The logs used from the SPSB
are relatively straight, since the maximum crook is 28 mm, and a distinct hornsdown position can thus be difficult to clearly define.
A previous study has successfully dealt with the validation of the vSM at the single log level (Grundberg and Gronlund 1998) and a large-scale validation approach of the vSM along with the SPSB has been carried out versus a real sawmill yield (Chiorescu and Groulund 2000).
This study uses the log quality information from the SPSB generated by only one professional log grader.
This study is entirely based on the material from the SPSB and on the Swedish visual grading rules for sawlogs and lumber.
Further analysis of the centerboard to sideboard quality relationship was carried out through the use of the vSM simulator together with the SPSB data.
A financial analysis focusing on the relationship between the commercial values of the sawlogs and the corresponding lumber output (centerboards and sideboards) for each log quality class within the SPSB material was also conducted.
There were on average three sideboards per sawlog, where the average small-end diameter for the 610 SPSB sawlogs was 196 mm.
The study was based on the simulation technique, as the SPSB and the vSM were employed.
Figure 2 shows the structure of the SPSB concerning the log offset parameter.
Figure 3 shows a quite uniform distribution of the sawlogs from the SPSB when plotting them in a diameter-length measurement accuracy coordinate system.
One simulation consisted of sawing all 625 logs from SPSB.
With the help of the SPSB and the vSM software, the simulation approach used to conduct this study made two important things workable: 1) it was possible to simulate the log measurement procedure (for both length and diameter) performed by a harvester in the forest; and 2) the downstream steps of the process followed by these sawlogs (diameter sorting, log breakdown, board grading) were all simulated.