Message posted by Eagle Scout on August 24, 2011 at 8:33:15 PST:

11.

I gather you're taking the length of a known object's shadow and calculating the ratio of shadow length to object height.

Another way, if you know the date & time the photo was made, and therefore the angle of the sun, is to do some trig and get the same number. If you have a vertical object casting a shadow on flat ground, you've got 2 angles and a length. Someone whose math is better than mine will have to confirm this, but I believe the tangent of the angle from the top of the object to the tip of its shadow is equal to the length of the shadow divided by the height of the object. Or,

tan(angle) = shadow length/tower height

To the extent the object isn't vertical &/or the ground isn't flat, the measurement would be off.

In Reply to: Re: can we share techniques? posted by greatguess on August 24, 2011 at 6:00:04 PST:

Replies: