How to Measure Height of Trees 



AN instrument for measuring the heights of trees can 

 easily be made at practically no cost. Take a piece of 

 ' half-inch board 7 by 9 inches and plane it smooth on 

 all sides. Draw the line AB }i of an inch from the lower 

 edge and parallel to it. Two inches from the left end of 

 the board draw CD at right angles to AB. Make a mark 

 at /:. 6' 4 inches from D, and another at F, 2> l /% inches 

 from D. Now draw a line JK through F parallel to AB. 

 Start at D, lay off inches and quarter inches on AB in 

 both directions, marking D as zero and putting down the 

 number of inches from D to each inch mark. Do the same 

 for the line JK. Take a brad or small nail and drive it in 

 carefully on the hne JK about an inch from the edge of 

 the board. Drive it in until the point comes out on the 

 back of the board ; then pull it out 

 and drive it in from the back until 

 the point sticks out about one-fourth 

 inch from the face of 

 the board. File off 

 or cut off with pliers 

 any part of the brad 

 that projects from the 

 back of the board. 

 In the same way in- 

 sert another brad 

 near the other end of 

 the line JK. These 



How to use it. To measure the total height of a tree, 

 stand at a distance of 100 feet from it and hold the 

 instrument in the right hand in such a way that the 

 pendulum swings freely but very near the board. Sight 

 along the brads at the top of the tree and let the pendulum 

 come to rest. Then with the left hand press the pendu- 

 lum against the board without giving it a chance to change 

 its position. Now read off the number of feet in height 

 on the lower scale. If the wire crosses the line 5 inches 

 from the point D, it indicates that the tree is five 16-foot 

 logs or 80 feet high above the level of the eye. Now 

 sight at the foot of the tree and take another reading. 

 If the pendulum hangs to the left of D, that is, between 

 A and D, add the amount indicated to the first reading, 

 and the result will be the total height of the tree. Thus, 

 if it hangs half an inch to the left of D, add half a log or 

 8 feet to the first reading, making a total of 5y 2 logs, or 88 



feet. But if the eye is below 

 the foot of the tree, the wire 

 will hang to the right of D 

 (between D and B) and then 

 the amount of the second 

 reading should be subtracted 

 from the amount of the first. 

 Thus, if the first reading is 

 96 feet and the second is 12 

 feet (to the right of D), the 

 total height of the tree will be 

 96 less 12, or 84 feet. If the 

 *"-. tree is less than about 75 feet 



A SIMPLE HOME-MADE INSTRUMENT FOR MEASURING HEIGHTS CF TREES 



brads are the sights, and it is important that they be 

 straight and true. 



Now take a piece of straight, heavy wire 10 inches 

 long, and bend one end of it into a loop about an eighth 

 of an inch in diameter. The center of the loop should be 

 in line with the straight part of the wire. Fasten this 

 piece of wire loosely to the board at E with a half-inch 

 screw, so that it will swing freely when the board is on 

 edge. The loop should be big enough to fit loosely over 

 the shank of the screw, but small enough so that it will 

 not slip off over the head. 



Screw a piece of wood about 6 inches long, 1 inch wide, 

 and half an inch thick to the back of the board to serve as 

 a handle, and the height measure is complete. 

 618 



high, or if it is difficult to see 



the top at a distance of 100' 



feet, the observer should 



stand 50 feet from the tree,. 



but in this case the readings- 



are on the line JK. 



When the instrument is sighted the pendulum can be 



kept in position by tilting the hand slightly to the right. 



This brings the wire against the board and holds it in 



place so that a reading can be obtained. Care should be 



taken, however, so that the wire will not slip after 



the board is tilted. 



In the example given, the total height of the tree has. 

 been measured. It is often of more practical importance 

 to measure the height to a point on the tree beyond which 

 there is no merchantable saw timber. This measurement 

 is made in the same way as that described above, except 

 that the instrument is pointed at what will be the top of 

 the last log when the tree is cut, and then at the point 

 where the top of the stump will be. Farmers' Bulletin 715.. 



