Epsilon Open Archive

Abstract

In 2008 a new method for automatic measurement of solid volume under bark (m3sub) of sawlogs was introduced in southern Sweden. In this method the diameters at 10 cm intervals are used, thus producing a section-wise volume (m3sub-sw). The scanners used are programmed to leave out bumps and indents when diameters are calculated. The objective of the study was to compare this method with two other methods used on the Swedish wood market; a) volume based on top and butt end diameters (m3sub-tb) and b) volume based on top end diameters and conversion factors to solid volume (m3sub-cf). The conversion factors are arranged as a matrix based on diameter and length of the logs. Volume m3sub-tb is the most widely used method for measuring m3sub in Sweden. M3sub-cf is partly used for payment but more widely for planning purposes, for example when the logs are priced as a cylinder volume based on top end diameter.

The study was performed on spruce (Picea abies). The three different volume estimates as well as the diameters obtained from the log scanners were evaluated on 435 manually measured control logs from five different mills. For an additional 180 000 automatically measured logs from four of the sawmills the m3sub-sw and m3sub-cf volume estimates were compared.

The results showed only minor differences between the methods. The volume m3sub-sw was, for the 180 000 logs, 0.6 % greater than the volume m3sub-cf. The analysis of the matrix for conversion factors showed that, if the matrix was to be revised, this should be done as slightly increased factors for small diameter logs and for big diameter logs. However, it was concluded that it would mean less implications for the wood market if the section-wise volume could be reduced to make this volume equal to m3sub-tb and m3sub-cf. This to achieve that all three methods, given a sufficient number of representative logs, would give the same volume