How Champion Trees are Measured
The size of a champion tree is calculated using a point system developed by the American Forestry Association. A Champion's total points is a composite of its circumference, its total height and one quarter of its average crown spread.
Measuring Circumference
Circumference is measure in inches using an ordinary tape measure. The first step in this process is to determine
the point of measurement. On flat ground, take the measurement at a height of 41/2 feet above the ground. If the tree is on a slope, take the measurement 41/2 feet up the bole (trunk of a tree) on the uphill side. Keep the tape perpendicular to the bole and read its circumference to the nearest inch.
Special rules apply for trees which fork below 41/2 feet, and for trees with abnormalities on the bole which affect its size at 41/2 feet. If the tree forks below 41/2 feet, measure only its largest fork. If an abnormality affects the tree's circumference at 41/2 feet, take the measurement at the smallest point below the abnormal growth.
Measuring Crown Spread
Crown Spread is measured in feet and is the average of the greates and least distance across the drip line of the tree (Figure 1). This measurement is often the least accurate, due to the subjective nature of the exact points to be measured. Once the widest and narrowest spread is averaged, points are calculated by dividing by four.
Figure 1.
Measuring Total Tree Height
Tree height is measured in feet and is most easily done using a special instrument called a "hypsometer". A hypsometer measures an angle and converts it to a direct height reading at a certain distance. Because most people do not have access to such an instrument, it is best to have a forester take this measurement prior to submitting an entry for consideration as a Champion Tree. For those adept in trigonometry, Figure 2 shows the trigonometric formula for determining height.
Figure 2.
Calculating Total Points
Once all measurements are taken, the Total Points are calculated using the following formula:
Total Points = Circumference (Inches) + Total Tree Height (Feet) + Average Crown Spread (Feet)/4
