this is only used in one place, and that place is called from the same routine setting the persistent state. The only other place which calls readIMUData shouldn't be running the prediction step, but mmay, depending on the previous setting of the prediction step.
We are not initialising this state on filter reset, so it's possible that the state will be set when we do an InitialiseFilterBootstrap, which is probably not desired
The previous method resulted in data incest and fusion of predicted airspeed on every EKF internal time step.
This was not apparent during flight where the vehicle was turning, but during long straight legs did not constrain along track drift.
Make it user selectable.
Remove potential for a race condition between decisions based on latest data and the EKF fusion processing which operates on a delayed time horizon. This is achieved by preventing data entering the buffer if awaiting checks to pass ensuring that no EKF fusion time horizon processes can use data that hasn't passed checks.
Log the waitingForGpsChecks class variable
These changes enable the EKF to use the last observable wind velocity vector estimate to synthesise an airspeed measurement if operating without an airspeed sensor and when all other measurement types that can constrain velocoty drift are lost. This enables the EKF to use dead reckoning to continue after loss of GPS when there is no air speed sensor fitted and without the need to set a default airspeed value.
The logic used to fuse a default airspeed value has also been cleaned up and the call to FuseAirSpeed() from inside SelectBetaDragFusion() has been removed.
AP_NavEKF3: Fix error in default airspeed observation variance
AP_NavEKF3: Enable shadow fusion of airspeed when sensor is disabled
The offset generated by the EK3_OGN_HGT_MASK parameter bit 2 option is applied to the baro or range finder sensor so it does not have to be applied to the local position height.
the fusionReport object is not being cleared when the filter undergoes a forced reset.
So delete and recreate the object. Will also make this sensitive to the number of beacons changing.
Also don't attempt to allocate zero bytes.
filter status was initially set to zero then updated. This interacts
with the IMU filtering code which checks filter status from a
different thread to determine active_EKF_type(). When the race
condition is hit then the IMU we are running notch filters on changes
for a single sample, causing a notch filter glitch
The ResetVelocity() function is only supposed to reset XY states, not
Z state. Resetting the Z state for velocity results in a large
velocity glitch if a vehicle is descending or ascending when aiding
switches to AID_NONE
this fixes#19386
