Log end face image and stem tapering indicate maximum bow height on Norway spruce bottom logs

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http://hdl.handle.net/10138/326661

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Raatevaara , A , Korpunen , H , Mäkinen , H & Uusitalo , J 2020 , ' Log end face image and stem tapering indicate maximum bow height on Norway spruce bottom logs ' , European Journal of Forest Research , vol. 139 , no. 6 , pp. 1079-1090 . https://doi.org/10.1007/s10342-020-01309-0

Title: Log end face image and stem tapering indicate maximum bow height on Norway spruce bottom logs
Author: Raatevaara, Antti; Korpunen, Heikki; Mäkinen, Harri; Uusitalo, Jori
Other contributor: University of Helsinki, Department of Forest Sciences
University of Helsinki, Natural Resources Institute Finland (LUKE)
University of Helsinki, Department of Forest Sciences

Date: 2020-12
Language: eng
Number of pages: 12
Belongs to series: European Journal of Forest Research
ISSN: 1612-4669
DOI: https://doi.org/10.1007/s10342-020-01309-0
URI: http://hdl.handle.net/10138/326661
Abstract: In cut-to-length logging, the harvester operator adjusts the bucking in accordance with visible defects on processed stems. Some of the defects, such as a sweep on the bottom of the stem, decrease the yield and quality of sawn products and are difficult for the operator to notice. Detecting the defects with improved sensors would support the operator in his qualitative decision-making and increase value recovery of logging. Predicting the maximum bow height of the bottom log in Norway spruce (Picea abies (L.) Karst.) with log end face image and stem taper was investigated with two modelling approaches. A total of 101 stems were selected from five clear-cut stands in southern Finland. The stems were crosscut and taper measured, and the butt ends of the bottom logs were photographed. The stem diameter, out-of-roundness, and pith eccentricity were measured from the images while the max. bow height was measured by a 3D log scanner at a sawmill. The bottom logs with an eccentric pith had higher max. bow height. In addition, a highly conical bottom part of the stem was more common on the bottom logs with a large max. bow height. Applying both log end face image and stem taper measurements gave the best model fit and detection accuracy (76%) for bottom logs with a large max. bow height. The results indicate that the log end face image and stem taper measurements can be utilised to aid harvester operator in deciding an optimised length for logs according to the bow height.
Subject: 4112 Forestry
Norway spruce
Bow height
Sweep
Log end face
Pith eccentricity
Stem taper
SCOTS PINE
COMPRESSION WOOD
PICEA-ABIES
SYLVESTRIS
POSITION
QUALITY
GROWTH
FOREST
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