Tomographic images of tree trunks generated using ultrasound and post-processed images: Influence of the number of measurement points

Abstract

Tomography is a technique increasingly used in tree inspections. This technique can be performed in two stages: field testing and postimage processing. To feed the tomographic image construction software, it is necessary to adopt a measurement grid composed of points positioned on the perimeter of the stem. The images are generated through spatial interpolation algorithms. From a theoretical point of view, more measurement points taken in the perimeter of the stem result in better interpolation results. However, an increase in the number of mesh points causes a substantial increase in field work and image processing time. The general objective of this study was to verify the influence of the number of measurement points of the diffraction mesh on the ultrasound tomography results. For this purpose, ten simulated discs were used, all 500 mm in diameter and with different defects in terms of size, position, and geometry. In each of the discs, diffraction grids were simulated with 6, 8, 10, 12, and 14 measurement points in the contour. The results showed that a favorable combination of accuracy and a minimization of effort can be achieved with diffraction mesh with number of measurement points calculated as five times the perimeter of the trunk in meters.

Assessment of Summer Branch Drop: A Case Study in Four Portuguese Cities

“…There has been considerable research on improving techniques that can detect and locate internal defects on woods using images obtained from tomography, and that can measure the accuracy of the acoustic tomograph [39,48,[50][51][52]. The results obtained with acoustic tomography must be interpreted taking into account the following inputs: the ones used during the measurement (type of mesh and number of measurement points), the construction of images (software, interpolation algorithms), and the reference velocity to identify areas inside the stem (sound and deteriorated wood as well as cavities) [53].…”

Tomographic Images Generated from Measurements in Standing Trees Using Ultrasound and Postprocessed Images: Methodological Proposals for Cutting Velocity, Interpolation Algorithm and Confusion Matrix Metrics Focusing on Image Quality

“…The algorithm allows not only to fill out velocities outside the mesh, but also to adapt the behavior of the routes as a function of the type of interpolation used, as proposed by [17], which considers velocity compensations as a function of anisotropy, correcting the theoretical routes. Thus, the tomography result is influenced by both the characteristics of the mesh, such as the number of measurement points [19,20], and the type of interpolation algorithm; therefore, it is necessary to calibrate this interference for the correct interpretation of the tomographic image, especially in the case of using less complex interpolators.…”

“…Tomographic image quality can also be improved through filters. Filters applied directly to ultrasound tomography images are useful in reducing interference caused by interpolation systems [19]. However, the author's research [19] was carried out with For this scan, the mesh created between the measurement points forms the theoretical routes (Ex: 1-2, 1-3, etc.…”

“…Filters applied directly to ultrasound tomography images are useful in reducing interference caused by interpolation systems [19]. However, the author's research [19] was carried out with For this scan, the mesh created between the measurement points forms the theoretical routes (Ex: 1-2, 1-3, etc. ), in which the velocities are calculated by the relationship between the theoretical length of the route and the time for the wave to cover it (TOF).…”

“…Filters applied directly to ultrasound tomography images are useful in reducing interference caused by interpolation systems [19]. However, the author's research [19] was carried out with simulated discs, and it is important to verify that the results are repeatable with real trunk cross-sections.…”