[time-nuts] Adafruit Ultimate GPS timing message arrival times

David J Taylor david-taylor at blueyonder.co.uk
Mon Aug 1 02:24:12 EDT 2016

From: Mark Sims

As mentioned in the post the times reported are the time stamp in the 
receiver packet  minus the system clock time when it was received... 
negative value indicate the message arrives after the PPS.  The polarity of 
the reported value is consistent with how Lady Heather makes use of the 

Thanks, Mark.  I'd missed that in the post.  I still find it confusing to 
plot positive times as negative ones.

>From your data and my own measurements, I feel that using the serial NMEA 
stream would, today, be a last resort, as an Internet sync would be 
considerably better.  Would you agree with that?

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