# SCIN135 Lab1

Forest Mensuration Techniques

For this lab you will need a tree, a yardstick (a measuring tape may also help), paper and pencil, this worksheet, and a stick of any sort. If you do not have a tree (desert deployment, etc.) you may use any tall object – a building, flagpole, utility pole, etc. The principles remain the same. You are to complete 3 exercises (I, II, & IIIa or IIIb)– each measures trees using variations on the same technique. Download this lab sheet to your computer and fill in the answers. Then use the worksheet to complete the Lab 2 assignment under Tests and Quizzes. Answer the set of questions following each exercise.

If you do not get a sunny day where you are located, please use Exercise IIIb below as an alternative to Exercise IIIa. Otherwise, you MUST do Exercise IIIa. Be SAFE and do not measure trees if thunderstorms are nearby.

USE THE SAME TREE FOR ALL THREE EXERCISES.

USE THE SAME TREE FOR ALL THREE EXERCISES.

I. Tree Height Measurement by Michael Kuhns, Extension Forestry Specialist You can measure heights of very tall objects such as trees by projecting a right triangle (one that includes a 90 degree angle) using your arm, a stick, and your line-of sight. Material: A stick that is equal in length to the distance from your eye (cheekbone) to your fingers when your arm is fully extended in front of your face. Break off part of the stick or mark it at the correct length if you don't find one that is exactly right. Procedure:

1. Grasp the stick by the tips of the thumb and index finger and hold it out in front of you with your arm fully extended. The stick must be held vertical. 2. Walk toward or away from the tree until the tip of the stick is visually lined up with the top of the tree and the bottom of the stick is lined up with the bottom of the tree. Your line of sight to the tree base should be as close as possible to horizontal. In sighting to the top and bottom of the stick rotate your eye rather than your head. 3. The distance from your eye to the base of the tree is equal to the height of the tree. Measure this distance with a measuring tape. If no long-distance measuring device is available, calibrate your step (the walking distance between your two feet--walk normal, don't stretch) or pace (walking distance for two steps) over a known distance (say 50 feet). Then measure the distance A-D in paces or steps and convert to feet, meters, etc.

Answer the following questions:

1. What was the length of the stick you used to help measure the tree?

2. What was the distance from you to the base of the tree?

3. How did you measure the distance from you to the base of the tree (e.g. paces, yardstick, tape measure, etc.)?

4. How tall did you calculate the tree to be?

5. What are possible sources of error with this technique?

II. Tree Height Measurement by Bizarre Labs:

The heights of trees (or any other tall object) can easily be found using a device called hypsometer. A hypsometer is basically a long stick divided into even units used to find height by triangulation.* A yardstick or meter stick will work just fine. http://bizarrelabs.com/tree.htm

Material: A yardstick

Procedure:

1. If you are using a yardstick, stand exactly 25 feet from the tree being measured. Hold the yardstick, with the zero ends downward, 25 inches from your eye. Line up the bottom of the yardstick with the base of the tree. Without moving your head, look to the top of the tree. Where it crosses the yardstick, read off the measurement in inches. Each inch will equal one foot in the tree's height. 2. If the tree is taller than your hypsometer will measure, stand 50 feet away. Again hold it 25 inches from your eye, as before, only this time multiply your result by 2 to get the correct height. If it is taller still, then step back to 75 feet, multiplying your result by 3, or 100 feet, multiplying the result...

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