Log sorting according to dimension and quality is the ®rst important step during conversion from sawlog to sawn timber. Crooked logs should be rejected or sawn to reduced yield. The 3D scanner furnishes detailed information about the log geometry. Based on cylindrical coordinates four new parameters describing the centroid were evaluated: Maximum Radial Deviation (MRD), Standard deviation of the Sweep Angle (SSA), Distance from Log End to MRD (DLE), and Residual between the Radial deviation and a skew sinusoidal Model (RRM). 56 unbarked spruce logs were sampled, representing six different crook types denoted I, J, C, V, Z and S according to their curvature. Algorithms were established by means of logistic regression models to distinguish between several crook classes. It was concluded that the 3D scanner can be programmed to effectively perform automatic crook detection and classi®cation.
Klassifizierung von nicht-entrindetem Fichtenrundholz hinsichtlich La Èngskru Èmmung mit Hilfe eines 3-D-ScannersSortierung von Rundholz nach Abmessung und Qualita Èt ist einer der ersten Schritte vor dem Einschnitt. Gekru Èmmtes Rundholz sollte aussortiert oder einem Einschnitt mit geringerer Ausbeute zugefu Èhrt werden. Ein 3-D-Scanner liefert detaillierte Daten zur Geometrie des Rundholzes. Auf der Grundlage zylindrischer Koordinaten werden hier vier neue Parameter zum Bestimmen der Mittelachse eingefu Èhrt: Maximale radiale Abweichung (MRD), Standardabweichung des Verschiebungswinkels (SSA), Abstand des Rundholzendes zum MRD (DLE) sowie Restwert zwischen Radialer Abweichung und dem Sinusmodel (RRM). Mit 56 nicht entrindeten Rundho Èlzern wurden sechs verschiedene Kru Èmmungstypen (I, J, C, V, Z und S) erfaût. Mit Hilfe von Regressionsmodellen wurden Alghorithmen entwickelt, die diese Typen differenzieren ko Ènnen. Die Ergebnisse lassen den Schluû zu, daû der 3-DScanner so programmiert werden kann, daû eine automatische Erkennung und Klassi®zierung erfolgreich durchgefu Èhrt werden kann.
GjerdrumThere is a great deal of interest involved in investigating and understanding grain angle in trees. The objective of the study presented in this paper has been to identify a joint, threedimensional model for grain angle in stems of Norway spruce (Picea abies (L.) Karst.) Five large spruce trees were sampled. Transverse disks were extracted at regular intervals along the stem, split through the pith with a blunt knife, and observed for grain angle and cambial age along the north radius, setting pith observation to zero angle. The overall finding confirmed grain pattern congruent to distance from pith along the stem, a pattern that varies from tree to tree. Models expressing distance from the pith in cambial age performed slightly better than models in spatial distance. Grain pattern changed slightly along the stem, and this change was found to be consistent for the five stems: the left-handed grain angle in the juvenile wood was more pronounced upwards in the stem, and the angle changed faster towards right-handed spiralling. The model did not account for grain variation related to knots, undulating pith or other irregularities. Model residuals were normally distributed and seemingly homogeneous for all trees and for all height levels. The model is an extension of existing two-dimensional models for stem cross-cuts. After verification in a wider sample, the results should be applicable in tree and wood modelling.
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