How Trees are Measured 



distance between the poles, the distance between the short pole 

 and the tree, and the distance between the two marks on the tall 

 pole. Suppose the marks on the pole to be six feet apart, the 

 poles five feet apart, and the short pole forty feet from the tree. 

 Then we have two similar triangles and a proportion with three 

 known quantities. The distance between the poles is to the 

 distance from the short pole to the tree as the distance between 

 the marks on the tall pole is to height of the tree. 5 : 40 :: 6 : x. 



Solved, =48. The tree is forty-eight feet high. 



A fourth method involves a right-angled isosceles triangle 

 and a plumb line, but it is extremely simple, and is in common 

 use by men who go out to estimate standing timber in terms 

 of board measure. Take a square of pasteboard or shingle, and 

 cut it in two diagonally. One of these halves is your tool. To 

 the square corner hang a plumb line — a string with a weight 

 attached — to indicate when you hold the triangle so that its 

 sides are exactly vertical and horizontal. Sight along the diagonal, 

 stepping backward or forward until the top of the tree is in line 

 with the diagonal and your eye. Now sight along the horizontal 

 base line of the triangle to get the point on the tree trunk at the 

 height of your eye. The tree's height above this point is 

 equal to your distance from the tree, for it is one base of 

 an isosceles right-angled triangle similar to your tool. Pace 

 the distance to the tree, add your height, and you have 

 the tree's height. In this method of measurement, level 

 ground is necessary to the amateur. The practised eye makes 

 due allowance for inequalities, which must be taken as they 

 come in the woods. 



The Faustman "mirror hypsometer" is a clever little instru- 

 ment by which the observer may get the height of trees by simply 

 pacing the distance from its base to the point where the treetop 

 is in line with an eye piece and a hair line set six inches away. 

 The treetop appears to. the observer, a slide is moved up to the 

 figure corresponding to the distance, a plummet swings over a 

 scale, and the figure it covers, reflected by a mirror to the observer's 

 eye, is the tree's height. This convenient tool does away with 

 computations, and enables the user to accomplish much in a 

 short time. 



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