Here is one way to do this.
I completed this instructable using three items. 1) Framing Square (24 x 16 inches), 2) Digital Photo, 3) MS paint.
I saw this software program on the internet at: http://www.stickyyard.com/
I wanted to challenge myself to see If I could recreate the function without the expense.
Soo.. Here it goes.
Please keep in mind that this is only an estimator and will not provide precision measurements. There are many factors that could affect your results. This should get you close if you do not have any other tools available.
Here is my first subject, my garage door. I want to find the length and the height around the frame of the door.
Step 1: Reference Object
From here on out it starts to get in depth. I will divide this up into two sections. One for the casual reader and one for the techno / geek / engineer in all of us.
The idea of this project is to scale up a known size to determine an unknown size.
TECHNO, GEEK, ENGINEER:
Of course the accuracy in doing this will be largely affected by a multitude of variables, not all of which I can or will address, but I will try to explain a few. Please remember I am not an expert so those of you that are, please enlighten me on my mistakes.