5 ms·

It's kind of neat how this works: > As part of the ADS-B messages we receive from each aircraft, the Navigation integrity category (NIC) encodes the quality an

It's kind of neat how this works: > As part of the ADS-B messages we receive from each aircraft, the Navigation integrity category (NIC) encodes the quality and consistency of navigational data received by the aircraft. The NIC value informs how certain the aircraft is of its position by providing a radius of uncertainty. > Poor NIC values alone might indicate a problem with an aircraft’s equipment or unfavorable positioning. However, when observed in multiple aircraft in close proximity during the same time frame, it suggests the presence of a radio signal interfering with normal GNSS operation. A single observer can't really say for certain that jamming is happening; you need a distributed sample from multiple different sensors over a period of time to have reasonably high confidence.

toomuchtodo 3y ago
> A single observer can't really say for certain that jamming is happening; you need a distributed sample from multiple different sensors over a period of time to have reasonably high confidence. Could you use RTLSDR triangulation to hone in on granular lat long of jamming sources? https://www.rtl-sdr.com/detecting-gps-jammers-in-augmented-reality/ https://www.rtl-sdr.com/detecting-gps-jammers-in-augmented-r... https://www.rtl-sdr.com/kiwisdr-tdoa-direction-finding-now-freely-available-for-public-use/ https://www.rtl-sdr.com/kiwisdr-tdoa-direction-finding-now-f...
- pierat 3y ago
  You can get rough areas with a GPS and a RTLSDR and a bunch of samples (either over time OR with lots of people with the same device) But to get fine granular data, you need a timestamping SDR. (each parcel of signal data for a quantum of data needs an exact time down to 6-8 significant figures, basically GPS timebase). Most your cheaper SDRs cant do that. Stuff like the BladeRF and higher do provide timestamped data.
- mNovak 3y ago
  With synchronized receivers you could do some rudimentary direction finding. Note that synchronizing SDRs is much more achievable if they're physically nearby (e.g. can run a cable between them for a common clock) vs if they're physically distant observers (can't exactly use GPS time for synchronization if you're measuring GPS interference)
  - toomuchtodo 3y ago
    Very helpful (as well as sibling comment by pierat). Thank you both. I will need to do some research with regards to pairing SDRs with local disciplined clock that can tolerate temporary loss of remote (stratum-0,1) time precision. https://en.wikipedia.org/wiki/GPS_disciplined_oscillator https://en.wikipedia.org/wiki/GPS_disciplined_oscillator
  - XMPPwocky 3y ago
    > can't exactly use GPS time for synchronization if you're measuring GPS interference Can other GNSSes (Galileo/BeiDou/GLONASS/etc) give usable timestamps? Seems like it'd be tricky for a jammer to target all of them simultaneously. (Of course, since they'd be on a different band, unless your SDR is wideband enough you'd need two RX heads which gives you potential issues with phase drift between the tuning VCOs even if your sampling is coherent). Perhaps a sufficiently directional antenna/phased array (for getting an actual satellite signal) as well as an omnidirectional one (for picking up the jamming signal) could get you somewhere... Or perhaps one could look at computing AoA at each receiver site (using MIMO-y techniques, e.g. Kraken/KerberosSDR) and triangulating based on angles instead, which wouldn't require synchronizing physically-distant sites at all... The problem definitely seems soluble, though I don't have the technical background to know how realistic that is.
