ZED-F9P - Integration manual
Where a fix has been achieved, a check is made to determine whether the fix should be classified as
valid or not. A fix is only valid if it passes the navigation output filters as defined in CFG-NAVSPG-
OUTFIL. In particular, both PDOP and accuracy values must be below the respective limits.
Important: Users are recommended to check the
gnssFixOK
flag in the UBX-NAV-PVT or
the NMEA valid flag. Fixes not marked valid should not be used.
UBX-NAV-STATUS message also reports whether a fix is valid in the
gpsFixOK
flag. These
messages have only been retained for backwards compatibility and users are recommended to use
the UBX-NAV-PVT message.
The CFG-NAVSPG-OUTFIL_TDOP and CFG-NAVSPG-OUTFIL_TACC configuration items also define
and time accuracy values that are used in order to establish whether a fix is regarded as locked
to GNSS or not, and as a consequence of this, which time pulse setting has to be used. Fixes that
do not meet both criteria will be regarded as unlocked to GNSS, and the corresponding time pulse
settings of CFG-TP-* configuration group will be used to generate a time pulse.
When in RTK float/fixed mode there are no navigation output filter settings for this mode.
This is handled internally in the RTK core.
3.1.7.3.1 Speed (3D) low-pass filter
The CFG-ODO-OUTLPVEL configuration item offers the possibility to activate a speed (3D) low-pass
filter. The output of the speed low-pass filter is published in the UBX-NAV-VELNED message (
speed
field). The filtering level can be set via the CFG-ODO-VELLPGAIN configuration item and must be
comprised between 0 (heavy low-pass filtering) and 255 (weak low-pass filtering).
The internal filter gain is computed as a function of speed. Therefore, the level as defined in
the CFG-ODO-VELLPGAIN configuration item defines the nominal filtering level for speeds
below 5 m/s.
3.1.7.3.2 Course over ground low-pass filter
The CFG-ODO-OUTLPCOG configuration item offers the possibility to activate a course over ground
low-pass filter when the speed is below 8 m/s. The output of the course over ground (also named
heading of motion 2D) low-pass filter is published in the UBX-NAV-PVT message (
headMot
field),
UBX-NAV-VELNED message (
heading
field), NMEA-RMC message (
cog
field) and NMEA-VTG
message (
cogt
field). The filtering level can be set via the CFG-ODO-COGLPGAIN configuration item
and must be comprised between 0 (heavy low-pass filtering) and 255 (weak low-pass filtering).
The filtering level as defined in the CFG-ODO-COGLPGAIN configuration item defines the
filter gain for speeds below 8 m/s. If the speed is higher than 8 m/s, no course over ground
low-pass filtering is performed.
3.1.7.3.3 Low-speed course over ground filter
The CFG-ODO-USE_COG activates this feature and the CFG-ODO-COGMAXSPEED, CFG-ODO-
COGMAXPOSACC configuration items offer the possibility to configure a low-speed course over
ground filter (also named heading of motion 2D). This filter derives the course over ground from
position at very low speed. The output of the low-speed course over ground filter is published in the
UBX-NAV-PVT message (
headMot
field), UBX-NAV-VELNED message (
heading
field), NMEA-RMC
message (
cog
field) and NMEA-VTG message (
cogt
field). If the low-speed course over ground filter
is not configured, then the course over ground is computed as described in section
.
3.1.7.4 Static hold
Static hold mode allows the navigation algorithms to decrease the noise in the position output when
the velocity is below a pre-defined "Static Hold Threshold". This reduces the position wander caused
UBX-18010802 - R08
3 Receiver functionality
Page 24 of 110
Early production information
