From what I am putting together the ogive based on caliber would look something like this.

We start with a 30 cal diameter. I then made 3 circles that were 6 8 and 10 times as big. If we use the section cut on a plane horizontal to the center of the caliber we end up with half of a bullet tip profile. I'm assuming this is a tangent ogive???

If this is right then how come in the graphic above we see .5 for the ogive that is semicircle instead of 1. Are we dealing with the caliber radius or the diameter?