[ntp:questions] First attempt GPSD/PPS ->NTP time server

Unruh unruh-spam at physics.ubc.ca
Sun Jan 27 07:29:17 UTC 2008

folkert at vanheusden.com (Folkert van Heusden) writes:

>> The GPS time is not very accurate anyway, and can vary wildly, probably 

>> depending on the device, so don't expect perfect offsets.  On my Garmin G

>> 18 LVC, I use 0.190 which gets it in the ballpark, but can randomly jump 

>> +16ms to -10ms at any time.

>But if you let ntp handle the pps signal it should be a steady 0.0-0.1ms
>difference as it then knows when this second started:

He was refering solely to the NMEA signal not the PPS. Some GPS receovers
have no pps.

>     remote           refid      st t when poll reach   delay   offset  jit
>+GPS_NMEA(0)     .GPS.            0 l   17   16  376    0.000   -0.001   0.
>oPPS(0)          .PPS.            0 l    5   16  377    0.000   -0.001   0.

I am afraid I simply do not believe this. NMEA is lucky to get a ms not a
usec. The offset on the NMEA should be a lot bigger than .001

>Folkert van Heusden


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