EndRun Meridian II, User Manual

Page: 215 / 240

M e r i d i a n I I U s e r M a n u a l 194
A P P E N D I X J
195 M e r i d i a n I I U s e r M a n u a l
S I M U L A T O R U S E
are compared to a historical record of previous UTC leap seconds and the GPS week numbers at
which they were inserted into the UTC timescale. Should a simulator be set with arbitrary values for
these UTC leap seconds that differ by more than a couple of seconds from the actual values currently
being transmitted by the GPS, the almanac data will be rejected.
The simulator should be set with realistic UTC leap second values.
If the simulator is set with incor-
rect UTC leap second values, yet they are close enough to pass the integrity screen, then they will be
accepted and it will be necessary to run the
resetleaphistory
command prior to reconnecting to
live GPS signals. Failure to do so would compromise the integrity checking algorithm.
Issuing this command will reset the stored GPS Leap Second History to the history that was correct at
the build date of the receiver firmware. As long as the firmware build date is not too many years old,
this will allow the receiver to operate properly when it receives signals from the actual GPS satellites.
SUMMARY
The simulator should be set with realistic UTC leap second values, such as those currently being transmit-
ted by GPS. If you simulate a leap second insertion then you MUST execute the
resetleaphistory
command before reconnecting the receiver to a live GPS signal.
IMPORTANT
This command should not be used unless you have reason to believe that operation with a GPS simulator
has previously taken place. Arbitrary usage of this command could cause important leap history events to
be lost. This will compromise the effectiveness of the integrity checking algorithm.
The command must be issued with one argument: TRUE
Command:
resetleaphistory TRUE
MeridianII reply:
Resetting Leap History