Clinometer

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Clinometer (forestry)
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A clinometer used in forestry
The clinometer, known in many fields as an inclinometer, is a common tool used in forestry to measure slope, vertical angles, and – in combination with distance measurements – elevation change or tree heights. How it works

A forester using a clinometer makes use of basic trigonometry. First the observer measures a straight-line distance D from some observation point O to the object. Then, using the clinometer, the observer measures the angle a between O and the top of the object. Then the observer does the same for the angle b between O and the bottom of the object. Multiplying D by the tangent of a gives the height of the object above the observer, and by the tangent of b the depth of the object below the observer. Adding the two of course gives the total height (H) of the object, in the same units as D.[1] Note that since multiplication is distributive it is equally valid to add the tangents of the angles and then multiply them by D: A = tan a

B = tan b
H = (A × D) + (B × D) = (A + B) × D
Note also that both angles should be positive numbers (i.e. ignore any minus sign on the clinometer's scale). Units of measure
There are typically three different units of measure that can be marked on a clinometer: degrees, percent, and topo. When buying a clinometer it is important to make sure it is calibrated to units suitable for the intended use. Tree height measurement

Tree height measurement
The forester stands at a fixed distance from the base of the tree. The most common distances in the United States are 50 feet (15.24 m), 66 feet (20.12 m), and 100 feet (30.48 m).[2] To obtain accurate readings it is best to use taped measured distance instead of paced distances. For the most accurate readings it is best to use a distance that is not less than the height of the tree being measured.[3], that is, that the clinometer will measure an...
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