GPS jammin'
June 7, 2016 11:41 AM   Subscribe

FAA warns of widespread GPS outage. The FAA advisory (pdf). The FAA is warning pilots that there will be several widespread outages of the GPS syste centered on China Lake, California, home of the Navy’s China Lake Naval Weapons Center. A military GPS jamming system? Let the conspiracy theories commence.
posted by GuyZero (77 comments total) 18 users marked this as a favorite
 
Do they retire and replace satellites? Would temporarily losing one sat even cause the sort of outage they warn about? Is there actually any plausible explanation other than some sort of jamming system being tested?
posted by Dysk at 11:46 AM on June 7, 2016


But what are the civilian applications?
posted by Slackermagee at 11:47 AM on June 7, 2016 [2 favorites]


It's a promotional stunt for GLONASS.
posted by mattamatic at 11:47 AM on June 7, 2016 [7 favorites]


GPS is designed to have global coverage at all times and you'd need a lot of satellites to be out to completely lose a signal.

Constellation Arrangement: "The satellites in the GPS constellation are arranged into six equally-spaced orbital planes surrounding the Earth. Each plane contains four "slots" occupied by baseline satellites. This 24-slot arrangement ensures users can view at least four satellites from virtually any point on the planet."
posted by GuyZero at 11:52 AM on June 7, 2016 [3 favorites]


How is the DoD doing regional jamming/degradation of GPS a conspiracy theory? The system was created in part to guide ballistic missiles, and it seems super-licit to keep other people from using it for that and related purposes.
posted by The Gaffer at 11:52 AM on June 7, 2016 [9 favorites]


Per the FAA advisory, there are commercial civilian aircraft that basically become non-functional without a GPS signal:

ADDITIONALLY, DUE
TO GPS INTERFERENCE IMPACTS POTENTIALLY AFFECTING EMBRAER PHENOM
300 AIRCRAFT FLIGHT STABILITY CONTROLS, FAA RECOMMENDS EMB PHENOM
PILOTS AVOID THE ABOVE TESTING AREA AND CLOSELY MONITOR FLIGHT
CONTROL SYSTEMS DUE TO POTENTIAL LOSS OF GPS SIGNAL.


Regardless of what GPS was designed to do, what it does today is mostly help civilians get around. Heck, they turned off selective availability in 2000 so clearly it's not considered that sensitive a military asset any longer.
posted by GuyZero at 11:54 AM on June 7, 2016 [3 favorites]


The memo is titled "GPS INTERFERENCE TESTING". Doesn't seem like you need to theorize too much of a conspiracy beyond "The government that launched and maintains the Global Positioning System is testing what happens when they turn it off, one way or another."
posted by Etrigan at 11:56 AM on June 7, 2016 [14 favorites]


Ah well, back to breadcrumbs.
posted by the uncomplicated soups of my childhood at 11:57 AM on June 7, 2016 [19 favorites]


They might be reconsidering selective availability and not sharing that decision, esp. given that Russia has adopted drone-spotted artillery as the best thing ever.
posted by The Gaffer at 11:58 AM on June 7, 2016 [3 favorites]


Hipsters using inertial navigation will be immune, of course.
posted by The Gaffer at 11:59 AM on June 7, 2016 [11 favorites]


GPS jamming is explicitly illegal so it does seem a little surprising that the FAA is so nonchalant about this announcement. The FCC usually moves pretty hard against jammers. Also the region covered by the outage is really, really large for a terrestrial transmitter. Although maybe jamming GPS doesn't take that much power.
posted by GuyZero at 12:00 PM on June 7, 2016


I can answer a few questions about this, but I'm not really an expert.

Would temporarily losing one sat even cause the sort of outage they warn about?

No, but because the whole system is in constant motion it's not unusual to have area outages like this. Not necessarily planned this well in advance or with such a high degree of precision, however.

Is there actually any plausible explanation other than some sort of jamming system being tested?

