Measuring Height of Trees
When each tree is to be measured separately two assistants will be required, one to carry the 18-ft. pole, and the other the girting-strap. Sometimes, when the timber is of great height, jointed bamboos are used, and a light ladder brought into requisition.
In carrying out the work in this way, the man with the pole declares the height of the tree, and the one with the tape the quarter-girth.
Measuring the Height of Trees.—There are several methods of ascertaining the heights of trees, but the two following are, perhaps, the most simple, and the appliances necessary quite inexpensive:—
No 1.—Take three laths, such as bricklayers use for tiling, and nail them in the shape of the frame shown; a a must be of equal length; a and b being placed on the ground, the eye must follow up the larger lath d d until it is in a line with e, the top of the tree or object you wish to measure.
The frame must be placed as level with the bottom of the tree as possible. Should the ground be very uneven you must give and take accordingly.
It will be seen that b to c is the same length as c to e, and this gives the height of the tree.
No 2.—Suspend the triangle between the thumb and forefinger of the left hand, knuckles down, upon the point a a, allowing it to swing freely. The edge b c will then fall perpendicularly, and c d will be horizontal. The remaining edge d b will then lie at an angle of 45 to the horizon. On this edge are two sights, e and f. Look through e until f is aligned with the tree-top, advancing or retiring till the sights point exactly to it.
Then, if the observer’s feet are level with the tree root, the height of the tree is the distance from his feet to the root, plus the height of the eye from the ground.
The dendrometer is perhaps the most useful instrument for taking the height of a tree and can be procured from some of our nurserymen.