Fig. 1. Location of study area and distribution of data

Fig. 2. Photons separated by quadtree

Fig. 3. Tree structure of photons separated by quadtree

Fig. 4. Photons incorrectly separated by quadtree

Fig. 5. Tree structure of photons incorrectly separated by quadtree

Fig. 6. Photons separated by pruned quadtree

Fig. 7. Tree structure of photons separated by pruned quadtree

Fig. 8. Outlier detection by box-plot

Fig. 9. Initial point cloud in study area 1

Fig. 10. Initial point cloud in study area 2

Fig. 11. Denoising result of quadtree method in study area1

Fig. 12. Denoising result of pruned quadtree method in study area1

Fig. 13. Denoising result of quadtree method and second-level denoising in study area 1

Fig. 14. Denoising result of pruned quadtree method and second-level denoising in study area 1

Fig. 15. Ground curves in study area 1

Fig. 16. Denoising result of quadtree method in study area 2

Fig. 17. Denoising result of pruned quadtree method in study area 2

Fig. 18. Denoising result of quadtree method and second-level denoising in study area 2

Fig. 19. Denoising result of pruned quadtree method and second-level denoising in study area 2

Fig. 20. Canopy top curves in study area 2

Fig. 21. Ground curves in study area 2