Since you know the length of the tree’s shadow, and you also know that a certain height (your height) produces a certain shadow length (the length of your shadow), you can determine the tree’s height with a little math. Calculate the tree’s height by using the proportion of your shadow’s length to your height.If you have an assistant, you can hold one end of the measuring tape while he or she measures the tree’s shadow, and then you can immediately measure your shadow. You want to do this as quickly as possible after measuring your shadow, since the sun’s position in the sky (and hence the shadow length) is slowly but constantly changing. This works best if the ground all along the shadow is fairly level if the tree is on a slope, for example, your measurement won’t be very accurate. Use your measuring tape to determine the length of the tree’s shadow from the base of the tree to the tip of the shadow. Measure the length of the tree’s shadow.Or better yet, place the rock anywhere on the ground, and then position yourself so the tip of your shadow is at the rock then measure from where you're standing to the rock. If you don’t have someone to assist you, you can mark the end of the shadow by tossing a rock onto it while you’re standing. Use a tape measure or yardstick (meter ruler) to measure your shadow from your feet to the tip of your shadow. If the sky is overcast, it may be difficult to tell exactly where the shadow’s tip is For best results, do this method on a bright, sunny day. Stand next to the tree or the object to be measured.Know your exact height in the shoes you will be wearing to perform this method.These methods can also give you a good approximation of the heights not only of trees, but also of telephone poles, buildings, magic beanstalks-pretty much anything tall. If you think you can find a tree that can break that record, or just want to measure that tree in your backyard, try these techniques. On Septemthe San Francisco Chronicle reported that researchers had just discovered a 378 foot (113 meters) tall tree that is probably the world's tallest living tree.