10 ms·

GPS Flaw: Security Expert Says He Won't Fly April 6

80 points by musha68k 8y ago

Arbalest 8y ago
For the majority of us, probably the only thing that will happen is some power outages in some areas. Charge some portable batteries and buy some bottled water (mains pumps maybe?). It won't be a problem for more than about a day.
- jimktrains2 8y ago
  I think you commented on the wrong article? Why would gps-derived date issues cause problems with electrical generation and distribution?
  - snowwindwaves 8y ago
    Gps timestamped electrical measurements are sent over fiber optic cables between substations on either end of transmission lines to make sure current in is the same as current out, roughly. Also for measuring and controlling power flows. https://www.smartgrid.gov/recovery_act/program_impacts/applications_synchrophasor_technology.html https://www.smartgrid.gov/recovery_act/program_impacts/appli...
    - jimktrains2 8y ago
      Interesting! Thanks for the link.
cylinder 8y ago
Can someone sensible with expertise comment on this please?
- Rebelgecko 8y ago
  It's like Daylight Savings time or Y2K. In theory, it could wreak all kinds of havoc on buggy software. However this isn't a surprise. It's a known thing that happens every 1024 weeks. I would be astounded if GPS receivers used for aviation purposes don't test for this. On the other hand, I was astounded when I heard that F-22s stopped working after flying across the international date line. And I was slightly less asounded when the Nexus S phones spat out broken GPS NMEA sentences on leap years
  - goodcanadian 8y ago
    On the other hand, I was astounded when I heard that F-22s stopped working after flying across the international date line. It's a pretty big oops, but they rebooted the computers, and the planes kept flying. That's the second place where these disaster predictions fall down. These systems are rarely designed with a single point of failure.
    - Rebelgecko 8y ago
      The articles I read made it sound like they continued to have nav and comm issues after rebooting, and that things could've been worse if they hadn't been able to follow their tankers home.
      - goodcanadian 8y ago
        I'll admit that I don't know the details, but I'll point out that they would not have been so far from land without tankers. If they were closer to a base or had longer range, a complete navigational failure would be far less of a problem as there are still pilots on board who know roughly where they are and what the heading is and where to find emergency airfields. They can make decisions and come up with a plan to get out of the situation. Perhaps, I'll claim that as the third error in doom predictions. When any real problems do come up, there are intelligent people working the problem.
  - function_seven 8y ago
    > On the other hand, I was astounded when I heard that F-22s stopped working after flying across the international date line. As was I, when I learned about taking off from the Dead Sea: https://www.avgeekery.com/challenge-flying-sea-level/ https://www.avgeekery.com/challenge-flying-sea-level/
    - dingaling 8y ago
      Most curious bug! My local airfield is at -19ft and the landed altitude reported by Mode-S varies from -25ft ( GNSS sourced ) to -275ft ( pressure based on 1013hPa ). Hence why asking for the local air pressure QFE is essential.
- mlaretallack 8y ago
  GPS provides the time (hour, minute, seconds) and date (day, month, year) over the NMEA messages. It also provides a week counter. This wraps around at 1024. The last time was about year 1999. With most of the things I have used NMEA for (time sync), I did not use the weeks counter. However if there is any software that does use it, it needs to be able to handle the rollover.
  - tonyarkles 8y ago
    This is where you have to dig a little deeper. Your receiver outputs the date in the NMEA messages, but the satellite doesn't actually transmit year/month/day. The satellite transmits the week number and the number of seconds that have passed since the start of the week. In your case, the receiver could potentially output incorrect dates in the NMEA output when the week number wraps around.
- elfchief 8y ago
  Sure, gps geek and time-nut here. The rollover problem is a hard one to fix, because there's no reasonable way for a GPS (at least one using LNAV (legacy) signals -- pretty much all of them, though I don't know what modern passenger jets use) to know which GPS "epoch" they're in. If you don't know what epoch you're in, you don't know what the date is. Some GPSs solve this by recording the week number of their firmware build, and if the signals they get indicate the week number is less than that, they assume they're in the next epoch and update accordingly. Still means you run out of time, but you get a full ~19 years of life first (and then fail at some random GPS week). Some use fuses to record when an epoch has passed. Some use out of band information. Some store the current epoch in flash or battery-backed RAM. Some just never address the problem. Thing is, though -- the only effect this has, is that it makes the GPS return the wrong date. That's it. The week rollover has no effect on navigation unless there's some significant bugs in the unit, or something external to the GPS relies on the date being output and doesn't deal well with the date suddenly going back in time. That's it. I'd be kinda shocked if airplanes were just jam-syncing the clocks of their nav computers to the output of a GPS, and then had those nav systems be dependent on that time. But then again, I work in the tech industry, and I've seen the kinda code that goes into most products, so maybe I wouldn't be that shocked. (I also can't imagine that GPS units used in aircraft aren't directly tested for their behavior during the week rollover. It's a well known and understood problem, and even if some random GPS manufacturer drops the ball, stuff that goes into aircraft has to go through certification for a reason...)
