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

Scott McGrath scmcgrath at gmail.com
Wed Oct 21 19:42:41 EDT 2015

I think it has to do more with battery life as the first release of iOS 9 drained battery faster than prior releases and the GPS is expensive from a power standpoint.   I think the non watch devices sacrificed precision time for runtime 

Content by Scott
Typos by Siri

> On Oct 20, 2015, at 12:09 PM, Paul <tic-toc at bodosom.net> wrote:
> On Tue, Oct 20, 2015 at 4:02 AM, Brian Garrett <garrettbrian1960 at gmail.com>
> wrote:
>> ...  As measured by NTP apps such as Emerald Time and Watchville,
> millisecond accuracy comparable to the soon-to-be-released Apple Watch was
> now commonplace, with typical offsets of 5 ms or less, rather than the
> several seconds of offset typical under the previous release.
> Network connected iOS devices not paired with a watch use (s)ntp at large
> intervals rather than the mobile network or GPS.  The offsets appear to be
> somewhat random -- both positive and negative, large (s) and small (ms).  I
> assume it's related to the environment and the last time the offset was
> corrected.
>> Now, with the latest version, iOS 9, the Apple Watch level accuracy
> previously available to iPhone users has gone away.  Once again, your
> iPhone will be as much as several seconds slow as measured by NTP, unless
> you force an update to the phone’s clock by opening a GPS app.
> I checked on an iPad (but presumably that shouldn't matter).  My current
> offset is -1.6 s (fast, and slowly increasing) as measured by Time
> independent of GPS which I woke with Observatory which uses both NTP (for
> time) and the GPS (for location).  Restarting the iPad causes a step. This
> compares with +1 to -3 ms on my phone.
> I'll admit the above is slightly speculative because I haven't checked
> network traffic yet but I will shortly.
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