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)
away
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,
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)
• (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
feet

Angle to tree base = 4%; Angle to
tree top = 76%

Tree height = 76 feet - 4 feet = 72
feet
Measuring Tools
Line of site limitations, expensive
Degree and Topographic Scales
Degree and Percent Scale
Left scale in
percent at 100
feet.
What is the tree
height?
Compensates for angle
Not Limited by Line of Sight like Laser or Optical
Problem Trees
Can use Pythagorean Theorem to solve
• You measure B normally
(not full tree height)
• To get true bole length
(A), you need angle C
also
• Then A = B/cos C
Measure
height of the stub
Measure
length of the piece on
the ground (trigonometry may
be needed)