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Can you explain what you mean by that? The only thing I can think of is that GPS has 2 modes : one civilian and other military use. But military use-case uses e

Can you explain what you mean by that? The only thing I can think of is that GPS has 2 modes : one civilian and other military use. But military use-case uses encryption so civilians can't use that mode anyway.

cmsj 2y ago
GPS was built primarily for the military and the signals available for civilian use were crippled to reduce accuracy. GPS receivers that provided high accuracy fell under the ITAR rules (ie you needed proper licensing to trade them) Over time such restrictions have largely been lifted, but there are still US export controls on GPS receivers with particular features, such as those designed for use in high speed aircraft, those able to decode the still-military-only encrypted signals that piggyback GPS and provide greater positioning precision, or those designed for use in rockets/UAVs. So, it's reasonable to assume that if you were to build your own, and do too good of a job, you would accidentally become subject to arms trade regulations, and that's probably not a place you want to unintentionally find yourself, particularly if you're publishing it as open source on the Internet :)
- AlexanderTheGr8 2y ago
  > those able to decode the still-military-only encrypted signals How? I was under the impression that military-only signal was encrypted. And if someone breaks that encrpytion, blame should go to the poor handling of encryption rather than the person breaking it? Analogy : if you leave a classified document on the train and a passenger reads it, whose fault is it?
  - cmsj 2y ago
    I'm relatively certain that the US government will be unmoved by your argument that it would be their fault if you built a GPS receiver that could decrypt the precise positioning signals ;)
  - dheera 2y ago
    Actually you can use the phase information in the encrypted signals to improve RTK stability, without decrypting them.
  - j16sdiz 2y ago
    Technological restrictions and Legal restrictions not always aligns. That's where the "restrictions have largely been lifted" part comes in. You can decrypt most of them, but it is illegal to export without a license.
  - tverbeure 2y ago
    The Kraken RF project, which has multiple SDR radios next to each other, had demo code of a passive radar: the slight time delay by which signals arrived at the antennas could be used to detect large metal bodies (IOW: planes) in the sky. They took down the demo code they were informed that they were violating ITAR regulations. https://www.reddit.com/r/RTLSDR/comments/yu9rei/krakenrf_pulls_passive_radar_code_from_github_due/ https://www.reddit.com/r/RTLSDR/comments/yu9rei/krakenrf_pul...
  - solidsnack9000 2y ago
    Well, consider another analogy: a person leaves their door unlocked and another person goes in their home. It is still trespassing, even though the physical barrier has been intentionally disabled. I'm not sure even what section of US code to check but it is certainly plausible that you can (for example) find a surplus device that decodes the signals on EBay and it's actually illegal to do it. You can find radios on EBay that broadcast on bands that are unlawful to use (or unlawful without certain licenses, &c).
nobodyknowin 2y ago
Not GP but modern GPS / GNSS manufacturers intentionally do not allow their devices to function over some speed (1000 mph or something like that). So they won't work on warheads as part of a guidance system.
- AlexanderTheGr8 2y ago
  I never really thought of that. That's a pretty interesting restriction. Although any party with access to warheads that can fly 1000+ mph probably can bypass the GPS restriction, no?
  - nobodyknowin 2y ago
    Not if they buy an off-the-shelf solution.
    - mbonnet 2y ago
      correct. and the idea here is to put up at least some form of barrier to entry, because any good guidance is also nuclear warhead delivery guidance at a certain point.
  - m463 2y ago
    Just don't let some future party use your code to do it.
  - askvictor 2y ago
    There was a guy in NZ (Bruce Simpson) who detailed on his blog how to make a DIY cruise missile. I think he got politely asked to stop doing so at some point.
    - cmsj 2y ago
      BPS.Space on youtube is working on a DIY space-capable rocket and in a recent video he mentioned that he is not doing this as a tutorial and that his guidance system likely already wanders into ITAR territory, and thus he's self-censoring which parts he shares and which parts happen off-camera. Ultimately these kinds of regulations are fairly silly because a sufficiently determined smart person can recreate the covered technologies from scratch, but here we are.
rich90usa 2y ago
I launched a high altitude balloon as part of a summer school program over a decade ago and we checked on edge cases. Off the shelf GPS are supposed to not work beyond a certain height 18,000 m and/or speed 515 m/s to be a barrier for use as a weapon. Some hardware treat that as AND; some treat that condition as OR. The term to look up is “CoCom Limits”.

