RCB-F9T - Integration manual
Platform
Max altitude [m]
Max horizontal
velocity [m/s]
Max vertical velocity
[m/s]
Sanity check type
Max
position
deviation
Airborne <1g
50000
100
100
Altitude
Large
Airborne <2g
50000
250
100
Altitude
Large
Airborne <4g
50000
500
100
Altitude
Large
Wrist
9000
30
20
Altitude and velocity
Medium
Table 7: Dynamic platform model details
3.1.7.2 Navigation input filters
The navigation input filters in CFG-NAVSPG-* configuration group provide the input data of the
navigation engine.
Configuration item
Description
CFG-NAVSPG-FIXMODE
By default, the receiver calculates a 3D position fix if possible but reverts to 2D
position if necessary (
auto 2D/3D
). The receiver can be forced to only calculate 2D
(
2D only
) or 3D (
3D only
) positions.
CFG-NAVSPG-CONSTR_ALT, CFG-
NAVSPG-CONSTR_ALTVAR
The fixed altitude is used if fixMode is set to 2D only. A variance greater than zero
must also be supplied.
CFG-NAVSPG-INFIL_MINELEV
Minimum elevation of a satellite above the horizon in order to be used in the
navigation solution. Low elevation satellites may provide degraded accuracy, due to
the long signal path through the atmosphere.
CFG-NAVSPG-INFIL_NCNOTHRS,
CFG-NAVSPG-INFIL_CNOTHRS
A navigation solution will only be attempted if there are at least the given number of
with signals at least as strong as the given threshold.
Table 8: Navigation input filter parameters
If the receiver only has three SVs for calculating a position, the navigation algorithm uses a constant
altitude to compensate for the missing fourth SV. When a SV is lost after a successful 3D fix (min.
four SVs available), the altitude is kept constant at the last known value. This is called a 2D fix.
u-blox receivers do not calculate any navigation solution with less than three SVs.
3.1.7.3 Navigation output filters
The result of a navigation solution is initially classified by the fix type (as detailed in the
fixType
field of UBX-NAV-PVT message). This distinguishes between failures to obtain a fix at all ("No Fix")
and cases where a fix has been achieved, which are further subdivided into specific types of fixes
(e.g. 2D, 3D, dead reckoning).
The RCB-F9T firmware does not support the dead reckoning position fix type.
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.
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
UBX-19003747 - R04
3 Receiver functionality
Page 13 of 54
Early production information
