I think you need more than that. How about the widths?
I am only really interested in the relative angle between AB and CD, as these are 2 parts in a machine that move and the relative angles are important.
I thought that if I just measure across AB and CD at any 3 or points, I would be able to fit a straight line. (Which I guess I can do manually via Visio or AutoCAD.)
Would it help if all the lengths were at right angles to CD?
Let that angle be alpha.
Get the meauments of AD and BC, and of CD.
Slope of AB = (BC -AD) /CD
Then, tan(alpha) = slope of AB
Therefore, alpha = arctan[(BC -AD)/CD] ------answer.