Accuracy and Reproducibility of Acoustic Tomography Significantly Increase with Precision of Sensor Position

Abstract

Acoustic tomograms are widely used in tree risk assessment. They should be accurate,
repeatable and comparable between consecutive measurements. Previous work has failed to address the effects of different approaches to record sensor positions, operators and models of tomograph on the resulting tomograms.

In this study, three operators used the two most common sonic tomograph
models to measure seven cross-sections of Norway spruce trees, which
were felled after the measurement. We evaluated the effects of model, operator, and different approaches to measure sensor positions on the quality of the tomograms.

The largest source of error was the position of sensors, affecting
estimated stress wave velocity, the shape of the tomogram, and the size
of the defect.

To produce accurate and repeatable tomograms of trees with complex shapes,
it is essential to measure the sensor positions precisely.