Earth Partnership for Schools
WOODLAND RESTORATION INTERACTIVE WORKSHOP > HOW TO RESTORE WOODLAND AT YOUR SCHOOL > STUDY THE SITE > MEASURE TREE HEIGHT
Measuring tree height is an important part of site analysis. Determine location, size and height of trees at your site. Trees affect the plants around them, the animals that will inhabit and live in the area, water availability, the microclimate, sunlight and soil type. Knowledge of how the tree casts a shadow through the day and through the seasons will affect what you and where you plant.
- Tree height data sheet
- Measuring tapes.
- Sighting stick - 10 inch long stick with a hole, large enough to see through, drilled at one inch.
- Clinometer (measures angles).
There are many ways to estimate tree height. Below are five methods, starting with the simplest and least accurate:
- Rough Estimate
Work in groups of two. Measure the height of one person and record. That person then stands straight against the tree. The second person stands at a distance and estimates how many "heights" of that person make up the tree height. Walk farther back and repeat. Do until you are getting a consistent estimate.
- Logger's Estimate
Work in groups of two. One person stands at a distance from the tree and extends their arm to full arm's length. Bracket the tree height between the thumb and forefinger. If the tree is too big, walk farther away from the tree. Without changing the distance between the fingers, rotate the hand so the distance runs along the ground from the base of the tree outward. The second student should locate the spot on the ground identified by the first student's forefinger. (Note: It is important that the first student keep their arm fully extended throughout this exercise.) The distance on the ground equals the height of the tree.
Work in groups of two. Measure the height of one person and the measure their shadow. Record. Measure the shadow length of the tree and record. The tree height can be calculated by the following proportion:
- height of tree = height of person
- length of tree's shadow length of person's shadow
- Sighting Stick
Work in groups of two. Using the sighting stick, move a distance from the tree such that, when held at arm's length, the base of the stick is at the base of the tree and the stick just covers the height of the tree. In this position, sight through the hole to the tree. The second person should mark the spot on the tree that is visible through the hole. Because the stick is ten inches long and the hole is drilled at one inch, tree height can be calculated using the following proportion:
- 1" = height of the marked spot on the tree
- 10" height of tree
Work in pairs. Pick a spot at some distance from the tree. Measure the distance from the base of the tree to the spot. Record. Measure the angle necessary to sight to the top of the tree from the spot. Be sure to sight from the ground. Tree height can be calculated using the following equation:
tan of angle = length of leg opposite angle = tree height
length of leg adjacent angle distance to tree
tree height = tan of angle X distance to tree
Distance to tree________
Tan of angle______
Height of tree________