Non-intentional jamming is becoming a significant issue as wireless companies are trying to utilize frequency bands very close to GPS frequency allocations. Intentional jamming is also definitely a thing, as experienced by South Korea within the past few months as the North tried to block their access to GNSS services.

it's not considered that sensitive a military asset any longer.

Not true at all! The whole civilian system can still be shut off, leaving it for military only. There are also mandated speed and altitude restrictions put in place by the government, imposed on manufacturers. (basically so you can't put a GPS on a ballistic missile).

Hipsters using inertial navigation will be immune, of course.

For about six hours give or take, depending on how good your INS is. Aviation systems aren't accurate much outside of that.

GPS jamming is explicitly illegal

Unless you're the Navy!
posted by backseatpilot at 12:01 PM on June 7, 2016 [24 favorites]


Also, this is why there's been such a renewed interest in "alternative PNT" (position, navigation, and time). GPS is inherently insecure and backup systems are required. eLORAN is making a comeback, baby!
posted by backseatpilot at 12:02 PM on June 7, 2016 [5 favorites]


Oh, I agree. GPS is much more than a super accurate position source - in fact, it's much more commonly used as a high precision timing source which is important in many, many applications. The most accurate timing systems in the world are atomic clocks, but the second most accurate is the GPS system that utilizes those atomic clocks and transmits out timing information.
posted by backseatpilot at 12:06 PM on June 7, 2016 [14 favorites]


ALIEN DISCLOSURE 2016
GET HYPE
posted by robocop is bleeding at 12:07 PM on June 7, 2016 [8 favorites]


There was a similar advisory centered on Jacksonville in 2013.
posted by RobotVoodooPower at 12:07 PM on June 7, 2016 [2 favorites]


Specifically, the rules requiring civilian GPS units to disable themselves above 59,000 feet and/or 1,200 mph were never lifted.
posted by fragmede at 12:07 PM on June 7, 2016 [1 favorite]


Note that this only applies to users at altitude (and increases with altitude). So basically only aircraft. No one else will be affected (excepting the very few people who are line-of-site to the base where their equipment is).
posted by Ivan Fyodorovich at 12:08 PM on June 7, 2016 [1 favorite]


There are also mandated speed and altitude restrictions put in place by the government, imposed on manufacturers. (basically so you can't put a GPS on a ballistic missile).

A coworker who is an amateur rocketry enthusiast put an early Android phone in a rocket to track it and the GPS data was very disappointing once it hit the mandated speed & altitude limits. :(
posted by GuyZero at 12:08 PM on June 7, 2016 [4 favorites]


>>>>Do they retire and replace satellites?
Yes they do. There are actually 24 (as of a few years ago) in orbit. Generally, 21 are active with the the others out of service for updates or other changes. The navsats are replaced on a schedule.

>>>Would temporarily losing one sat even cause the sort of outage they warn about?
No. As noted above, 21 satellites are orbiting the earth. A survey grade GPS receiver will track what ever is above the horizon and that could be as many as 12. Even if the signal from one drops out, you will still see all the others.

As for what's going on, I'm guessing it's a ground based interference. If you read the notice, you will note that as you move farther from the center of the area, the interference occurs at increasingly higher altitudes. Meaning, the interference is a broad, line of sight cone originating from a land based location. If ALL the satellites above the horizon can not be seen within the area but the GPS signal is still available outside the area for navigation, then again, it stands to reason it's a localized interference.

As far as I know, there are two basic ways to jam the GPS. First is just overpower and block out the satellite signal from the ground which is generally what happens. Second is the more insidious method which is to over power the satellite signal with a feed of false information to skew and distort navigation.

If I were to hazard a guess, it would be someone is firing up a big electronic device of some kind to test out their new toy.
posted by Oh_Bobloblaw at 12:10 PM on June 7, 2016 [9 favorites]


GPS is much more than a super accurate position source - in fact, it's much more commonly used as a high precision timing source which is important in many, many applications.

