• [Trigonomentric approaches]
• [Geometric approaches]

• [Ranking]

• Measurement techniques

Abney Level: An engineering instrument that can be used to determine height. Degrees or percentage slope are read from the scale.

It is moderately expensive and of medium size and weight. The Abney Level is relatively robust but the bubble tube can be knocked out of alignment. Periodic checking of alignment by siting and back sighting to a reference height is needed.

Blume Leiss: A height measuring instrument of medium size and weight. It is robust and only moderately expensive.

Heights above and below the observer's eye can be read directly from the scale if the observer is 15, 20, 30 or 40 m from the tree.

Haga: A height measuring instrument of medium size and weight. It is robust and only moderately expensive.

Heights above and below the observer's eye can be read directly from the scale if the observer is 15, 20, 25 or 30 m from the tree. The appropriate scale can be selected by rotating the selection dial at the front of the instrument.

Spiegel Relaskop (Relascope): Commonly referred to as a Relaskop. A sophisticated, compact and robust device for measuring range, tree height and diameter, and stand parameters. It is relatively expensive.

Heights can be read from an internal scale if the user is 20, 25 or 30 m from the tree. However, there are a number of scales visible and novice users are often confused by the apparent reading complexity.

Suunto Clinometer: A small, light, robust and inexpensive instrument for measuring height. An internal scale normally indicates percentage slope. Height above or below the operator is calculated by multiplying the percentage slope by the distance from the tree. Thus, there is no fixed distance for common use.

Some people experience difficulties sighting through the Suunto. You must look into the Suunto while simultaneously sighting along side it to see the tree. Particular care is needed if the operator suffers from astigmatism.

Telerelaskop: A research quality instrument that is no longer in production. The Telereskop is similar in principle to the [Relaskop] except that it includes 5 x optical magnification.

Vertex: A height and range measuring instrument of medium size and weight. It is robust and only moderately expensive. A transponder (temporarily attached to the tree at breast height) and the hand unit use sonic pulses to determine range from the tree. The hand unit contains an angle reading device and a simple computer chip to calculate height above the transponder.

Care is needed on leaning trees. A transponder attached to a tree bole on a leaning tree will result and a biased estimate of tree height unless the lean is exactly at 90^o to the observer. Some problems have also been reported with environmental sounds (e.g. crickets in Tasmania) interfering with the sonic pulses.

Criterion Laser: A heavy height, diameter and range measuring instrument. The Criterion uses laser light to determine distance from a tree. A built in angle reader and a simple computer chip calculates tree height.

LEM-300: A relatively heavy height, diameter and range measuring instrument. The LEM uses laser light to determine distance from a tree. A built in angle reader and a simple computer chip calculates tree height.

Indirect measurement of height using geometric principles

The bottle-opener dendrometer: A very cheap instrument for estimating height and some stand parameters. Working on the principle of similar triangles, you hold the dendrometer between you and the tree and move back or forwards until the tree appears to lie exactly between the top and bottom overhangs on the left side. The point that corresponds to a mark one-tenth up the left side of the dendrometer is then identified on the tree. The height from the ground to the identified mark is multiplied by 10 to determine the total tree height.

JAL: A more precise tool for applying geometric principles to measuring tree height. It is widely used in Europe but is not found in Australia.