> 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 _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