cmsj 2y ago

GPS was built primarily for the military and the signals available for civilian use were crippled to reduce accuracy. GPS receivers that provided high accuracy fell under the ITAR rules (ie you needed proper licensing to trade them) Over time such restrictions have largely been lifted, but there are still US export controls on GPS receivers with particular features, such as those designed for use in high speed aircraft, those able to decode the still-military-only encrypted signals that piggyback GPS and provide greater positioning precision, or those designed for use in rockets/UAVs. So, it's reasonable to assume that if you were to build your own, and do too good of a job, you would accidentally become subject to arms trade regulations, and that's probably not a place you want to unintentionally find yourself, particularly if you're publishing it as open source on the Internet :)

AlexanderTheGr8 2y ago
> those able to decode the still-military-only encrypted signals How? I was under the impression that military-only signal was encrypted. And if someone breaks that encrpytion, blame should go to the poor handling of encryption rather than the person breaking it? Analogy : if you leave a classified document on the train and a passenger reads it, whose fault is it?
- cmsj 2y ago
  I'm relatively certain that the US government will be unmoved by your argument that it would be their fault if you built a GPS receiver that could decrypt the precise positioning signals ;)
- dheera 2y ago
  Actually you can use the phase information in the encrypted signals to improve RTK stability, without decrypting them.
- j16sdiz 2y ago
  Technological restrictions and Legal restrictions not always aligns. That's where the "restrictions have largely been lifted" part comes in. You can decrypt most of them, but it is illegal to export without a license.
- tverbeure 2y ago
  The Kraken RF project, which has multiple SDR radios next to each other, had demo code of a passive radar: the slight time delay by which signals arrived at the antennas could be used to detect large metal bodies (IOW: planes) in the sky. They took down the demo code they were informed that they were violating ITAR regulations. https://www.reddit.com/r/RTLSDR/comments/yu9rei/krakenrf_pulls_passive_radar_code_from_github_due/ https://www.reddit.com/r/RTLSDR/comments/yu9rei/krakenrf_pul...
- solidsnack9000 2y ago
  Well, consider another analogy: a person leaves their door unlocked and another person goes in their home. It is still trespassing, even though the physical barrier has been intentionally disabled. I'm not sure even what section of US code to check but it is certainly plausible that you can (for example) find a surplus device that decodes the signals on EBay and it's actually illegal to do it. You can find radios on EBay that broadcast on bands that are unlawful to use (or unlawful without certain licenses, &c).

nobodyknowin 2y ago

Not GP but modern GPS / GNSS manufacturers intentionally do not allow their devices to function over some speed (1000 mph or something like that). So they won't work on warheads as part of a guidance system.

AlexanderTheGr8 2y ago
I never really thought of that. That's a pretty interesting restriction. Although any party with access to warheads that can fly 1000+ mph probably can bypass the GPS restriction, no?
- nobodyknowin 2y ago
  Not if they buy an off-the-shelf solution.
  - mbonnet 2y ago
    correct. and the idea here is to put up at least some form of barrier to entry, because any good guidance is also nuclear warhead delivery guidance at a certain point.
- m463 2y ago
  Just don't let some future party use your code to do it.
- askvictor 2y ago
  There was a guy in NZ (Bruce Simpson) who detailed on his blog how to make a DIY cruise missile. I think he got politely asked to stop doing so at some point.
  - cmsj 2y ago
    BPS.Space on youtube is working on a DIY space-capable rocket and in a recent video he mentioned that he is not doing this as a tutorial and that his guidance system likely already wanders into ITAR territory, and thus he's self-censoring which parts he shares and which parts happen off-camera. Ultimately these kinds of regulations are fairly silly because a sufficiently determined smart person can recreate the covered technologies from scratch, but here we are.

rich90usa 2y ago

I launched a high altitude balloon as part of a summer school program over a decade ago and we checked on edge cases. Off the shelf GPS are supposed to not work beyond a certain height 18,000 m and/or speed 515 m/s to be a barrier for use as a weapon. Some hardware treat that as AND; some treat that condition as OR. The term to look up is “CoCom Limits”.