  - sho 8y ago
    > I'd be kinda shocked if airplanes were just jam-syncing the clocks of their nav computers to the output of a GPS, and then had those nav systems be dependent on that time Obligatory not an aircraft software engineer, but I can say with some certainty that this is not the case. Aviation software, despite the recent issues with the 737 MAX, is generally designed and implemented to very high level of redundancy and SPOF-avoidance. From an airbus manual, to give you some idea: A300-600s, A310s, A320s, A330s and A340s with GPS PRIMARY The navigation system of these aircraft consists of 2 FMS, 3 IRS, 2 GPS and radio navaid sensors. The GPS position is primarily used for FM position updates, however if GPS PRIMARY is lost, FM reverts to radio updates or to IRS ONLY navigation when outside radio navaid coverage. FM(S) = Flight Management (System). IRS = inertial reference system (THREE of them). If GPS is lost or malfunctioning, the FMS falls back to that - which is periodically updated by reference to RNAV ground-based radio beacons. GPS could simply switch off worldwide and aircraft would be fine, just like they were pre-GPS. There is no conceivable reason the navigation system would especially care about the time being received from its GPS units, let alone perform some critical calculation based upon it. This article is pretty uninformed fear-mongering.
- jtolmar 8y ago
  There's an edge case in the GPS spec that only comes up every 20 years. It's well-documented and everything, but it only comes up every 20 years and software is terrible, so not every GPS unit is going to handle it well. Last time this happened, GPS wasn't nearly as widely used. I would expect some percent of phones to flip out (try force restarting, or waiting a day and restarting). Which ones are a mystery - the GPS chip in a phone isn't even consistent for a particular model. I wouldn't expect planes to fall out of the sky. I wouldn't be surprised by flight delays though; just because the safety critical stuff is well tested doesn't mean the rest is. And the errors aren't going to be confined to April 6th. We're talking about software bugs here, and it's dealing with a number that counts in weeks. So while bugs should center on the 6th, anything within a week of that is pretty plausible too. (I wrote the GPS tracking algorithm used for navigation in Google Maps. Nothing above is based on Google-specific knowledge. It's still just someone's opinion.)
  - jimktrains2 8y ago
    Why would phones use the GPS date over the cellular-provided date?
    - jtolmar 8y ago
      The GPS unit needs to figure out the locations of all the satellites before it can use them to figure out your positions. The satellite positions are expressed as a function of time, and the times used are measured in seconds within the current GPS week[1]. This is the mechanism that I'd expect someone messed up. I'd expect location errors more than time errors, but because you can get time out of GPS then someone probably has. [1] https://gssc.esa.int/navipedia/index.php/GPS_and_Galileo_Satellite_Coordinates_Computation https://gssc.esa.int/navipedia/index.php/GPS_and_Galileo_Sat...
      - elfchief 8y ago
        The week number is (somewhat) used for navigation, but the way it is used is not affected in any way by the rollover, and there's not really a way (even taking into account bugs) that not knowing what the current GPS epoch is could affect navigation. This is purely a matter of an issue with the time that's output for human consumption, the GPS functionality itself doesn't care in the least.
olliej 8y ago
Ok so just to be clear this isn’t the first time a gps time rollover has occurred. The only real difference between this time and last time is that god technology is widely deployed at the consumer level. As for the risk to flights: * this has happened before, and I don’t recall any plane accidents then * I assume pilots would notice if they’re suddenly substantially off course - it’s not a gradual drifting change, it’s a big kachunk change if software isn’t handling it correctly. * there are many other (non-gps) signals including radio that are used to track where an aircraft is. If anything I’d be more concerned about drivers getting lost in their cars
- userbinator 8y ago
  Also, earlier this year the military was messing with the GPS too, apparently they do it pretty often: https://news.ycombinator.com/item?id=16244298 https://news.ycombinator.com/item?id=16244298 Planes can use GPS as a navigation aid, but they definitely do not rely on it as the only source of information. god technology Damn you autocorrect!
  - sundvor 8y ago
    God tech made me smile and think of "Any sufficiently advanced technology is indistinguishable from magic." :) With a subtle pun in the clouds somewhere.
- dsl 8y ago
  > this has happened before, and I don’t recall any plane accidents then ADSB (the "non-gps" radio signals you mention) broadcasts the planes location... sourced from GPS. Because of deployment requirements there are tons of sub-$2000 ADSB out boxes on the market now that didn't exist in 1999, and hardware wise they are a race to the bottom. (Edit: I also just realized the software could have been written by someone who wasn't alive in 1999). I don't think anything is going to happen. But I also don't like saying nothing is going to happen, because that is when you get a complex failure.
  - 7952 8y ago
Zombiethrowaway 8y ago
