Question about measuring camber angle in simmechanics

Hi everyone, currently i am working on my university project about vehicle dynamics. I'm trying to use Simmechanics to model our suspension system. But i don't know how to use Transform Sensor to measure the camber angle of the wheel. Since the frame of the wheel hub will be steered and it rotates because of the kingpin inclination i find it difficult to measure the actual camber angle. Does anyone know how to do it? Thanks so much!

[Birdman]

The important question is, relative to which frame you want to measure the angle?