Normally, the GPRMC gets sent every second even when the puck doesn't have
a
fix. There is a field that says OK vs no-fix. ntpd checks that field.
10 satelite fix indoors. GPS is operating.
Normal timing setup is to have the device send only one NMEA GPRMC message
at 1s interval, and tweak driver fudge time1 until offset measured against
other sources averages around zero.
the GPS sends 3 GPRMC messages in a 3 second window but NOT 1 per second.
Beware. The SiRF chips are well known not co cooperate with that approach,
depending upon what you expect. They have lots of wander that you can't
filter out. If you tweak the fudge so that it is working correctly, it
will
This is my problem. I bought a GPS based on an inferior chipset.
My GPS18xLVC+PPS averages within 1us and peaks about 50us jitter on
Windows,
Garmin is a real GPS. please don’t mock me...
it is because of these instability that I analyzed that messages in detail
and noticed GPGBS being sent every 3 seconds with under 10 ms jitter. This
is the reason I am asking how difficult will it be for me to modify the NMEA
driver to accept GPGBS messages with mode 16? Should this question be on
another list?
Leon
_______________________________________________
questions mailing list
questions@lists.ntp.org
http://lists.ntp.org/listinfo/questions
