[email protected] wrote: > On Jan 19, 10:26 pm, Terje Mathisen <[email protected]> > wrote: >> [email protected] wrote: >>> Hello everybody, >>> I'm trying to track (offline) the drift of my gps clock relative to my >>> hw clock (the clock that I would have obtained without GPS). >>> My final goal is to convert a series of gps timestamps to the >>> equivalent hw timestamps (with microsec precision).
You can get us precision but not accuracy! >> This is actually quite easy: >> >> Just enable logging of the loop frequency (i.e. the freq offset), and >> integrate that value over time. >> >> This gives you the offset at any given time. > > Smart, > your method uses the SW clock not the HW clock > (which eliminates the problem of the 11 mn mode) > > But what I do not understand is why are integrating frequency (f)?. > It would be easier to add the clock offset (o) (i agrre that the > result should be the same)? The clock offset will always tend to zero, that is after all exactly what NTP is working so hard to achieve! Running with logging a GPS which isn't used to steer the clock is actually much easier and more accurate. You'll find that you don't need us precision: After a few hours the offsets will probably be into the multiple seconds range, and go off from that. Terje -- - <[email protected]> "almost all programming can be viewed as an exercise in caching" _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
