Measuring Forest Trees Height

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Measuring Forest Trees Height
JWAN M. ALDOSKI Geospatial Information Science
Research Center (GISRC), Faculty of Engineering,
Universiti Putra Malaysia, 43400 UPM Serdang,
Selangor Darul Ehsan. Malaysia.
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Hypsometer

• - an instrument for measuring heights (of trees)

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Tree Heights

• 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)

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Scales of Measure

• 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
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Trigonometry of right triangles
a b(tan A)
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Measuring Height with degrees
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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
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General Formula

• 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

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Sloping Plots
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Trigonometry of slope correction
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Slope Correction
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Slope Correction

• 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

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Tree Heights

• Measuring Tools

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Abney Level
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Blume-Leiss Altimeter
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Haga Altimeter
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Laser Hypsometers
Line of site limitations, expensive
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Measuring Rod
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Merritt Hypsometer
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Merritt Hypsometer Make your own
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Look Ma! - No Tools
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Suunto Clinometer
Degree and Topographic Scales
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Suunto Clinometer
Degree and Percent Scale
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Clinometer on the cheap
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Clinometer Toys
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Spiegel Relaskop
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Tree Height
Left scale in percent at 100 feet. What is the
tree height?
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Upper Stem Diameter
Compensates for angle
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Ultrasonic
Not Limited by Line of Sight like Laser or Optical
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Apps
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iHypsometer Lite
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Merchantable height

• A normal trees merchantability stops at the
  narrowest diameter that the lumber mill can
  handle
• This is usually 4 to 6 inches

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Vertical Limits to Merchantability

• Stoppers are occurrences in the tree that can not
  be productively sawn through and limit the length
  of a potential log section.

• Forks that are at least 1/3 diameter of main bole
  at point of occurrence and 45 degrees or less in
  angle from the main bole.
• Branches, stubs, remnant bumps. ½ diameter of
  main stem.
• Any embedded metal excluding aluminum.
• Sudden dramatic change in bole diameter

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Measuring Tree Heights

• Problem Trees

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Leaning Trees
Measure perpendicular to the lean, angling your
hypsometer (reads normally)
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Measured from the direction of the lean
Can use Pythagorean Theorem to solve
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Conversely

• You measure B normally (not full tree height)
• To get true bole length (A), you need angle C
  also
• Then A B/cos C

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Avoid this mistake
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Irregular Stems
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Broken Tree

• Measure height of the stub
• Measure length of the piece on the ground
  (trigonometry may be needed)
• Add the two measurements to obtain total height

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Recap and Questions