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Measuring Tree Heights for Urban Forest Inventories

Publication Number: IS2008
Updated: February 14, 2018
View as PDF: IS2008.pdf

Note: These instructions are for SUUNTO clinometers with a topographical scale (feet).

A clinometer is an instrument that measures slope.

The concept of the clinometer is rooted in the trigonometry of a right triangle. The volunteer measures slope (the hypotenuse, or rise over run) twice. First, measure to the top of the tree. If you stop here, you have only measured the tree starting at the height of your eye. So you must then measure to the base of the tree (where the tree meets the ground), creating two right triangles. Add these two measurements together to get height.

Drawing showing that you should stand 66 ft from the tree with clear vision of the entire tree from top to base.
This is an image of a man using a diameter tape to measure 66 feet from the base of the tree.
Step 1: Use the diameter tape and measure 66 feet from the base of the tree. Be sure to walk up-slope and have a clear line-of-sight to the top of the tree (if you are down-slope from the tree, a different calculation must be used). 

 

This is an image of a man using a clinometer and a diagram of the clinometer.
Step 2: Standing 66 feet from the tree, use the clinometer to measure to the topmost green leaf that you can see. The dot on the clinometer should be on the top side, facing the tree. The brass loop should be on the bottom, facing the user. Keep both eyes open when looking into the peephole. This produces an optical effect that transposes the cross hair onto the tree you are measuring. If you tilt the clinometer up and down, you will notice the scales have positive and negative numbers. The scale to the right is the topographical scale in feet. Note the negative scale (–) appears when you tilt the clinometer down) and the positive scale (+) appears when you tilt the clinometer up. You must always be aware of whether the number is positive or negative.

Step 3: Remaining 66 feet from the tree, measure the base of the tree. This measurement represents the lower triangle in the graphic above. Add the two measurements, in feet, together. The sum is the total height. For example, you get 30 feet to the top, and negative 5 feet to the bottom. The total height of the tree is 35 feet.

This images shows to tilt the clinometer to the top of the tree and measure.
Tilt the clinometer to the top of the tree and measure.
This is an image of a man using a clinometer tilted to the base of the tree and measure.
Tilt the clinometer to the base of the tree and measure. Add the two metrics to complete the height measurement.
 


Information Sheet 2008 (POD-01-16)

By Jason Gordon, Assistant Extension Professor, Forestry.

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