    - mNovak 3y ago
      >> Can other GNSS give usable timestamps? Seems like it'd be tricky for a jammer to target all of them Actually the opposite; GNSS systems are all purposely designed to operate at virtually the same frequency (check out this figure [1]) while cleverly not interfering with each other. There are sub-bands within each constellation too (L1,L2,L5 etc) but it's very easy to pump out wideband noise across all the GNSS bands. [1] https://www.researchgate.net/figure/The-spectrum-of-current-GNSS-signals-in-15-17-GHz_fig1_259435730 https://www.researchgate.net/figure/The-spectrum-of-current-...
- CogniDizz 3y ago
  KrakenSDR would do a good job of this, they combine five RTLSDR into a coherent array. The top end of their tuning range is 1766 MHz which would include the 1575 MHz of the GPS L1 signal. The little five antenna array can even attach on the roof of a car for a handy ground plane. Prob not a good idea to drive with it out there tho.
- pgorczak 3y ago
  You could also use a single receiver with a small antenna array (GPS wavelength is around 20 cm) to estimate the angle of arrival of the incoming signals.
  - deleted 3y ago
    [deleted]
adolph 3y ago
Do aircraft systems really only use GPS and not the full constellation of navigational satellite systems? Besides GPS, the GNSS currently includes other satellite navigation systems, such as the Russian GLONASS, and may soon include others such as the European Union’s Galileo and China’s Beidou. https://www.terrisgps.com/gnss-gps-differences-explained/ https://www.terrisgps.com/gnss-gps-differences-explained/
- ptaipale 3y ago
  The linked page already says that it reports on the constellation, not just GPS: "The map uses are color coded overlay to indicate low (green) to high (red) levels of interference with global navigation satellite systems (GNSS). Often just referred to as GPS, there are actually multiple systems beside the US GPS constellation, such as Russia’s GLONASS, Europe’s Galileo, China’s BeiDou, and others."
  - blauditore 3y ago
    Just came here to wonder who came up with the beautiful name of CLOWNASS... er, I mean GLONASS.
    - hylaride 3y ago
      GLObalnaya NAvigatsionnaya Sputnikovaya Sistema in Russian.
- mNovak 3y ago
  Like the article states, many people use GPS as a shorthand for GNSS generally. In any case, they're all at similar frequencies, so typically they'll all go out together if there's significant interference.
  - anticensor 3y ago
    GLONASS notoriously uses its own band and data format, while following the same basic working principle.
throwmenow99 3y ago
Airplanes.Live has an API that you can use to play with this data. https://airplanes.live/api-guide/ https://airplanes.live/api-guide/ Pretty neat! I starting sending data from my ASD-B feeder as well. https://airplanes.live/get-started/ https://airplanes.live/get-started/ This is really cool since ASDBExchange was bought out by a private equity firm and has since stopped giving out data to cool projects. I see they are being sued for IP theft and a couple other items. Link to Lawsuit in CA is below because I was reading it tonight. https://www.documentcloud.org/documents/23963235-golden-hammer-v-jetnet-et-al https://www.documentcloud.org/documents/23963235-golden-hamm... https://www.lacourt.org/casesummary/ui/index.aspx?casetype=civil https://www.lacourt.org/casesummary/ui/index.aspx?casetype=c... 23CHCV02662

