We recently hired a Civil Engineering grad and are putting him through his paces Sometime in the near future we have to drop an exhaust stack. So I asked him a simple question "Will it fit"
He said "I think so" (bad answer).
I asked him "What is the height?"
He said "I don't know we don't have the plans "
I said "So how do you know it's going to fit then?"

I was leading him down the path a little but if you let them get away with being sloppy early on there is no hope later.

So I taught him how to always be able to determing the height of an object. Pretty soon I was giving a lesson to 10 people then I figure out maybe more people would like to know an easy accurate method, so here it is.

1. Place a small mirror on the ground between you and the structure. Position the mirror or your self (in a straight line of course) so that you can just see the reflection of the very top of the structure in the mirror.

2. Now you have created 2 triangles where:

h = height of person
d = distance from person to mirror
D = Distance between mirror and structure
H = Height of structure

H/D = h/d so H=hD/d