estimating lenth from a distance

[Unregistered]

Is there a formula to estimate the lenth or diameter of a structure from a distance if you know how far from the object you are standing. Can you hold up a transparent ruler for instance and measure the object as 5 inches?

[Robert Fogt]

I think you can. I have seen several golf tools that calculate the distance to the hole based on how high the flag is. Since the flag is a set height you can calculate with our good friend geometry.

You would need to know more information though.

Take a piece of paper, and draw a right triangle.

side a would be the height of the object, side b would be the distance you are standing from the object.

Since you know the length of side b, you only need to know the angle A to calculate side a.

Possibly lay a protractor flat on the ground, and look at the top of the building to estimate the angle?