GPS & Glonass time difference

5 thoughts on “GPS & Glonass time difference

  1. For the SL869 & SL869-T, assuming a mix of satellite sources, how is the difference in GPS and Glonass time allowed for? Is the 1PPS output an average of the two?

    1. Dear Mr. Courtney,

      The time of both version of SL869 is sync with the UTC time.

       

      On standard version of SL869 before the PPS will blink is required to have a valid 3D fix. Regarding SL869-T variant it requires to have a valid UTC time and after the fix the PPS is sync with 20ns.

      Let me know if you need more info

       

      Best Regards,

       

      Matteo Manca

       

       

      GNSS Application Engineering

      1. Matteo,

        Here are the timing references from ESA –

        GPS Time (GPST)

        GPS Time (GPST) is a continuous time scale (no leap seconds) defined by the GPS Control segment on the basis of a set of atomic clocks at the Monitor Stations and onboard the satellites. It starts at 0h UTC (midnight) of January 5th to 6th 1980 (6.d0). At that epoch, the difference TAI?UTC was 19 seconds, thence GPS?UTC=n ? 19s. GPS time is synchronised with the UTC(USNO) at 1 microsecond level (modulo one second), but actually is kept within 25 ns.

        GLONASS Time (GLONASST)

        GLONASS Time (GLONASST) is generated by the GLONASS Central Synchroniser and the difference between the UTC(SU) and GLONASST should not exceed 1 millisecond plus three hours (i.e.,GLONASST = UTC(SU) + 3h ? ?, where | ? | < 1milisec.), but ? is typically better than 1 microsecond. Note: Unlike GPS, Galileo or BeiDou, GLONASS time scale implements leap seconds, like UTC.

        Galileo System Time (GST)

        Galileo System Time (GST) is a continuous time scale maintained by the Galileo Central Segment and synchronised with TAI with a nominal offset below 50 ns. The GST start epoch is 0h UTC on Sunday, 22 August 1999 (midnight between 21 and 22 August).

        BeiDou Time (BDT)

        BeiDou Time (BDT) is a continuous time scale starting at 0h UTC on January 1st, 2006 and is synchronised with UTC within 100 ns< (modulo one second).

        The maximum deviation for Glonass is 1ms which is a concern for timimg applications.

        1. Please let me know how the SL869 & SL869-T devices deal with the variations in time reference for the different groups of satellites.

          Matteo,

          Here are the timing references from ESA –

          GPS Time (GPST)

          GPS Time (GPST) is a continuous time scale (no leap seconds) defined by the GPS Control segment on the basis of a set of atomic clocks at the Monitor Stations and onboard the satellites. It starts at 0h UTC (midnight) of January 5th to 6th 1980 (6.d0). At that epoch, the difference TAI?UTC was 19 seconds, thence GPS?UTC=n ? 19s. GPS time is synchronised with the UTC(USNO) at 1 microsecond level (modulo one second), but actually is kept within 25 ns.

          GLONASS Time (GLONASST)

          GLONASS Time (GLONASST) is generated by the GLONASS Central Synchroniser and the difference between the UTC(SU) and GLONASST should not exceed 1 millisecond plus three hours (i.e.,GLONASST = UTC(SU) + 3h ? ?, where | ? | < 1milisec.), but ? is typically better than 1 microsecond. Note: Unlike GPS, Galileo or BeiDou, GLONASS time scale implements leap seconds, like UTC.

          Galileo System Time (GST)

          Galileo System Time (GST) is a continuous time scale maintained by the Galileo Central Segment and synchronised with TAI with a nominal offset below 50 ns. The GST start epoch is 0h UTC on Sunday, 22 August 1999 (midnight between 21 and 22 August).

          BeiDou Time (BDT)

          BeiDou Time (BDT) is a continuous time scale starting at 0h UTC on January 1st, 2006 and is synchronised with UTC within 100 ns< (modulo one second).

          The maximum deviation for Glonass is 1ms which is a concern for timimg applications.

          1. Hello,

            the SL869 or SL869-T variant can track only GPS +Glonass constellation.

            From default these modules use UTC time as reference derived from GPS and GLonass time.

            Thanks

            Best Regards,