The task is to measure the height of a tree at a distance of 25 m / 82 ft. on level ground. The instrument is tilted so that the hair line is seen against the
obtained will be 48 per cent (ca
25.5°). As the distance is 25 m / 82 ft. the height of the tree is 48 / 100 x 25 m = ca. 12 m or equally 48 / 100 x 25 m = ca. 12
m or equally 48 / 100 x 82 ft. = ca. 39 ft. To this must be added the eye’s height from the ground, e.g. 1.6 m or 5 ½ ft.
Their sum is 13.6 m or 44 ½ ft,
the height of the tree.
In very exact measurements, and particularly on sloping ground two readings are taken,
one to the top, the other to the base of the trunk. When the trunk base is below eye level the percentages obtained are added. The total height is the sum percentage of the horizontal distance. For example, it the apex reading is 41 % and the ground reading 13 %, the total height of the tree measured from a distance of 25 m / 82 ft. is (41 + 13) / 100 x 25 m = 54 / 100 x 25 m = ca. 13.5 m or equally in feet (41 + 13) / 100 x 82 ft = 54 / 100 x 82 ft = ca. 44 ½ ft.
11
