Measuring Trees

Part 2 - Height
- an instrument for measuring
heights (of trees)
 Total
height = height (or stem length)
from ground line to top of terminal bud.
 Merchantable
height = stem length (or
height) from assumed stump height to an
arbitrary, fixed upper-stem diameter (ib
or ob)
 Degree
– reads angle from horizontal for
trigonometric calculations
 Percentage
– reads directly in feet of
height at 100 feet distance (rise/run) (45
degrees equals 100 percent slope)
 Topographic
– reads directly in feet of
height at 66 feet (1 chain or 20 meters)
This is where your pacing or hipchain really comes in handy
Trigonometry of right triangles
a = b(tan A)
Measuring Standing Tree Height
Percentage Scale
Percent slope =
(rise / run) x 100
If distance from tree (D), or
"run" is 100 feet,
The reading from horizontal
to Stump height (A) is 5 feet
and tree height above
the horizontal plane (B) or
"rise" is 80 feet
Total Tree height equals A + B = 85 feet
H = (HT - HB)*(HD/BD)
HT = Height to top (BA)
HB = Height to Base (BC)
• Reading will be negative
• (unless tree above you)
HD = Horizontal Distance
• From person to tree
BD = Base Distance
66 (for topographic scale)
Or 100 (for percent scale)
If you are at scale distance,
This factor (HD/BD) equals 1
and can be ignored
Desired horizontal distance to the
tree = 100 feet
Slope to the tree = 32% (slope
correction needed)
Slope correction factor = 1.05
Taped distance to the tree = 100
feet * 1.05 = 105 feet
The measuring instrument is
moved to a taped distance of 105
Angle to tree base = 4%; Angle to
tree top = 76%
Tree height = 76 feet - 4 feet = 72
Measuring Tools
Line of site limitations, expensive
Degree and Topographic Scales
Degree and Percent Scale
Left scale in
percent at 100
What is the tree
Compensates for angle
Not Limited by Line of Sight like Laser or Optical
Problem Trees
Measure perpendicular to the lean, angling your hypsometer (reads normally)
Can use Pythagorean Theorem to solve
• You measure B normally
(not full tree height)
• To get true bole length
(A), you need angle C
• Then A = B/cos C
height of the stub
length of the piece on
the ground (trigonometry may
be needed)
the two measurements to
obtain total height

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