There are four common methods of measuring the height of a tree, the shadow method, the pencil method, angle of elevation method, and the fixed angle of elevation method. These methods are also useful in determining the height of buildings, or any tall objects.
Shadow method: This method of measurement can be accomplished without the need of an assistant. Best results will be obtained on a bright sunny day.
- Determine your exact height in the shoes you are wearing on that day
- Measure your shadow. Place a rock or stick anywhere on the ground. Stand next to the tree; position yourself so that the tip of your shadow is at the marker. Using a tape measure, measure from your feet to the tip of your shadow.
- Quickly measure the length of the tree's shadow, measuring from the base of the tree to the tip of the shadow. The need for urgency is due to the length of the shadow changing as the position of the sun changes.
- Now the math starts: Multiply the length of the tree's shadow by the length of your shadow, and divide the outcome by the length of your shadow, and you have the height of the tree. Use the same units of measurement, inches by inches or feet by feet.
Pencil method. This method requires an assistant.
- Stand on ground that is level with the base of the tree; stand far away enough to see the whole tree without moving your head.
- Hold a pencil in one hand at arm's length in front of you.
- Close one eye and sight the top of the tree with the top of the pencil.
- Move your thumb up or down the pencil until your thumbnail is aligned with the base of the tree.
- Keeping your thumbnail aligned with the base of the tree, rotate the pencil horizontally.
- Have your assistant move away from the tree as you sight his feet through the point of the pencil, aligning his feet with the tip of the pencil.
- Measure the distance between your assistant and the tree. This measurement is the height of the tree.
Angle of elevation method.
- Stand with your back to the tree, walk to a place that is level with the ground at the base of the tree, and where you can see the top to the tree clearly.
- Use a clinometer or transit to measure the angle of elevation between the ground and the tree.
- Find the tangent of the angle of elevation; this can be accomplished with the use of a calculator.
- Multiply the distance you are from the tree, by the tangent to the angle of elevation, add your height, and you have the height of the tree.
- Your height must be added because you measured the angle of elevation from eye level.
Fixed angle of elevation method.
- Fold a piece of paper to create a triangle, with one 90-degree angle and two 45-degree angles.
- Place the paper near one eye with the right angle pointing away from and one side parallel to the ground.
- Step back from the tree, sighting the top of the tree at the top tip of the triangle. Close one eye and sight the top of the tree. Locate the point where your line of sight follows the hypotenuse of the triangle to the top of the tree.
- Measure the distance from this mark to the base of the tree: This number plus your height is the height of the tree. Again, you must use your height because you determined the angle of elevation from eye level not ground level.
You now have four methods of measuring the height of a tree. The shadow and pencil method work best on trees that are straight, while the latter two methods are of more value in determining the height of a tree that is less than perfectly vertical.