Discussion and conclusion
Many research groups [4,5,6] tested the use of x-ray to get information about the internal structures of a log. This study contains first results about the use under industrial conditions. The possibility to split up the round-wood (before sawing it) into two quality classes due to year ring width is a first step to increase yield. The same separation is possible with ultrasound at a comparable accuracy. Earlier studies, however, emphasized the problems arising with sample dimension, moisture content and grain angle [7,8,9].
Results con-cerning the prediction of strength classes for boards are promising. However, until now the use of ultrasound is not possible under industrial conditions with fast moving logs and other difficulties such as dirt and varying temperatures. Furthermore, single ultrasound measurements can neither define the location nor the kind of internal defects. For a more efficient utilization this information would be of interest, and the potential of further technologies and their combination has to be investigated.

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