Development and evaluation of a novel 3D simulation software for modelling wood stacks

Abstract

Assessing the solid wood content is crucial when acquiring stacked roundwood. A frequently used method for this is to multiply determined conversion factors by the measured gross volume. However, the conversion factors are influenced by several log and stack parameters. Although these parameters have been identified and studied, their individual influence has not yet been analyzed using a broad statistical basis. This is due to the considerable financial resources that the data collection entails. To overcome this shortcoming, a 3D-simulation model was developed. It generates virtual wood stacks of randomized composition based on one individual data set of logs, which may be real or defined by the user. In this study, the development and evaluation of the simulation model are presented. The model was evaluated by conducting a sensitivity and a quantitative analysis of the simulation outcomes based on real measurements of 405 logs of Norway spruce and 20 stacks constituted with these. The results of the simulation outcomes revealed a small overestimation of the net volume of real stacks: by 1.2% for net volume over bark and by 3.2% for net volume under bark. Furthermore, according to the calculated mean bias error (MBE), the model underestimates the gross volume by 0.02%. In addition, the results of the sensitivity analysis confirmed the capability of the model to adequately consider variations in the input parameters and to provide reliable outcomes.

Estimation of conversion factors for wood stacks in landings and their influencing parameters: a comprehensive literature review for America and Europe

“…However, this model had important shortcomings, such as it was not able to generate the logs thoroughly virtually, e.g., it could not simulate the bark. Moreover, the results provided by that 3D simulation model were not validated with real measurements (Miesner 2021;De Miguel-Díez et al 2022a). In contrast, another 3D simulation model was developed and evaluated based on real measurements.…”

“…In contrast, another 3D simulation model was developed and evaluated based on real measurements. The validation results showed its high accuracy in virtually generating and stacking the logs and estimating the stack gross and net volumes (De Miguel-Díez et al 2022a). This simulation model was specifically designed and developed to estimate conversion factors, analyze the influence of the log and stack parameters on the conversion factors, and determine stack volume and solid wood content on a statistical basis.…”

“…According to the analysis conducted by Nikkilä et al (1974), that increase compared to the original stack net volume was up to 1.4 % for manually formed stacks and between 2.9% to 6.2% for mechanically formed stacks. This can be due to the bark is lost when logs are repetitively stacked (De Miguel-Díez et al 2022a). In contrast, Dos Santos Lisboa et al (2009 stated that the number of times the roundwood is handled or moved also plays a certain role.…”