Benchmarking of Individual Tree Segmentation Methods in Mediterranean Forest Based on Point Clouds from Unmanned Aerial Vehicle Imagery and Low-Density Airborne Laser Scanning

• Published in: Remote sensing (Basel, Switzerland) Vol. 16; no. 21; p. 3974
• Main Authors: Nemmaoui, Abderrahim, Aguilar, Fernando J., Aguilar, Manuel A.
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-11-2024
• Subjects: Accuracy; Aerial photography; Airborne lasers; Algorithms; Analysis; Benchmarks; Biomass; Carbon; crown diameter; Data collection; Density; Drone aircraft; Estimation; forest inventory; Forests; Geospatial data; Ground stations; Height; Image processing; Image resolution; Image segmentation; individual tree detection; Laser applications; Lasers; low-density ALS; Methods; PCB; Photogrammetry; Pine trees; point clouds; Polychlorinated biphenyls; Raster scanning; Remote sensing; tree height; Trees; Unmanned aerial vehicles; Syria; Spain
• ISSN: 2072-4292; 2072-4292
• DOI: 10.3390/rs16213974

Three raster-based (RB) and one point cloud-based (PCB) algorithms were tested to segment individual Aleppo pine trees and extract their tree height (H) and crown diameter (CD) using two types of point clouds generated from two different techniques: (1) Low-Density (≈1.5 points/m2) Airborne Laser Scanning (LD-ALS) and (2) photogrammetry based on high-resolution unmanned aerial vehicle (UAV) images. Through intensive experiments, it was concluded that the tested RB algorithms performed best in the case of UAV point clouds (F1-score > 80.57%, H Pearson’s r > 0.97, and CD Pearson´s r > 0.73), while the PCB algorithm yielded the best results when working with LD-ALS point clouds (F1-score = 89.51%, H Pearson´s r = 0.94, and CD Pearson´s r = 0.57). The best set of algorithm parameters was applied to all plots, i.e., it was not optimized for each plot, in order to develop an automatic pipeline for mapping large areas of Mediterranean forests. In this case, tree detection and height estimation showed good results for both UAV and LD-ALS (F1-score > 85% and >76%, and H Pearson´s r > 0.96 and >0.93, respectively). However, very poor results were found when estimating crown diameter (CD Pearson´s r around 0.20 for both approaches).