Measurement of scan length

I work in a facility where we make transmission insulators for power lines. We have to measure what they call leakage per customer drawing. We recently purchased a CMM machine and now EVERYONE wants EVERYTHING checked on it. Of course it's a new toy I get it. But I am trying to perform a scan without the model to measure leakage, but I am drawing a blank on how to measure them length of the actual scan that has traveled over the surface of the part. I tried it with free form scan, as well as linear open. Attached is a photo of the part thanks in advance for the help!