Abstract
Within a research project investigating the applicability and performance of modified harvesting heads used during the debarking of coniferous tree species, the actual debarking percentage of processed logs needed to be evaluated. Therefore, a computer-based photo-optical measurement system (Stemsurf) designed to assess the debarking percentage recorded in the field was developed, tested under laboratory conditions, and applied in live field operations. In total, 1720 processed logs of coniferous species from modified harvesting heads were recorded and analyzed within Stemsurf. With a single log image as the input, the overall debarking percentage was calculated by further estimating the un-displayed part of the log surface by defining polygons representing the differently debarked areas of the log surface. To assess the precision and bias of the developed measurement system, 480 images were captured under laboratory conditions on an artificial log with defined surface polygons. Within the laboratory test, the standard deviation of average debarking percentages remained within a 4% variation. A positive bias of 6.7% was caused by distortion and perspective effects. This resulted in an average underestimation of 1.1% for the summer debarking percentages gathered from field operations. The software generally performed as anticipated through field and lab testing and offered a suitable alternative of assessing stem debarking percentage, a task that should increase in importance as more operations are targeting debarked products.
Highlights
Remote sensing technologies play an important role as nondestructive tools used to evaluate numerous scientific questions and approaches
The systems mentioned above have all been tested and generally perform very well. Because of their location at an industrial plant, they do not allow for measurements to be recorded directly in the forest. This precondition was a requirement for our project, since the aim was to assess the debarking efficiency of modified harvesting heads during live forest operations
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Summary
Remote sensing technologies play an important role as nondestructive tools used to evaluate numerous scientific questions and approaches. In addition to tree morphology and stand structure, optical measurement systems are increasingly used for detailed investigations of the resulting forest products Such radioscopic and nondestructive measurement systems (flat X-ray, CT scanners, laser, or photo-optical systems) are normally positioned at the in-feed of debarking facilities or the first manufacturing line within an industrial plant to search for beneficial or undesirable log characteristics such as resin pockets, branches, cracks, impurities, and foreign bodies [20,21,22]. Because of their location at an industrial plant, they do not allow for measurements to be recorded directly in the forest This precondition was a requirement for our project, since the aim was to assess the debarking efficiency of modified harvesting heads during live forest operations. Such harvesting heads are used in mechanized forest operations to fell, delimb, and process trees into assortments of varying lengths
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