Google's "Spanner" storage system does distributes transaction coordination by having extremely synchronized distributed clocks via GPS.
posted by GuyZero at 12:10 PM on June 7, 2016 [2 favorites]


If I were to hazard a guess, it would be someone is firing up a big electronic device of some kind to test out their new toy.

The truth is out there.

Maybe it's a marketing stunt with real aliens for the Independence Day: Resurgence release.
posted by GuyZero at 12:16 PM on June 7, 2016


Hipsters using inertial navigation will be immune, of course.

*dusts off trusty LORAN-C*
posted by leotrotsky at 12:20 PM on June 7, 2016 [5 favorites]




EM spectrum disruption? China Lake?

I'm going to throw a guess out there that some High Powered Microwave testing is going to be trashing the spectrum at times that day.
posted by Talez at 12:35 PM on June 7, 2016


Do VORs still work?
posted by bondcliff at 12:36 PM on June 7, 2016


Do VORs still work?

Absolutely. There are even a bunch of NDBs out there, but not a ton of planes with ADF receivers. My club's planes have them, though - original equipment from their manufacture in 1968 and 1969. Mostly I use it for tuning in to AM radio stations (they operate in the same frequency band).
posted by backseatpilot at 12:39 PM on June 7, 2016 [3 favorites]


Weather Modification & China Lake - you got your chemtrails, your HAARP, your secret military base - maybe we should be asking how Paris can be having floods at the same time this is happening?????????
posted by GuyZero at 12:43 PM on June 7, 2016


If you'd like get an idea of how your phone's GPS works there is an android app called GPS status that has a nice display of the conceptual guts of GPS. You'll need to read the dense FAQ on the developer's website to really understand it. I use it to prime my run tracking apps which sometimes don't seem to properly pick up GPS. With GPS status I can see that it does before i start my run. Anyway, I enjoy seeing it pick up the satellites and update my location while I walk to the park. It reminds me of the science behind the magic.
posted by srboisvert at 12:43 PM on June 7, 2016 [10 favorites]


It reminds me of the science behind the magic.

The science is really something amazing, too, and is one of those things that you can point to when people start questioning why we need funding for basic science research. Like, isn't it neat that we found out that this one particular atom vibrates at such a regular rate? What a cool thing to find out. That simple discovery revolutionized navigation, communications, worldwide trade... and, yeah, ballistic missile targeting, but let's look on the positive side of things.
posted by backseatpilot at 12:58 PM on June 7, 2016 [13 favorites]


Theory heard elsewhere - the FAA/DoD wants a way to prevent GPS-guided terrorist attacks, and since you can't switch the satellites off, they need to come up with a reliable way to jam and/or spoof GPS. These are the tests.
posted by the painkiller at 1:02 PM on June 7, 2016


One wonders why they couldn't pick an area less densely populated with aircraft like North Dakota, unless they want some unwilling participants in the experiment. It's interesting how the wording changed from the Jacksonville notice ("Pilots are strongly encouraged to report anomalies") to this one ("Pilots are encouraged to report anomalies only when ATC assistance is required.)
posted by RobotVoodooPower at 1:06 PM on June 7, 2016 [2 favorites]


Presumably you can't just drive sensitive military microwave transmitters all over the place.
posted by GuyZero at 1:13 PM on June 7, 2016 [1 favorite]


And sometimes you just have to do your super-science experiments where the ley lines already happen to intersect.
posted by paper chromatographologist at 1:16 PM on June 7, 2016 [16 favorites]


As far as I know, there are two basic ways to jam the GPS. First is just overpower and block out the satellite signal from the ground which is generally what happens. Second is the more insidious method which is to over power the satellite signal with a feed of false information to skew and distort navigation.

At least for the military GPS stream, spoofing is avoided by encryption + authentication. Not sure if the civilian channels are authenticated.

