The angle of attack as I describe it would incorporate a bit of calculation by using the span of the tip of the nose to the chin.  So imagine you put a large book surface to your face and try to kiss it hard.  Well the front facing tip of the nose and chin would encounter the book cover at two points and the span between them creates an angular arc when you use the earhole as the pivot.  You then bisect this angle and measure the resulting angle to the horizontal line.