Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

A Straightforward Frequency-Estimation Technique for GPS Carrier-Phase Time Transfer



C Hackman, Judah Levine, Thomas E. Parker, Dirk Piester, Juergen Becker


GPS carrier-phase time transfer (GPSCPTT) offers high frequency stability at short averaging times, approaching a fractional frequency stability of 10-15 at an averaging time of 1 d. However, a discontinuity occurs in the time-transfer estimates between the end of one processing batch (typically 1-3 d in length) and the beginning of the next. To compute the average frequency over the analysis period, we usually join the batches into one continuous data set by estimating and removing the discontinuities at the boundaries. We present a new technique in which frequencies are computed from the individual batches and then averaged to obtain the mean frequency for the period. Advantages of this technique include: it allows the frequency to be computed without the uncertainty associated with the removal of the day-boundary discontinuities, it requires fewer computational resources and it can be applied to the time-transfer estimates produced by virtually any software. The new technique was tested by comparing the fractional frequency-difference values it yields with those obtained from the ¿conventional¿ GPSCPTT technique and from two-way satellite time and frequency transfer (TWSTFT). The clocks studied were located at the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig, Germany and at the National Institute of Standards and Technology (NIST) in Boulder, Colorado USA. The frequencies obtained from the GPSCPTT measurements using either method agreed with those obtained from TWSTFT at several parts in 1016. This suggests that both TWSTFT and GPSCPTT are approaching frequency-transfer performance sufficient for use during simultaneous fountain evaluations. The frequency values obtained from the GPSCPTT data using the new method agreed with those obtained using the conventional technique at 1-4¿10-16.
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control


carrier phase time transfer, frequency standard, frequency transfer, GPS, GPSCPTT, primary frequency standard, two way satellite time transfer, TWSTFT, TWSTT


Hackman, C. , Levine, J. , Parker, T. , Piester, D. and Becker, J. (2006), A Straightforward Frequency-Estimation Technique for GPS Carrier-Phase Time Transfer, IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control, [online], (Accessed May 23, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created September 15, 2006, Updated January 27, 2020