[time-nuts] GPS message jitter (preliminary results)

Mark Sims holrum at hotmail.com
Mon Jul 18 16:37:44 EDT 2016

I have seen some reports of some Skylab GPS boards that had some rather sketchy GPS code.   A friend had one that was off around 0.5 degrees in longitude... but only if your location was between +/- 90 degrees longitude.  He was on the east coast and had the problem.  He sent it to me (96 dgrees west) and I didn't see it.  Same for a tester on the west coast.  He spend weeks going over his code and could not find what the problem was.   He sent me a raw data dump and sure enough, I got the same (wrong) location that he did.   I seem to remember the NMEA messages were correct, but the binary message (which was in Ublox format) had the issue.

For comparison with your data, attached is the ADEV+MDEV plot [1] for the SkyLab / MG1613S GPS board [2], the one with the 350 ms offset and 11 ms stdev. 		 	   		  

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