Abstract
A new method for determining cross-sectional shape of logs is presented. The model takes as input data three xray projections from different angles around the log, and models the cross sections as arbitrarily oriented ellipses. For each log cross section the exterior shape, the shape under bark and the shape of the heartwood zone are determined. The shape under bark is also determined with models using input data from a 2-axis shadow scanner. The accuracy of the models is estimated by the added and lost fiber percentages, which are the areas of erroneous prediction relative to the true area. The best mean values of lost and added fiber percentages obtained on a sample of 40 Scots pine logs were 1.57 and 1.64% respectively. Comparisons with the best case possible from 2-axis shadow scanners show that a three-sources x-ray log scanner would be superior to the shadow scanners in describing the shape of logs.
Zusammenfassung
Eine neue Methode zur Bestimmung der Querschnittsform yon Rundholz wird vorgestellt. Als Eingabegrößen dienen drei Röntgenstrahl-Projektionen unter verschiedenen Winkeln. Der Querschnitt wird als willkürlich orientierte Ellipse modelliert. Für jeden Querschnitt werden die äußere Form, die Querschnittsform unter der Rinde und die Form des Kernholzes bestimmto Die Form unter der Rinde wird zusätzlich noch aufgrund der Daten eines 2-Achsen-Scanners berechnet. Die Genauigkeit des Modells wird geschätzt anhand der Anteile an verlorenem bzw. zusätzlichem Fasermaterial, das sich aus dem Verhältnis der vorhergesagten und der tatsächlichen Fläche ergibt. Die besten Mittelwerte für 40 Rundhö1zer yon (nordischer) Kiefer betrugen 1,57% bzw. 1,64%. Im Vergleich mit den bestmöglichen Ergebnissen eines 2-Achsen-Scanners erweist sich die Bestimmung mit einem 3-achsigen Scanner als deutlich überlegen.
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This work has been supported by the Norwegian Research Council. The author wants to thank Johan Oja, Dept. Of Wood Technology, Skellefteå, Lulea University, for providing the data from the Swedish stem Bank used in this study and Xinli Wang for helpful discussions.
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Skatter, S. Determination of cross-sectional shape of softwood logs from three x-ray projections using an elliptical model. Holz als Roh-und Werkstoff 56, 179–186 (1998). https://doi.org/10.1007/s001070050295
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DOI: https://doi.org/10.1007/s001070050295