Connection to the Network
43
GNSS status Displays the current status of the NMEA interface used for
communication with the built in GPS / Glonass module or an
external GPS receiver connected to the unit through a 1 PPS /
ToD interface. The possible values of GPS status are listed
below:
• No data: There is no connection between the test unit and
the GPS / Glonass receiver or the receiver is not generat-
ing any data.
• Acquiring fix: The GPS / Glonass receiver is generating
NMEA data but it is still not synchronized. Achieving syn-
chronization may take some time. The equipment may fail
to achieve synchronization if there are not enough satel-
lites in sight.
• Waiting for PPS: The GNSS receiver has acquired position
and time and it is reporting this information but it is not yet
generating the 1 PPS signal required for a correct assess-
ment of the position / time.
• Synchronized To GNSS: The GNSS receiver is reporting
that it has achieved synchronization from the timing data
received from the satellite constellations. This is a required
condition before the system time becomes locked to the
GNSS time.
Satellites received This is a read only field that displays the number of satellites
on sight. These satellites may correspond to any of the
constellations currently enabled.
Satellites used This field shows the number of satellites actually used by the
test unit. One satellite may be on sight but it may not be used
by the unit for different reasons. The Satellites used
parameter is the only one relevant to rate the accuracy of the
GNSS-derived timing reference
PDOP Some tests may require a minimum number of satellites or an
specific satellite geometry to achieve the required accuracy
level. The Position Dilution of Precision (PDOP) gives
information about how good is the current satellite geometry
to achieve an accurate position estimate.
The PDOP is a positive number. The smaller the number, the
better is the accuracy. A minimum value of PDOP of 1.5 is
recommended to get accurate results in critical tests.
Table 2.13: GNSS Receiver Options
Parameter Description
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