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13 Essential Tools Every Forester Needs

Rangers or forest agents use different tools and instruments to measure trees and record their development. Some of the most common are the diameter tape, the clinometer, the dendrometer, the calipers and the compass, among others. This article presents the most common instruments in the measurement and protection of forests.

What is and what does a forest agent do?

Forest agents, also called forest rangers or rangers, are people dedicated to the protection of natural resources, mainly the flora and fauna of a place. Most of them work in forests, nature reserves and national parks.

The functions of a forest agent include:

  • Monitor population, habitat and well-being of animals and vegetation.
  • Manage and promote the conservation of the environment.
  • Guarantee that regulations related to forest preservation are complied with: flora, fauna, hunting and fishing activities, ecosystems, etc.
  • Prevent, detect, extinguish and investigate forest fires.
  • Perform technical tasks such as tree measurement, as well as maintenance, including weeding, cleaning ponds, repairing fences, etc.
  • Educate the public on environmental issues and nature conservation.
  • Monitor the natural space.
  • Control pests and human activities that may cause damage to flora or fauna.
  • Inspect industrial activities, such as logging, mining extractions, industrial discharges and constructions on forest land, among others.
  • Carry out conservation projects for endangered species.

13 Tools Forest Agents Use

In order to carry out all the mentioned functions and, in particular, to control and conserve natural forests, forest agents use different tools, instruments and special equipment.

These instruments allow, in an effective way, to measure, control and analyze the state of the forests. In addition, they make it possible to record the distribution, density and growth of trees, as well as the characteristics of their bark.

Not only forest agents use these instruments. They are also commonly used in other activities that are within forestry, the discipline that focuses on the management of forests or forest forests, either for preservation or commercialization purposes.

The 13 most common tools are:

  • linear measurements
    • diameter tape
    • rod biltmore
    • dendrometer
    • caliper
    • Gunther’s Chain
  • bark measurement
    • bark gauge
  • height measurement
    • hypsometer
    • Inclinometer
  • Basal area measurement
    • wedge prism
    • Goniometer
  • other tools
    • marking tape
    • borer
    • Compass

Diameter tape, D tape measure or diameter tape

Diameter tapes, also known as D tape measures or diameter tapes, are essential for measuring the diameter of a tree trunk. They are also used to measure the external diameter of any cylindrical object. They are very similar to a common tape measure and are characterized by having a double graduated scale. On one side are common length measurements such as centimeters and millimeters, and on the other are conversions of diameter to PI units.

The diameter tape is placed around the trunk of the tree, at chest height of the person measuring, approximately 1.3m from the ground.

This type of tape measure is often used to record the size of specimens from a location and when buying and selling stumpage.

tools for forest agent or ranger - diameter tape, diameter tape, tape measure D diameter tape

Biltmore rod or cruise stick

The Biltmore rod is a ruler-like tool, usually made of wood, used to measure tree trunks. It allows you to calculate the diameter and height of a tree and has a relatively low margin of error.

This method is ideal for trees with a nearly perfect circumference. Otherwise, the measurement may be inaccurate.

tools for forest agent or ranger - Biltmore stick. cruise stick biltmore stick


Since trees vary in size, shapes, and growth, other tools are needed to measure them more accurately. Dendrometers measure the height and diameter of the trunks of standing trees and make it possible to calculate the volume of wood they have or can produce. They also help control tree growth, its water status and the influence of environmental factors on its condition and development.

There are different types of dendrometers. Some of them measure the height of trees and vary in size and technology. The one that appears in the image is used to measure its growth. It is a device that is placed around the trunk and has a needle that moves as the tree increases its diameter.

tools for forest agent or ranger - dendometer dendrometer


Calipers are more accurate calipers for measuring log diameters. In fact, there are calipers of different sizes and materials to be able to measure trees of different dimensions.

The caliper is formed by a clamp on a rectangular ruler, with scales on both sides. One of its advantages is its stability and precision. Like the diameter tape, it is placed at chest level but, in this case, perpendicular to the trunk; then adjust as needed.

In addition to the common caliper, there are other types of calipers such as the Finnish or the fork one.

tools for forest agent or ranger - caliper caliper

bark gauge

The Swedish caliper is a small instrument used to measure the bark of trees, especially pine trees.

The sharp part is pressed against the bark until it penetrates the wood. The tab is then moved to view the bark thickness measurement on the caliper scale.

tools for forest agent or ranger - bark gauge bark gauge

Gunther’s Chain

Gunter’s chain is the brainchild of the English mathematician Edmund Gunter, after whom it is named. It is also known as surveyor’s chain or surveyor’s chain. It is a tool that is commonly used to measure the horizontal distance of forests or mountains.

This chain is made up of 100 equal links. Most of Gunter’s chains measure between 20 and 30 meters in length in total.

