6 research outputs found
ESTIMATION OF TREE POSITION AND STEM DIAMETER USING SIMULTANEOUS LOCALIZATION AND MAPPING WITH DATA FROM A BACKPACK-MOUNTED LASER SCANNER
A system was developed for automatic estimations of tree positions and stem diameters. The sensor trajectory was first estimated
using a positioning system that consists of a low precision inertial measurement unit supported by image matching with data from a
stereo-camera. The initial estimation of the sensor trajectory was then calibrated by adjustments of the sensor pose using the laser
scanner data. Special features suitable for forest environments were used to solve the correspondence and matching problems. Tree
stem diameters were estimated for stem sections using laser data from individual scanner rotations and were then used for calibration
of the sensor pose. A segmentation algorithm was used to associate stem sections to individual tree stems. The stem diameter estimates
of all stem sections associated to the same tree stem were then combined for estimation of stem diameter at breast height (DBH). The
system was validated on four 20 m radius circular plots and manual measured trees were automatically linked to trees detected in laser
data. The DBH could be estimated with a RMSE of 19 mm (6 %) and a bias of 8 mm (3 %). The calibrated sensor trajectory and the
combined use of circle fits from individual scanner rotations made it possible to obtain reliable DBH estimates also with a low precision
positioning system