The science is really something amazing, too, and is one of those things that you can point to when people start questioning why we need funding for basic science research. Like, isn't it neat that we found out that this one particular atom vibrates at such a regular rate? What a cool thing to find out. That simple discovery revolutionized navigation, communications, worldwide trade... and, yeah, ballistic missile targeting, but let's look on the positive side of things.

Not to mention one of the few (that I know of) practical applications of relativity!
posted by indubitable at 1:16 PM on June 7, 2016 [8 favorites]


Since we're all here to pull wild speculation out of our asses, I'll just chip in with one: China Lake is a test range, perhaps they're testing missile performance in a GPS-denied area.
posted by indubitable at 1:18 PM on June 7, 2016 [7 favorites]


Hipsters using inertial navigation will be immune, of course.


Real hipsters use artisanal, hand-crafted compasses and astrolabes as well as vintage nautical charts! Jam that, DoD!
posted by GenjiandProust at 1:19 PM on June 7, 2016 [2 favorites]


I guess I may as well also admit that China Lake and China Grove by the Doobie Brothers are somehow inexplicably linked in my mind and it's playing on repeat in my head right now.
posted by backseatpilot at 1:21 PM on June 7, 2016 [1 favorite]


srsly, the SR-71's nav system used the positions of stars in the sky. they just knew how to be more in tune with nature in those days, you know?
posted by indubitable at 1:23 PM on June 7, 2016 [11 favorites]


Real hipsters use artisanal, hand-crafted compasses and astrolabes as well as vintage nautical charts!

The Navy has started training all midshipmen this way again.
posted by GuyZero at 1:27 PM on June 7, 2016 [10 favorites]


I guess I may as well also admit that China Lake and China Grove by the Doobie Brothers are somehow inexplicably linked in my mind and it's playing on repeat in my head right now.
posted by backseatpilot at 1:21 PM on June 7 [+] [!]


Goddammit, backseatpilot! Me too now.
posted by Abehammerb Lincoln at 1:36 PM on June 7, 2016 [1 favorite]


Chicka wow wow, chicka chicka wow wow..dunh dunh dunh dunh duuuuunh!
posted by Abehammerb Lincoln at 1:37 PM on June 7, 2016 [1 favorite]


$20 says this is less about jamming GPS (which is apparently easy enough that we need to have laws about it) and more about testing some system or another's ability to deal with someone jamming it.
posted by Kid Charlemagne at 1:42 PM on June 7, 2016 [4 favorites]


Not to mention one of the few (that I know of) practical applications of relativity!

And both special and general relativity!

Because the satellites are in motion, their clocks are slower, according to special relativity.
But because they are higher up in earth's gravity well, their clocks tick faster according to general relativity.

These effects don't cancel each other out but they both have to be taken into account.
posted by vacapinta at 1:50 PM on June 7, 2016 [18 favorites]


$20 says this is less about jamming GPS (which is apparently easy enough that we need to have laws about it) and more about testing some system or another's ability to deal with someone jamming it.

This. Or they're testing something that blocks GPS as a side-effect, and are doing it on such a scale that if they don't announce via FAA there will be fatalities.
posted by thecjm at 2:12 PM on June 7, 2016 [3 favorites]


Man that's really long range. 400 miles is a really long way to disrupt radio signals. Admittedly the GPS signals are awfully weak, but most airplane antennas are pointed up and the source of interface looks like it's coming from below. Curious how significant the outage will actually be.

I'm pretty sure I've seen much smaller GPS outage NOTAMs like this before. Not the usual constellation malfunction stuff either, but ground-localized. But nothing of this scope.
posted by Nelson at 2:13 PM on June 7, 2016 [2 favorites]


I guess I may as well also admit that China Lake and China Grove by the Doobie Brothers are somehow inexplicably linked in my mind and it's playing on repeat in my head right now.

