Uporaba iPhone tehnologije lidar za izmero dreves na vzorčnih ploskvah gozdne inventure (= Use of iPhone LiDAR technology for measuring tree parameters in forest inventories sampling plots)

Laser scans of trees in the field could represent a useful technology for complementing and controlling information measured in the context of classic forest inventory. Professional terrestrial and mobile laser scanners remain, however, expensive and require professional handling. For this purpose, we wanted to evaluate the application of low-cost Apple lidar technology for measuring two important forest inventory parameters – the diameter of trees at 1.3 m above ground level (d1,3) and horizontal distances to the centre of sampling inventory plots. These parameters were measured by four independent groups of forest inventory experts on four circular plots near the Slovenian Forestry Institute for all trees with d1,3 ≥ 10 cm, using traditional methods. Subsequently, the plots were scanned with lidar-equipped Apple iPhone 13 Pro Max. The scan data were analysed using open-source software. On average d1,3 values from laser scans were 0.95 cm (RMSE = 2.43 cm) greater than reference values, with larger discrepancies for thinner trees. Conversely, horizontal distances were on average underestimated by 6.7 cm (RMSE = 24.1 cm). Discrepancies in horizontal distances were greater for trees that were measured toward the end of the scanning process, while no such influence of the scanning time was apparent for d1,3. Additionally, we found that growing stock values were overestimated by 2.6%.