toomuchtodo 3y ago

> A single observer can't really say for certain that jamming is happening; you need a distributed sample from multiple different sensors over a period of time to have reasonably high confidence. Could you use RTLSDR triangulation to hone in on granular lat long of jamming sources? https://www.rtl-sdr.com/detecting-gps-jammers-in-augmented-reality/ https://www.rtl-sdr.com/detecting-gps-jammers-in-augmented-r... https://www.rtl-sdr.com/kiwisdr-tdoa-direction-finding-now-freely-available-for-public-use/ https://www.rtl-sdr.com/kiwisdr-tdoa-direction-finding-now-f...

pierat 3y ago
You can get rough areas with a GPS and a RTLSDR and a bunch of samples (either over time OR with lots of people with the same device) But to get fine granular data, you need a timestamping SDR. (each parcel of signal data for a quantum of data needs an exact time down to 6-8 significant figures, basically GPS timebase). Most your cheaper SDRs cant do that. Stuff like the BladeRF and higher do provide timestamped data.
mNovak 3y ago
With synchronized receivers you could do some rudimentary direction finding. Note that synchronizing SDRs is much more achievable if they're physically nearby (e.g. can run a cable between them for a common clock) vs if they're physically distant observers (can't exactly use GPS time for synchronization if you're measuring GPS interference)
- toomuchtodo 3y ago
  Very helpful (as well as sibling comment by pierat). Thank you both. I will need to do some research with regards to pairing SDRs with local disciplined clock that can tolerate temporary loss of remote (stratum-0,1) time precision. https://en.wikipedia.org/wiki/GPS_disciplined_oscillator https://en.wikipedia.org/wiki/GPS_disciplined_oscillator
- XMPPwocky 3y ago
  > can't exactly use GPS time for synchronization if you're measuring GPS interference Can other GNSSes (Galileo/BeiDou/GLONASS/etc) give usable timestamps? Seems like it'd be tricky for a jammer to target all of them simultaneously. (Of course, since they'd be on a different band, unless your SDR is wideband enough you'd need two RX heads which gives you potential issues with phase drift between the tuning VCOs even if your sampling is coherent). Perhaps a sufficiently directional antenna/phased array (for getting an actual satellite signal) as well as an omnidirectional one (for picking up the jamming signal) could get you somewhere... Or perhaps one could look at computing AoA at each receiver site (using MIMO-y techniques, e.g. Kraken/KerberosSDR) and triangulating based on angles instead, which wouldn't require synchronizing physically-distant sites at all... The problem definitely seems soluble, though I don't have the technical background to know how realistic that is.
  - mNovak 3y ago
    >> Can other GNSS give usable timestamps? Seems like it'd be tricky for a jammer to target all of them Actually the opposite; GNSS systems are all purposely designed to operate at virtually the same frequency (check out this figure [1]) while cleverly not interfering with each other. There are sub-bands within each constellation too (L1,L2,L5 etc) but it's very easy to pump out wideband noise across all the GNSS bands. [1] https://www.researchgate.net/figure/The-spectrum-of-current-GNSS-signals-in-15-17-GHz_fig1_259435730 https://www.researchgate.net/figure/The-spectrum-of-current-...
CogniDizz 3y ago
KrakenSDR would do a good job of this, they combine five RTLSDR into a coherent array. The top end of their tuning range is 1766 MHz which would include the 1575 MHz of the GPS L1 signal. The little five antenna array can even attach on the roof of a car for a handy ground plane. Prob not a good idea to drive with it out there tho.
pgorczak 3y ago
You could also use a single receiver with a small antenna array (GPS wavelength is around 20 cm) to estimate the angle of arrival of the incoming signals.
- deleted 3y ago
  [deleted]

adolph 3y ago

Do aircraft systems really only use GPS and not the full constellation of navigational satellite systems? Besides GPS, the GNSS currently includes other satellite navigation systems, such as the Russian GLONASS, and may soon include others such as the European Union’s Galileo and China’s Beidou. https://www.terrisgps.com/gnss-gps-differences-explained/ https://www.terrisgps.com/gnss-gps-differences-explained/

ptaipale 3y ago
The linked page already says that it reports on the constellation, not just GPS: "The map uses are color coded overlay to indicate low (green) to high (red) levels of interference with global navigation satellite systems (GNSS). Often just referred to as GPS, there are actually multiple systems beside the US GPS constellation, such as Russia’s GLONASS, Europe’s Galileo, China’s BeiDou, and others."
- blauditore 3y ago
  Just came here to wonder who came up with the beautiful name of CLOWNASS... er, I mean GLONASS.
  - hylaride 3y ago
    GLObalnaya NAvigatsionnaya Sputnikovaya Sistema in Russian.
mNovak 3y ago
Like the article states, many people use GPS as a shorthand for GNSS generally. In any case, they're all at similar frequencies, so typically they'll all go out together if there's significant interference.
- anticensor 3y ago
  GLONASS notoriously uses its own band and data format, while following the same basic working principle.

throwmenow99 3y ago

Airplanes.Live has an API that you can use to play with this data. https://airplanes.live/api-guide/ https://airplanes.live/api-guide/ Pretty neat! I starting sending data from my ASD-B feeder as well. https://airplanes.live/get-started/ https://airplanes.live/get-started/ This is really cool since ASDBExchange was bought out by a private equity firm and has since stopped giving out data to cool projects. I see they are being sued for IP theft and a couple other items. Link to Lawsuit in CA is below because I was reading it tonight. https://www.documentcloud.org/documents/23963235-golden-hammer-v-jetnet-et-al https://www.documentcloud.org/documents/23963235-golden-hamm... https://www.lacourt.org/casesummary/ui/index.aspx?casetype=civil https://www.lacourt.org/casesummary/ui/index.aspx?casetype=c... 23CHCV02662