Forest Mensuration. Brack and Wood


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Height sticks (rods):
Measuring tree height©


Height sticks provide a direct method for measuring tree height. Height sticks are the most reliable instrument for measuring tree height with an instrument error less than l%.

Each stick is usually l.5 m long and constructed of tubular duralumin or fibreglass. A base stick is typically, l.5 m in length, and graduated in decimeters. Some sticks have a locking device which makes them safer but dearer and slower. Use of height sticks is generally confined to forests less than 25 m tall (although experienced users may successfully use sticks in forests up to 30 m). Use of height sticks is rare in native hardwood forests where the clear boles offer little support.

General instructions

  1. Team size: 3 persons.
    • l booker / observer: stands well away from tree but keeps in constant contact with the stick person. Must have a clear view of the sticks as they are fed up the tree and warn of any danger, eg falling cones.
    • l stick person: feeds the sticks up the tree. Attempts to keep the sticks safely against the tree trunk and branced by branches where possible.
    • l assistant: puts the sticks into the stick person's hands so that person does not need to take concentration away from feeding the sticks up the tree. The assistant with the sticks must stand close beside the stick person and hand over (and retrieve) the sticks from him/her in a manner similar to that of a scalpel being passed between a nurse and surgeon. The stick person should be looking upwards most of the time.
  2. Before commencing to measure the height of a tree, quickly observe its branching habit and other features and choose a position for erecting the sticks which will facilitate the measuring process. Do not erect the sticks from a position at which you will face into the sun.

    • With leaning trees that have self corrected, erect the sticks from a position directly below the point of correction.
    • For trees that have not corrected, attempt to lay the sticks along the upper side of the stem.
    • Keep the centre of gravity of the sticks between your person and the tree. This is essential to prevent the sticks falling out of the tree.
  3. The sticks are fed up the tree. Count the sticks as they are fed up the tree.
    • If upward movement of the sticks is impeded by a branch or cone, simultaneously shake the sticks laterally and push upwards to guide the tip onto a new path.
    • Whenever pressure is felt when pushing up the sticks, stop, retrieve at least one stick and seek a new path before proceeding further.
    • To correct sticks which begin to splay outwards on the side of the tree opposite to the stick person, retrieve several sticks, move closer to the tree and re-erect the sticks.
    • To correct sticks which begin to splay outwards behind the stick person, retrieve several sticks, move back 30 to 100 cm from the tree base, hold the basal sticks vertical and proceed to re-erect the sticks.
    • If the sticks splay to the point where they begin to fall out of the tree, do not fight them but guide them down so that they fall flat on the ground.
  4. The observer finds a position at right angles to plane of tree bole and upper set of sticks to avoid parallax error as the tree approaches the tip.
  5. Place the graduated pole against the base of the tree and record the measurement when the height sticks have reached the tip of the tree.
  6. Count the number of height sticks as they are retracted - to ensure no mistakes were made and to ensure none are left hanging in the tree.
    • Keep the feet well apart and the sticks immediately in front of you. Either let the sticks slide through your hands and clamp and retrieve the sections one by one or retrieve them hand over hand. Allow the detached stick to fall into the waiting hands of the assistant.
    • Right-handed persons should hold the right hand high and remove the bottom stick with the left hand. The converse applies to left-handed persons.
    • Do not jerk or pull the sticks suddenly downwards. Retrieve smoothly. If pressure is felt during retrieval proceed very cautiously until release is felt. If the sticks suddenly feel light, they have probably parted. If this happens, do not panic. The assistant should move to a safe place away from the tree base while the stick person attempts to reconnect the sticks. Should this cause the parted stick(s) up the tree to fall, the stick person should drop everything and move rapidly to the opposite side of the tree and away from it.

    Warnings and notes

    Watch out for falling cones. Should you be aware that a cone has been dislodged, do not move and do not look upwards. Stand erect with shoulders hunched and head inclined slightly forward until the cone hits the ground.

    Only experienced people (in the use of height sticks) or persons in training should be permitted to use height sticks. Do not attempt to measure trees greater than 20 m in height until you are experienced.

    Do not use height sticks in strong winds.

    A crew of two persons is permissible when measuring trees less than 10 metres in height, but for trees higher than 10 m, a 3-person crew comprising a stick person, assistant and recorder is essential.

    Hard hats must be worn always.

    Field boots preferably should have a steel toe cap.

    When many trees are being measured, protective glasses should be worn to prevent pine needles and other dislodged debris from lodging in the eye.

    Proper maintenance of height sticks is important to crew safety. Sticks, particularly the ferrules, should be cleaned after each day's use and thoroughly checked each season for straightness and "smooth action".

    While sticks are being hoisted, distractions such as chatting must be avoided. Concentration is essential to crew safety.

    The recorder must be alert and active at all times. It is his/her duty to follow the progress of the sticks up the tree from a favourable viewing position and warn the stick person and assistant when the tip of the sticks begins to splay and when cones are dislodged. (This is apart from the recorder's other roles of recording data and ensuring parallax error is minimised.)

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    http://online.anu.edu.au/Forestry/mensuration/HGTSTICK.HTM
    Cris.Brack@anu.edu.au
    Fri, 6 Jun. 1997