u-blox ZED-F9P Interface Description - Manual
Advance Information
(1) Possible values for status: V = Data invalid, A = Data valid
(2) Possible values for quality: 0 = No fix, 1 = Autonomous GNSS fix, 2 = Differential GNSS fix, 4 = RTK fixed, 5
= RTK float, 6 = Estimated/Dead reckoning fix
(3) Possible values for navMode: 1 = No fix, 2 = 2D fix, 3 = 3D fix
(4) Possible values for posMode: N = No fix, E = Estimated/Dead reckoning fix, A = Autonomous GNSS fix, D =
Differential GNSS fix, F = RTK float, R = RTK fixed
Flags in NMEA 2.1 and below
The flags in NMEA 2.1 and below are the same as NMEA 2.3 and above but with the following differences:
• The posMode field is not output for GLL, RMC and VTG messages (each message has one field less).
• The GGA quality field is set to 1 (instead of 6) for both types of dead reckoning fix.
4.1.7 Multi-GNSS Considerations
Many applications which process NMEA messages assume that only a single GNSS is active. However, when
multiple GNSS are configured, the NMEA specification requires the output to change in the following ways:
NMEA output for Multi-GNSS
Change Description
Main Talker ID The main Talker ID will be 'GN' (e.g. instead of 'GP' for a GPS receiver)
GSV Talker IDs The GSV message reports the signal strength of the visible satellites. However,
the Talker ID it uses is specific to the GNSS it is reporting information for, so
for a multi-GNSS receiver it will not be the same as the main Talker ID. (e.g.
other messages will be using the 'GN' Talker ID but the GSV message will use
GNSS-specific Talker IDs)
Multiple GSA and GRS
Messages
Multiple GSA and GRS messages are output for each fix, one for each GNSS.
This may confuse applications which assume they are output only once per
position fix (as is the case for a single GNSS receiver).
4.1.8 Output of Invalid/Unknown Data
By default the receiver will not output invalid data. In such cases, it will output empty fields.
A valid position fix is reported as follows:
$GPGLL,4717.11634,N,00833.91297,E,124923.00,A,A*6E
An invalid position fix (but time valid) is reported as follows:
$GPGLL,,,,,124924.00,V,N*42
If Time is unknown (e.g. during a cold-start):
$GPGLL,,,,,,V,N*64
Note:
Output of invalid data marked with the 'Invalid/Valid' Flags can be enabled using the configuration
items CFG-NMEA-*.
4.1.9 Messages Overview
When configuring NMEA messages using the UBX protocol message UBX-CFG-MSG, the Class/Ids shown in
the table shall be used.
Page Mnemonic Cls/ID Description
NMEA Standard Messages Standard Messages
UBX-18010854 - R04 Advance Information Page 10 of 259
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