[ntp:questions] Odd offset for PPS DCD w/ Garmin GPS 18x LVC
unruh at wormhole.physics.ubc.ca
Tue Mar 22 19:06:18 UTC 2011
On 2011-03-22, David J Taylor <david-taylor at blueyonder.co.uk.invalid> wrote:
> "lellis" <larry.ellis at gmail.com> wrote in message
> news:efc6e755-c213-4a10-90f9-420384001da3 at s18g2000prg.googlegroups.com...
>> On Win XP, I am seeing an odd positive offset of about 128ms on the
>> Atom driver, relative to other sources:
>> remote refid st t when poll reach delay
>> offset jitter
>> *GPS_NMEA(1) .GPS. 0 l 6 16 377 0.000
>> 0.373 0.919
>> xPPS(1) .PPS. 0 l 5 16 377 0.000
>> 125.447 0.830
>> -clock.team-cymr 172.16.65.22 2 u 39 64 77 12.989
>> -41.044 44.960
>> +ntp.okstate.edu .USNO. 1 u 42 64 77 28.906
>> -18.762 25.784
>> +navobs1.wustl.e .GPS. 1 u 38 64 77 19.133
>> 1.819 19.599
>> Normally, I just use NMEA with fudge, but that was also showing the
>> odd offset so I removed fudge and added the Atom driver to help debug
>> (Normally the status shows oPPS(1) but xPPS(1) is seen above for the
>> obvious reason.
>> ntpd is Dave Hart release 4.2.7p138; I have a serialpps-ppsapi-
>> provider.dll dated 6/6/2009.
>> Any ideas or recommendations.
> You may want to revert to the 3.20 firmware for you GPS 18x LVC - see what
> others have written:
A .128 or .3 second offset really seems strange for this cause. I guess
it could be if the 1 second offset from the Garmin 18x only happens
occasionaly, and this is being averaged out.
> and there is a somewhat flawed analysis here:
> (flawed in that I was being helped by a UNIX person, and the Windows
> driver does not work in exactly the same way as we had assumed).
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