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Positioning Application: How is a Leap second event simulated in the GLONASS constellation?

  • Positioning Application
  • SimGEN
  • SimREPLAYplus
  • A leap second event will be simulated in the PosApp scenario if the event is selected in the Options area of the scenario tree (Figure.1) and the scenario start time and duration are set to include the period the event will take place e.g the scenario spans midnight on the 30th June or 31 December.


                                    Figure 1


  • The GLONASS ICD is not explicit when describing what will happen to the navigation data following the leap second event.
  • Spirent researched data captured during previous leap second events and observed there was always a period of approximately 60 seconds of disruption following a leap second insertion.
  • The leap second event will occur at midnight UMT on the 30th June and or 31st December.
  • Figure 2 below shows how the navigation data captured using the GLONASS Navigation data extract utility  is effected by the insertion of a leap second.
  • The message strings have valid data prior to the leap second event, 16 seconds into the run the message strings contain only 0.


  • The message strings will be populated with zero for a period of 56 - 60 seconds following the leap second.
  • After this period the Navigation data strings will again be populated with valid characters.
  • See the attached example files for comparison.
Attachment Description
Examples of an extracted navigation data file without a leap second event for comparrison.

Attachment Description
Examples of an extracted navigation data file with a leap second event for comparrison.

Product : SimREPLAYplus,SimREPLAY,SimGEN,PosApp