Height is the linear distance of an object normal to the surface of the earth. Tree height is the vertical distance measured from the ground surface.

## Why measure tree height?

To calculate a tree’s volume, its height is measured. Reading volume tables, form factor tables, yield tables, etc., also calls for the height of a few chosen trees in a forest. In order to determine the site’s potential for productivity, tree heights are also necessary. Height is typically regarded as a fertility indicator, and age provides a valid indicator of a location’s site quality.

## Principles of tree height measurement

Instruments used for measuring tree heights are collectively referred to as hypsometers.

All height measuring instruments are based either on geometric principles of similar triangles or on trigonometric principles based on relations between the sides of a right-angled triangle

## Tools to measure tree height

Christen, Merritt, Chapman, and JAL hypsometers, as well as other instruments based on similar triangles, are widely employed. These devices are less accurate than those that make use of trigonometric relations. The geometric-based hypsometers have the benefit of being straightforward, easily made, and reasonably priced.

##### Sunto clinometer:

The Suunto clinometer is a portable instrument with an aluminum body that resists corrosion. It is based on the tangent of angles.

When the baseline can be seen at the measurement location, the instrument is elevated and lowered while being held to one eye. The reading is simultaneously provided by the location of the hairline on the scale. There are many scale combinations for the instrument, including percent and degrees, percent and topographic, degrees and topography, and feet and meters. The Suunto Clinometer offers a +/- 0.5 m (or 2.5%) accuracy when used correctly on a 20 m tall tree.

##### Christen’s Hypsometer:

It is based on the geometric relationships between similar triangles. The top and bottom flanges, or protruding edges, are both present. There is a hole in each flange; the higher hole is used to hang the instrument by a thread, while the lower hole is used to hang a weight from to keep it from swinging. To utilize it, either a pole (often 5 or 10 feet long) or a mark (5 or 10 feet above the ground) must be attached to the tree. The observer might need to adjust their distance from or proximity to the tree. The scale’s graduation, also known as the mark, that is parallel to the pole’s top indicates the height of the tree.

Pros:

- It is lightweight, simple to make, and portable.
- It is easier to use and effective in situations where speed is necessary because it allows for the direct reading of the tree’s height.

Cons:

- When reading the heights, extra care must be given to keep the top and bottom of the tree inside the flanges.
- It ought to be supported in the genuine vertical plane.
- It is not appropriate for trees taller than 30 meters.
- It necessitates the employment of personnel.
- To utilize the instrument consistently accurately, skill is required.

##### Abney’s Level:

Both land elevations and tree heights are measured using it. The device consists of a graded arc set on a 6-inch-long sighting tube. The arc may be scaled in terms of degree, percent, or topography. A tiny mirror within the tube allows one to see when the level bubble is horizontal when it is spun when sight is being taken while it is attached to the instrument.

The Abney Level has an accuracy of roughly +/- 0.5 m (or about 2.5%) when used appropriately for a 20 m tall tree.

Pros:

- It provides precise elevation and depression angles.
- After spotting the tree, reading can be done without disrupting the index.
- It is compact and lightweight, making it easy to use even on hills.

Cons:

- The top or bottom of the tree can be seen, but it takes some time and effort because of handshaking.
- By turning the screw head while simultaneously looking at the top or bottom of the tree, the spirit level must be adjusted.