Softwood Log Shape Modelling with Shadow Scanners


  • Jean-Pierre Mongeau
  • Robert Beauregard
  • Thomas E. G. Harless


Log model, scanning, mathematical representation, accuracy


This paper describes and evaluates new and existing models for exterior log geometry. Compatibility with 1, 2, 3, and 4-axis shadow scanners determined which models were selected for evaluation. Models were considered for potential use in sawmilling process simulation and optimization. The accuracy evaluation compared models based upon lost and added fiber percentages. All models tended to overestimate log cross section area. Popular circular and elliptical models provided the poorest accuracy. Elliptical models used with 2-axis or 3-axis scanners generated up to 8% lost fiber and up to 15% added fiber. The 3-axis dyadic and Chaikin models provided the best overall performance: lost fiber under 3.5% and added fiber under 13%. Results from the evaluation recommend a 3-axis scanner system for automatic positioning and breakdown optimization. The small benefit obtained from 4-axis models does not justify their use. Other technologies are recommended where better accuracy is needed.


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Research Contributions