6
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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