Application and accuracy of smart technologies for measurements of roundwood: Evaluation of time consumption and efficiency

Several options are currently available for wood measurement and grading and the manual ones are still widely used in many countries. In the last decade, LiDAR-based methods have been successfully tested in several forestry-related applications, in particular in forest inventory applications, with the main focus on data accuracy. Their usefulness for the quantitative assessment of the harvested wood was less investigated. In particular, studies on resource accounting, including the time needed for various log scanning options, are still missing. In the framework of the Hypercube 4.0 project, this study evaluated and compared the field measurement time consumption of manual (M) and LiDAR-based methods applied to logs characterized by various grouping degrees, namely individual logs, log bunches and piles. Two LiDAR-based platforms were tested, namely a smartphone (S) and a mobile laser scanner (MLS). As these platforms hold different sensing, data storing and processing capabilities, scanning procedures were designed and tested in accordance with their sensing distance capabilities and with the potential of using them in real-world applications. Scanning individual logs by smartphones returned an average cycle time which was lower, though close to that of a detailed manual measurement option, accounting for ca. 1.5 min. When scanning log bunches and piles, the cycle time increased to ca. 2.8 and 7 min, respectively; however, the scanning efficiency increased also as an effect of the scanning scale from ca. 92 s per log, when scanning individual logs, to ca. 67 and 46 s per log, when scanning log bunches and piles, respectively. The MLS option was tested for small and big groups of individual logs and log bunches scanned in one turn, as well as for scanning individual piles of logs; in general, these options returned the best efficiency rates, accounting in the best case for ca. 19 s per log. Depending on the type of wood measurement application, by their efficiency, smartphone and MLS scanning platforms hold the potential of replacing the manual measurement, particularly when the use of manual procedures is limited. While this study evaluated the time consumption and efficiency of several scanning options, the question on data accuracy remains open and needs to be approached by future studies, some of which are already running in the framework of the Hypercube 4.0 project.