Throw in VIOLATION 1.3 in NIT SEMI

[CoachW]

How is 3 ft. measured?

I could not find in rulebook, maybe in casebook which I do not own, but how is the three feet measured? Is it 1.5 feet from the center of the body of the thrower, or some other way? I've wondered for a while, but have never seen it called other than when it was REALLY obvious (Thrower runs baseline when they shouldn't, something like that) but I just wondered.

Thanks, Coach W