How to measure the angle of curve from a real object?

[ken022]

I have print knife handle before and I just draw the outlined onto white paper and capture it with camera, after that I draw it with photoshop to make the lines more clear, next step imported the image into Freecad and just make the model from the picture and that does not really have an exact curve, but still acceptable.I know a little about design model in Freecad and Fusion360 and sometimes I curious how you all measure the angle of a curve from a real object? Did you need a 3d scanner or what?It would be a great skill for 3d printer hobbyist like me. Sorry if my English is not clear. I am not a native English speaker.

jiofi.local.html
192.168.8.1
router network