What does a hypsometer or Biltmore stick measure?

A hypsometer, including the Biltmore stick, is primarily used to measure tree height. It is an essential tool in forestry, allowing foresters and land managers to estimate the height of trees accurately. The instrument functions by applying principles of trigonometry; the user measures the angle of elevation to the top of the tree from a certain distance away and uses this information, along with the distance to the tree, to calculate its height.

While the provided answer indicates that the Biltmore stick measures the diameter of the tree and determines how many 16-foot logs can be produced from it, this statement focuses incorrectly on the primary use of the instrument. Although the Biltmore stick can be used to estimate the volume of wood and the log production per tree based on diameter measurements, it does not directly measure height itself, which is the primary function of a hypsometer.

Understanding the purpose of a hypsometer clarifies why the correct answer is the height of the tree, as that is its fundamental capability in forestry surveying and management. The other options, such as root depth and leaf density, are unrelated to the primary function of a hypsometer and do not align with the measurements that the tool is designed to provide.