Methods that require a person or team of people physically working on the ground measuring physical quantities are described as terrestrial inventory. A wide array of methods from, traditional tape measurements and clinometers, to sophisticated electronic laser equipment is currently available for forest assessment. Examples of such work can be found in Seidel et al. (2012).

Inventory requires a proper sampling plan, which includes the aim or result of the measurement, error tolerance, sampling procedure, available budget, trained people and equipment. The required result will determine the error margin, which will dictate the intensity of the sample for each method selected. The method selected
will determine the equipment selected, which will indicate the size and level of training of the person or team. Finally, the available budget will have an influence on the detail of outcome, as well as the intensity of the inventory and the error of the result.

This section will focus on an overview of methods used with references to texts that provide detailed discussions on each of the methods.