Basic Height Measurement

The Biltmore stick is one of the basic tools all foresters have for use in the field. One side of the stick is used for measuring tree diameter at 4'6" above the ground, and the flip side has a scale to meaure the merchantable height of trees. These sticks use similar triangles to measure height, and are set up to be held 25" from the eye, 66' away from the tree, to measure the number of 16' logs.

I teach forestry basics to FFA students from several schools and use a simple setup for them to learn how to pace a chain (66') and to measure with the hypsometer. We set up three stakes with 16' between two of them, 66' away from the third one. Pacing is just normal and consistent walking and counting every other step. We always start with the left foot and count on the right foot. A few trips back and forth establish the number of paces each student uses to cover one chain. Note the spot that you call one chain, turn around and place your eye above the one chain mark.

The stick is designed to be held 25" from your eye. We check everyone's reach with a tape. If a student cannot adjust their reach to 25", they will need to make a custom stick. With your eye at a distance of 66' feet from the stakes spaced 16' apart, hold your stick at your 25" reach, line up the bottom of the stick with one stake, and holding your head motionless, rotate your eye to the second stake. It should be lined up with the 1 log mark on the hypsometer. You are ready to measure the number of logs in trees when you can do this consistently.


Merchantable height measurement goes like this:

1. Size up the tree from a distance to determine the upper cutoff point.
2. Go up to the tree and measure the diameter.
3. Select a clear horizontal path away from the tree so you can pace one chain.
4. Pace out one chain, turn around and check to see if both the bottom of the tree
and the upper cutoff point are visible. Lateral moves are often necessary at this step.
5. Extend your arm with the stick to your 25" reach
6. Tilt your head back, roll your eye to the stump height on the tree,
line up the bottom of the stick with the stump.
7. Hold your head motionless and roll your eye upward to the cutoff point on the tree.
Read the number of logs on the stick. Estimate to the nearest 1/2 log. Don't round up.

Tilting your head back before measuring is important. If you don't do this, you will find that you can't roll your eye up far enough to reach the upper cutoff point.