On Tue, 23 Apr 2013 14:36:45 -0500 David <davidwh...@gmail.com> wrote:
> I always suspected something like this was at work. > > This would explain the ambiguous 1uS specification common in GPS > receivers that are not intended for rigorous timing applications which > I asked about a couple months ago. I did not ask the right question. > :) There is more to that than just sky view. Navigational and timing receivers differ slightly in the way they solve the equations. How and what exactly, i don't know, but guess it's optimizations for the common use case in timing receivers (fixed position, high precision time but low precision position required) > With this in mind, I would assume that averaging over multiples of 12 > hours would be necessary for maximum accuracy and days would be > required to account for atmospheric transmission effects. Now I have > a much better idea about how good the disciplined oscillator will need > to be. If you go for 12h integration time, you have to have a very good temperature compensation (ofcourse under the assumption you have a very stable oscillator in the first place). > A receiver intended for timing applications using position hold should > allow accurate locking in a hundredth the time or less. I think you overestimate what a timing receiver can do and what not. You cannot compensate for atmospheric effects with just a single frequency receiver unless you use WAAS/EGNOS/... and even that is not super accurate. For reference, u-blox specifies their timing models as being within +/-40ns and their navigational models being within +/-100ns. >From what i know about how these things work, that factor two is about what i would expect in imporvement in precision, probably even less. (those numbers are under "ideal" conditions, with good antenna position) Attila Kinali -- The people on 4chan are like brilliant psychologists who also happen to be insane and gross. -- unknown _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.