Assessing the Accuracy of Tree Diameter Measurements Collected at a Distance

The ability to measure trees remotely or at a distance may be of value to forest inventory processes. Within three forest types (young coniferous, old coniferous, and deciduous), we compared laser caliper measurements collected at distances up to 12 m from each tree, to direct contact caliper measurements. Bitterlich sector-fork measurements and diameter tape measurements were also collected for reference purposes. We used non-parametric tests to evaluate three of our four hypotheses that suggest there are no significant differences between direct and remote diameter measurements, between caliper measurements and sector-fork measurements, and between diameter measurement errors across forest types. In general, most of the differences in diameters were small (≤ 0.8 cm) and were observed within the 0–6 m measurement distance from each tree. These results suggest that forest characteristics and measurement distance may play a role in remote diameter measurement accuracy. We also performed a correlation analysis between light conditions and remote measurements. The correlation analysis suggested light conditions were not significantly correlated to diameter measurement accuracy.