Well. That is an enduring earworm I am also now playing host to.
posted by ricochet biscuit at 2:50 PM on June 7, 2016 [1 favorite]


Hipsters using inertial navigation will be immune, of course.

From the Navy's test, perhaps, but have you ever seen one of those hipsters experience a gimbal lock event?

It's not pretty - a mess of glasses, beard, skinny jeans, arms akimbo, dropping iPhones and vinyl records, careening out of some dive bar, and they usually end up on a collision course with an accountancy firm, an insurance company, or a notary public. Some may be able to recover before impact, but often they just end up being stuck there and accept their fate as a assistant manager of HR.
posted by chambers at 3:01 PM on June 7, 2016 [15 favorites]


Since we're all here to pull wild speculation out of our asses, I'll just chip in with one: China Lake is a test range, perhaps they're testing missile performance in a GPS-denied area.

Or, say, a drone that someone like the Iranians can't pull out of the sky with spoofed GPS data (if that was true)?
posted by JoeZydeco at 3:21 PM on June 7, 2016 [1 favorite]


I'm thinking this is likely going to be some kind of high altitude radio energy testing, similar to HAARP (and no, I am not a conspiracy nutter on this, I actually like the physics and ionospheric research they were doing).

If they think they are going to get a huge LF bounce-back off the ionosphere, especially during the daytime, it will likely block out any incoming radio signals coming from GPS satellites.

I would definitely be curious if any HAM or other short-wave radio operators in the area will notice anything (it "should" be in the wrong frequency range). Though with some of the ionospheric tests, the whole point was to create daytime ionospheric bouncing (which is usually only possible at night because of the lower altitude portions of the ionosphere blocking out most bouncing).

I think I will play around with my RF scanner on those days. See if there is any new signals popping up.
posted by daq at 4:02 PM on June 7, 2016 [1 favorite]


Oh good lord. This happens all the time. There are NOTAMS out for GPS interference pretty much every week. There are about 20 airports with it happening today that you can see if you click the GPS/WAAS button here. It's quite openly talked about. There's a link on the front page of GPS.gov to search for the outages.

It even says...
On occasion, the US Federal Government is required to conduct GPS tests, training activities, and exercises that involve interfering with GPS receivers. These events go through a lengthy coordination process involving the Federal Aviation Administration (FAA), the US Coast Guard (USCG), the Department of Defense (DoD) and other government agencies.
Yes, yes, China Lake, oooh oooooh ooh, I know, but this is no more weird than the flight restriction that has suddenly appeared over parts of Los Angeles this afternoon.*


* It's for the baseball game
posted by DangerIsMyMiddleName at 4:07 PM on June 7, 2016 [6 favorites]


fragmede: "Specifically, the rules requiring civilian GPS units to disable themselves above 59,000 feet and/or 1,200 mph were never lifted."

It should be noted that these limits are US ITAR and not something inherent in the technology (obviously because the US military isn't bound by it). The limits are enforced in software. Not only is there open source software available for GPS IC hardware; the hardware can be built up from discrete components. The limitations are essentially no barrier at all to any half way determined attacker and not even a minor speed bump to anyone capable of manufacturing a guided missile.
posted by Mitheral at 4:11 PM on June 7, 2016 [1 favorite]


GPS (INCLUDING WAAS, GBAS, AND ADS-B) MAY NOT BE AVBL WI A 448NM RADIUS

Serious America, it's time to move on. I get that you love Nautical Miles but every time i read announcements like this I wonder why anyone cares about a 400 nanometer area of effect.
posted by GuyZero at 4:27 PM on June 7, 2016 [2 favorites]


At least for the military GPS stream, spoofing is avoided by encryption + authentication. Not sure if the civilian channels are authenticated.

