RCB-F9T - Integration manual
UTC(USNO), ensure GPS signals are available, and for GLONASS time or UTC(SU) ensure
the presence GLONASS signals). This will involve coordinating the setting of CFG-SIGNAL-*
configuration group with the choice of time pulse time base.
• When using time pulse for timing applications requiring absolute time accuracy, e.g. with
requirements specifying offset to UTC, it is recommended to calibrate the user's full setup for
TP output against a reference timing source. To achieve best absolute and consistent accuracy
(e.g. for mass deployment), it is recommended that the user should calibrate each single setup
and calibrate under different GNSS modes and different temperatures which are applicable to
the user's application and operating requirements. The user should take the calibrated values
and configure the compensation accordingly (see the section on
)
• To get the best timing accuracy with the antenna, a fixed and
accurate
position is needed.
• If relative time accuracy between multiple receivers is required, do not mix receivers of different
product families. If this is required, the receivers must be calibrated accordingly, by setting
cable delay and user delay.
• The recommended configuration when using the UBX-TIM-TP message is to set both the
measurement rate (CFG-RATE-MEAS) and the time pulse frequency (CFG-TP-*) to 1 Hz.
Since the rate of UBX-TIM-TP is bound to 1 Hz, more than one UBX-TIM-TP message can
appear between two pulses if the time pulse frequency is set lower than 1 Hz. In this case
all UBX-TIM-TP messages in between time pulses T1 and T2 belong to T2 and the last UBX-
TIM-TP before T2 reports the most accurate quantization error. In general, if the time pulse
rate is not configured to 1 Hz, there will not be a single UBX-TIM-TP message for each time
pulse.
It is not recommended to use SBAS for timing applications.
The sequential order of the signal present at the TIMEPULSE pin and the respective output message
for the simple case of 1 pulse per second (1PPS) is shown in the following figure.
Figure 10: Time pulse and TIM-TP
3.10.1.3 GNSS time bases
GNSS receivers must handle a variety of different time bases as each GNSS has its own reference
system time. What is more, although each GNSS provides a model for converting their system time
into UTC, they all support a slightly different variant of UTC. So, for example, GPS supports a variant
of UTC as defined by the US National Observatory, while BeiDou uses UTC from the National Time
Service Center, China (NTSC). While the different UTC variants are normally closely aligned, they
can differ by as much as a few hundreds of nanoseconds.
Although u-blox receivers can combine a variety of different GNSS times internally, the user must
choose a single type of GNSS time and, separately, a single type of UTC for input (on EXTINT pins)
and output (via the TIMEPULSE pin) and the parameters reported in corresponding messages.
UBX-22004121 - R01
3 Receiver functionality
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C1-Public
Early production information
