Timber cruising is a term used for any method of estimating timber volumes on a given acreage. The term was coined a long time ago, when timber buyers would walk through a stand of timber, eyeball it, and estimate the volume of sawtimber that it would produce. Though some still use the eyeball method today, cruising typically refers to a more scientifically based method of sampling timber volumes.
These scientific methods, taught in the accredited forestry programs of colleges and universities, rely on statistics and volume estimation formulas derived using trigonometry and calculus. Typically, the forester will design a method for placing sample plots or points on a measured grid within a forest stand. They will then measure each tree that falls within the plot or point, and tally it according to its species, diameter, and merchantable height.