10 - VBOX II Smoothing and Filtering

Velocity

VBOX II units has three smoothing settings (Dynamic Modes) for velocity: High Dynamics, Normal and Low Dynamics. High dynamics has the least amount of smoothing and must be used for high dynamic tests where Time or Distance measurements are critical, such as brake stop and acceleration tests.

Slip, Pitch, Roll Angle and Acceleration Channels

The smoothing routine is set by selecting a value from 0 – 5.0 in 0.1 steps. This value corresponds the size in time (S) of a moving window smoothing routine.

e.g. if 0.3 is selected then a smoothing window of 0.3 seconds (6 samples @20 Hz) will be applied to the data.

Kalman Filter

This facility provides filtering separately to the Velocity and Position channels (long, lat and height). Note that with any live filter routine more latency will occur if higher levels of filtering are used, hence the Kalman Filter velocity settings should be set to zero for brake stops and acceleration runs.

It is often better to record unfiltered data then use the software filter routines available within the VBOX Setup Software as these will have much less impact on latency.

The levels of filtering cannot be adjusted; the Kalman filter can only be enabled or disabled.

Note: Once the filter is turned on in the VBII, it remains on until it is manually turned off or a GPS Cold Start is performed, even if the VBOX is disconnected from its power supply.