[time-nuts] GPS message jitter (was GPS for Nixie Clock)

David J Taylor david-taylor at blueyonder.co.uk
Sun Jul 17 02:31:13 EDT 2016

From: Mark Sims

I just added some code to Lady Heather to record and plot the time that the 
timing message arrived from the receiver (well, actually the time that the 
screen update routine was called,  maybe a few microseconds difference). 
I am using my existing GetMsec() routine which on Windoze actually has 
around a 16 msec granularity.  The Linux version uses the Linux nanosecond 
clock (divided down to msec resolution).  I just started testing it on a 
Ublox 8M in NMEA and binary message mode...  really surprising results to 
come shortly...


Thanks for those updates.

For Windows lower than 8, turn on the high-resolution timer and you can get 
millisecond level (0.977 ms IIRC).  You can also use the 
QueryPeformanceCounter and related functions for better precision.


However for current Windows (8, 8.1 10) the situation is much better as you 
can get 100 ns precision using the new GetSystemTimePreciseAsFileTime call:


I wrote up a little more here:


based on:


I look forward to your results.

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Email: david-taylor at blueyonder.co.uk
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