5 ms·

this will be a fun thread! high frequency trading relies on gps disciplined osscilators for the precise timing needed (ntp isn't good enough, ptp isn't even goo

this will be a fun thread! high frequency trading relies on gps disciplined osscilators for the precise timing needed (ntp isn't good enough, ptp isn't even good enough, though White rabbit should be). so hft would cease or go wonky trucking companies rely on it to enforce rest periods. so more truck accidents? turn by turn direction on phones would go out. wi fi is enough for nav, unless your phone and the wifi are on different ntp networks maybe I had a phone with broken gps and I didn't really notice.

a3n 7y ago
American trucker here. Occasionally I will lose the GPS signal in my truck, but my hours of service still counts down. The electronic logs are kept onboard, and transmitted at some point to headquarters. I suppose the Qualcomm unit might eventually be off by a second or three. But I don't know if its clock is updated by GPS, phone or wifi. I'm guessing phone. We're also required to carry paper log sheets in case of Qualcomm outage. So then it would be paper, watch and honesty. The honesty can be sanity checked by speed an distance.
- sethhochberg 7y ago
  I don't know much about Qualcomm's gear for truckers, but FWIW even if the machine does pull its time data over the cellular network (possible on CDMA, less likely - impossible? - on GSM), the cell tower itself likely relies on GPS for its own time sync. Its very common for GPS to be used as a globally-accurate source of time data even in applications that have nothing to do with location.
  - toast0 7y ago
    GSM also provides a time reference. I seem to recall connecting to some networks that didn't provide it though. Base stations should be using GPS (and others) to discipline a local oscilator that should be ok enough for a while in absence of signal. They can probably also get a timing signal from their backhaul. It works better with precise timing, but I think it's workable with best efforts.
rtkwe 7y ago
Datacenters use GPS as a timekeeping source to keep synchronization across multiple locations more closely (or did who knows what Google actually uses, I could believe they wait till they move to a better solution to release their whitepapers).
Angostura 7y ago
> I had a phone with broken gps and I didn't really notice. I certainly noticed in the UK on an iPhone 6 where the GPS chip was borked. You would drive for 10 minutes and then you would get an updated location. This was in outer London.
- galangalalgol 7y ago
  my experience was with lineage os in the burbs of dfw. Samsung device on att, all of which probably matters. yeah fragmentation

a3n 7y ago

American trucker here. Occasionally I will lose the GPS signal in my truck, but my hours of service still counts down. The electronic logs are kept onboard, and transmitted at some point to headquarters. I suppose the Qualcomm unit might eventually be off by a second or three. But I don't know if its clock is updated by GPS, phone or wifi. I'm guessing phone. We're also required to carry paper log sheets in case of Qualcomm outage. So then it would be paper, watch and honesty. The honesty can be sanity checked by speed an distance.

sethhochberg 7y ago
I don't know much about Qualcomm's gear for truckers, but FWIW even if the machine does pull its time data over the cellular network (possible on CDMA, less likely - impossible? - on GSM), the cell tower itself likely relies on GPS for its own time sync. Its very common for GPS to be used as a globally-accurate source of time data even in applications that have nothing to do with location.
- toast0 7y ago
  GSM also provides a time reference. I seem to recall connecting to some networks that didn't provide it though. Base stations should be using GPS (and others) to discipline a local oscilator that should be ok enough for a while in absence of signal. They can probably also get a timing signal from their backhaul. It works better with precise timing, but I think it's workable with best efforts.

rtkwe 7y ago

Datacenters use GPS as a timekeeping source to keep synchronization across multiple locations more closely (or did who knows what Google actually uses, I could believe they wait till they move to a better solution to release their whitepapers).

Angostura 7y ago

> I had a phone with broken gps and I didn't really notice. I certainly noticed in the UK on an iPhone 6 where the GPS chip was borked. You would drive for 10 minutes and then you would get an updated location. This was in outer London.

galangalalgol 7y ago
my experience was with lineage os in the burbs of dfw. Samsung device on att, all of which probably matters. yeah fragmentation