When you are measuring the slip angle of a vehicle with your VBOX test setup,
Heading is a parameter that differs in value at different points on a vehicle; specifically on a motorbike due to the vertical position (height) of measurement.
If you set the contact patch on the rear tyre and the ground as the reference point in the IMU offsets section, the heading and the corresponding slip angle measurements will be made at the rear tyre.
Slip_Head is a parameter that is the same value anywhere on a vehicle. Therefore, this parameter does not need to be translated around the body of the vehicle. In the case of a motorbike, however, the exception is the steering yoke, the handlebars, and the front wheel, as they articulate separately from the rest of the body.
When using a VBOX 3i in a vehicle setup, we typically use the IMU translation facility to measure body slip angle at multiple locations. These channels (Slip Angle FL, Slip Angle FR, Slip Angle RL, Slip Angle RR) are body slip angle measurements translated to different locations on the vehicle, using yaw rate and X and Y offsets in metres. To find the slip angle at the wheels on the rear axle of a car, you need to refer to the Slip Angle RL and Slip Angle RR.
The computation of the channels Slip_COG, Slip_RL/RR and Slip_FL/FR does not include height. To use these channels, we recommend that you translate the IMU position to lower the height of the IMU measurement point on the vehicle frame, and then use the Slip_COG, Slip_RL/RR and Slip_FL/FR facility to create multiple slip angle measurements around the body of the vehicle.
However, these channels will not be representative on motorcycles. When you use IMU translation to shift the point of measurement of the Heading to a chosen point on the bike (for example, the rear axle/tyre), the standard channel for slip angle will also be calculated from the translated point.