Acta Scientiarum Polonorum
Silvarum Colendarum Ratio et Industria Lignaria

Volume of large-sized cut to length timber is typically determined based on measurement of top diameter inside bark (dg). In practice this measurement is taken at the smallest diameter and the result is rounded down to full number of cm. The primary aim of this study was to assess the effect of the manner of measuring the top diameter on the resulting calculation of log volume. Changes in the number and total volume of logs in individual size classes. Measurements were taken on 1200 pine logs in all size classes (1K – dg<22 cm, 2K – dg: 23–32 cm, 3K – dg≥33 cm). The top diameter of logs was measured using four methods: in two methods a single measurement was taken on the smallest diameter rounding the results to full cm: down (method 1), either up or down (method 2) (rounding up in the case of results >5 mm after the decimal point, rounding down the results £5 mm after the decimal point). In the next two methods the smallest and the largest diameters were measured, with the results rounded down to full cm. The mean of these measurements was rounded down in method 3 to full cm, while in method 4  the mathematical rules were followed. In methods 2, 3 and 4 increased values were obtained for means of log volume by 1.6%, 2.6% and 3.8%, respectively, in relation to method 1. The increase in means of volume was 2-fold greater. In methods 2, 3 and 4 an increase was recorded in the number (and total volume) of logs in size classes 2K and 3K (which was particularly evident in the case of the thickest logs with dg ≥33cm). Analyses showed statistically greater log volume in method 4 compared to method 1 (results for all  logs). In size classes 1K and 2K significantly greater volumes than in method 1 were recorded not only in method 4, but also in method 3. In the case of the thickest logs of size class 3K no statistically significant effect on log volume results was found for the method to determine the top diameter.