A timber cruise is a sample measurement of a stand  used to estimate the amount of standing timber

Timber

Timber may refer to:* Timber, a term common in the United Kingdom and Australia for wood materials * Timber, Oregon, an unincorporated community in the U.S...

 that the forest

Forest

A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...

 contains. These measurements are collected at sample locations called plots or quadrants. Each of these individual plots is one observation in a series of observations called a sample. These plots are generally laid out in some random fashion usually in the form of a line plot survey

Line plot survey

Line plot survey is a systematic technique of laying out sample plots in a forest inventory within a rectangular grid. It is also an application of systematic sampling, similar to statistical properties as random sampling, but often easier to carry out....

. Depending on the size of the plot and the number of plots measured, the data gathered from these plots can then be manipulated to achieve varying levels of certainty for an estimate that can be applied to the entire timber stand. This estimate of stand conditions, species composition, volume and other measured attributes of a forest system can then be used for various purposes. For example in British Columbia the sale of Crown timber is a business proposition and both the buyer and the Ministry of Forests and Range (seller) must know the quantity and the quality of timber being sold. The cruise provides the essential data for determining stumpage rates, for establishing conditions of sale and for planning of the logging operations by the licensee.

Fixed area plot

Fixed area plot sample measurements are taken so that they are a fraction of the entire timber stand. This means that the numbers are all proportional to the actual stand values and that by multiplying by the correct corresponding value you can obtain the actual tract values. These plots are taken randomly so that each sample point has an equal probability of being included in the random sample

Random sample

In statistics, a sample is a subject chosen from a population for investigation; a random sample is one chosen by a method involving an unpredictable component...

.

Variable size plots

A variable size plot is more dependent of the size of the trees. The tract is measured on a series of points and the trees are tallied for being in or out depending on their size and location relevant to the plot center. Usually an angle gauge

Angle gauge

An angle gauge is a tool used by foresters to determine which trees to measure when using a variable radius plot design in forest inventory. Using this tool a forester can quickly measure the trees that are in or out of the plot. An angle gauge is a very similar tool to a wedge prism though it...

 or a wedge prism

Wedge prism

The wedge prism is a prism with a shallow angle between its input and output surfaces. Refraction at the surfaces causes the prism to deflect light by a fixed angle...

 are used to gather data for this type of plot. This allows for a very quick estimate of the volume and species of a given tract.

Timber metrics

The amount of standing timber that a forest contains is determined from
'

• Diameter at breast height
  Diameter at breast height
  Diameter at breast height, or DBH, is a standard method of expressing the diameter of the trunk or bole of a standing tree. DBH is one of the most common dendrometric measurements....
  
   (DBH) - measurement of a tree's girth standardized at 1.3 meters (about 4.5 feet) above the ground
• Basal area
  Basal area
  Basal area is the term used in forest management that defines the cross-sectional area of a tree at DBH, inside the bark.In most countries, this is usually a measurement taken at a specimen's breast height above the ground and includes the entire diameter of every tree, including the bark...
  
   - defines the area of a given section of land that is occupied by the cross-section of tree trunks and stems at their base
• Tree taper
  Tree taper
  -Definition:Taper is the degree to which a tree's stem or bole decreases in diameter as a function of height above ground. Trees with a high degree of taper are said to have poor form, while those with low taper have good form...
  
    - the degree to which a tree's stem or bole decreases in diameter as a function of height above ground
• Girard form class
  Girard form class
  Girard Form Class is a form quotient calculated as the ratio of diameter inside bark at the top of the first 16 foot log to the diameter outside bark at breast height . Girard form class is the primary expression of tree form in the United States....
  
   - an expression of tree taper calculated as the ratio of diameter inside the bark at 16 feet above ground to the to that outside bark at DBH, primary expression of tree form used in the United States
• Quadratic mean diameter
  Quadratic mean diameter
  The Quadratic mean diameter is a statistical measurement often used in timber cruises to estimate the standing volume of timber in a forest. In professional forestry, it is more widely used than volume tables....
  
