Ground-based digital imagery for tree stem analysis
In the USA, a subset of permanent forest sample plots within each geographic region are intensively measured to obtain estimates of tree volume and products. The detailed field measurements required for this type of sampling are both time consuming and error prone. We are attempting to reduce both of these factors with the aid of a commercially-available solid-state matrix camera. This device, along with clinometer angle measurements and distance, can be used to rapidly capture data of an entire tree stem. Subsequent analysis can generate bole heights, diameters, and form measurements. We have found the diameter measurements taken from digital images to be nearly equal to caliper measurements on felled trees. We are developing specifications for both the camera system and data collection protocol. This includes potential sources of error that may adversely affect diameter measurements, which we enumerate in this paper.