How to Estimate Height of Tall Objects

Eyeballing the height of a building or tree can sometimes be frighteningly inaccurate. Many a daredevil has injured himself or herself by critically underestimating the height of a tree, cliff or building. Or maybe you just want to know how far you'd have to jump if your fire escape broke. Luckily, there are two methods for obtaining more-accurate height estimates without trying to find a long-enough tape measure.

Wired explains it all.