Shutting Down the GPS Network

More stupid security from our government. From an AP story:

President Bush has ordered plans for temporarily disabling the U.S. network of global positioning satellites during a national crisis to prevent terrorists from using the navigational technology, the White House said Wednesday.

During a national crisis, GPS technology will help the good guys far more than it will help the bad guys. Disabling the system will almost certainly do much more harm than good.

This reminds me of comments after the Madrid bombings that we should develop ways to shut down the cell phone network after a terrorist attack. (The Madrid bombs were detonated using cell phones, although not by calling cell phones attached to the bombs.) After a terrorist attack, cell phones are critical to both rescue workers and survivors.

All technology has good and bad uses — automobiles, telephones, cryptography, etc. For the most part, you have to accept the bad uses if you want the good uses. This is okay, because the good guys far outnumber the bad guys, and the good uses far outnumber the bad ones.

Posted on January 5, 2005 at 8:49 AM25 Comments


Zwack January 5, 2005 10:52 AM

<Sarcasm>I think that we should ban cheap disposable pens. I mean yes, they can be used to perform emergency tracheotomies, but that good is outweighed by the potential for harm that they can cause. Pens are frequently used in Identity theft and there is the possibility that one could be used in a similar manner to a stiletto.

Ban pens now! </Sarcasm>


Michael Slater January 5, 2005 11:04 AM

“The Madrid bombs were detonated using cell phones, although not by calling cell phones attached to the bombs.”

I don’t understand. How then were they used?

joe January 5, 2005 11:56 AM

This really doesn’t make much sense when we have other GPS-like constellations flying… like Russia’s GLONASS and (in the future?) EU’s GALILEO. Then, we’ll be depriving mostly our own citizens and infrastructure of navigation, while attackers will only need one other such device.

Trey Jackson January 5, 2005 12:30 PM

Not only are there more good uses for the technologies than bad, but disabling the use of the GPS system can only be done after a terrorist attack. So, unless the terrorists cannot time things (a possibility, but less likely now that they know the need for synchronization), disabling the systems can really only lead to harm as they won’t be usable for the necessary good purposes of recovering from such an event. Kind of like shutting the barn door after the cow has left.

Roger Bush January 5, 2005 12:49 PM

Come now, do we have any evidence that this Administration is capable of implementing anything that is GOOD for America? There must be a report somewhere from a “reliable source” that says terrorists rely on GPS postitioning to hide their WMD…or that Halliburton will gain market share once GPS is disabled.

Creating this capability will not only weaken the American electronics market for GPS technology, but it will continue the global trend of questioning and doubting the motives behind the fast power-grab by our current Administration and the radical right. Maybe the EU will invade us (running on GALILEO) and save us from another Bush being propped into office in 2008.

Tim Green January 5, 2005 12:50 PM

“develop ways to shut down the cell phone network after a terrorist attack”

What use is “after”? Stable door now firmly closed and locked.

Stephen Pollei January 5, 2005 2:11 PM

Zwack asked “How then were they used?” …

The probably rigged the ringer up to a detonator, and then set up a alarm timer to a certain time in the future.

Woody January 5, 2005 2:13 PM

As a volunteer firefighter that’s looking into the use of GPS to help locate houses that are well off the beaten path in our rural fire district (roads are often a single lane, unpaved, and look less like roads than 4×4 trails…), we would be losing a great asset if this were to happen.

The amount of time it takes to locate houses on medical calls, or to locate the seat of a wildland fire from a distant ridgetop is quite long. GPS and good maps of the area (especially digital maps showing current location and the location of the destination) would be an amazing asset. And this would be removing it, at a time when it might be most necessary for us to have it.

Chris Smith January 5, 2005 2:47 PM

Zwack asked “How then were they used?” …
Stephen Pollei’s answer is confirmed by this report ->
One bomb had it’s timer set wrong – 7:40pm instead of 7:40am – and was discovered and disabled without damage to anyone OR the bomb.
Many cellphones now have both time-of-day and countdown timers, and most also have an audio output that would generate an electrical impulse to an external circuit. And, not inconsequentially – until it is plugged in, the cellphone is ONLY a cellphone and not a suspicious bomb component.

AC January 5, 2005 3:04 PM

What use is “after”? Stable door now firmly closed and locked.

Exactly. How insanely reactionary. We should disable them now!

Gerald Fraenkl January 5, 2005 3:37 PM

Such stories are one of the main reasons why the European Union (now including China and others) has decided to set up Galileo – kind of a european GPS with better technology and most important: not depending on US military operations (and other situation of “national crisis”.

Bruce Schneier January 5, 2005 4:46 PM

“‘The Madrid bombs were detonated using cell phones, although not by calling cell phones attached to the bombs.’ I don’t understand. How then were they used?”

They were used as timers.

yitz January 6, 2005 4:40 AM

i know that in jerusalem when there are suicide bombings, the israeli army has some way of jamming all cellphone and radio transmissions in a reasonably sized radius around the attacked area. the rationale, i think, is that the terrorists used to set off one bomb, wait for the security and rescue forces to arrive and then remotely detonate a second bomb (and/or third bomb etc) [note that this is actually a useful thing to do, because rescue workers and security that need to be reached by cellphone/radio are usually (at least initially) outside of this jammed radius anyway]

i know this only from personal experience: whenever i found myself on a bus travelling around jerusalem and suddenly noticed my (fm) radio went dead, or i couldn’t get any signal (or get a call through) on my cell, it usually meant there was just a terrorist bombing somewhere nearby.

ps. i presume the army would shut down gps in a way that the army would still have access too it. (maybe that is giving them too much credit?) Could they encrypt the signals or transmit in a different range or something that would render all proprietary (civillian) gps systems useless?

Eddie Brown January 6, 2005 5:11 AM

Prior to the war in Iraq there was a warning doing the rounds amongst merchent ships that GPS might be rendered unreliable, and as such other fixes should be used (e.g. bearings from landmarks when near the solid stuff, and stellar sights when not in sight of land) kinda illustraits how everyone has now adopted GPS as the common navigational aid. And maybe highlights the need for other systems to prevent some brightspark realising that if they could induce someoen to turn off the system they could impact many transport systems.

Boyd January 6, 2005 8:01 AM

Vitz, up until May 2000, the GPS system operated under what was called “Selective Availability,” which introduced random errors in position reports up to 100 meters. The military had special GPS receivers that eliminated these errors and achieved the typical (at that time) 10-meter accuracy.

I don’t believe SA would be of any use any more, because too many of the government’s GPS units these days don’t have the ability to eliminate the SA error.

For the record, while I think this is a supremely bad idea that merits the shooting of a bureaucrat or two, I don’t think it would ever be implemented. In the end, cooler heads will prevail.

Kevin Rowett January 6, 2005 11:18 AM

GPS signals are also an excellent source of TOD, relative timing, and frequency accuracy.

The frequency source for newer FM broadcast stations is 10MHz derived from the GPS signal.

As for timing, it’s also used by many cell networks in various ways.

It’s very likely that if GPS is turned off, a number of radio stations will go off the air, and large portions of the NA cell network will go silent.

Don January 6, 2005 11:28 AM

One of the other reasons SA was turned off was that it had become pretty pointless in the face of differential receivers which used additional sources (LORAN, etc) to pinpoint actual position. You could get under 1m resolution w/o SA if you spent a few more bucks.

It was never terribly clear what SA meant to accomplish in the continental US anyway. If you have a human “pilot” of whatever source they have additional methods of fine-tuning (eyes and brain) within that 100m range. If you have the resources to launch a missile of some sort you probably can enhance it sufficiently with gyro guidance or the above differential systems to make the SA irrelevant.

And of course when it comes to terrorism the most pertinent question is probably what difference does 100m make for targeting the kind of thing they want to do anyway? Aimed dead center into a park or stadium anything they’d be likely to do isn’t going to be negatively impacted by a few hundred feet of spread – their whole point is more fear than anything else.

Kinda like these announcements and efforts by DHS 🙂

Andrew Plotkin January 6, 2005 2:28 PM

The idea of taking down GPS for security reasons is not new. It was
originally operated by the US military. I think it’s now nominally
under civilian control, but it’s always been clear that if the DOD
wanted GPS offline, GPS would go offline.

This is why the EU wanted to build their version (Galileo) in the first

Fred January 6, 2005 4:01 PM

And if one is thinking of a big plane being used as a missile, GPS is not that critical. There is inertial systems for positioning, which I think are mandated by the FAA on all of the big planes. It really does not take a genius to fly by dead reckoning either. Like someone said, it will mainly hurt the people trying to do something about it.

On the other hand, it never hurts to make plans for any contingency and think about the consequences BEFORE hand and just save them somewhere. It makes sense in disaster planning, to think what would happen if we turn off the GPS system, and how it can be done.

Sometimes newspapers can blow things out of proportion too.

Roger January 17, 2005 6:21 AM

The original reason for SA, as I understand it, was fear of turning a small plane into an accurate, long-range poor man’s cruise missile. Just pack it with explosives, set the autopilot with GPS update, and parachute out. Inertial navigation is far less of a threat here; because the relative effectiveness of a blast goes inversely as the cube of the proximity to the target, a small plane packed with explosives and landing within 10 m of the target would be far more effective against a modest sized target (up to ~100m) than a 747 on inertial nav, which would typically miss by a few hundred metres laterally, and a km or so longitudinally–enough to totally miss our hypothetical stadium. Plus, a well resourced group of terrorists could presumably organise far more Cessnas than 747s.

What makes the rule relatively pointless today is the increasing prevalence of suicide bombers (plus the fact that in today’s climate, after one such attack any aircraft not giving a satisfactory response on voice freqs would be shot down).

It should be noted that the capacity for denying GPS access in a region is not a reference to SA, which has been turned off permanently; rather, particular regions can have the SPS (civilian) signal excluded from them altogether. Thus, DGPS systems would stop working too, but NATO military receivers picking up the encrypted PPS signal would still work. (Note that Galileo–which will not be operational until 2008–has been designed so it can blocked in the same way.) As Bruce comments, it would probably be an exceptionally bad idea to do this over the US after a terrorist attack on US soil, but it is not difficult to see that in some cases for some regions it could be very useful to have the capability. The availability of GLONASS might obviate this, but non-military GLONASS still has SA, and currently is not fully operational (it is hoped to be restored by 2007, pending funding availability and a deal with the Indian government).

Oh, and one final note: according to FAA, the GPS program transitioned to joint civilian/military control in 1966. That’s SIXTY-six, 12 years before the first GPS satellite was launched. So it has never been a purely military system.

Steve January 19, 2005 4:04 AM

Re: cellphones. See Lawnmower Man? (pretty bad movie) When we find ourselves in times of trouble (TM), why not make all the cellphones ring? Could be random, could be all in a cell/city/etc.

It would make arming those cell-triggered bombs just a bit trickier…

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