[time-nuts] TruePosition GPSDO Holdover Issues

Mark Sims holrum at hotmail.com
Tue May 15 17:20:49 EDT 2018

Lasy Heather can read a receiver data capture file as a "simulation" file.  Use the /rs=filename command line option.   You can also specify the /0 command line option (don't use serial port) and /rx= command line option to specify the receiver type.   The simulation file reads in at around 20-30 times faster than real time (goes faster when the mouse cursor is kept out of the plot area),


>First is to collect the data.  I have a python 
script that grabs everything from a NMEA device and logs each line with a 
time stamp.  The GPS orbit period is 12 hours so you need 12 hours of data to 
see everything.  But there are 30 satellites, so a few hours will show the 

The next step is to extract the data into a useful format.  That's another 
python script.  Then, just feed that to gunplot.

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