Good afternoon,
How would I go about using Datum A, which is a curved surface to level to? Ais the underside of the part, B is a flat spot on the top side of the part and datum C is a slot on the top of the part.
If there are no datum targets, then the entire surface should be used, as I said in my previous comment. You should take enough hits to accurately capture the shape and form of the surface. It's the same philosophy as if it were a plane, only taking three points would result in a perfect plane with no form deviation. To capture the flatness, you would need to spread your points over the whole plane and choose a sufficient point density to capture the expected amount of deformity.
