How Big is Your Tree? Activity #67: Measuring Circumference and Diameter

Measure three different tree’s circumferences using different measuring techniques. Then determine the diameter of each tree. Remember to include units of measurement.

Tree 1 / Tree 2 / Tree 3
Circumference
estimate
arm spans *
ruler/ tape
measure
Diameter

*wrapping arms around the trunk

Diameter is based on the geometric formula

d = C/pi (diameter = circumference divided by pi, pi = 3.14 in.)

The above measurements will be used by a forester to determine if trees are large enough to be harvested. How does your group know if your measurements are accurate?

How Big is Your Tree? Activity #67: Measuring Height

Foresters use a tool called a clinometer. When one is not available they use shadows to determine a tree’s height. Your team will use your heights to determine the height of the trees.

1. Measure your height.

2. Measure the length of your

shadow.

3. Measure the length of the

tree’s shadow

4. Use the equation to find the

tree’s height. Remember to

include units of measurement.

Tree’s height = Student’s height x Tree’s shadow

Student’s shadow

Tree #1

Student 1 height ______Student 2 height ______

Student 1 shadow ______Student 2 shadow ______

Tree shadow ______Tree shadow ______

Tree height ______Tree height ______

Tree #2

Student 1 height ______Student 2 height ______

Student 1 shadow ______Student 2 shadow ______

Tree shadow ______Tree shadow ______

Tree height ______Tree height ______

Any difference between the two heights calculated for each tree? Explain.

Let’s try another way to measure tree height using proportions. (over)

Since shadows are not always available, foresters can determine a tree’s height using the proportional method.

1.  One student stand at the base of Tree #1 (use the same trees as earlier).

2.  Another student should stand in front of this student, holding a ruler vertically at arm’s length and walk backwards, keeping arm stiff, until the bottom and top of the ruler line up with the top and bottom of the tree.

3. The student with the ruler should record where the top of their partner’s head appears on

the ruler (for example, at 2”) ______

4. Divide the length of the ruler by this figure. For example. 12” ÷ 2” = 6”______

5. Measure your partner’s actual height and multiply it by the previous result. For example, if

the student’s height was 55”, then the height of the tree would be 55” x 6” = 330”

______

Convert to feet (inches ÷ 12, 330” ÷ 12 = 27.5’) ______

Do again for Tree #2

Student height based on ruler ______

Divide length of the ruler by this figure ______

Student’s actual height ______Convert to feet ______

Compare to first calculations. What might explain any differences?

How Big is Your Tree? Activity #67: Measuring Crown Spread

A tree’s crown spread is the distance the tree’s branches spread away from its trunk. Measure the crown spread for three trees using different measuring techniques. Remember to include units of measurement.

1. One student should stand under the branch tip

farthest from the trunk (A).

2. One student should stand under a branch tip

opposite that one (B).

3. Measure the distance between A and B.

4. Then have one student stand under the branch

tip closest to the trunk (C).

5.  One student should stand under a branch tip opposite that one (D).

6.  Measure the distance between C and D.

7.  Calculate the average of the two measurements.

Tree 1 / Tree 2 / Tree 3
Estimate
Arm spans *
Ruler/ tape measure
Distance between A and B
Distance between C and D
Crown spread

*wrapping arms around the trunk

Compare crown spread measurements to each other. What might explain any differences? Why would the measurement of a tree’s crown be important?