DETECTION OF DECAY IN TREES WITH STRESS WAVES AND INTERPRETATION OF ACOUSTIC TOMOGRAMS

Sonic Tomograph as a Tool Supporting the Sustainable Management of Historical Greenery of the UMCS Botanical Garden in Lublin

The mission of botanical gardens is to work towards the conservation and sustainable use of plant diversity. In the case of gardens established on the premises of former manor estates, actions are also being taken to properly manage existing natural resources, e.g., historic tree stands. This article is based on the case study of the Botanical Garden in Lublin. To assess the health condition of the trees growing in the oldest part of the park—Kościuszko Redoubt—sonic tomography examinations were performed. The article presents the practical application of a newer form of digital imaging, put to the service of assessing the health of old trees in an important public space. The Redoubt is the only work of defense architecture in Poland related to the activity of General Tadeusz Kościuszko, the hero of Poland and the United States of America. It has survived in an excellent condition, preserved without significant changes, as an earth structure with ramparts; an interior, i.e., a yard; a cannon post located on an inaccessible cliff; and a brick basement serving as a shelter for soldiers and a warehouse. The entire surroundings also survived: ravines masked with a wild green, embankments with a safe hidden access road to the Redoubt, and a shaped defense line. The Botanical Garden area is located in the Sławinek district, in the valley of the Czechówka River, and includes a fragment of it and the slope adjacent to the west, cut by three loess ravines. The Botanical Garden was established in 1965, where there was a manor farm earlier, and then in the 19th century, a spa that was destroyed during World War I and II. Good soils and a varied microclimate provide the right ecological conditions for the high biodiversity of plants. With an area of 21.15 ha, the Garden area has the character of a landscape park with the theme of a manor garden from the turn of the 18th/19th century and a spa garden. The primary purpose of the work was to investigate the effectiveness of the use of computer tools in the sustainable management of historical greenery in the Botanical Garden. Research has shown that diagnostics with the use of sound waves allow for an accurate diagnosis and quick protective measures against the tree, improving the safety of visitors to the botanical garden. Moreover, the obtained results and a historical query were used to prepare an application to recognize Redoubt as a monument.

Image Reconstruction of Internal Defects in Wood Based on Segmented Propagation Rays of Stress Waves

In order to detect the size and shape of defects inside wood, an image reconstruction method based on segmented propagation rays of stress waves is proposed. The method uses sensors to obtain the stress wave velocity data by hanging around the timber equally, visualizes those data, and reconstructs the image of internal defects with the visualized propagation rays. The basis of the algorithm is precisely segmenting the rays to benefit the spatial interpolation. First, a ray segmentation algorithm using the elliptical neighborhood technique is proposed, which can be used to segment the rays and estimate the velocity values of segmented rays by the nearby original rays using elliptical zones. Second, a spatial interpolation algorithm utilizing a segmented ellipse according to the segmented rays is also proposed, which can be used to estimate the velocity value of a grid cell by the segmented ellipses corresponding to the nearby segmented rays. Then, the image of the internal defect inside the wood is reconstructed. Both simulation and experimental data were used to evaluate the proposed method, and the area and shape of the imaging results were analyzed. The comparison results show that the proposed method can produce high quality reconstructions with clear edges and high accuracy.