[time-nuts] Advantages of GNSS ???

[Mark Sims]

A big issue with using the sawtooth correction message from a GPS receivers is the issue of just what that sawtooth value is related to and how to apply it to the measured PPS value / phase.

I added the ability to Lady Heather to calculate a sawtooth corrected "paper clock" by applying the sawtooth correction message value to the PPS output measured by an external counter like the TAPR TICC.   

There are around a dozen different combinations of sawtooth value and PPS measurements...  only one of which minimizes the PPS error.   Do you add or subtract the sawtooth value to the PPS measurement?  Do you apply the sawtooth value to the previous/current/next PPS measurement?  Do you apply the sawtooth correction to the PPS itself or the accumulated phase of the PPS?

I don't think that I have ever seen what to do  with the sawtooth value documented in any receiver documentation...  Heather has default receiver dependent correction strategies or lets you specify the correction  strategy to use.