>> Do you expect the ZDA message to be better synchronized than any of >> the others?
> Yes. In SiRF receivers ZDA is specifically aligned to the second. I > just checked my copy of the manual I got with my BU-353, and Table 1-1 > NMEA Output Messages says "ZDA PPS timing message (synchronized to > PPS)." RMC is produced after the navigation solution is computed and > that does not happen in constant time. My documentation for ZDA says "Each message is output within a few hundred ms after the 1 PPS pulse..." I was hoping for something (much) better than that. I don't actually care about the offset, I can correct for a constant. It's the jitter/wander that I'd like to avoid. I finally got time to try it. The released ntpd doesn't support ZDA, but I hacked in some code. ZDA isn't any better than RMC. That's just an eyeball of a graph of the peerstats offset, not a formal mathematical analysis. It's still got roughly 100 ms of wander/jitter, probably more if I wait longer to collect more data. I don't see anything good enough to be worth any effort to investigate more. Another problem is that ZDA doesn't have a status field to tell you if the time is invalid because it isn't seeing enough satellites. It's also got the leap second bug. -- These are my opinions, not necessarily my employer's. I hate spam. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
