Questions tagged [gps]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
0 votes
1 answer
187 views

Do NTP pool servers use gpsd?

A bug in gpsd upon which some NTP servers rely, has been known for a couple of months, but it hasn't really become general knowledge until recently, just before the October 24, 2021 rollover that ...
user avatar
  • 187
2 votes
0 answers
530 views

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 ...
user avatar
  • 669
0 votes
0 answers
110 views

querying data from NTP in ubuntu using socket

I have configured ntp to use gpsd as reference server on my machine. I am querying data from ntp directly, using udp socket. For ip address I use localhost and port_number = 123. Packet structure I ...
user avatar
  • 101
6 votes
1 answer
413 views

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 ...
user avatar
3 votes
1 answer
691 views

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://...
user avatar
1 vote
0 answers
299 views

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 ...
user avatar
  • 111
1 vote
0 answers
20 views

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 ...
user avatar
-4 votes
1 answer
392 views

Ping latency vs location on a map (x kilometer of a trip) | ping-latency vs distance

Orange is having problem delivering the internet between biggest cities (I'm traveling via train). There are white spots on the way... They do not see the problem, so I thought - lets make a chart ...
user avatar
  • 121
1 vote
1 answer
5k views

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 ...
user avatar
4 votes
1 answer
790 views

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 ...
user avatar
1 vote
2 answers
3k views

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 ...
user avatar
  • 202
8 votes
2 answers
2k views

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 ...
user avatar
  • 202
3 votes
1 answer
3k views

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 ...
user avatar
10 votes
1 answer
533 views

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 ...
user avatar
  • 1,191
3 votes
2 answers
3k views

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 -...
user avatar
  • 215
1 vote
1 answer
2k views

Access NMEA reference clock and GPS position simultaneously

I noticed two approaches to get an accurate time from GPS (with PPS). Using ntpd either with NMEA reference clock or Shared Memory Driver My problem: I want to have a very accurate time and access ...
user avatar
  • 215
2 votes
1 answer
3k views

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/...
user avatar
  • 215
7 votes
3 answers
11k views

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 ...
user avatar
  • 669
37 votes
12 answers
21k views

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. ...