How to extract 3D information from a 3D model for calibration?
Extracting various measurements from 3D models is easily done using the following free online tool:

https://0x00019913.github.io/meshy/

I scanned a person using the Sense 2 scanner and I compared the values from meshy for the hip and waist with those measured in real life one day after the scan: the difference was about 1 cm, which can easily be explained by the uncertainties in the choice of the measurement point and moment of the day.

This shows that both the 3D scanner and meshy are quite accurate. The tool is also very easy to use.