[time-nuts] ublox NEO-M8T improved by insulated chamber?

[Tom Van Baak]

> How exactly do you measure offset of your GPS time output to absolute UTC time?

Conceptually it's no different from measuring your favorite resister or thermometer: you compare your DUT against a standard REF and the difference is your error, a process called calibration. So the same is true for SI second (time interval, frequency) and UTC (time epoch). As I mentioned earlier, calibrating your SI second is quite simple. Calibrating your UTC is harder.

Here are couple examples:

(1) Years ago fellow time-nut Doug loaned out his and my antenna/receiver to be calibrated. The report will give you an idea of what's involved:

"Absolute Calibration of a Geodetic Time Transfer System"
http://xenon.colorado.edu/paperIrevise2.pdf


(2) Here's classic report from fellow time-nut Rick:

http://www.cnssys.com/files/PTTI/PTTI_2002_CNS_Testbed.pdf
and
http://www.cnssys.com/files/PTTI/Low_cost_GPS-based_time_and_frequency_products.pdf


(3) In both cases above there is transport of equipment involved. But the equipment can come to you instead:

http://www.usno.navy.mil/USNO/time/twstt/calibration-services
see also
http://tycho.usno.navy.mil/twstt.html
and a nice photo of the traveling time van:
http://tycho.usno.navy.mil/gif/2waytruck.jpg


(4) NIST also offers time & frequency calibration services:

https://www.nist.gov/calibrations/calibration-areas/time-and-frequency

"A NIST Disciplined Oscillator: Delivering UTC(NIST) to the Calibration Laboratory"
https://www.nist.gov/sites/default/files/documents/calibrations/NCSLI.pdf

"Remote Time Calibrations via the NIST Time Measurement and Analysis Service"
https://www.nist.gov/sites/default/files/documents/calibrations/Remote-Time-Calibrations.pdf

That's enough reading to keep you busy for a few days.

/tvb