the A code and summing over time to extract useful information.

Precision Ag

[Tsu-na-mi]

I for one couldn't care less if hikers' GPS accuracy is reduced to 100m, but for the industry I work in (Precision Agriculture), this presents a huge problem. Many of our clients used DGPS back in the day, and in some areas where it is freely available (along the coast, mostly), still do. However, most do not. 3m was already bad enough, but 100m is a real problem. I'm sure there are other industries being affected by the use of SA as well.

Comment removed

[account_deleted]

Comment removed based on user account deletion

Re:Army's stuff

[fname]

Here's the dirty little secret. Many soldiers use their own civilian GPS devices, b/c they have better features. So, I'd bet there are more American and British soldiers using civilian GPS than there are Iraqis. I doubt GPS will be degraded, and if so, it will be brief.

Re:Sanity checks..

[mlazareff]

Or during full night either, except using an artificial horizon on your sextant (bubble sextant), requires a big ship's stability.

"Night" sights for celestial navigation are usually made when the sun is some (5~10) degrees under the horizon, so that both the stars and the horizon line are visible. This allows (with ex. 3 stars) a full position to be determined in a few minutes.

The moon may also be used, but precision is usually bad, because of unprecise (complex and rapidly evolving) ephemerids (almanac) and raised horizon (glare) under the moon at night.

By day, if both the ship's and sea current's course / speed are steady, the classical method of the running fix allows the ship's position and course to be determined using only sun sightings.

This may be performed (provided that sun and horizon are clearly visible) using only a precise timepiece, a sextant and special "sight reduction" tables. The latter item is preferably replaced with a programmable calculator, which will run for tens of hours on a single set of batteries, although the tables should be on board and understood.

This old technique is not as fast or as precise as the GPS, and requires a clear sky, but does not depend on the ship's power supply or on the fast-emptying batteries of a hand-held GPS unit, and because of this is mandatory for navigation on Class 1 yachts (allowed on the high seas).

This follows the sailors' habit of never discarding old-but-working methods, especially if they are more robust than new-fangled ones.

Re:Army's stuff

[Rich0]

I don't think the army is too worried about DGPS. It would solve the civian problems of accessing accurate GPS data, but not the military problems. Why? Because the DGPS station would need to have a transmitter, and it would have to remain at a very precisely fixed geographic location, and transmitters don't last long in war - especially if they are in fixed locations.

I know the US is actively looking to find ways to deny potential enemies access to 3rd party satellite services. If the EU launces their own GPS system, they would be expected to play ball with the US and turn it off in areas where the US military is operating. If they don't the satellites could be considered a military device (since they would be used by a military), and they would probably be jammed at the least, and if that doesn't work then they could be targetted. I'm guessing most corporations that own satellites would just play ball - those satellites cost big money and I doubt their insurance protects against US anti-satellite weapons. Government-owned satellites might be a different story - depending on whether the foreign government wants to make the political move of standing up to the US.

Keep in mind that providing targetting data to a military is hardly a neutral stance. If the US provided military GPS receivers to Chechen rebels, you can bet the Russians would be ticked.

Probably already happening...

[Anonymous Coward]

www.faa.gov [faa.gov] has already got NOTAMs posted regarding inaccurate GPS readings and not to rely solely on GPS for IFR flight.

Re:This was *exactly* why we here in Europe...

[sphealey]

I thought there was a GPS hack anyhow, where if you fed the data of 3 GPS located in the same place into a computer, it would triangulate and correct for the distortion error.

Nope. Remember the quote from The Firm: "Remember - I'm smarter than you."? The guys who designed GPS were better mathematicans and better planners than just about everyone else. This possibility is covered in the design such that SA really does work. Until you get into post-processing, etc.

sPh

There's a BIG problem with this....

[mark-t]

I know a guy that's legally blind, and uses his GPS every once in a while to confirm his location -- specifically, he sometimes needs to confirm where he is at from time to time. This is particularly important when he is travelling to an address he has not been to for some time. A computer-synthesized voice tells him almost exactly where he is, in terms of the streets and avenue names of the city as well as an address range. This guy is amazingly self-reliant for someone who is blind, in my opinon (he actually isn't completely blind, but he can't make anything out other than blobs of color that are more than a few inches from his face).

Now correct me if I'm mistaken here, but wouldn't deliberately decreasing the accuracy of GPS signals essentially create a further handicap for this person who uses the equipment in his day to day life to function more like a "normal" person. Somehow that just seems wrong to me.

And on the up-side, it's great news for people who don't want the rental car companies tracking where they drive.

It'll cost you $1000-2000, Yankees

[billstewart]

The early news discussions were predicting the war would cost about $200 billion. That's about $1000-2000 per American taxpayer. Of course, that doesn't count the cost of taking that money out of the civilian economy, which had better things to do with it. If they'd really wanted to take out Saddam because he was a mean nasty ugly guy, a Mossad hit squad could have probably done it for $5-10M, and the CIA could have probably done it for well under a billion, without the need to kill thousands or hundreds of thousands of Iraqi civilians or risk the lives of large numbers of US soldiers.