Article (Scientific journals)
Canopy Gap Mapping from Airborne Laser Scanning: An Assessment of the Positional and Geometrical Accuracy
Bonnet, Stéphanie; Gaulton, Rachel; Lehaire, François et al.
2015In Remote Sensing, 7, p. 11267-11294
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Keywords :
forest canopy gaps; ALS; raster-based approach; segmentation; random forest; geometric accuracy; stand types
Abstract :
[en] Canopy gaps are small-scale openings in forest canopies which offer suitable micro-climatic conditions for tree regeneration. Field mapping of gaps is complex and time-consuming. Several studies have used Canopy Height Models (CHM) derived from airborne laser scanning (ALS) to delineate gaps but limited accuracy assessment has been carried out, especially regarding the gap geometry. In this study, we investigate three mapping methods based on raster layers produced from ALS leaf-off and leaf-on datasets: thresholding, per-pixel and per-object supervised classifications with Random Forest. In addition to the CHM, other metrics related to the canopy porosity are tested. The gap detection is good, with a global accuracy up to 82% and consumer’s accuracy often exceeding 90%. The Geometric Accuracy (GAc) was analyzed with the gap area, main orientation, gap shape-complexity index and a quantitative assessment index of the matching with reference gaps polygons. The GAc assessment shows difficulties in identifying a method which properly delineates gaps. The performance of CHM-based thresholding was exceeded by that of other methods, especially thresholding of canopy porosity rasters and the per-pixel supervised classification. Beyond assessing the methods performance, we argue the critical need for future ALS-based gap studies to consider the geometric accuracy of results.
Disciplines :
Agriculture & agronomy
Author, co-author :
Bonnet, Stéphanie ;  Université de Liège > Ingénierie des biosystèmes (Biose) > Gestion des ressources forestières et des milieux naturels
Gaulton, Rachel
Lehaire, François
Lejeune, Philippe ;  Université de Liège > Ingénierie des biosystèmes (Biose) > Gestion des ressources forestières et des milieux naturels
Language :
English
Title :
Canopy Gap Mapping from Airborne Laser Scanning: An Assessment of the Positional and Geometrical Accuracy
Alternative titles :
[fr] Cartographie de trouées forestières à partir de LiDAR aérien : Une évaluation de la précision de positionnement et géométrique
Publication date :
2015
Journal title :
Remote Sensing
eISSN :
2072-4292
Publisher :
MDPI
Volume :
7
Pages :
11267-11294
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 03 October 2015

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