@article{deMiguelDiezTolosanaEstebanPurfuerstetal.2021, author = {de Miguel-D{\´i}ez, Felipe and Tolosana Esteban, Eduardo and Purf{\"u}rst, Thomas and Cremer, Tobias}, title = {Analysis of the Influence That Parameters Crookedness and Taper Have on Stack Volume by Using a 3D-Simulation Model of Wood Stacks}, series = {Forests}, volume = {12}, journal = {Forests}, number = {2}, publisher = {MDPI}, issn = {1999-4907}, doi = {10.3390/f12020238}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:eb1-opus-2527}, pages = {10}, year = {2021}, abstract = {The influence that parameters crookedness and taper have on the stack volume was analyzed by using a 3D-simulation model in this study. To do so, log length, diameters at the midpoint and both ends, crookedness, bark thickness, taper and ovality were measured in 1000 logs of Scots pine. From this database, several data sets with different proportions of crooked and tapered logs in stack as well as with different degrees of taper and crookedness were created and taken as basis to simulate the stacks and carry out the analysis. The results show how the variation of these parameters influences the stack volume and provide their volume variation grades. These rates of variation were compared with measurement guidelines of some countries and previous research works. In conclusion, the parameters crookedness and taper influence the stack volume to a considerable extent. Specifically, the stack volume is increased as the crookedness degree or the proportion of crooked logs increases. In contrast, the stack volume is reduced as the taper degree or the proportion of tapered logs increases. Furthermore, the results demonstrate the capability of this simulation model to provide accurate results which can serve as a basis for future studies.}, language = {en} } @inproceedings{deMiguelDiezTolosanaEstebanCremer2021, author = {de Miguel-D{\´i}ez, Felipe and Tolosana-Esteban, Eduardo and Cremer, Tobias}, title = {3D-Simulation of Wood Stacks to Analyze the Influence of Log Properties on Stack Volume}, series = {Environmental Sciences Proceeding}, booktitle = {Environmental Sciences Proceeding}, number = {3(1)}, publisher = {MDPI}, issn = {2673-4931}, doi = {10.3390/IECF2020-08063}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:eb1-opus-4452}, pages = {6}, year = {2021}, abstract = {The quantification of the solid wood content in a wood stack has been an object of investigation since the 18th century. Particularly, the log parameters exert a considerable influence on the volume of the stack, such as (1) the log midpoint diameter, (2) average bark thickness, (3) crookedness, and (4) log taper. Although many of these parameters have already been studied and some are already considered in many countries when measuring wood stacks, their influence has not been analyzed individually so far since a broad statistical database is needed and the data collection is very costly. Consequently, a 3D-simulation model was developed based on a cross-platform game engine. This model generates virtual wood stacks based on a data set of logs which are defined by the user. The simulation of a stack can be done in a few seconds only and each stack generated can be visualized once all iterations are done. The simulation results are the stacked cubic volume, solid wood cubic volume, and the respective conversion factors. The model, fed with both real data and user-defined data, allows for a detailed analysis of the effect of each parameter on the results, as the user can vary their values discretionary. To obtain the first results from real data, 1000 logs of Scots pine (Pinus sylvestris L.) were measured. The first simulations based on these data show reliable results and it is possible to quantify the influence of the proportion of crooked wood in a pile on the stack volume and the conversion factor. In addition, the results are highly in line with the real trials that have already been performed in parallel. A further scientific evaluation and statistical analysis will be done in a second study phase. However, the model already provides a reasonable tool that is easy to apply for the forest and wood industry in order to make the most accurate estimate possible of the solid wood content in a wood pile.}, language = {en} } @article{deMiguelDiezGuiguePettenkoferetal.2022, author = {de Miguel-D{\´i}ez, Felipe and Guigue, Phillippe and Pettenkofer, Tim and Tolosana-Esteban, Eduardo and Purf{\"u}rst, Thomas and Cremer, Tobias}, title = {Development and evaluation of a novel 3D simulation software for modelling wood stacks}, series = {PLoS ONE}, journal = {PLoS ONE}, number = {17(3)}, issn = {1932-6203}, doi = {10.1371/journal.pone.0264414}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:eb1-opus-4472}, pages = {17}, year = {2022}, 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.}, language = {en} } @article{deMiguelDiezPettenkoferWalloretal.2022, author = {de Miguel-D{\´i}ez, Felipe and Pettenkofer, Tim and Wallor, Evelyn and Tolosana-Esteban, Eduardo and Purf{\"u}rst, Thomas and Cremer, Tobias}, title = {Influence of log and stack parameters on the conversion factors for Norway Spruce wood stacks using a 3D simulation model}, series = {International Journal of Forest Engineering}, volume = {33}, journal = {International Journal of Forest Engineering}, number = {2}, publisher = {Taylor \& Francis}, issn = {1494-2119}, doi = {10.1080/14942119.2022.2038023}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:eb1-opus-4482}, pages = {119 -- 128}, year = {2022}, abstract = {One method for estimating the solid wood content in a stack involves using conversion factors and multiplying these by the measured gross volume. The conversion factors can vary depending on several log and stack parameters. The aim of this study was to analyze eleven parameters using a 3D simulation model based on 541 measured logs of Norway spruce. To this end, 50 data sets were created from measured logs, where the parameters of interest in this study (e.g., length, crookedness, taper …) were classified according to different ranges. After that, 64 runs of simulations were carried out. In each simulation run, 150 stacks were modeled. The simulation results were compared with previous studies and with the measurement guidelines of several countries. This analysis revealed that the parameters midpoint diameter, length, crookedness, delimbing quality and the proportion of moderately and highly crooked logs in a stack have a considerable influence on the conversion factors. Taper, proportion of butt logs in a stack and stack height have a modest effect as do the proportion of tapered and crooked logs for low and high taper and low crookedness. In contrast, ovality and the proportion of logs stacked in opposite directions have a marginal influence on the conversion factors. Based on findings from these analyses, the current measurement guidelines of different countries can now be adapted to achieve a higher degree of accuracy.}, language = {en} } @article{deMiguelDiezPurfuerstAcunaetal.2023, author = {de Miguel-D{\´i}ez, Felipe and Purf{\"u}rst, Thomas and Acuna, Mauricio and Tolosana-Esteban, Eduardo and Cremer, Tobias}, title = {Estimation of conversion factors for wood stacks in landings and their influencing parameters: a comprehensive literature review for America and Europe}, series = {Silva Fennica}, volume = {57}, journal = {Silva Fennica}, number = {1}, publisher = {The Finnish Society of Forest Science}, issn = {2242-4075}, doi = {10.14214/sf.22018}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:eb1-opus-6459}, pages = {47}, year = {2023}, abstract = {In commercial transaction of stacked roundwood, the estimation of the stack net volume plays a key role. One generalized method to determine the net volume is using conversion factors that relate the gross and net volumes. In this literature review the developed methods to estimate the conversion factors as well as their influencing parameters were analyzed based on 153 references from America and Europe. According to the results, 48 different methods (including their variants) for estimating the conversion factors were developed. The newest methods enabled their accurate determination inexpensively, e.g., photo-optical methods or 3D simulation models. The analyzed references revealed that 30 parameters influence the conversion factors. Based on this comprehensive review, each stakeholder involved in the roundwood supply chain can know which method is used for estimating the conversion factors in the analyzed territories and which influencing parameters should be considered when purchasing roundwood in order to accurately assess the solid wood content in the stacks.}, language = {en} }