@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} } @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} } @article{PurfuerstdeMiguelDiezBerendtetal.2023, author = {Purf{\"u}rst, Thomas and de Miguel-D{\´i}ez, Felipe and Berendt, Ferr{\´e}ol and Engler, Benjamin and Cremer, Tobias}, title = {Comparison of wood stack volume determination between manual, photo-optical, iPad-LiDAR and handheld-LiDAR based measurement methods}, series = {iForest - Biogeosciences and Forestry}, volume = {16}, journal = {iForest - Biogeosciences and Forestry}, number = {4}, publisher = {Italian Society of Silviculture and Forest Ecology}, issn = {1971-7458}, doi = {10.3832/ifor4153-016}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:eb1-opus-8062}, pages = {243 -- 252}, year = {2023}, abstract = {The measurement of roadside wood stacks in the forest still plays an important role in many forestry operations. Traditional manual measuring methods can be laborious, inaccurate and error-prone. Therefore, the issue is whether 2.5D or 3D optical remote sensing measuring methods provide more precise or detailed results and advantages in further data processing. This study examined and partly developed nine different manual, photo-optical, iPad®-LiDAR and handheld laser scanner-LiDAR-based wood stack measurement methods. Forty-seven wood stacks, ranging from 8.9 to 209.3 m3 (totalling approximately 2700 m3), were measured and compared using these nine methods. All the methods give volume estimations, and none can be seen to give the real or true wood stack gross volume. Surprisingly, the results varied significantly within and between the individual methods, with up to a 9\% mean relative deviation. The relative deviation is strongly dependent on the size of the wood stack. The 3D measurement methods using iPad® RGB and LiDAR recorded lower timber volumes than the other methods, in contrast to the method based on samples taken with handheld laser scanner-LiDAR, which overestimated the volume. Generally, optical- and laser-based surveying techniques could be more widely applied in measuring wood stacks in the future. However, such automatic wood stack gross volume determination approaches still face some challenges, regarding accuracy in the case of the 2.5D methods and the lack of automatisation in the case of 3D methods. Consequently, further research is required in the near future.}, language = {en} }