Not GPS related, but the day I am really worried about is January 19th 2038 3:14:07AM... Unix time will roll over if stored in a signed four byte integer field.
- isostatic 8y ago
  We’re already seeing problems from that. It will be handled, probably without the financial bonanza of 2k, but as such will probably cause more problems.
- SAI_Peregrinus 8y ago
  Or slightly later the use of a 2-digit year in x509 certificates. The standard assumes that dates with year <50 are 20xx, and >=50 are 19xx. It doesn't help that this is one of the best designed, most understandable, and well-thought-out parts of the x509 standard.
jlgaddis 8y ago
> Universal Time Code (UTC) Uh, Coordinated Universal Time [0]? I can't be the only one who, upon seeing little things like this, immediately has doubts about the accuracy of everything else in the article. [0]: https://en.wikipedia.org/wiki/Coordinated_Universal_Time https://en.wikipedia.org/wiki/Coordinated_Universal_Time
- sho 8y ago
  Apropos: https://en.wikipedia.org/wiki/Gell-Mann_amnesia_effect https://en.wikipedia.org/wiki/Gell-Mann_amnesia_effect
  - dingaling 8y ago
    That keeps getting quoted but with no evidence that it exists on a large scale. If I read a $NEWS_SOURCE article and they get something wildly incorrect I don't just proceed to the next article, I close the tab / newspaper.
    - ben_w 8y ago
      I’ve caught myself making that mistake for literally years after learning about it. I am trying to train myself not to continue. I think I’m getting there now.
    - sho 8y ago
      Well, as the wikipedia article states, it is somewhat tongue-in-cheek, and yet seems intuitively correct to me. I've certainly recognised the phenomenon in my own behaviour. Instead of as a hard fact to be evidenced and justified, I think a better way of thinking about it might be as a kind of parable - a reminder to keep an open mind and not just blindly accept everything you see in the newspaper, or anywhere else.
    - TeMPOraL 8y ago
      > If I read a $NEWS_SOURCE article and they get something wildly incorrect I don't just proceed to the next article, I close the tab / newspaper. Then couple hours or days later you get an article on a different topic from the same $NEWS_SOURCE, and you read it like gospel. What changed over past decades is the way we consume news - it's "unbundled" now; much like we consume movies per-title and not per-channel, we consume news per-story, not per-newspaper. But this didn't improve news quality. Gell-Mann amnesia exists at scale, it's one of the most trivial things to verify - you just need to talk with people. With your family, friends, or with folks on any social media site / on-line bulletin board. You'll see countless of examples of people who suffer from this amnesia, who can't perform the most obvious generalization from observation - to conclude that, since for any topic they know anything about every news article is utter bullshit, and since their friends report the same observations for their domains, the news on the topics they're not experts on must be bullshit too.
nullc 8y ago
Most GPS devices made at least after 1999 implement an unwrapping algorithm that has an epoch at some random date set by the maker in the firmware. Essentially the firmware knows that the day is later than say, July 4th 2004 because that's when it was built. If the GPS date is less than that date, it adds 1024 weeks repeated until its greater than the hardcoded date. This means that the exact wrap date will depend on the receiver, though some will wrap on April 6th Fortunately GPS rollover doesn't normally get in the way of positioning. The only way it would is if the 'wrong' dates triggered some other bug.
- makomk 8y ago
  Apparently it did cause positioning issues last time around. One major problem was that GPS receivers calculate which satellites they expect to see in the sky based on the current time and the almanac+ephemeris data, and at the wraparound some receivers started expecting all the satellites to be where they would've been 1024 weeks ago and completely lost lock. I think there were some problems caused by individual satellites wrapping their counts slightly before the actual GPS time too. Receivers which are started up after the 6th should be fine though.
  - gsich 8y ago
    Wrong almanac means a somewhat longer time for first fix.
cheesedoodle 8y ago
What he is pertaining to is WNRO, the 10-bit binary counter representing the GPS Week Number, a key piece of the date and time information. Every 19.7 years this week number counter reaches its limit and rolls back to zero. [0] [0] https://www.trimble.com/wnro/ https://www.trimble.com/wnro/
wildylion 8y ago
He probably won't fly April 5, or April 7, either.
bronco21016 8y ago
In the US at least I’m not aware of a single certified aircraft that relies on GPS as the primary and only means of navigation. Even brand new Airbus 320/321s and Boeing 737-700/800/900s have INS installed and is considered primary. GPS and radio based navigation add correction and cross checking to the INS derived position. GPS is necessary for RNP but RNP procedures are not yet widespread enough to cause major disruption to the national airspace system. As we move closer and closer to primarily an RNP system a GPS outage may become more disruptive but for at least several more decades the infrastructure and equipment to navigate using INS and radio based means such as VORs will provide a proven and safe backup.
yuchi 8y ago
> So that this doesn't happen again any time soon, GPS devices made in the past decade use 13 bits for the week counter, yielding a total of 8,192 weeks or 157 years. Those devices will not have to restart time until 2137, by which time our descendants will have created a whole new set of technological problems. I love the snarky final sarcasm.

