Terje Mathisen wrote: > [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.
Errrr. . . . Did you have a little slip of the mind there? Offsets in multiple SECONDS?????? Mine generally range in the multiple MILLISECONDS! And not a very large multiple either! _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
