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Used to measure diameter at breast height

(DBH) of a tree

  • DBH is a standard forestry measurement that is

taken 1.37m (4.5 ft) up from the ground, approximately breast height for most people.

  • Unless otherwise stated all tree diameters refer to measurements taken at breast height.

Process of measuring tree diameter is as follows:

1. locate height of tree 1.4m off the ground.

2. use hook at end of diameter tape to grasp into bark of tree.

3. walking around the tree, measure tree diameter, ensuring to keep the tape straight all the way around the tree.

4. record the measurement to the nearest millimetre.

Tree calipers can also be used for quick and accurate measurements of tree diameters.

1. hold calipers at DBH and ensure both sides of caliper are tight against the stem.

2. record the reading.

3. In some cases 2 measurements may be recorded and an average taken as not all trees grow in a perfect circle, many trees produce reaction wood resulting in oblong shapes.

Look into the lens while looking

at the tree

You should see several number scales

  • in this case a 20m and 15m scale
  • ensure you are reading the proper scale

"-" numbers on this side of zero

"0" indicates you are looking directly straight in front of you

different numbers represent different scales

1:20: Stand 20 metres away from base of tree

1:15: Stand 15 metres away from base of tree

"+" numbers on this side of zero

horizontal crosshair

Tree Measuring Tools

Clinometer, Calipers, Diameter Tape

Math formula to find tree height:

a-b=tree height in metres.

  • where (a)= top of tree reading
  • where (b)= bottom of tree reading

Example:

We want to know the height of this

beautiful Dawn-Redwood

  • Using 1 eye to view through the lens of the

Suunto, locate the horizontal cross hair line.

  • Use your other eye line up the cross hair with the top of the tree.
  • Read the number that is represented at the crosshair.

top reading is + 18

remember to project your sight

through the canopy to the highest

point (if necessary)

remember: if standing on level ground a bottom reading of "0"would read approximately at eye level up on the tree

Calculations:

formula: a-b= tree ht.

18-(-1.5)

=18+1.5

=19.5

Therefore the height of the tree

is 19.5 metres.

bottom reading is -1.5

  • Repeat the same process to take a

reading at the base of the tree, where

the trunk meets the ground.

  • Make sure to locate if the number is "-" or "+".

using 1:20 scale.

(we have measured 20m on

the ground from the base of the tree

to take the reading).

2 sided: Back side is standard metric tape (decimetres).

Front side appears as imperial tape (inches) but it is not! It has done the math by measuring circumference and converting to a diameter measurement

A standard tape measure would be measuring circumference, however we want to know DIAMETER

Therefore Circumference/3.14 (Pi) has already been done to save us a step.

www.georgiacountry.com

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