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Volumetric overestimation of small branches in 3D reconstructions of Fraxinus excelsior

Demol, M; Wilkes, P; Raumonen, P; Moorthy, SMK; Calders, K; Gielen, B; Verbeeck, H; (2022) Volumetric overestimation of small branches in 3D reconstructions of Fraxinus excelsior. Silva Fennica , 56 (1) , Article 10550. 10.14214/sf.10550. Green open access

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Abstract

Terrestrial laser scanning (TLS) has been applied to estimate forest wood volume based on detailed 3D tree reconstructions from point cloud data. However, sources of uncertainties in the point cloud data (alignment and scattering errors, occlusion, foliage…) and the reconstruction algorithm type and parameterisation are known to affect the reconstruction, especially around finer branches. To better understand the impacts of these uncertainties on the accuracy of TLS-derived woody volume, high-quality TLS scans were collected in leaf-off conditions prior to destructive harvesting of two forest-grown common ash trees (Fraxinus excelsior L.; diameter at breast height ~28 cm, woody volume of 732 and 868 L). We manually measured branch diameters at 265 locations in these trees. Estimates of branch diameters and tree volume from Quantitative Structure Models (QSM) were compared with these manual measurements. The accuracy of QSM branch diameter estimates decreased with smaller branch diameters. Tree woody volume was overes-timated (+336 L and +392 L) in both trees. Branches measuring < 5 cm in diameter accounted for 80% and 83% of this overestimation respectively. Filtering for scattering errors or improved coregistration approximately halved the overestimation. Range filtering and modified scanning layouts had mixed effects. The small branch overestimations originated primarily in limitations in scanner characteristics and coregistration errors rather than suboptimal QSM parameterisation. For TLS-derived estimates of tree volume, a higher quality point cloud allows smaller branches to be accurately reconstructed. Additional experiments need to elucidate if these results can be generalised beyond the setup of this study.

Type: Article
Title: Volumetric overestimation of small branches in 3D reconstructions of Fraxinus excelsior
Open access status: An open access version is available from UCL Discovery
DOI: 10.14214/sf.10550
Publisher version: https://doi.org/10.14214/sf.10550
Language: English
Additional information: © 2022 The Finnish Society of Forest Science. This is an Open Access article distributed under the terms of the Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/deed.en).
Keywords: aboveground biomass; common ash; crown architecture; lidar; quantitative structure models; woody tree volume
UCL classification: UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS
UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS > Dept of Geography
UCL > Provost and Vice Provost Offices > UCL SLASH
UCL
URI: https://discovery.ucl.ac.uk/id/eprint/10144123
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