exactly correct result you have to proceed as stated below. On level ground, the tree top readings is usually sufficient: one only has to add the height of the observer`s eye level (1.60 m in this case), which is already known.
INSTRUCTIONS FOR USE OF
NOMOGRAM
If the distance, because of very uneven ground, cannot de determined horizontally as stated above, the nomogram on page 7 should be used.
ESTABLISHING THE BASIC DISTANCE
Because this instrument does not incorporate a prism, the basic distance e.g. 15 m has to be determined using a tape measure along the ground. Take the top and base readings and add or subtract them to get the apparent height. On the nomogram on page 7, locate the apparent height on the right hand scale. On the double scale on the left, locate the reading obtained from sighting the base of the tree. Note that readings for falling and rising gradients should be taken from different sides of the scale. Connect these two points of the nomogram with a straight line. The centre scale of the nomogram now indicates the true height of the tree.
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