Tools for Measuring Tree Height

Following are the most common tools for Tree Height Measurement. This list is alphabetical. Different tools have different pros and cons, and also their price is an important determiner.
At the end of the post, you will see a table that shows you which is the best instrument under what conditions.

Abney Level:

The Abney Level is an engineering instrument which can be used to determine height. It is moderately expensive and of medium size and weight. Although the Abney Level is relatively robust, the bubble tube can be knocked out of alignment during rough treatment.
When used correctly, the Abney Level has an accuracy of about +/- 0.5 m for a 20 m tall tree (ie about 2.5%).

1. Measure the horizontal distance from the base of a vertical tree (or the position directly beneath the tree tip of a leaning tree) to a location where the required point on the tree (e.g. tree tip) can be seen.
2. Sight at the required point and move the index arm over the scale until the bubble tube is level.
3. Read the percentage scale (or the degrees and minutes of the angle).
4. Calculate the height by multiplying the percentage read by the horizontal distance (or by multiplying the horizontal distance by Tan of the angle).
5. Site to the base of the tree and repeat steps 2 – 4.
6. Combine the heights from steps 4 and 5 to determine total tree height:
   • Add the 2 heights together if you looked up to the required point in step 2 and down to the base of the tree in step 5.
   • Subtract the height to the base of the tree from the height to the required point if you are on the sloping ground and had to look up to both the required point and the base of the tree.
7. Check all readings and calculations.

Blume Leiss:

The Blume Leiss is a height measuring instrument of medium size and weight. It is robust and moderately expensive.
When used correctly, the Blume Leiss has an accuracy of about +/- 0.5 m for a 20 m tall tree (ie about 2.5%).

1. Select a location, preferably 15, 20, 30 or 40 meters horizontal distance from the base of a vertical tree (or the position directly beneath the tree tip of a leaning tree) where the required point on the tree (e.g. tree tip) can be seen.
2. Release the pointer by pressing the button on the side of the instrument.
3. The sight at the required point on the tree, wait for a moment for the pointer to settle then pull the trigger.
4. Read the height directly from the appropriate scale if you are 15, 20, 30, or 40 meters away from the tree. If you were unable to find a position at one of these distances:
   • If the horizontal distance is a simple fraction of one of the scale distances (e.g. 10 m is half of 20 m), read from the scale distance and multiply by the appropriate fraction.
   • Read from the percent scale and multiply this percentage by the horizontal distance measured in step 1.
5. Site to the base of the tree and repeat steps 2 – 4.
6. Combine the heights from steps 4 and 5 to determine total tree height:
   • Add the 2 heights together if you looked up to the required point in step 2 and down to the base of the tree in step 5.
   • Subtract the height to the base of the tree from the height to the required point if you are on the sloping ground and had to look up to both the required point and the base of the tree.
7. Check all readings and calculations.

‘Bottle Opener’ Dendrometer

The Dendrometer II – nicknamed the Bottle opener because of its looks – is a cheap instrument to measure tree height, stand basal area using Basal Area Factors of 1, 2, or 4 and estimate volume.
Due to difficulties aligning the tree and ensuring that the instrument is at the correct distance and angle, accuracy is relatively poor. No better than an accuracy of about +/- 1 m in a 20 m tall tree (ie about 5%) should be expected.

Measuring height
An indentation runs almost the entire length of the left side of the instrument. Within this indentation, there is a cut out notch exactly 10% up from the base.
To measure the height of a tree, hold the Dendrometer in front of your eye at the same angle as the tree and either walk back/forward or move the instrument close/further from your eye until the base of the tree corresponds to the base of the indentation and the top of the tree corresponds to the top of the indentation. Observe where the 10% notch falls on the tree (get an assistant to mark this point). Measure the actual height from the base to the marked point on the tree – this is 10% of the total tree height, so multiply this measurement by 10 to get the total tree height.

Haga:

A height measuring instrument of medium size and weight. It is robust and only moderately expensive.
When used correctly, the Blume Leiss has an accuracy of about +/- 0.5 m for a 20 m tall tree (ie about 2.5%).

1. Select a location, preferably 15, 20, 30 or 40 meters horizontal distance from the base of a vertical tree (or the position directly beneath the tree tip of a leaning tree) where the required point on the tree (e.g. tree tip) can be seen.
2. Select the appropriate distance scale on the rotating rod.
3. Release the pointer by pressing the button on the side of the instrument.
4. The sight at the required point on the tree, wait for a moment for the pointer to settle then pull the trigger.
5. Read the height directly from the appropriate scale if you are 15, 20, 30, or 40 meters away from the tree. If you were unable to find a position at one of these distances:
   • If the horizontal distance is a simple fraction of one of the scale distances (e.g. 10 m is half of 20 m), read from the scale distance and multiply by the appropriate fraction.
   • Read from the percent scale and multiply this percentage by the horizontal distance measured in step 1.
6. Site to the base of the tree and repeat steps 3 – 5.
7. Combine the heights from steps 5 and 6 to determine total tree height:
   • Add the 2 heights together if you looked up to the required point in step 2 and down to the base of the tree in step 6.
   • Subtract the height to the base of the tree from the height to the required point if you are on the sloping ground and had to look up to both the required point and the base of the tree.
8. Check all readings and calculations.

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.
Check here the detailed note on Relaskop (Relascope)

Suunto Clinometer:

The Suunto Clinometer is a height measuring instrument of small size and lightweight. It is robust and inexpensive. The Suunto has a peep-hole at the rear but none at the front. A weighted wheel within the Suunto rotates. When looking through the peephole, a circular field of view of the scales and a horizontal line is seen. Scale readings are taken from the line.
When used correctly, the Suunto Clinometer has an accuracy of about +/- 0.5 m for a 20 m tall tree (ie about 2.5%).

1. Measure the horizontal distance from the base of a vertical tree (or the position directly beneath the tree tip of a leaning tree) to a location where the required point on the tree (e.g. tree tip) can be seen.
2. The sight at the required point on the tree:
   • Using one eye: Close one eye and simultaneously look through the Suunto at the scale and ‘beside’ the Suunto at the tree. Judge where the horizontal line on the Suunto scale would cross the tree.
   • Both eyes: With one eye looking at the Suunto scale and the other looking at the tree, allow the images to appear to be superimposed on each other and read where the horizontal line on the Suunto scale crosses the tree. Note: If you suffer from astigmatism (a common situation where the eyes are not exactly parallel), use the one eye approach.
3. Read from the percent scale and multiply this percentage by the horizontal distance measured in step 1.
4. Site to the base of the tree and repeat steps 2 – 3.
5. Combine the heights from steps 3 and 4 to determine total tree height:
   • Add the 2 heights together if you looked up to the required point in step 2 and down to the base of the tree in step 6.
   • Subtract the height to the base of the tree from the height to the required point if you are on sloping ground and had to look up to both the required point and the base of the tree.
6. Check all readings and calculations.

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 the 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 the distance from a tree. A built-in angle reader and a simple computer chip calculate tree height.

LEM-300:

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

Which Tree Height Measuring Instrument is Best?

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Naeem Javid Muhammad Hassani is working as Conservator of Forests in Balochistan Forest & Wildlife Department (BFWD). He is the CEO of Tech Urdu (techurdu.net) Forestrypedia (forestrypedia.com), All Pak Notifications (allpaknotifications.com), Essayspedia, etc & their YouTube Channels). He is an Environmentalist, Blogger, YouTuber, Developer & Vlogger.

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