X-ray measurement of properties of saw logs

Abstract: A nondestructive method of measuring knot parameters for research purposes has been compared to alternative, destructive methods. The method is based on automatic analysis of CT-images. The image analysis algorithms were adjusted to and evaluated on Norway spruce. The possibilities of measuring resin pockets in CT-images have been studied and stereological methods have been applied on volume estimation of resin pockets in saw logs. For research purposes the study showed that compared to destructive methods, both accuracy and speed of the CT-method were competitive. It was also shown that resin pockets can be detected and measured in CT-images of Norway spruce. Data from the CT-scanned logs was used to simulate an industrial X-ray LogScanner. The X-ray LogScanner was based on two X-ray sources and designed for scanning at 3 m/s. The possibility of using this X-ray LogScanner to make nondestructive measurements of properties of saw logs has been investigated. The study showed that the X-ray LogScanner measures minimum shadow diameter under bark before debarking with an accuracy comparable to a 3D-scanner and that the sawing position could be controlled based on X-ray LogScanner measurements of the best half of the logs. The X-ray LogScanner could also be used to measure percentage of heartwood and green heartwood density. Based on the X-ray LogScanner measurements it was possible to calibrate PLS-models for prediction of the bending stiffness of the centerboards.