Height
Measuring tree heights using the Master TreeGrower
TapeTotal Tree Height (Ht) refers to the vertical height from
ground level to the tip of the tree. In many cases the grower
may be interested in the height to a particular point, such
as the pruned height (PHt) or the height to an obvious defect.
In any event, the same measuring techniques can be used.
The height of young trees, up to six metres,
is easy to measure with a height measuring pole or a simple
plastic plumbing pipe marked at 0.1 metre intervals. But,
as trees grow, measuring their heights becomes increasingly
difficult. Although foresters use a number of expensive optical
and laser tools to measure heights, it is possible to use
very simple and cheap tools. Extra care is required when measuring
leaning trees.
Measuring height with a tape or ruler
This technique requires two people. One person
with the tape needs to stand well back at a point approximately
equal to the height of the tree. The second person needs to
stand at the base of the tree. The first person, holding the
tape vertically out in front, closes one eye and looks past
the tape so that the tree appears next to the rule. It is
important to ensure the tape is vertical. For greater accuracy
a level and ruler could be used. The tape should be moved
so that the "0" point on the rule corresponds to
the base of the tree. The apparent height to the top (or any
other point) of the tree can then be measured. The person
standing beside the tree should move their hand up or down
the stem, to the point that corresponds to 10% of the total
"apparent" height. Clearly this point on the tree
will correspond to 10% of the total tree height. The first
person then returns to the tree and measures the height from
the base to the second person's mark on the tree. The total
tree height is simply this height multiplied by 10.
For heights of less than 10 metres, the operator
should use a point that is 20% (one 5th of the apparent height)
of tree height rather than 10%. For very tall trees, over
25 metres, they might find they need to use 5% (one 20th of
total tree height).This technique simply involves the projection
of two triangles of proportional dimension as shown in the
figure below. There is no need to know how far away the operator
is from the tree or to worry about sloping land. Geometrically
the technique is accurate.
Measuring tree height with a tape or ruler
Precautions
To be effective, care must be taken to ensure
that:
 The tape is held vertically at arms length
(the tape should be let hang momentarily before being pulled
tight and sighting).
 When sighting it is important for the operator
not to move their head. Standing well back from the tree
it should be possible to sight the top and bottom of the
tree without moving one’s head.
 Careful note should be taken of the bottom
of the tree so the vertical measure on the tree is made
from the same point. It may be helpful to have the second
person mark the basepoint with their foot and for the operator
to sight their boot.
Other height measurement techniques
Measuring tree height using a Clinometer.
There is a range of expensive tools available
to estimate tree height. The most common is the Clinometer
which measures angles and allows the operator to determine
the height of a tree once the horizontal distance to the base
of the tree is known. Laser tools that can accurately determine
distance and angle are also becoming more common in forestry.
The advantage of these tools is that they reduce the likelihood
of operator error and speed up the procedure, but they are
expensive.
Back to top
