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
Tree #1
= Student’s height x Tree’s shadow
Student’s shadow
Student 1 height
_________
Student 2 height
_________
Student 1 shadow
_________
Student 2 shadow
_________
Tree shadow
_________
Tree shadow
_________
Tree height
_________
Tree height
_________
Student 1 height
_________
Student 2 height
_________
Student 1 shadow
_________
Student 2 shadow
_________
Tree shadow
_________
Tree shadow
_________
Tree height
_________
Tree height
_________
Tree #2
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?