Beacon Lesson Plan Library

Measuring the Merchantable Height of a Tree

Jacqueline Roberts
Bay District Schools


In this activity, students learn techniques that determine the merchantable height of a tree and the number of logs a tree provides.


Uses concrete and graphic models to derive formulas for finding perimeter, area, surface area, circumference, and volume of two- and three- dimensional shapes including rectangular solids, cylinders, cones and pyramids.

Solves real-world and mathematical problems involving estimates of measurements including length, time, weight/mass, temperature, money, perimeter, area, volume, and estimates the effects of measurement errors on calculations.

Determines the level of accuracy and precision, including absolute and relative errors or tolerance, required in real-world measurement situations.

Selects and uses appropriate instruments, technology, and techniques to measure quantities in order to achieve specified degrees of accuracy in a problem situation.


-Biltmore Stick with Hypsometer
-Tape measure
-Area to do the activity
-Copies of Tree Measurement Attachment, Diagram of Hypsometer Scale, Data Sheet, Rubrics (one per student)(see associated file)

Helpful Resources:
Florida Division of Forestry - Education Department
715 W. 15th Street
Panama City, Florida

INTRODUCTION TO FORESTRY IN FLORIDA, Florida Department of Agriculture and Consumer Services, Division of Forestry Service, Tallahassee, Florida.

FLORIDA'S FOREST FACTS, Florida Division of Forestry, pamphlet


1. Make copies of the documents in the associated file for students. 2. Determine where students will complete the activities and mark trees.

Be prepared to:
1. Review Pacing.
2. Review Gunther Chain.
3. Review use of Hypsometer.
4. Review definition of merchantable height.
5. Review definition of pulpwood and sawtimber.
6. Review uses of pulpwood (paper products).
7. Review uses of sawtimber (lumber).
8. Review definition of "eyeball" observation.
9. Review margin of error and importance of accurate estimations.


(Note: The associated file contains information which may be helpful in determining some of the information below.)

(Note: Share the handouts and rubrics with students prior to beginning this lesson. Students will need to understand how they will be assessed before beginning the activity. Once they have complete understanding, then begin the activity.)

(Note: As with the other lessons in this unit, be sure to use the vocabulary found in the first lesson of this unit called Wanted Dead or Alive....How Big Is It? By now, students should know the definitions and be able to use them accurately as they are completing the activities.)

Conduct a review of the previous lessons in this unit. Make sure each student:

1. Understands merchantable tree height is the upper limit of usable wood on a tree stem.

2. Understands that measurement of tree height is accomplished with a Merrit Hypsometer Scale which is found on a Biltmore Stick.

3. Understands that the Hypsometer is -ruler-like- in that it has increments numbering from 1 through 5. Each increment represents a sixteen foot log.

4. Understands how to -sight - height with a Hypsometer. (Continue reading for guidance.)

5. Understands how to pace a Gunther Chain.

6. Understands that to use the Hypsometer requires an individual pace a Gunther Chain (66ft) away from the tree.

7. Understands the uses of sawtimber.

8. Understands the uses of pulpwood.

9. Understands circumference.

10. Understands diameter.

11. Understands the forest industry's standard of measurement for diameter is at breast height.

12. Understands that when measuring for sawtimber an "eyeball" observation is made to determine where the upper most limit of the stem is 8 inches in diameter

13. Understands that when measuring for pulpwood an "eyeball observation is made to determine where the upper most limit of the stem is 4 inches in diameter.

14. Understands that the hypsometer must be held upright and at a distance of twenty-five inches away from the body. (This is approximately an arm length.)

15. Understands that to measure accurately the base of the hypsometer must be aligned with the bottom or base of the tree.

16. Understands that the scale is read to location (height) of ocular estimation previously established.

17. Understands the concept of margin of error.

For the remainder of the time, students demonstrate their knowledge through laboratory assessment and oral presentation. Explain the following steps and make sure students know what to do.

STUDENT ACTIVITY: (Show students the rubric prior to beginning this activity.)
1. Student works with a partner to complete this activity. (See associated file)

2. Students measure the circumference of a tree at breast height.

3. Students record this on Data Sheet. (See Associated File)

4. Students divide circumference by 3.14 (Pi) to establish diameter.

5. Students record diameter on data sheet.

6. Students then determine if the tree is sawtimber or pulpwood and record this information on the data sheet.

7. Students pace a Gunther Chain (66 ft.) away from the tree. Student maintains clear sight of base and top of the tree at the end of paced chain.

8. Students estimate the merchantable height of the tree and record on data sheet.

9. Student estimates how many 16 foot logs the tree could produce.

10. Students estimate location at the top of the tree where the diameter might be 4 inches if measuring pulpwood or 8 inches if measuring saw timber.

11. Student hold Hypsometer directly in front of the body and twenty-five inches away from the body. (Twenty-five inches is approximately arm's length.)

12. Student maintains alignment of Hypsometer. The stick should be even with the base or bottom of the tree.

13. Student holds the Hypsometer steady, sighting the stick upward to the point student previously established as merchantable top of tree.

14. Student reads Hypsometer scale and records to the nearest stick of pulpwood or sawtimber.

15. Student converts the number of sticks to merchantable height and records data.

16. Student compares his personal estimate with the measurement taken with the Hypsometer and records margin of error data.

17. Student shares his findings with the class.


Formativley assess students' work and oral presentations by using the
Oral Presentation and Lab Rubrics located in the associated file. This lesson does not assess all of MAB. 1.4.1 (cones and pyramids). Students may need feedback, reteaching, and additional practice since these skills are covered on the summative assessments.


The Beacon Unit Plan associated with this lesson can be viewed by clicking on the link located at the top of this page or by using the following URL: Once you select the unit’s link, scroll to the bottom of the unit plan page to find the section, “Associated Files.” This section contains links to the Unit Plan Overview, Diagnostic and Summative Assessments, and other associated files (if any).

Web Links

Web supplement for Measuring the Merchantable Height of a Tree
Florida Forests Forever

Obtain all needed information for the unit, including assessments, lessons, and file attachments.
Wanted Dead or Alive

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