5 ms·

What countries have you seen GPS jamming in? And if in the US, which airports? If in North America, I suspect there’s another explanation for what you’ve seen

What countries have you seen GPS jamming in? And if in the US, which airports? If in North America, I suspect there’s another explanation for what you’ve seen given the degree to which civilian air traffic relies on GPS for navigation, including for precision approaches at many airports.

madaxe_again 8y ago
Jamming - Brazil, Argentina, Russia, China, and there’s a small dead zone in the UK over the Brecon Beacons.
- therein 8y ago
  Is the in-flight map often fictional data then?
  - racingmars 8y ago
    Not necessarily. Even without GPS, commercial airliners have a good idea of where they are using their INSes (inertial navigation systems). That technology well predates GPS receivers being common in aircraft. Most of the Boeing and Airbus aircraft you fly, for example, have 3 INSes and probably 2 GPS receivers. All of the data feeds into the computers to average to the position the plane thinks it's actually at. When the GPS signal is reliable, that may be used as the actual position and can be used to keep the INS drift minimized, so if the GPS signal is lost (or the receivers malfunction), the INS takes over as the primary source of position data. This is all further supplemented and verified with radio navigation aids -- as the planes fly along their routes, the airplane computers automatically tune in to various radio navigation aids. In short, even for the newest big commercial jets, functional GPS is very much optional and positional data is quite good without it. As for the moving maps on the seat-back displays: I guess it all depends on the data source they use. If they have their own GPS receiver for the plane's "entertainment" system, that doesn't get the computed current position from the real navigation systems, then the map would presumably stop working or make up (e.g. interpolate) data from when it last had good position data. But now that I think about it... I've only ever seen those maps draw the route as the great-circle path from the departure airport to the destination airport. So they're fictional in that regard -- whether they're interpolating the position on the great-circle path as a percentage of the actual track distance flown and remaining from the real navigation data, or doing something even more fictional, I don't know.
    - madaxe_again 8y ago
      It varies between airlines - off the top of my head I couldn’t tell you which does what, but some are completely accurate, others are essentially a great circle progress bar - and they always turn it off for the interesting bits around takeoff and landing.
    - therein 8y ago
      > But now that I think about it... I've only ever seen those maps draw the route as the great-circle path from the departure airport to the destination airport. So they're fictional in that regard -- whether they're interpolating the position on the great-circle path as a percentage of the actual track distance flown and remaining from the real navigation data, or doing something even more fictional, I don't know. Very interesting. Thanks for the detailed answer. Next time I'll make sure to record the position information independently as well. For some reason I had just taken their great-circle path at its face value and never questioned it. In hindsight, it was all too perfect. :)
- PoachedSausage 8y ago
  Intriguing, I wonder what could be the reason for and source of jamming over the Brecon Beacons? One possible explanation is that your GPS receiver front-end was overloaded by transmissions from Woofferton transmitting station[0]. [0] https://en.wikipedia.org/wiki/Woofferton_transmitting_station https://en.wikipedia.org/wiki/Woofferton_transmitting_statio...
  - MagnumOpus 8y ago
    Brecon beacons are a training ground for UK special forces soldiers - maybe either testing their ability to cope with jamming, or testing their offensive jamming equipment?
- nbabitskiy 8y ago
  Allegedly, airports' coordinates are hard coded into consumer drones' firmware, at least in Russia. That's the reason why gps devices at Moscow Kremlin walls think, that they are at VKO airport. So jamming gps signal in the airports seems counterproductive. I would think that they'd want drones to know they are in a no-flight zone.

madaxe_again 8y ago

Jamming - Brazil, Argentina, Russia, China, and there’s a small dead zone in the UK over the Brecon Beacons.

therein 8y ago
Is the in-flight map often fictional data then?
- racingmars 8y ago
  Not necessarily. Even without GPS, commercial airliners have a good idea of where they are using their INSes (inertial navigation systems). That technology well predates GPS receivers being common in aircraft. Most of the Boeing and Airbus aircraft you fly, for example, have 3 INSes and probably 2 GPS receivers. All of the data feeds into the computers to average to the position the plane thinks it's actually at. When the GPS signal is reliable, that may be used as the actual position and can be used to keep the INS drift minimized, so if the GPS signal is lost (or the receivers malfunction), the INS takes over as the primary source of position data. This is all further supplemented and verified with radio navigation aids -- as the planes fly along their routes, the airplane computers automatically tune in to various radio navigation aids. In short, even for the newest big commercial jets, functional GPS is very much optional and positional data is quite good without it. As for the moving maps on the seat-back displays: I guess it all depends on the data source they use. If they have their own GPS receiver for the plane's "entertainment" system, that doesn't get the computed current position from the real navigation systems, then the map would presumably stop working or make up (e.g. interpolate) data from when it last had good position data. But now that I think about it... I've only ever seen those maps draw the route as the great-circle path from the departure airport to the destination airport. So they're fictional in that regard -- whether they're interpolating the position on the great-circle path as a percentage of the actual track distance flown and remaining from the real navigation data, or doing something even more fictional, I don't know.
  - madaxe_again 8y ago
    It varies between airlines - off the top of my head I couldn’t tell you which does what, but some are completely accurate, others are essentially a great circle progress bar - and they always turn it off for the interesting bits around takeoff and landing.
  - therein 8y ago
    > But now that I think about it... I've only ever seen those maps draw the route as the great-circle path from the departure airport to the destination airport. So they're fictional in that regard -- whether they're interpolating the position on the great-circle path as a percentage of the actual track distance flown and remaining from the real navigation data, or doing something even more fictional, I don't know. Very interesting. Thanks for the detailed answer. Next time I'll make sure to record the position information independently as well. For some reason I had just taken their great-circle path at its face value and never questioned it. In hindsight, it was all too perfect. :)
PoachedSausage 8y ago
Intriguing, I wonder what could be the reason for and source of jamming over the Brecon Beacons? One possible explanation is that your GPS receiver front-end was overloaded by transmissions from Woofferton transmitting station[0]. [0] https://en.wikipedia.org/wiki/Woofferton_transmitting_station https://en.wikipedia.org/wiki/Woofferton_transmitting_statio...
- MagnumOpus 8y ago
  Brecon beacons are a training ground for UK special forces soldiers - maybe either testing their ability to cope with jamming, or testing their offensive jamming equipment?
nbabitskiy 8y ago
Allegedly, airports' coordinates are hard coded into consumer drones' firmware, at least in Russia. That's the reason why gps devices at Moscow Kremlin walls think, that they are at VKO airport. So jamming gps signal in the airports seems counterproductive. I would think that they'd want drones to know they are in a no-flight zone.