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

Tom Van Baak tvb at LeapSecond.com
Sat Jul 16 16:03:39 EDT 2016


Hi Mark,

As one example of what you'll see, scroll down to the NMEA Latency/Jitter plot at:
http://leapsecond.com/pages/MG1613S/

In that 900 sample (15 minutes) run, the mean latency was 350.2 ms with a standard deviation (jitter) of 10.7 ms. I'll dig out some other data I may have. It will be quite different depending on receiver make/model.

For this plot I made TIC measurements between the leading edge of the 1PPS and the leading edge of the start bit of the first byte of the first NMEA sentence.

BTW, on Windows use QueryPerformanceCounter if you want granularity-free millisecond or even microsecond time interval resolution.

/tvb

----- Original Message ----- 
From: "Mark Sims" <holrum at hotmail.com>
To: <time-nuts at febo.com>
Sent: Saturday, July 16, 2016 12:13 PM
Subject: [time-nuts] GPS message jitter (was GPS for Nixie Clock)


>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...
> 
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