80 points by musha68k 8y ago

For the majority of us, probably the only thing that will happen is some power outages in some areas. Charge some portable batteries and buy some bottled water (mains pumps maybe?). It won't be a problem for more than about a day.

jimktrains2 8y ago
I think you commented on the wrong article? Why would gps-derived date issues cause problems with electrical generation and distribution?
- snowwindwaves 8y ago
  Gps timestamped electrical measurements are sent over fiber optic cables between substations on either end of transmission lines to make sure current in is the same as current out, roughly. Also for measuring and controlling power flows. https://www.smartgrid.gov/recovery_act/program_impacts/applications_synchrophasor_technology.html https://www.smartgrid.gov/recovery_act/program_impacts/appli...
  - jimktrains2 8y ago
    Interesting! Thanks for the link.

cylinder 8y ago

Can someone sensible with expertise comment on this please?

Rebelgecko 8y ago
It's like Daylight Savings time or Y2K. In theory, it could wreak all kinds of havoc on buggy software. However this isn't a surprise. It's a known thing that happens every 1024 weeks. I would be astounded if GPS receivers used for aviation purposes don't test for this. On the other hand, I was astounded when I heard that F-22s stopped working after flying across the international date line. And I was slightly less asounded when the Nexus S phones spat out broken GPS NMEA sentences on leap years
- goodcanadian 8y ago
  On the other hand, I was astounded when I heard that F-22s stopped working after flying across the international date line. It's a pretty big oops, but they rebooted the computers, and the planes kept flying. That's the second place where these disaster predictions fall down. These systems are rarely designed with a single point of failure.
  - Rebelgecko 8y ago
    The articles I read made it sound like they continued to have nav and comm issues after rebooting, and that things could've been worse if they hadn't been able to follow their tankers home.
    - goodcanadian 8y ago
      I'll admit that I don't know the details, but I'll point out that they would not have been so far from land without tankers. If they were closer to a base or had longer range, a complete navigational failure would be far less of a problem as there are still pilots on board who know roughly where they are and what the heading is and where to find emergency airfields. They can make decisions and come up with a plan to get out of the situation. Perhaps, I'll claim that as the third error in doom predictions. When any real problems do come up, there are intelligent people working the problem.
- function_seven 8y ago
  > On the other hand, I was astounded when I heard that F-22s stopped working after flying across the international date line. As was I, when I learned about taking off from the Dead Sea: https://www.avgeekery.com/challenge-flying-sea-level/ https://www.avgeekery.com/challenge-flying-sea-level/
  - dingaling 8y ago
    Most curious bug! My local airfield is at -19ft and the landed altitude reported by Mode-S varies from -25ft ( GNSS sourced ) to -275ft ( pressure based on 1013hPa ). Hence why asking for the local air pressure QFE is essential.
mlaretallack 8y ago
GPS provides the time (hour, minute, seconds) and date (day, month, year) over the NMEA messages. It also provides a week counter. This wraps around at 1024. The last time was about year 1999. With most of the things I have used NMEA for (time sync), I did not use the weeks counter. However if there is any software that does use it, it needs to be able to handle the rollover.
- tonyarkles 8y ago
  This is where you have to dig a little deeper. Your receiver outputs the date in the NMEA messages, but the satellite doesn't actually transmit year/month/day. The satellite transmits the week number and the number of seconds that have passed since the start of the week. In your case, the receiver could potentially output incorrect dates in the NMEA output when the week number wraps around.
elfchief 8y ago
