Students
discussed what tree measurements (age, circumference, and height)
are needed in order to calculate the amount of timber that can
be collected from a tree. Students were introduced to the forester's
tools (clinometer, Loggers' tape and diameter tape measures, and
increment borer) that make the job faster. Then, students conducted
field investigations in in which the tools were used to take the
appropriate measurements.
 Age of
trees: The age of the trees is determined by taking a core sample
from the tree and counting the rings. Students realized very
quickly that there were 2 methods for calculating the age: count
all the rings and divide by 2, or count only the dark rings.
 Diameter
and circumference: The diameter and circumference of the trees
are calculated using 2 special measuring tapes. A diameter tape
is calibrated in increments of pi which converts the measurement
from circumference to diameter for the forester.
A logger's tape is calibrated in increments of inches and feet
and is used for measuring distance from a tree. (The other side
is often calibrated in increments of pi so that the logger's
tape can serve as a regular measure and a diameter tape).
 Angles
to measure height: Height is measured using a clinometer. The
clinometer uses trigonometry to calculate the height by determining
the angle opposite the tree. The forester stands 100 feet from
the base of the tree (a distance measured using the logger's
tape). Then, the clinometer reads the angle between the forester's
eye and the top of the tree. At 100 feet, the angle measurement
is the same as the height of the tree (plus the height of the
forester!)
 Estimation:
The number of board feet is estimated using a forester's chart
that converts the height of the tree and the circumference of
the tree into board feet.
