Mike Davison, September, 2020
This is a technique to quickly measure a tree height and crown width.
The basic method uses 2 yardsticks. One yardstick is leaned against the tree as a reference and the other yardstick is used as a scale reference. However, leaning a staff of know length against the tree and using a tape measure as the scale reference also works.
- Lean a yardstick against the tree nearly vertical.
- From a distance (roughly 75’), hold the second yardstick at a distance from your eye (about 25”) so that the first yardstick appears 1” tall with zero at the tree base.
- Moving only your eye, sight the treetop across the yardstick and note the inches. The tree height will be this in yards tall.
- If the tree exceeds 36 yards tall, you can use 1/2” for sighting the first yardstick and double the inch sighting for the tree height.
- Note the crown height.
- Rotate the yardstick keeping it at the same distance from your eye and note the crown width.
The reason this works is that the triangles created from the sight lines to the scale reference are an exact scale of the triangles formed by the sight lines to the yard references at the tree. Therefor the scale reference displays 1 inch to the yard.
The author uses a 6′ staff and a tape measure, sighting the staff leaning on the tree at 2″ to maintain 1″ per yard scale.