   - diameter of the tree that coordinates to the stand's basal area
• Site index
  Site index
  Site index is a term used in forestry to describe the potential for forest trees to grow at a particular location or "site." Site is defined as “inherent characteristics of the physical environment”; furthermore, the word site is used in forestry to refer to a distinct area where trees are found....
  
   - a species specific measure of site productivity and management options, reported as the height of dominant and co-dominant trees (site tree
  Site tree (forestry)
  Site tree refers to a type of tree used in forestry to classify the quality of growing conditions at a particular forest location. A site tree is a single tree in a stand that gives a good representation of the average dominant or co-dominant tree in the stand. Site trees are used to calculate the...
  
  s)in a stand at a base age such as 25, 50 and 100 years

Tools used

• Biltmore stick
  Biltmore stick
  The Biltmore stick is a tool used to measure various tree dimensions, such as diameter at breast height and height. It looks much like an everyday yardstick. A Biltmore stick is considered to be only marginally accurate...
  
   - utilizes ocular trigonometry to quickly measure diameter and height
• Diameter tape
  Diameter Tape
  A Diameter tape is a form of dendrometer that consists of a cloth or metal tape that is mainly used to measure diameter at breast height . DBH is measured at a fixed height of 4.5 feet above the ground, where it is most convenient to measure diameter. DBH is measured up high so to avoid measuring...
  
   - cloth or metal tape that is wrapped around the bole, scaled to diameter
• Caliper
  Caliper
  A caliper is a device used to measure the distance between two opposing sides of an object. A caliper can be as simple as a compass with inward or outward-facing points...
  
   - two prongs connected to a measuring tape are placed around the most average part of the bole to determine diameter
• Relascope
  Relascope
  The relascope, invented by Walter Bitterlich, is a multi-use instrument for forest inventory. It is primarily used to find height of a tree, basal area of a tree and diameter of a tree anywhere along the bole...
  
   - multiple-use tool that is able to find tree height, basal area, and tree diameter anywhere along the bole
• Clinometer
  Clinometer (forestry)
  The clinometer, known in many fields as an inclinometer, is a common tool used in forestry to measure slope, vertical angles, and – in combination with distance measurements – elevation change or tree heights.-How it works:...
  
   - common tool used to measure changes in elevation and tree height
• Cruising rod
  Cruising rod
  A cruising rod is a simple computing device that to quickly estimate the number of pieces of lumber yielded by a given piece of timber. Similarly to a yardstick, it is a rod with markings. The estimation is carried out as follows. Standing at arm's length from the tree, estimate its average...
  
   - similar to a caliper, calculates the number of pieces of lumber yielded by a given piece of timber by measuring its diameter

Volume estimation

• Stocking
  Stocking (forestry)
  In forestry, stocking , is a quantitative measure of the area occupied by trees, usually measured in terms of well-spaced trees or basal area per hectare, relative to an optimum or desired level of density...
  
   - a quantitative measure of the area occupied by trees relative to an optimum or desired level of density
• Stand Density Index
  Stand Density Index
  Stand density index is a measure of the stocking of a stand of trees based on the number of trees per unit area and diameter at breast height of the tree of average basal area...
  
   - a measure of the stocking of a stand of trees based on the number of trees per unit area and DBH of the tree of average basal area
• Volume table
  Volume table
  A Volume table is a chart to aid in the estimation of standing timber volume. These tables are based on volume equations and use correlations between certain aspects of a tree to estimate the volume to a degree of certainty. The DBH and the merchantable height are used to determine the total volume...
  
   - a chart based on volume equations that uses correlations between certain aspects of a tree to estimate the standing volume
• Stand density management diagram
  Stand density management diagram
  A stand density management diagram is a simple biological model relating forest yield to forest density at any stage of a particular forest stand's development. Stand density management diagrams are used in forest management and designed to use a current stand's density to project its future yield...
  
  - model that uses current stand density to project future stand composition