On Fri, 2008-04-25 at 00:01 +0200, Jan Hoevers wrote: > > I agree with your conclusion that 30ns is meaningless for NTP use. > > > > However why do you say the GPS system itself does not have 30ns > > accuracy. > > > > The signal in space (SIS) accuracy quoted for the current constellation > > is between 1 and 2 meters, which is well below 10ns. > > Well, maybe you're right and my information is outdated. > This page (http://tycho.usno.navy.mil/gpstt.html) speaks about "a few > hundred nanoseconds". I recall 340 ns but I forgot where I read it.
340ns is quoted for L1 CA with SA dithering of the SV clocks active. Together with a 156 meter horizontal accuracy. The SA intentional error generation was turned off 7/8 years ago. http://igscb.jpl.nasa.gov/components/prods.html > Anyhow, a 30 ns accuracy cannot be transferred over an ethernet, let > alone the internet. It cannot be maintained without a cesium time base. What is the accuracy of PTP? 100ns? A good OCXO maintain it plenty good in a GPSDO. > This may be interesting for a well equipped lab, but not for us. Like I wrote before, I agree with you conclusions wrt NTP use. > Jan > > > _______________________________________________ > timekeepers mailing list > [email protected] > https://fortytwo.ch/mailman/cgi-bin/listinfo/timekeepers _______________________________________________ timekeepers mailing list [email protected] https://fortytwo.ch/mailman/cgi-bin/listinfo/timekeepers
