Hoi Michael, On Mon, 2 May 2016 07:52:09 +1000 Michael Wouters <michaeljwout...@gmail.com> wrote:
> I don't think a cheap receiver like a LEAxxx will quite get you there. I have some numbers of an project of the ETH that did use standard LEA-6T recording the phase data and got in the post processing to an uncertainty of <4mm averaging over several hours. Translating that to timing resolution would mean an uncertainty of less than 13ps. Of course, this number is completely theoretical, but it shows that it should be possible to go below 1ns in time resolution, if the phase data could be related to a stable reference oscillator in post-processing and if the offsets between the different receiver and antenna combinations are calibrated out. > The number I quoted is for high quality geodetic receivers. There are > crucial differences between these and the cheap receivers in regard to > time-transfer. The first is how you relate your external clock's 1 pps > to GPS time. That's why I'm proposing timing receivers. They are the ones that have the additional software and hardware bits which allow to relate an external oscillator to the satellite phases. > The other important difference is the resolution of the receiver's > measurements. A cheap receiver reports the code measurements at > relatively coarse resolution, sometimes a few ns, whereas a geodetic > receiver reports at much higher resolution. If you had a cheap > receiver, the code measurement resolution is seldom specified so you > would have to test candidate receivers. I don't know what resolution the LEA family offers there, but the spec of the protocol defines a 1ps resolution in the data. So I would guess that the phase data resolution is probably in the order of 10-100ps. > I have many years of raw code measurement data from many identical > receivers operating on baselines of a few km up to 20 km. I will try > to have a look later this week to confirm/deny/make ambiguous what I > said above. If you have time to dig that data out, that would be very nice. Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson _______________________________________________ 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.