Sure, gps geek and time-nut here. The rollover problem is a hard one to fix, because there's no reasonable way for a GPS (at least one using LNAV (legacy) signals -- pretty much all of them, though I don't know what modern passenger jets use) to know which GPS "epoch" they're in. If you don't know what epoch you're in, you don't know what the date is. Some GPSs solve this by recording the week number of their firmware build, and if the signals they get indicate the week number is less than that, they assume they're in the next epoch and update accordingly. Still means you run out of time, but you get a full ~19 years of life first (and then fail at some random GPS week). Some use fuses to record when an epoch has passed. Some use out of band information. Some store the current epoch in flash or battery-backed RAM. Some just never address the problem. Thing is, though -- the only effect this has, is that it makes the GPS return the wrong date. That's it. The week rollover has no effect on navigation unless there's some significant bugs in the unit, or something external to the GPS relies on the date being output and doesn't deal well with the date suddenly going back in time. That's it. I'd be kinda shocked if airplanes were just jam-syncing the clocks of their nav computers to the output of a GPS, and then had those nav systems be dependent on that time. But then again, I work in the tech industry, and I've seen the kinda code that goes into most products, so maybe I wouldn't be that shocked. (I also can't imagine that GPS units used in aircraft aren't directly tested for their behavior during the week rollover. It's a well known and understood problem, and even if some random GPS manufacturer drops the ball, stuff that goes into aircraft has to go through certification for a reason...)
- sho 8y ago
  > I'd be kinda shocked if airplanes were just jam-syncing the clocks of their nav computers to the output of a GPS, and then had those nav systems be dependent on that time Obligatory not an aircraft software engineer, but I can say with some certainty that this is not the case. Aviation software, despite the recent issues with the 737 MAX, is generally designed and implemented to very high level of redundancy and SPOF-avoidance. From an airbus manual, to give you some idea: A300-600s, A310s, A320s, A330s and A340s with GPS PRIMARY The navigation system of these aircraft consists of 2 FMS, 3 IRS, 2 GPS and radio navaid sensors. The GPS position is primarily used for FM position updates, however if GPS PRIMARY is lost, FM reverts to radio updates or to IRS ONLY navigation when outside radio navaid coverage. FM(S) = Flight Management (System). IRS = inertial reference system (THREE of them). If GPS is lost or malfunctioning, the FMS falls back to that - which is periodically updated by reference to RNAV ground-based radio beacons. GPS could simply switch off worldwide and aircraft would be fine, just like they were pre-GPS. There is no conceivable reason the navigation system would especially care about the time being received from its GPS units, let alone perform some critical calculation based upon it. This article is pretty uninformed fear-mongering.
jtolmar 8y ago
There's an edge case in the GPS spec that only comes up every 20 years. It's well-documented and everything, but it only comes up every 20 years and software is terrible, so not every GPS unit is going to handle it well. Last time this happened, GPS wasn't nearly as widely used. I would expect some percent of phones to flip out (try force restarting, or waiting a day and restarting). Which ones are a mystery - the GPS chip in a phone isn't even consistent for a particular model. I wouldn't expect planes to fall out of the sky. I wouldn't be surprised by flight delays though; just because the safety critical stuff is well tested doesn't mean the rest is. And the errors aren't going to be confined to April 6th. We're talking about software bugs here, and it's dealing with a number that counts in weeks. So while bugs should center on the 6th, anything within a week of that is pretty plausible too. (I wrote the GPS tracking algorithm used for navigation in Google Maps. Nothing above is based on Google-specific knowledge. It's still just someone's opinion.)
- jimktrains2 8y ago
  Why would phones use the GPS date over the cellular-provided date?
  - jtolmar 8y ago
    The GPS unit needs to figure out the locations of all the satellites before it can use them to figure out your positions. The satellite positions are expressed as a function of time, and the times used are measured in seconds within the current GPS week[1]. This is the mechanism that I'd expect someone messed up. I'd expect location errors more than time errors, but because you can get time out of GPS then someone probably has. [1] https://gssc.esa.int/navipedia/index.php/GPS_and_Galileo_Satellite_Coordinates_Computation https://gssc.esa.int/navipedia/index.php/GPS_and_Galileo_Sat...
    - elfchief 8y ago
      The week number is (somewhat) used for navigation, but the way it is used is not affected in any way by the rollover, and there's not really a way (even taking into account bugs) that not knowing what the current GPS epoch is could affect navigation. This is purely a matter of an issue with the time that's output for human consumption, the GPS functionality itself doesn't care in the least.

