Velocity Thresholds for Ultrasonic Tomographic Imaging Aimed at Detecting Cavities and Decay in Trees

Abstract

Trees play a vital role in urban environments by mitigating heat islands, floods, and pollution, while promoting public health and well-being. Acoustic tomography is an effective tool for assessing tree integrity, but its high-cost limits widespread use. To reduce costs, this study evaluated the use of ultrasonic tomography with standardized velocity thresholds (VTs) for detecting cavities and decay in trunks. A total of 38 discs from 21 trees species were analyzed using different VTs (35%, 40%, 45%, and 50%). The results showed that thresholds of 35% Vmax for cavity detection and 50% Vmax for cavity with decay detection can be adopted for tomographic image assessments of trees, regardless of species. Using the same velocity thresholds regardless of species enables the practical application of the technology, with average accuracy losses (below 5%) that are quite reasonable considering the variability of the material under inspection. These findings support the broader use of technology in tree failure risk assessments.