It's a little sad that phones themselves, whilst smart enough to get
network time, do not use the GPS NEMA time info provided in the data
stream coming out of the GPS reciever.
Many standalone dedicated time standard servers (e.g. for datacentre
use) use GPS as a reference time source (and some use CDMA/GSM, too). I
have a GPS evaluation board intended to connect to my local firewall to
implement a 'stratum 0' time standard for my connected clients to
access.
davidt
On Sat, Jul 14, 2018 at 05:21:29PM -0700, Chris Trask wrote:
> I had a similar problem with the GPS app on my smart phone. I was out
> on a cycling run and suddenlyit said that I was 400 feet below ground level.
> It pretty much stayed that way for about 25 minutes, then jumped up to the
> correct altitude. All the time the UTM was correct, as shown on the route
> tracker.
>
> It happened again a few days later. Then a couple of days ago I could
> not get a 3D lock at all. Turned out the smart phone clock was way off as I
> had not connected it to a wifi for more than a week. Once I did, everything
> returned to normal. I obviously need to do that more often.
>
> The clock oscillators in these things are not exactly space shuttle
> quality, and the crystal oscillators used in formal GPS receivers are TCXOs
> (temperature compensated crystal oscillators).
>
> To make up for this deficiency, I instaled the ClockSync.apk
> application, which synchronises the smart phone clock to an NIST or other
> comparable time standard. I still have to connect it to a wifi, but I know
> that I'm getting the best possible synchronisation outside of GPS.
>
> My laptops and desk computer all have NetTime installed, which performs
> the same function.
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