Hello,
I'm using a Garmin 18 LVC connected using LinuxPPS with mostly good results.
I am curious about one thing though. The offset reported by the GPS18
differ from the public NIST servers by around 1.7-1.9MS. as shown in the
offset numbers of ntpq below.
remote refid st t when poll reach delay offset jitter
==============================================================================
*GPS_NMEA(0) .GPS. 0 l 4 16 377 0.000 -0.448 0.189
+bigben.cac.wash .USNO. 1 u 34 1024 377 11.134 0.283 2.645
All of the server's internet peers are ahead by around that same value so
I'm guessing that when the GPS18 loses sync, ntpd would have to bring the
clock up by 2MS and reverse when signal is reacquired.
Is there any way to know whether it's our internet link (ADSL) causing the
internet servers to appear off or does the GPS18 need a time1 fudge to bring
it in line with the others? That is, is there a 2MS lag in processing the
interrupt for PPS?
Best,
Shane
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