Even if there is some horizontal motion, a passing check should be
accepted as the terrain can be flat. However, the vehicle must not be
moving horizontally to invalidate the consistency as a change in terrain
can make the kinematic check temporarily fail.
To pass from invalid to valid:
- time hysteresis
- some vertical velocity
- test ratio < 1
- low-passed signed test ratio < 1
To pass from valid to invalid:
- low-passed signed test ratio >= 1
At each new valid range measurement, the time derivative of the distance
to the ground is computed and compared with the estimated velocity.
The average of a normalized innovation squared statistic check is used
to detect a bias in the derivative of distance measurement,
indicating that the distance measurements are kinematically inconsistent
with the filter.
bresch