It is used mainly in Anglo-Saxon countries to measure land and calculate areas.

tools for forest agent or ranger - Gunter's chain, surveyor's chain, surveyor's chain Gunther’s Chain


The hypsometer is an instrument that determines the height of an object with respect to sea level, through geometric calculations.

Hypsometers measure the height of trees in meters, based on three points: the horizontal distance, the angle of the crown, and the angle of the base of the tree.

Commonly used hypsometers include: the Christen hypsometer, the Merritt, and the Blume-Leiss.

tools for forest agent or ranger - hypsometer hypsometer


The clinometer measures the height and slope of the trees. This is very useful in the timber trade and in topographical measurements that are made during road construction.

Clinometers measure elevation in percentages or topographic scales. For height and slope calculations, look at the clinometer with one eye, and use the other to adjust the instrument with reference points on the tree, such as the trunk, top end, or full height.

tools for forest agent or ranger - clinometer Inclinometer


Goniometers, also known as sextants, are angle indicators. They are usually in the shape of a circle or semicircle, 180° or 360°, respectively, and allow you to measure the angles between two objects, such as the tree and the sun or the horizon, for example.

They are generally used to calculate the slope of a tree, the basal area and the density in a given area.

Theodolites and tachymeters are also included in the group of goniometers.

tools for forest agent or ranger - goniometer or sextant Goniometer

wedge prism

The wedge prism, optical wedge or deviating prism, is a wedge-shaped piece of glass that refracts light. This produces an image offset of the tree trunk when viewed through it. The offset is made at a specific angle, depending on the degree of refraction of the prism.

This optical device is used to perform angle sampling and is also used to estimate the basal area, that is, count the trees in a given area and find out their density or thickness.

To do this, it is observed through the prism, through a point inside it, and it remains fixed. Then he turns to look at the surrounding trees. There are different varieties of prisms available in various sizes.

tools for ranger or ranger - wedge prism, optical wedge or deflection prism wedge prism

Recording tape or marking tape

Marking tape, also called registration tape or forest marking tape, is a vinyl tape used to inventory trees, identify them, delimit areas, or mark dangerous areas.

They are easy to install and highly durable. They can withstand low temperatures and are fluorescent, that is, they can be easily seen and glow in the dark.

tools for forest agent or ranger - marking tape or recording tape marking tape


The compass is an essential item of any ranger. It has existed for almost two thousand years and is used to orientate in the forests and in unknown or wild areas.

The compass is an instrument that is made up of a magnetized needle that indicates magnetic north, and the wind rose, which is a circle that marks the cardinal points north, south, east, and west, as well as the intermediate directions. The needle rotates on an axis and always points to magnetic north.

In order to orient yourself, the compass should be placed on a surface that is as flat as possible. Then wait until the needle stops and points to magnetic north. Once the needle is stabilized, the user can head in the desired direction. It is advisable to carry out this process several times along the way to obtain greater precision.

tools for forest agent or ranger - compass Compass


Borers are used to extract core samples from trees. This makes it possible to determine the age, growth and soundness of the trees.

The auger is normally between 10 and 70 cm in length and between 0.4 and 1.2 cm in diameter.

This tool is one of the least invasive methods of counting tree rings. It works by placing a very fine rod from the bark of the tree to its pith and extracting a small sample, approximately 0.5 cm.

Although it makes a very small hole in the tree, it can cause damage to the tree and make it more prone to disease. Because of this, this procedure is only done once every six years. The removed material is placed back after being examined.

tools for forest agent or ranger borer

Other common tools

In addition to the instruments mentioned, there are other common tools used in forestry:

  • Pick: It is a tool with a wooden handle and a metal part. It is used to dig.
  • Shovel: It has a metal blade and a long wooden handle with a handle. It is used to till the land.
  • Machete: it is a tool with a long metal blade and a small handle, used for weeding.
  • Bark Probe: It is similar to the Swedish caliper, but much smaller. Instead of a chisel, it has a needle that is inserted into the wood. It is used to measure the bark of eucalyptus and other trees.
  • Vertex measurer: It is a two-part electronic device, with a sensor that allows you to measure height and distance.
  • Abney level: is another instrument to measure the height of trees.
  • Graduated rods: they are thin tubes approximately 1.5 m long that are joined together and allow trees to be measured up to 25 m tall.
  • Other dendrometers such as the “bottle opener” dendrometer, which is very similar to this everyday tool. Wheeler’s pentaprism or Bitterlich’s relascope is also used. They are larger and more expensive devices and allow greater precision in measurements.


  • Various authors. General Agenda Forest Agents. Madrid’s community. (2019). Spain. Adams.
  • Barchuk, AH Manual of good practices for the conservation of native forests . (2021). Spain. Ariel.
  • Villa Castillo, B. Valuation of Environmental Services: Conservation of Biodiversity in Forests of Mexico. (2020). Mexico. Spanish Academic Editorial.