How EXACTLY do you measure the length of the facial middle third?

[UnderTheKnife]

I believe the lower point is the base of the nose.

But what about the upper point? I can't find consistency regarding this matter.
The most common answer is the "glabella". But what point exactly of the glabella? It is a vertical line. Should you just take the middle of this line?

 

[Orc]

what is the point of measuring it, whether it's too long or too short all just depends on harmony which has so many factors it's tricky to calculate.

 

[UnderTheKnife]

what is the point of measuring it, whether it's too long or too short all just depends on harmony which has so many factors it's tricky to calculate.

I know, but behind that harmony there exists fundamental objective ratios. I'm curious to see how they're determined.

 

[Orc]

I know, but behind that harmony there exists fundamental objective ratios. I'm curious to see how they're determined.

in my opinion it's the eyebrows that dictate the length of your mid face, not the skeletal structure underneath but the actual hairs.