My understanding is that this is basically never used, since there's no public key crypto in the system and thus anything that can decrypt/authenticate can, if compromised, encrypt/sign.
posted by effugas at 5:27 PM on June 7, 2016 [1 favorite]


According to Google Maps (which I can't rely on anymore either), I'm 254 miles from China Lake by highway, clearly less 'as the crow flies' (and the GPS signal). I'm just glad I wasn't planning on going anywhere today... or tomorrow.
posted by oneswellfoop at 5:33 PM on June 7, 2016


Daq: I think I will play around with my RF scanner on those days. See if there is any new signals popping up.

Please report back!
posted by quinndexter at 6:19 PM on June 7, 2016


Again, not an expert (but somehow thrown into this at work), but the C and P codes aren't encrypted or protected in any way. The military M code is encrypted and the carrier PRN signal is significantly longer than the civil codes; the civil signal relays every 20 hours or so and the M code repeats every few weeks.

What this means in practice is that civil GPS is vulnerable to spoofing and jamming but the military code presumably is not. The interesting(?) wrinkle on all this is that many military aircraft use civil GPS for day to day navigation.
posted by backseatpilot at 7:18 PM on June 7, 2016 [1 favorite]


Oh good lord. This happens all the time.

Not on this scale, this doesn't happen all the time. Or if it does, could you please post another 400 mile radius outage scheduled for 8 hours on six different days? The link you provide is mostly NOTAMs for this very event.

The ordinary GPS outages that get NOTAMed that I talked about above are generally problems with the satellite configuration where there's temporarily not enough backup coverage to guarantee safe navigation, particularly for WAAS. Those outage are of an entirely different character and scale than the event we are discussing here.
posted by Nelson at 7:29 PM on June 7, 2016 [2 favorites]


Serious America, it's time to move on.

It's not just an American thing, everyone uses nautical miles and knots for aviation and nautical purposes. Even the French navy. It'll be convenient, if GPS is ever out of service for some reason and we need to use paper charts.
posted by sfenders at 7:54 PM on June 7, 2016 [3 favorites]


Sure, here's one with a 340 mile radius, for 12 days in Alaska in 2014. Another for a 289 mile radius, off South Carolina, earlier this year. Here's one for 499 miles from January last year. This one from 2012 was the same spot, but 546 miles

I mean, it's a big toy they've got, but they've played with it a lot.
posted by DangerIsMyMiddleName at 8:25 PM on June 7, 2016 [3 favorites]


Not on this scale, this doesn't happen all the time. Or if it does, could you please post another 400 mile radius outage scheduled for 8 hours on six different days?

Best I can do is this 245 Nautical Mile radius one that was scheduled for 8 hour stretches on 3 different days, from back at the end of March.
posted by radwolf76 at 8:27 PM on June 7, 2016 [1 favorite]


GPS jamming is pretty well understood, they don't need to do a huge test of it on its own. But they do need to test various planes, drones, and missiles to make sure they function fine with jammed GPS. That's probably what they're doing here.
posted by miyabo at 8:47 PM on June 7, 2016 [1 favorite]


Serious America, it's time to move on. I get that you love Nautical Miles but every time i read announcements like this I wonder why anyone cares about a 400 nanometer area of effect.

Derail: A nautical mile isn't a mile. The nautical mile was intended to represent one minute-arc of distance along a meridian for ease of use on charts and maps. The US actually has dropped its definition of nautical miles based on feet in favor of the international nautical mile based on meters.

posted by stopgap at 9:28 PM on June 7, 2016 [6 favorites]


Can you get a different abbreviation then? Maybe the issue is all-caps bulletins mixing up mm and NM.
posted by GuyZero at 9:37 PM on June 7, 2016


