Digital measurement of wood stacks: evaluating light detection and ranging and photo-optical methods for volume and conversion factor determination

Accurately measuring the volume of timber is essential for forestry and the wood industry. While manual measurements remain relevant in many countries, digital methods for assessing the volume of entire wood stacks offer greater efficiency and reduce the potential for human error. This study evaluates LiDAR-based and photo-optical methods for wood stack measurement under conditions representative of Austrian forestry practice. Three LiDAR devices (a terrestrial laser scanner (TLS), a personal laser scanner (PLS), and a LiDAR-equipped tablet) as well as four photo-optical applications (iFovea, LogStackLIDAR, PolterMAX, and Timbeter) were used to determine the gross volume, net volume, and conversion factor of 22 wood stacks. The LiDAR-equipped tablet achieved the highest overall accuracy (RMSEgross = 2.44%; RMSEnet = 3.58%; RMSEconversion = 3.26%) in comparison to reference data, demonstrating that even low-cost sensors can deliver precise results. The best performing photo-optical solution was LogStackLIDAR, which also showed good agreement with the reference (RMSEgross = 2.41 %; RMSEnet = 5.28 %; RMSEconversion = 6.06 %). On average, Timbeter and PolterMAX enabled the fastest field measurements per solid cubic meter (scm) of wood (00:02 min/scm and 00:03 min/scm, respectively), followed by the PLS and LiDAR-equipped tablet (00:04 min/scm and 00:05 min/scm, respectively). These results highlight the strong potential of digital measurement technologies, particularly of the LiDAR-equipped tablet, for accurate and efficient wood stack assessment, suggesting their viability as as an alternative to conventional measurement methods.