[time-nuts] Precise Time transfer and relative position over ashort baseline

[Attila Kinali]

On Mon, 11 Apr 2016 09:46:17 -0700
"Tom Van Baak" <tvb at LeapSecond.com> wrote:

> Another way might be to use single-channel common view GPS. I've not
> checked recently to see if 100 ps is possible over a 1 km baseline. If so
> that would be a less expensive solution. Someone should dig into the RINEX
> mode of the ublox 6T. It's on my list but the list is long.

The baseline is not the problem in this case, but the delay within
the GPS receivers and the cables. To keep their variation below 1ns
is already quite a challenge. The usual method for this is to have
the whole GPS receiver setup temperature stabilized, then feed the
reference point with a low phase-drift cable. After installation of
all sites, use a special traveling GPS reveiver as a calibration
standard between the sites. The BIPM uses something like this and
achieves <200ps over a calibration period of 3 weeks for the traveling
GPS receiver.

For the BIPM GNSS calibration setup, there is a paper from Jiang and
Tisserand that spells out the seen uncertainties[1]. And there is a paper
from last year, that compares the GNSS calibrator to a fiber link
with a 400km baseline[2].


			Attila Kinali


[1] "Stability of the BIPM GNSS travelling calibrator",
Jiang and Tisserand, EFTF 2014 (you can find the proceedings on eftf.org)


[2] "Comparing a GPS time link calibration with an optical fibre
self-calibration with 200ps accuracy", by Jiang, Czubla, Nawrocki,
Lewandowski and Arias, 2015
http://dx.doi.org/10.1088/0026-1394/52/2/384


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