3 ms·
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
by 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 agoI 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 agoGSM 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.