Specifications

VP ONCORE COMMAND REFERENCE
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MEASUREMENT EPOCH OFFSET OPTION
(@@Ax)
NOTE: The input/output messages described here are available only if
VP receiver Option ‘A’ or ‘I’ is installed.
The VP receiver computes a position relative to a measurement epoch
that occurs once per second. The receiver can place the measurement
epoch on any of 1000 one-millisecond measurement sample points. This
one-millisecond time reference clock is synchronous to the receiver's
internal oscillator and is asynchronous to GPS/UTC system time. The
user can move the measurement epoch with this command.
At power-up, the receiver selects a measurement epoch by simply
choosing one of the 1000 clock cycles. This epoch is asynchronous to
GPS/UTC time mark. When the GPS receiver acquires satellites, it will
compute the local time of the asynchronous measurement epoch (one of
the 1000 1 kHz clock cycles), and then skew receiver timing so as to
place the measurement epoch within 0.001 seconds of the desired
measurement epoch offset. The skew action inserts between 0.000 and
0.999 seconds between measurement epoch so as to move the epoch to
the desired sample point. In addition, the GPS receiver automatically will
insert or delete one millisecond when necessary to keep the
measurement epoch on the selected time because of the receiver local
oscillator drift.
As an example, consider the case where the user specifies 0.333 for the
Measurement Epoch Offset. For this case, the receiver skews the
receiver times so that the fractional part of local receiver time is 0.333 for
the Measurement Epoch Offset. For this case, the receive skews the
receiver timing so that the fractional part of the local receiver time is
0.333xxxx... The receiver position output will be relative to this new
measurement epoch until this parameter is changed again.
The corrected time reference is relative to either GPS or UTC time, as
specified and set by the user via the
@@Aw command.
Range: 0.000 to 0.999 seconds
Default value: 0.000 seconds
Resolution: 0.001 second
64 Synergy Systems, LLC 05OCT01