Hi

I have a an STL model of a human head. I want to measure the distance across the surface of the model between chosen points, the points of interest are based on ratios of head circumference, distance between the ears ect. I have inserted some images to illustrate what I am trying to describe. How do I go about doing this?

The second challenge I have is once I have selected a bunch of points over the surface of the head from careful measurements over the surface, how do I extract those points and flatten them onto a 2D  plane. In such a way that if you covered part of the head with the 2D plane it would line up with the points of interest on the head like mask.

Previously I have only designed electronics enclosures in Solidworks and I don't have a lot of experience designing or messing around with complex curved models. Any help would be much appreciated, I am in way over my head (excuse the pun).

Kind regards,
James