olliej 8y ago

Ok so just to be clear this isn’t the first time a gps time rollover has occurred. The only real difference between this time and last time is that god technology is widely deployed at the consumer level. As for the risk to flights: * this has happened before, and I don’t recall any plane accidents then * I assume pilots would notice if they’re suddenly substantially off course - it’s not a gradual drifting change, it’s a big kachunk change if software isn’t handling it correctly. * there are many other (non-gps) signals including radio that are used to track where an aircraft is. If anything I’d be more concerned about drivers getting lost in their cars

userbinator 8y ago
Also, earlier this year the military was messing with the GPS too, apparently they do it pretty often: https://news.ycombinator.com/item?id=16244298 https://news.ycombinator.com/item?id=16244298 Planes can use GPS as a navigation aid, but they definitely do not rely on it as the only source of information. god technology Damn you autocorrect!
- sundvor 8y ago
  God tech made me smile and think of "Any sufficiently advanced technology is indistinguishable from magic." :) With a subtle pun in the clouds somewhere.
dsl 8y ago
> this has happened before, and I don’t recall any plane accidents then ADSB (the "non-gps" radio signals you mention) broadcasts the planes location... sourced from GPS. Because of deployment requirements there are tons of sub-$2000 ADSB out boxes on the market now that didn't exist in 1999, and hardware wise they are a race to the bottom. (Edit: I also just realized the software could have been written by someone who wasn't alive in 1999). I don't think anything is going to happen. But I also don't like saying nothing is going to happen, because that is when you get a complex failure.
- 7952 8y ago

Zombiethrowaway 8y ago

Not GPS related, but the day I am really worried about is January 19th 2038 3:14:07AM... Unix time will roll over if stored in a signed four byte integer field.

isostatic 8y ago
We’re already seeing problems from that. It will be handled, probably without the financial bonanza of 2k, but as such will probably cause more problems.
SAI_Peregrinus 8y ago
Or slightly later the use of a 2-digit year in x509 certificates. The standard assumes that dates with year <50 are 20xx, and >=50 are 19xx. It doesn't help that this is one of the best designed, most understandable, and well-thought-out parts of the x509 standard.

