Position of a hole normal to a large radial surface

Position of a hole normal to a large radial surface

What is the best way to verify the position of a hole that is normal to a large radial surface?  We have tried the following methods below and get somewhat different results for both.  

1.  Hole measured as a cylinder and reporting position.
2.  Intersecting the cylinder with the radial surface and reporting position of the pierce point.