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Questions tagged [gps]

19 questions
37
votes
12 answers

Is anyone using GPS for time sync?

I've come across a handful of GPS NTP servers, as well as some inexpensive solutions using off-the-shelf receivers and software. Right now I'm just using NTP with a list of servers over the Internet. What is the advantage to using GPS instead…
user640
10
votes
1 answer

Linux ntpd leap second preparation

There will be a leap second on June 30, 2015 at 23:59:60 UTC. I have a Linux based stratum 1 NTP server which uses GPS as a reference clock. The server is using the "default" ntp.org ntpd. How should I prepare for the leap second to ensure that the…
snap
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2 answers

Getting gpsd address for ntpd

I'm working through some tutorials for setting ntpd clock from gpsd. The guides that I'm working from list adding something like this: server 127.127.46.0 fudge 127.127.46.0 time1 0.0 time2 0.0 refid GPS to /etc/ntp.conf however every tutorial…
timlyo
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7
votes
3 answers

Seemingly poor quality of NTP time synchronization using a GPS clock

I have a Linux server which has its time synchronized to a GPS-based NTP appliance located close by. Ping times from the server to the appliance are circa 1ms, with very low jitter: --- x.x.x.x ping statistics --- 100 packets transmitted, 100…
NPE
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6
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1 answer

Using GPS as only source for NTP daemon

I have questions regarding the use of a GPS receiver as an external clock source for realization of a time server with NTP daemon (client version 3), on a local network with no connection to external time servers. I tried using three different GPS…
waldemar
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4
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1 answer

Is PTP really more precise than NTP? If so, why?

I have read quite a bit about NTP and PTP time keeping protocols. While many sources claim that PTP is more precise than NTP for that type of granularity - the reason is not as clear. Why can't NTP be just as accurate if a stratum 0 reference clock…
Palace Chan
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3
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1 answer

are ntp.org pools and time.windows.com safe from gps 2019 week rollover?

Can anyone point to any public doc stating that pools from ntp.org and time.windows.com are safe from next thrusday gps week rollover ? I am looking to something similar to this Red Hat KB https://access.redhat.com/solutions/4018911 thanks g
golemwashere
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3
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1 answer

NTP using GPS and PPS as clock, PPS is marked as falseticker

I am attempting to add a GPS-based clock source to my network, using a GPS which emits a 1-PPS clock pulse. This is connected to a GPIO pin. After allowing ntpd to run for 30 minutes or so, the PPS clock is still not used, and marked as bad, but I…
Michael Graff
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3
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2 answers

configuration to use gps time with no internet connection

I use ntp with a GPS device with PPS on port /dev/ttyS0. All seems to be fine if the machine is connected to the internet. Output looks correct. But if there is no internet connection I get: $ ntpq -p remote refid st t when poll…
wenzul
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2
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0 answers

Local GPS clock is marked as falseticker by ntpd — why?

I have a Linux NTP server with a ublox M8Q GPS module connected via GPIO (UART @ 9600bps and PPS). What I observe is that the local GPS source — SHM(0) — gets marked as falseticker and I'd like to understand why. clock@clock:~ $ ntpq -p remote …
NPE
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1 answer

udev rule running setserial low_latency don't work

My server runs Ubuntu 14.04.1. I created udev rules in /etc/udev/rules.d/09-pps.rules to get GPS with PPS support work. KERNEL=="ttyS0", SYMLINK+="gps0", MODE="0666" KERNEL=="ttyS0", RUN+="/bin/setserial -q /dev/%k low_latency" KERNEL=="ttyS0",…
wenzul
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1
vote
0 answers

NTP does not update until after I poll it

I have NTP setup to run with GPSd and all is well. The issue arises after about a week of my raspberry pi being disconnected, NTP will trust the old date on the system clock. Since the GPS takes a couple seconds to get power and acquire a lock it…
Chaos
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0 answers

Changing Polling times on a VM running under Server2012 R2?

Is there a way to know or change the polling times of VMs running under a Hyper-V 2012 R2 server? We have set all the hosts and physical domain controllers to keep time with our new GPS time server on location. WE have read to keep the VMs set to…
Wayne Caudle
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1
vote
1 answer

chrony and gpsd: socket or PPS connection

I've try to get high precision time from gps receiver GlobalSat BU-353s4 (/dev/ttyUSB0) through gpsd in Raspberry PI with ArchLinux. /etc/chrony.conf contains: refclock SHM 0 delay 0.5 refid NEMA refclock SHM 1 offset 0.0 delay 0.1 refid…
Stanislav Ivanov
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2 answers

Setting ntp time from gpsd

I'm trying to configure ntpd to source it's time from a gps receiver (BU-353S4) but I'm getting some errors. I'm using ntpd 4.2.8.p6-3 and gpsd 3.16-2 on Arch Linux Arm. I've been following the tutorial on the arch wiki but it doesn't have any…
timlyo
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