Tom Van Baak wrote: > "David J Taylor" wrote: >> I seem to recall reading somewhere that you could tell a GPS receiver >> where it was, so that the PPS signal would depend on fewer >> satellites - i.e. you didn't need four visible satellites to get a >> complete 3D fix all the time. Perhaps I simply mis-understood the >> purpose of the "initial location" command? >> >> Did I dream this? Does the GPS 18 LVC have this option and, if so, >> what's the correct NMEA command to enable "fixed position" >> operation? Has anyone tried this - what improvements did you see? > > The GPS 18 LVC doesn't have a zero-D mode. However > it is a very nice, compact, easy-to-interface, GPS timing > receiver with a 1 us 1 PPS accuracy spec. > > Although this makes it a poor choice for work with atomic > clocks it should be more than enough for NTP, yes? > > Recent GPS 18 LVC measurements I made showed it > much better than spec; a couple hundred ns peak to > peak and just 80 ns RMS for the 1 PPS output. > > /tvb > http://www.LeapSecond.com
Thanks to Tom, Terje and Richard (hope that's everyone). It seems the GPS 18 LVC does have a 2D mode (I hadn't known the correct term before) which can be enabled by the $PGRMC statement. You need to tell it the height, of course. I'm interested because my system only has a 180 degree view of the sky, and hence I would like to get the best performance with the fewest number of visible satellites. I'm glad to hear the timing performance is good - it think the sensitivity could be a little better, though (it's not as good as my GPS 12XL with an external active antenna puck, used indoors). Cheers, David _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
