4 ms·

Fun fact: Smartphone GPS doesn't work above 10K feet, such that it can't be used to terrorize airplanes.

mseebach 13y ago
Don't you see, you're only helping the TERRORISTS by pointing that out. :) Anyway, in that case, they'd have to remember to buy one of these first, then: http://www.amazon.com/Bad-Elf-1000-30-Pin-Receiver/dp/B0035Y7ZJ2/ http://www.amazon.com/Bad-Elf-1000-30-Pin-Receiver/dp/B0035Y...
gizmo686 13y ago
Is that an actual limitation of the GPS network, or a limitation of the client-side software. My understanding is that GPS satellites broadcast a timestamp, and the receivers use that information to compute their position. Assuming that this is accurate, devices should still be able to get the signal at higher altitudes. The only way I can think of this not working is if the geometry works out so that at 10K feet you are no longer in ranges of 4 satellites. I suppose this could be done my calibrating how wide to make the signal (which would make the signals stronger on the ground, but require more satellites for full coverage). This would likely also require having been thought of back when the GPS network was planned. Also, I would imagine that planes use GPS, in which case it would have to be a client-side restriction.
- toast0 13y ago
  Client side (may be in firmware or software): GPS above certain elevations or speeds requires a special export license that your smartphone probably doesn't have. An unlicensed device is required to output no fix (but it has to be able to calculate that the parameters are outside the allowed range). http://ravtrack.com/GPStracking/cocom-gps-tracking-limits/469/ http://ravtrack.com/GPStracking/cocom-gps-tracking-limits/46...
  - gizmo686 13y ago
    How difficult would it be for someone to work around these restrictions? If I have an unlocked Android phone, would I be able comment out the range check and recompile the gps software?
    - toast0 13y ago
      It's probably either in the driver for the gps chip or the gps firmware; neither of which are likely to have source available for you.
tacticus 13y ago
10k feet sounds a bit low. i thought the limit was at 60k feet and 600MPH

Don't you see, you're only helping the TERRORISTS by pointing that out. :) Anyway, in that case, they'd have to remember to buy one of these first, then: http://www.amazon.com/Bad-Elf-1000-30-Pin-Receiver/dp/B0035Y7ZJ2/ http://www.amazon.com/Bad-Elf-1000-30-Pin-Receiver/dp/B0035Y...

gizmo686 13y ago

Is that an actual limitation of the GPS network, or a limitation of the client-side software. My understanding is that GPS satellites broadcast a timestamp, and the receivers use that information to compute their position. Assuming that this is accurate, devices should still be able to get the signal at higher altitudes. The only way I can think of this not working is if the geometry works out so that at 10K feet you are no longer in ranges of 4 satellites. I suppose this could be done my calibrating how wide to make the signal (which would make the signals stronger on the ground, but require more satellites for full coverage). This would likely also require having been thought of back when the GPS network was planned. Also, I would imagine that planes use GPS, in which case it would have to be a client-side restriction.

toast0 13y ago
Client side (may be in firmware or software): GPS above certain elevations or speeds requires a special export license that your smartphone probably doesn't have. An unlicensed device is required to output no fix (but it has to be able to calculate that the parameters are outside the allowed range). http://ravtrack.com/GPStracking/cocom-gps-tracking-limits/469/ http://ravtrack.com/GPStracking/cocom-gps-tracking-limits/46...
- gizmo686 13y ago
  How difficult would it be for someone to work around these restrictions? If I have an unlocked Android phone, would I be able comment out the range check and recompile the gps software?
  - toast0 13y ago
    It's probably either in the driver for the gps chip or the gps firmware; neither of which are likely to have source available for you.

tacticus 13y ago

10k feet sounds a bit low. i thought the limit was at 60k feet and 600MPH