A Type 3 force platform records information according to its four corners, which are named 1, 2, 3, and 4.

A Type 3 force platform records 8 ANALOG channels containing the following information:

[Original Analog] = [Fx12, Fx34, Fy14, Fy23, Fz1, Fz2, Fz3, Fz4]

Note that a Type 7 force platform has the same analog channels as a Type 3 force platform but also includes a CalMatrix. Alternatively, a Type 3 force platform can be thought of as a Type 7 force platform where the CAlMatrix is the identity matrix.

Calculating the desired force signals in the force platform's coordinate system consists of the following steps:

1. Compute baselines by averaging the analog signals for the specified FP_ZERO frames
2. Subtract each channel's baseline from its recorded signal
3. Calculate the force signals of interest
4. Transform the signals into the Laboratory Coordinate System

The Force vector for a Type 3 force platform is calculated as follows:

Force[X] = Fx12+Fx34
Force[Y] = Fy14+Fy23
Force[Z] = Fz1+Fz2+Fz3+Fz4

The COFP signal for a Type 3 force platform is calculated as follows:

COP[X] = (-M.Y/Force.Z) + a
COP[Y] = ( M.X/Force.Z) + b
COP[Z] = az0

Where

a = Origin.X
b = Origin.Y
az0 = Origin.Z

M[X] = b*( Fz1 + Fz2 - Fz3 - Fz4) + az0*(Fy14 + Fy23)
M[Y] = a*(-Fz1 + Fz2 + Fz3 - Fz4) - az0*(Fx12 + Fx34)
M[Z] = b*(-Fx12 + Fx34) + a*(Fy14 - Fy23)

The FreeMoment signal for a Type 3 force platform is calculated as follows:

FreeMoment[X] = 0
FreeMoment[Y] = 0
FreeMoment[Z] = M[Z] + Force[Y]*(M[Y]-az0*Force[X]) + Force[X]*(M[X]+az0*Force[Y])

The transformation is defined by the location of the force platform corners, and is common to all force platforms.