[ntp:questions] custom NMEA messages

Brian Inglis Brian.Inglis at SystematicSw.ab.ca
Tue Dec 29 21:08:50 UTC 2015

On 2015-12-29 11:25, Hal Murray wrote:
>> Garmin is a real GPS. please don?t mock me...
> The timing on the GPS-18x is also horrible.  The GPS-18 (no x) was good, but
> it wasn't very sensitive.
>    http://users.megapathdsl.net/~hmurray/ntp/GPS18LVCx-off.gif

You must have had one of the bad firmware releases: David Taylor's site shows
the improvement he got after upgrading to better firmware releases, in which
I believe you were involved with "Kiwi" Geoff on analysis.

If you are looking at NMEA message timing - that's all over the board on every
device, as those serial interface messages get to use only the time left after
SV tracking and GPS message processing is handled, which may not be a lot on the
microcontrollers used. Nav GPS receivers with PPS are good enough with NTP
for most of us who want consistent, correct system time but do not need lab
quality timing.

Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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