Two sensors, split at (hardcoded?) y_split:
- sensor 1 means y < y_split
- sensor 2 means y > y_split

u1:         x shift  
v1:         y shift
w1:         z shift
slopeX1:    slope along x (<=> beta [!])
slopeY1:    slope along y (<=> alpha [!] around sensor [!] x-axis)
gamma1:     rotation around module (!) z-axis
sagittaX1:  bow along x 
sagittaXY1: bow mixed term
sagittaY1:  bow along y

u2:         x shift  
v2:         y shift
w2:         z shift
slopeX2:    slope along x (<=> beta [!])
slopeY2:    slope along y (<=> alpha [!] around sensor [!] x-axis)
gamma2:     rotation around module (!) z-axis
sagittaX2:  bow along x 
sagittaXY2: bow mixed term
sagittaY2:  bow along y