I spent a night over the hill from Area 51, in a campsite along a public road. I perceived the entire night sky was a hologram. I wasn't even thinking about location or this stuff, I just woke up in the night and realized I was seeing some sort of overlay, and then I thought, "Idiot, you are just having double vision from driving forever into the night" But dang me, I just planned out a road trip that goes right by China Lake, no kidding, this evening! Anything to drive the 120 again. Whatever they are doing, any of them, they are actively fucking up the whole, for some small sum that makes them feel safe. I measure everything by the cruise missile yardstick. I, and my entire lineage, excluding one brother, have never made the money it takes to purchase one cruise missile off the rack. We are screwed. I have been out in those areas, because if you take any route from Utah, but I15, you go by those places, if you want to meander south to Bako. Once I was driving in the Great Basin National Park, when I noticed this white pick up was slowing me down, and I just kept at getting along. Coming over a hill and down into a valley, was a parked semi on the right side of the road, then across the valley a small car stopped suddenly and a pair of people jumped out with the biggest binoculars I have ever seen. Looking up I caught the flight of a couple of experimental aircraft. I guess the folks with the binoculars might have been from Jane's or a foreign nation. I was really into the rocks there, so round and soft, and so many of them. I am the Mrs. Magoo of military weird.
posted by Oyéah at 9:55 PM on June 7, 2016 [3 favorites]


If you'd like get an idea of how your phone's GPS works there is an android app called GPS status that has a nice display of the conceptual guts of GPS.

Yeah, I like that app too. Neat thing: many commercial "GPS" receivers these days (including most if not all recent smartphones) actually pick up signals from both GPS (US) and GLONASS (Russian) satellites. You can see that on the app display, even though it's not immediately obvious. Satellites with low numbers (up to somewhere in the 30s) are the GPS satellites, and the high numbers (60s and above) are the GLONASS satellites.
posted by DevilsAdvocate at 6:49 AM on June 8, 2016 [4 favorites]


Well I'll be damned, DangerIsMyMiddleName. Thanks for posting those examples.
posted by Nelson at 8:18 AM on June 8, 2016


But, I got an idea last night after thinking of chemtrails, perhaps they are just a scrim for projecting images on. Like recreating the landscape underneath, without certain features.
posted by Oyéah at 8:45 AM on June 8, 2016


Just for reassurance sake -- ground vehicle GPS will be functioning normally in SoCal tomorrow, right? No chance of some kind of multi path interference at ground level?
posted by snuffleupagus at 9:37 AM on June 8, 2016


The notice only really mentions it starting at 50 feet but I suppose there's a chance it will have a ground level effect very close to the center. In LA I expect it won't be an issue, especially in urban areas since you're well-shaded laterally and GPS signals already have problems getting past building shadows, but maybe out in the country there might be? The FAA really only cares about pilots so it's inconclusive based on the announcement.
posted by GuyZero at 9:59 AM on June 8, 2016 [1 favorite]


The radii are consistent with a jamming source at an altitude of about 50,000 feet.
posted by the Real Dan at 10:35 AM on June 8, 2016


Also, keep in mind that your phone is probably getting much of it's location data from the relative location of WiFi SSIDs and mobile phone towers in the area, verses actually using the GPS satellites themselves.
posted by sideshow at 11:44 AM on June 8, 2016 [2 favorites]


These jamming exercises happen in the UK as well. Really no big deal.

If you want to keep a very close eye on things, you can sign up for email notifications here at the US Coastguard's Navigation Center, which include all the in-orbit reconfigurations and outages that don't necessarily generate NOTAMs.
posted by Devonian at 7:16 PM on June 8, 2016


Further derail: the SI unit for nautical miles is radians. 1 nautical mile = 290.88 microradians.
posted by memetoclast at 1:20 PM on June 9, 2016 [1 favorite]


That's rad!
posted by miyabo at 2:54 PM on June 9, 2016 [1 favorite]


Navy cancels planned GPS outage in Southern California
The Navy did not reveal the cause of the cancellation, other than to say the reason was “internal.”

... The Department of Defense conducts an estimated 50 GPS jamming events each year to train personnel to operate in an environment where the GPS signal is degraded or unavailable.
posted by Nelson at 8:25 AM on June 10, 2016


Sure, that's what they want you to think.
posted by Etrigan at 9:45 AM on June 10, 2016 [1 favorite]


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