Where did the OBS occur?

[SC Ump]

Originally posted by UmpireErnie
...but what about when she is at, on, or straddling a base?

I'm a project manager for a computer corporation. I'm in Mensa and my fellow umpires accuse me of being over analytical. But, man, you are making my brain hurt.

Just remember that it was the defense performing the offending action. Apply the ruling fairly and don't worry about whether the runner's center point of gravity was two nanometers left or right of an imaginary plane that vertically dissects the base's midpoint from the adaxial corner.