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Measuring Trees. Part 2 - Height. Hypsometer. - an instrument for measuring heights (of trees). Tree Heights. Total height = height (or stem length) from ground line to top of terminal bud .
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Measuring Trees Part 2 - Height
Hypsometer - an instrument for measuring heights (of trees)
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)
Scales of Measure This is where your pacing or hipchain really comes in handy 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
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
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
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
Tree Heights Measuring Tools
Laser Hypsometers Line of site limitations, expensive
Suunto Clinometer Degree and Topographic Scales
Suunto Clinometer Degree and Percent Scale
Tree Height Left scale in percent at 100 feet. What is the tree height?
Upper Stem Diameter Compensates for angle
Ultrasonic Not Limited by Line of Sight like Laser or Optical
Measuring Tree Height Review Show General Formula Slide Show iTunesU video Show iHypsometer App Questions so far?
Measuring Tree Heights Problem Trees
Leaning Trees Measure perpendicular to the lean, angling your hypsometer (reads normally)
Measured from the direction of the lean Can use Pythagorean Theorem to solve
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
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