[time-nuts] "Selective availability" af accurate time for Appleusers?

Eric Scace eric at scace.org
Wed Oct 21 15:10:02 UTC 2015


Warning: the following may be apocryphal. I was once told:
Sprint PCS networks distributed very accurate time to cell phones because GPSDO & accurate time was essential to the multiplexing technology then in use.
In contrast, time of day at an AT&T GSM cell site depending on the accuracy of the technician’s watch when setting up the site. Hence, each site could be many seconds different from its neighbors.
I have never verified this information, and it is 10 years old.

> On 2015 Oct 21, at 01:41 , David J Taylor <david-taylor at blueyonder.co.uk> wrote:
> 
> Has anybody else observed this with their iPhone since “upgrading” to iOS 9? Anyone know of any difference in the reference time ( e.g. GPS vs. network time) that Apple is using to “dumb down’ their smartphones in favor of Apple Watch?
> 
> Brian Garrett
> ====================================
> 
> Yes, on one quick check, I now see an accuracy (or rather error) o my iPad of up to several seconds (iOS 9.0.2) compared to my recollection of sub-second accuracy under iOS 8.0.2x.
> 
> My £50 Windows 10 tablet using real NTP does /much/ better!
> 
> Cheers,
> David
> --
> SatSignal Software - Quality software written to your requirements
> Web: http://www.satsignal.eu
> Email: david-taylor at blueyonder.co.uk
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