5 ms·

I, for one, cannot believe that GPS doesn't have a pre-prod environment. I guess they just don't grok dev ops like us young hip developers. No but seriously, t

I, for one, cannot believe that GPS doesn't have a pre-prod environment. I guess they just don't grok dev ops like us young hip developers. No but seriously, the fact that we don't have a backup for when GPS inevitably shits the bed sometime in the future is a fundamental existential threat to mankind. We should probably do something about that.

deleted 10y ago
[deleted]
jessriedel 10y ago
There already is a partial backups, and eventually there will be three: Galileo, Beidou, GLONASS. Many devices can access multiple systems.
Artlav 10y ago
The existing backup is the Russian GLONASS system, which many consumer chips support since the start of this decade or so, and there are two more constellations being deployed, by ESA and China. I'm not sure how you can test such things not in the production environment. The early development was done with the transmitters on airplanes, but i would guess that the jammability can't really be tested that way.
- paulgerhardt 10y ago
  GPS uses a certain frequency. Use the high side band for prod, the low side band for staging. Simple :)
  - hamiltonkibbe 10y ago
    The nice thing about PRN codes is that you can just use a different set of gold codes in the same band, as long as they have low enough cross-correlation
- brianwawok 10y ago
  Yup my GPS watch does GLONASS. Have never tried GLONASS only, but GPS + GLONASS is a fair bit faster to lock on to.
  - mikeash 10y ago
    Most smartphones do both now as well. iPhones got it starting with the 4S, and various Android devices support it. I believe it's a requirement to be able to sell them in Russia, but it benefits us all.
- selvakn 10y ago
  And India's own: http://www.thehindu.com/sci-tech/science/irnss-launch-indias-own-regional-navigation-satellite-system-takes-shape/article8531388.ece http://www.thehindu.com/sci-tech/science/irnss-launch-indias...
- WorldMaker 10y ago
  Commercial vendor Iridium as part of their "Iridium NEXT" constellation currently being deployed will have a secure alternative to GPS as well, their STL service. [1] [1] http://gpsworld.com/iridium-launches-alternative-gps-pnt-service/ http://gpsworld.com/iridium-launches-alternative-gps-pnt-ser...
hamiltonkibbe 10y ago
I suspect this is because AWS hasn't yet added an API call for placing a fleet of satellites in semi-synchronous orbit
- dwyerm 10y ago
  I can neither confirm nor deny that AWS is working on an API call for placing a fleet of satellites in orbit. On a more serious note, I'm excited to see what happens to the NTP pools in the area, since GPS is often a timing source for them. It should be a non-event, but it could get interesting. Oh, and what happens to CDMA cell towers that use GPS to sync? Do they go off-line?
  - toomuchtodo 10y ago
    Anything relying on GPS for timing is going to revert to an onboard crystal timer for the outage duration.
  - elfchief 10y ago
    Anywhere that GPS is used in a timing-critical application, they'll be using a timing receiver (like http://www.trimble.com/timing/thunderbolt-e.aspx http://www.trimble.com/timing/thunderbolt-e.aspx) to handle their time reference; those use the GPS signal (when they have it) to discipline a (ovenized) quartz crystal, so that they have good performance during "holdover" (loss of GPS) especially for short-term outages. In its default configuration, the Thunderbolt-E linked above, for example, will be within +- 8us after being in holdover for 24 hours.
    - cynix 10y ago
      ±8µs can be rather bad, e.g. for financial applications.
      - elfchief 10y ago
        There is certainly hardware available that can do better than this, but the parent asked about cell sites in specific (and cell sites are one of the top users of the Thunderbolt). You can get GPS hardware based on atomic references, for example, that will do better over these kinds of timespans. (You really need GPS or some other precision time transfer mechanism for long-term accuracy, though ... there's no getting past that.)
djsumdog 10y ago
I thought it was pretty obvious from the article that they're most likely testing GPS jammers. In the case of a war, the US probably doesn't want anyone else to be able to use their GPS network.

deleted 10y ago

[deleted]

jessriedel 10y ago

There already is a partial backups, and eventually there will be three: Galileo, Beidou, GLONASS. Many devices can access multiple systems.

Artlav 10y ago

The existing backup is the Russian GLONASS system, which many consumer chips support since the start of this decade or so, and there are two more constellations being deployed, by ESA and China. I'm not sure how you can test such things not in the production environment. The early development was done with the transmitters on airplanes, but i would guess that the jammability can't really be tested that way.

paulgerhardt 10y ago
GPS uses a certain frequency. Use the high side band for prod, the low side band for staging. Simple :)
- hamiltonkibbe 10y ago
  The nice thing about PRN codes is that you can just use a different set of gold codes in the same band, as long as they have low enough cross-correlation
brianwawok 10y ago
Yup my GPS watch does GLONASS. Have never tried GLONASS only, but GPS + GLONASS is a fair bit faster to lock on to.
- mikeash 10y ago
  Most smartphones do both now as well. iPhones got it starting with the 4S, and various Android devices support it. I believe it's a requirement to be able to sell them in Russia, but it benefits us all.
selvakn 10y ago
And India's own: http://www.thehindu.com/sci-tech/science/irnss-launch-indias-own-regional-navigation-satellite-system-takes-shape/article8531388.ece http://www.thehindu.com/sci-tech/science/irnss-launch-indias...
WorldMaker 10y ago
Commercial vendor Iridium as part of their "Iridium NEXT" constellation currently being deployed will have a secure alternative to GPS as well, their STL service. [1] [1] http://gpsworld.com/iridium-launches-alternative-gps-pnt-service/ http://gpsworld.com/iridium-launches-alternative-gps-pnt-ser...

hamiltonkibbe 10y ago

I suspect this is because AWS hasn't yet added an API call for placing a fleet of satellites in semi-synchronous orbit

dwyerm 10y ago
I can neither confirm nor deny that AWS is working on an API call for placing a fleet of satellites in orbit. On a more serious note, I'm excited to see what happens to the NTP pools in the area, since GPS is often a timing source for them. It should be a non-event, but it could get interesting. Oh, and what happens to CDMA cell towers that use GPS to sync? Do they go off-line?
- toomuchtodo 10y ago
  Anything relying on GPS for timing is going to revert to an onboard crystal timer for the outage duration.
- elfchief 10y ago
  Anywhere that GPS is used in a timing-critical application, they'll be using a timing receiver (like http://www.trimble.com/timing/thunderbolt-e.aspx http://www.trimble.com/timing/thunderbolt-e.aspx) to handle their time reference; those use the GPS signal (when they have it) to discipline a (ovenized) quartz crystal, so that they have good performance during "holdover" (loss of GPS) especially for short-term outages. In its default configuration, the Thunderbolt-E linked above, for example, will be within +- 8us after being in holdover for 24 hours.
  - cynix 10y ago
    ±8µs can be rather bad, e.g. for financial applications.
    - elfchief 10y ago
      There is certainly hardware available that can do better than this, but the parent asked about cell sites in specific (and cell sites are one of the top users of the Thunderbolt). You can get GPS hardware based on atomic references, for example, that will do better over these kinds of timespans. (You really need GPS or some other precision time transfer mechanism for long-term accuracy, though ... there's no getting past that.)

djsumdog 10y ago

I thought it was pretty obvious from the article that they're most likely testing GPS jammers. In the case of a war, the US probably doesn't want anyone else to be able to use their GPS network.