Study on Tree Volume Measurement Using Terrestial and Airbone Laser Scanners†

This study aimed to utilize LiDAR, a high-precision surveying technology, to compensate for errors caused by human measurements and obtain accurate and consistent data for tree volume measurement. To this end, a comparative verification of measured tree volume values by each method was conducted using terrestrial LiDAR (TLS) and drone LiDAR (ALS). As a result of examining the 3D data of trees according to the measurement method, it was confirmed that the output data of terrestrial LiDAR had insufficient crowns, and the output data of drone LiDAR had insufficient trunks. Therefore, the study attempted to establish a complete form by aligning the two data sets. In addition, two verifications of tree volume values were conducted using the point cloud data output by each method. As a result of the first verification, the accuracy verification of terrestrial LiDAR showed a difference of 1-3 m in tree height compared to the existing field survey measurement value. The discrepancy is believed to be due to the density of trees or terrain and features according to the principle of LiDAR. In the second verification, terrestrial LIDAR, drone LIDAR, terrestrial LIDAR, and drone LIDAR alignment data were compared. In order to compare the tree height and breast height diameter according to each measurement method, Bland-Altman descriptive statistics were performed based on the field survey measurement values. Considering the results, the drone LIDAR measurement method showed the highest repeatability coefficient, indicating the least consistency, while the drone and terrestrial LIDAR alignment data values showed the lowest repeatability coefficient, indicating high consistency. For the breast height diameter, the terrestrial LIDAR measurement method showed a low repeatability coefficient similar to the drone and terrestrial LIDAR alignment data values, indicating high consistency. Therefore, it is judged that the method of overlapping drone and terrestrial LIDAR data when measuring the structure of trees can derive more precise tree volume information.