Kathy L. Smith, Extension Associate–Forestry
and David K. Apsley, Natural Resources Specialist
The tree measuring stick is a useful tool for measuring trees and logs. Although not as precise as more specialized tools, it is inexpensive, easy to carry, and accurate enough for most of your tree and log measurement needs. This stick incorporates several tools that are commonly used by foresters and the forest industry, and can help woodland owners better understand and manage their forest resource.
What can you measure with this stick? The stick is primarily used to measure the diameter of standing trees in inches, their height in 16 foot logs, and the volume they contain in board feet or cords. It can also be used to measure diameters of logs and estimate their volume. Additionally, the stick has an angle gauge that can be used to determine basal area—a measurement of tree density or crowding.
Even though the stick is a useful tool, it will not eliminate the woodland owner’s need for the assistance of a professional forester. A woodland owner should utilize a professional forester to develop a management plan and to assist with forest management activities such as timber harvests and tree planting.
There are two important factors to keep in mind when measuring tree diameter: 1) the diameter of a tree should be measured at a point on the tree 4 feet off of the ground (this is known as Diameter at Breast Height or d.b.h.) on the uphill side of the tree, and 2) trees are often not perfectly round; therefore, it is a good idea to take two measurements perpendicular to each other and average them.
When measuring tree diameter be sure to utilize the side of the stick labeled “Tree Scale Stick” (Figure 1) and follow the steps outlined below:
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| Figure 1. A tree measuring stick showing the “Tree Scale Stick” side. | ||
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| Figure 2a. The stick should be placed against the tree 4 1/2 feet from the ground. | Figure 2b. Make sure the distance from your eye to the stick is 25 inches. | |
The merchantable height of a tree, the height to which logs can be cut, is commonly measured in 16 ft. logs and 8 ft. 1/2 logs. To measure merchantable height of a tree with the measuring stick, use the scale along the bottom edge of the “tree scale” side of the stick (Figure 4). When the stick is held vertically the numbers on the scale will be on the right (approximately 6 inches apart). This scale is calibrated to be used at a distance of 66 feet from the base of the tree. Since this scale is used to estimate heights to the nearest 1/2 log (8 ft) pacing 66 feet from the tree is usually an adequate distance measure.
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| Figure 4. Using the diameter and height in 16 foot logs, read the volume of board feet in the tree. |
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| Figure 3. Measuring height of tree in 16 foot logs. |
A pace is the length of one or two of your steps. Measure 66 feet on a relatively flat surface, and beginning with your left foot, walk at a comfortable speed and count every time your right foot hits the ground. Determine the number of paces that it takes to cover the 66-foot distance. Repeat this process at least once and determine the average number of paces. Calculate your pace by dividing the distance by the number of paces.
Example: If your right foot hits the ground an average of 13 times over the 100-foot distance, divide 66 feet by 13 to get a pace of 5.1 feet.
After the diameter and height in 16 foot logs have been determined for a tree, the tree’s volume in board feet can be read from the table on the Tree Scale Stick (Figure 4).
Example: A tree that measures 18 inches d.b.h. and is 3–16 foot logs in merchantable height would contain an estimated 215 board feet of timber.
A board foot is a piece of wood that contains 144 cubic inches, commonly visualized as a piece of wood 12 inches square and 1 inch thick.
It is very difficult to estimate the amount of defect present in a standing tree because the entire defect is not visible. Trees can have a number of defects (knots, holes, branch stubs, or hollows due to past fire or other damage) that can cause all or a portion of the tree to be unusable. Deductions should be made for estimated loss due to these defects. Trees that are over 50 percent defect are commonly labeled “cull” and are often not utilized for lumber. Based on the tree’s apparent defects, use your judgment in making deductions that reduce the volume between 10 and 50 percent.
The amount of cordwood for use as firewood or to be sold as pulp can be estimated using the “Cords Per Tree” table found on the “Log Scale” of the stick (Figure 5).
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| Figure 5. Utilize the “Cords Per Tree” chart to figure the amount of firewood cords in each tree. |
Example: A 20-inch dbh tree that is 60 feet tall contains approximately 0.630 cords of wood.
Most 1/2-ton pickups can hold approximately 1/3 to 1/2 cord of wood depending on how high and how well the wood is stacked. In other words, most pickups haul about a rick of wood.
Considerable variation in solid wood content of a cord may be encountered due to such factors as how tightly the wood is stacked, the diameter of the wood (larger diameters usually stack better), how well the wood is trimmed, and whether it is split or round.
The log scale stick is a tool for use in estimating the volume of logs. Use the following steps to estimate the volume of a log:
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| Figure 6. Use the “Log Scale Stick Doyle Rule” with the “Diameter of Log (inches)” to estimate the volume of board feet in logs. |
Example: A log with an average diameter of 15 inches on the small end (inside bark), and a shortest length of 14'6" would have an estimated volume of 106 board feet (Doyle Rule). If there is a need to take a deduction for defect in this log, it is done in the same manner as for standing trees.
Basal area (B.A.) per acre is a method of expressing forest stand density. It is the sum, in square feet, of the cross-sections of all of the tree stems (at breast height) in an acre of forest. Basal area includes the bark with the wood. In simple terms, basal area is a measure of the level of crowding of trees in a forest, and it is used by foresters to make thinning, harvesting, and other forest management recommendations.
Near the end of the stick on the log scale side (Figure 7) is a 10 factor angle gauge used to estimate basal area. The gauge is the width of the black square. The factor of the gauge is 10 square feet basal area per acre if the stick is held vertically, with the square perpendicular to the line of sight, and at exactly 25 inches from the eye.
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| Figure 7. Basal Area Factor Gauge. |
To estimate basal area at a given location:
To estimate the BA for a forest stand, a number of sample points should be taken, usually a minimum of 10 or at least 1 per acre in large stands. The BA for all sample points should be totaled and averaged to determine an estimate of BA for the stand.
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| Count Tree | Do Not Count | Borderline Tree—counts as 1/2 |
| Figure 8. Using the Basal Area Factor Gauge to determine how crowded your forest is. | ||
All of the tools presented on the scale stick will help woodland owners better understand the forest resources found in their woodlands. This information along with the assistance of a professional forester will help woodland owners make informed decisions about the management of their woodlands.
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Keith L. Smith, Associate Vice President for Agricultural Administration and Director, OSU Extension TDD No. 800-589-8292 (Ohio only) or 614-292-1868