Could anyone help me with Garmin GPS 18lvc device that comes with PPS output. I've been trying to configure the device to achieve about 1ms accuracy. The specification of this device states it could achieve about 1ns accuracy. Im quite puzzled as to why i can't achieve such accuracy. My software include:
ntp-4.2.2p3-RC
Debian Kernel 2.6.16-2-486
gpsd 2.33
My content of ntp.conf is:
-------------------------------------------------------------
server 127.127.28.0 minpoll 4 maxpoll 4
fudge 127.127.28.0 time1 0.320 refid GPS
server 127.127.28.1 minpoll 4 maxpoll 4 prefer
fudge 127.127.28.1 refid GPS1
------------------------------------------------------------
My command line arguments for gpsd is:
gpsd /dev/ttyS0 -n -D 5 -N 2
When i run ntpq the output i get is:
ntpq> peers
remote refid st t when poll reach delay offset jitter
======================================
*SHM(0) .GPS. 0 l 4 16 377 0.000 -6.006 6.758
SHM(1) .GPS1. 0 l - 16 0 0.000 0.000 0.004
ntpq> assoc
ind assID status conf reach auth condition last_event cnt
=======================================
1 1576 9624 yes yes none sys.peer reachable 2
2 1577 8015 yes yes none reject clock expt 1
ntpq> rl
assID=0 status=0964 leap_none, sync_telephone, 6 events, event_peer/strat_chg,
version="ntpd [EMAIL PROTECTED] Tue Jul 25 02:07:02 UTC 2006 (1)",
processor="i686", system="Linux/2.6.16-2-486", leap=00, stratum=1,
precision=-18, rootdelay= 0.000, rootdispersion=15.597, peer=1576,
refid=GPS, reftime=c877d40c.174f6c36 Mon, Jul 31 2006 10:57:48.091,
poll=4, clock=c877d418.085b5148 Mon, Jul 31 2006 10:58:00.032, state=4,
offset=-6.472, frequency=1.799 , jitter=8.704, noise=4.119,
stability=2.464
So im unable to achieve accuracy anywhere around 1ns, Some times i get offset about 8ms. There seesm to be something weird about:
remote refid st t when poll reach delay offset jitter
==========================================
SHM(1) .GPS1. 0 l - 16 0 0.000 0.000 0.004
and when i envoke the ntpq > assoc with the information about SHM(1).
If anyone can offer me some assistants and help it would be greatly appreciated. Thanks in advance.
Cheers,
Sleek
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