jlgaddis 8y ago

> Universal Time Code (UTC) Uh, Coordinated Universal Time [0]? I can't be the only one who, upon seeing little things like this, immediately has doubts about the accuracy of everything else in the article. [0]: https://en.wikipedia.org/wiki/Coordinated_Universal_Time https://en.wikipedia.org/wiki/Coordinated_Universal_Time

sho 8y ago
Apropos: https://en.wikipedia.org/wiki/Gell-Mann_amnesia_effect https://en.wikipedia.org/wiki/Gell-Mann_amnesia_effect
- dingaling 8y ago
  That keeps getting quoted but with no evidence that it exists on a large scale. If I read a $NEWS_SOURCE article and they get something wildly incorrect I don't just proceed to the next article, I close the tab / newspaper.
  - ben_w 8y ago
    I’ve caught myself making that mistake for literally years after learning about it. I am trying to train myself not to continue. I think I’m getting there now.
  - sho 8y ago
    Well, as the wikipedia article states, it is somewhat tongue-in-cheek, and yet seems intuitively correct to me. I've certainly recognised the phenomenon in my own behaviour. Instead of as a hard fact to be evidenced and justified, I think a better way of thinking about it might be as a kind of parable - a reminder to keep an open mind and not just blindly accept everything you see in the newspaper, or anywhere else.
  - TeMPOraL 8y ago
    > If I read a $NEWS_SOURCE article and they get something wildly incorrect I don't just proceed to the next article, I close the tab / newspaper. Then couple hours or days later you get an article on a different topic from the same $NEWS_SOURCE, and you read it like gospel. What changed over past decades is the way we consume news - it's "unbundled" now; much like we consume movies per-title and not per-channel, we consume news per-story, not per-newspaper. But this didn't improve news quality. Gell-Mann amnesia exists at scale, it's one of the most trivial things to verify - you just need to talk with people. With your family, friends, or with folks on any social media site / on-line bulletin board. You'll see countless of examples of people who suffer from this amnesia, who can't perform the most obvious generalization from observation - to conclude that, since for any topic they know anything about every news article is utter bullshit, and since their friends report the same observations for their domains, the news on the topics they're not experts on must be bullshit too.

nullc 8y ago

Most GPS devices made at least after 1999 implement an unwrapping algorithm that has an epoch at some random date set by the maker in the firmware. Essentially the firmware knows that the day is later than say, July 4th 2004 because that's when it was built. If the GPS date is less than that date, it adds 1024 weeks repeated until its greater than the hardcoded date. This means that the exact wrap date will depend on the receiver, though some will wrap on April 6th Fortunately GPS rollover doesn't normally get in the way of positioning. The only way it would is if the 'wrong' dates triggered some other bug.

makomk 8y ago
Apparently it did cause positioning issues last time around. One major problem was that GPS receivers calculate which satellites they expect to see in the sky based on the current time and the almanac+ephemeris data, and at the wraparound some receivers started expecting all the satellites to be where they would've been 1024 weeks ago and completely lost lock. I think there were some problems caused by individual satellites wrapping their counts slightly before the actual GPS time too. Receivers which are started up after the 6th should be fine though.
- gsich 8y ago
  Wrong almanac means a somewhat longer time for first fix.

cheesedoodle 8y ago

What he is pertaining to is WNRO, the 10-bit binary counter representing the GPS Week Number, a key piece of the date and time information. Every 19.7 years this week number counter reaches its limit and rolls back to zero. [0] [0] https://www.trimble.com/wnro/ https://www.trimble.com/wnro/

wildylion 8y ago

He probably won't fly April 5, or April 7, either.

bronco21016 8y ago

In the US at least I’m not aware of a single certified aircraft that relies on GPS as the primary and only means of navigation. Even brand new Airbus 320/321s and Boeing 737-700/800/900s have INS installed and is considered primary. GPS and radio based navigation add correction and cross checking to the INS derived position. GPS is necessary for RNP but RNP procedures are not yet widespread enough to cause major disruption to the national airspace system. As we move closer and closer to primarily an RNP system a GPS outage may become more disruptive but for at least several more decades the infrastructure and equipment to navigate using INS and radio based means such as VORs will provide a proven and safe backup.

yuchi 8y ago

> So that this doesn't happen again any time soon, GPS devices made in the past decade use 13 bits for the week counter, yielding a total of 8,192 weeks or 157 years. Those devices will not have to restart time until 2137, by which time our descendants will have created a whole new set of technological problems. I love the snarky final sarcasm.