Question for admissible speed verification and 3 channel dash cams???

So I understand that gps data for speed verification may be inadmissible in many jurisdictions if wanting to show evidence for speeding tickets using dash cam footage.

My question for the sub is this, What if I use a 3 channel dash cam and point the third channel at my speedometer?? Front, rear, speedometer? Admissible?? No longer gps data but direct readings...