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Re: [gpsd-users] [gpsd newbie] Wrong time using Ublox

From: Michele
Subject: Re: [gpsd-users] [gpsd newbie] Wrong time using Ublox
Date: Thu, 17 Mar 2022 10:36:47 +0100
User-agent: Mozilla/5.0 (X11; Linux i686; rv:68.0) Gecko/20100101 Firefox/68.0 Thunderbird/68.10.0

Hi Gary, thanks for support.

Sorry Gary, I've read about private mails, just a mistake during sending 
between gmail draft and mozilla....

I'll update gpsd as soon.

Why date to Jan 2000? Why using ntpdate instead ntpd? Why not taking
a look to cell phone? Why usingwww.timeanddate....?
Ok, let's say I'm using (several) Raspberry pi for data analysis on
acceleration/deformation on buildings during earthquakes, I need to
collect data at 200 samples per second, I need all devices to be
synced. I need at least all devides inside a same building eith the
same time, ntp is not accurate as GPS but I'll solve this later....
Using Raspberry pi, even if no internet connection available, I get
different date depending of OS version installed, it could be one
says "22 Oct 2019" while other "12 Dec 2020". System can't know if
date is real or fake, that's why as first step I set date to 1 Jan
2000, acquisition can't start if date is before 2020 (for
compatibility on previous system).

I made tests using industrial ntp server on my devices but I can't
install industrial ntp server on every house, that's why I moved to
ntp server using Raspberry: on our tests NTP misalignment (using
Raspberry ntp server) compared to GPS was within 10ms.
During these tests I manually update time in my scripts using ntpdate
(that's also for compatibility for old systems I used before), I also
need to manage hardware signals every time I sync.

As reference device I use MikroTik routers for debug: inside there is
ntp client telling me time misalignment, ntp next time poll, logs and
so on. Using industrial ntp server I always get time misalignment of
fews milliseconds (obviously except first sync), using Raspberry NTP
server I often get about 4 seconds misalignment at third sync, that's
why this makes me think about flags of Ublox: I observed this on NEO
6M logs. For coarse comparison I use several websites (such
timeanddate and others), I can understand misalignment within 1
second among websites and my NTP but I get up to 4 seconds

My ntp.conf is that I usually find on NTP server examples (my Pi is
offline, I'll post it as soon as possible).

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