Fast and Reliable: Evaluating Smartphone LiDAR App for Stem Diameter Measurement and Tree Mapping

Tree inventories require rapid, accurate measurements of stem diameter at breast height (DBH) and precise tree locations for monitoring, planning, and decision-making. We evaluated the smartphone-based LiDAR application (SBLA) ForestScanner across forest plots in the Czech Republic, Mexico, and the USA, comparing it with a diameter tape for DBH and a Vertex ultrasonic device for tree coordinates. Across 725 trees, SBLA-derived DBH closely matched tape measurements: discrepancies >5 cm occurred in 10.5% of trees and >10 cm in 3.5%. The mean absolute error was 2.85 cm, and the root mean squared error was 5.24 cm. Errors were concentrated in smaller trees, where SBLA tended to overestimate stem diameter because of occasional point-cloud misfitting, whereas agreement was consistently high for medium and large trees. Tree coordinates from SBLA and the ultrasonic device were broadly comparable at fine scales. Field efficiency was substantially improved: a 1,000 m2 plot with 70–80 trees required ~2 hours using the traditional approach versus ~20 minutes with one SBLA operator. Current limitations are mainly software-related. Overall, SBLA provides an efficient, auditable, and operationally relevant tool for tree inventories.