Lumber value differences from reduced CT spatial resolution and simulated log sawing

In the past few years, computed tomography (CT) scanning technology has been applied to the detection of internal defects in hardwood logs for the purpose of obtaining a priori information that can be used to arrive at better log sawing decisions. Because sawyers currently cannot even see the inside of a log until the log faces are revealed by sawing, there is little perceived need to obtain scan images as detailed as those obtained in medical CT imaging. Yet, CT scanner speed and the usefulness of CT data for decision-making are dependent on the spatial resolution of scans. Spatial resolution is a function of three factors: physical pixel size, scan thickness, and scan frequency (pitch). A 3*23 factorial experiment was designed with two levels for each of these three factors, to test their effect on lumber values. Three hypothetical logs corresponding to three hardwood log grades were simulation-scanned, then simulation-sawed by a human operator using a modified Malcolm opening face heuristic. Log grade affected lumber value recovery as expected, although reduced spatial resolution (by doubling the pitch, thickness, and pixel size) exhibited no discernible pattern in our statistical tests for effects. Volume recovery for below grade boards was predicted very accurately by size, thickness, and pitch-size. The greatest opportunity for lumber value recovery improvement using information-augmented sawing appears to be in grade #2 logs.