scholarly journals Accounting for Wood, Foliage Properties, and Laser Effective Footprint in Estimations of Leaf Area Density from Multiview-LiDAR Data

2019 ◽  
Vol 11 (13) ◽  
pp. 1580 ◽  
Author(s):  
François Pimont ◽  
Maxime Soma ◽  
Jean-Luc Dupuy
Keyword(s):  
Leaf Area ◽  
Point Clouds ◽  
Tree Canopy ◽  
New Approach ◽  
Area Density ◽  
Leaf Area Density ◽  
Previous Formulation ◽  
Lad Estimation ◽  
New Formulation ◽  
Correction Terms

The spatial distribution of Leaf Area Density (LAD) in a tree canopy has fundamental functions in ecosystems. It can be measured through a variety of methods, including voxel-based methods applied to LiDAR point clouds. A theoretical study recently compared the numerical errors of these methods and showed that the bias-corrected Maximum Likelihood Estimator was the most efficient. However, it ignored (i) wood volumes, (ii) vegetation sub-grid clumping, (iii) the instrument effective footprint, and (iv) was limited to a single viewpoint. In practice, retrieving LAD is not straightforward, because vegetation is not randomly distributed in sub-grids, beams are divergent, and forestry plots are sampled from more than one viewpoint to mitigate occlusion. In the present article, we extend the previous formulation to (i) account for both wood volumes and hits, (ii) rigorously include correction terms for vegetation and instrument characteristics, and (iii) integrate multiview data. Two numerical experiments showed that the new approach entailed reduction of bias and errors, especially in the presence of wood volumes or when multiview data are available for poorly-explored volumes. In addition to its conciseness, completeness, and efficiency, this new formulation can be applied to multiview TLS—and also potentially to UAV LiDAR scanning—to reduce errors in LAD estimation.

scholarly journals Accounting for Wood, Foliage Properties and Laser Effective Footprint in Estimations of Leaf Area Density from multiview-LiDAR Data

2019 ◽  
Author(s):  
Francois Pimont ◽  
Maxime Soma ◽  
Jean-Luc Dupuy
Keyword(s):  
Maximum Likelihood ◽  
Leaf Area ◽  
Point Clouds ◽  
Tree Canopy ◽  
Estimation Methods ◽  
Numerical Comparison ◽  
Area Index ◽  
Area Density ◽  
Leaf Area Density ◽  
Contact Frequency

The amount and spatial distribution of foliage in a tree canopy have fundamental functions in ecosystems as they affect energy and mass fluxes through photosynthesis and transpiration. They are usually described by the Leaf Area Index (LAI) and the Leaf Area Density (LAD), which can be measured through a variety of methods, including voxel-based methods applied to LiDAR point clouds. A theoretical study recently compared the numerical errors arising from different voxel-based estimation methods for Plant Area Density (PAD) based on Beer’s law-based, contact frequency and Maximum-Likelihood Estimation, showing that the bias-corrected Maximum Likelihood Estimator was theoretically the most efficient. However, this earlier study i) ignored wood volumes; ii) neglected vegetation clumping inside the voxel; iii) ignored instrument characteristics in terms of effective footprint, iv) was limited to a single viewpoint. In practice, retrieving LAD from PAD is not straightforward, vegetation is not randomly distributed in volumes of interest, beams are divergent and forestry plots are usually sampled from more than one viewpoint, to mitigate the effect of occlusion. In the present short communication, we extend the previous efficient formulation to actual field conditions to i) account for the presence of both wood volumes and wood hits, ii) rigorously include correction terms for vegetation and instrument characteristics, iii) integrate multiview data. A numerical comparison with other methods commonly used to combine information from different viewpoints led to error reduction, especially in poorly-explored volumes, which are frequent in actual canopies. Beyond its concision, completeness and efficiency, this new formulation -which can be applied to multiview TLS, but also UAV LiDAR scanning - can help reducing errors in LAD estimation.

scholarly journals Estimation of maize plant height and leaf area index dynamics using an unmanned aerial vehicle with oblique and nadir photography

2020 ◽  
Vol 126 (4) ◽  
pp. 765-773 ◽  
Author(s):  
Yingpu Che ◽  
Qing Wang ◽  
Ziwen Xie ◽  
Long Zhou ◽  
Shuangwei Li ◽  
...  
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Plant Height ◽  
Large Scale ◽  
High Efficiency ◽  
Point Clouds ◽  
Phenotypic Traits ◽  
Area Index ◽  
Area Density ◽  
Leaf Area Density

Abstract Background and Aims High-throughput phenotyping is a limitation in plant genetics and breeding due to large-scale experiments in the field. Unmanned aerial vehicles (UAVs) can help to extract plant phenotypic traits rapidly and non-destructively with high efficiency. The general aim of this study is to estimate the dynamic plant height and leaf area index (LAI) by nadir and oblique photography with a UAV, and to compare the integrity of the established three-dimensional (3-D) canopy by these two methods. Methods Images were captured by a high-resolution digital RGB camera mounted on a UAV at five stages with nadir and oblique photography, and processed by Agisoft Metashape to generate point clouds, orthomosaic maps and digital surface models. Individual plots were segmented according to their positions in the experimental design layout. The plant height of each inbred line was calculated automatically by a reference ground method. The LAI was calculated by the 3-D voxel method. The reconstructed canopy was sliced into different layers to compare leaf area density obtained from oblique and nadir photography. Key Results Good agreements were found for plant height between nadir photography, oblique photography and manual measurement during the whole growing season. The estimated LAI by oblique photography correlated better with measured LAI (slope = 0.87, R2 = 0.67), compared with that of nadir photography (slope = 0.74, R2 = 0.56). The total number of point clouds obtained by oblique photography was about 2.7–3.1 times than those by nadir photography. Leaf area density calculated by nadir photography was much less than that obtained by oblique photography, especially near the plant base. Conclusions Plant height and LAI can be extracted automatically and efficiently by both photography methods. Oblique photography can provide intensive point clouds and relatively complete canopy information at low cost. The reconstructed 3-D profile of the plant canopy can be easily recognized by oblique photography.

Detecting seasonal change of broad-leaved woody canopy leaf area density profile using 3D portable LIDAR imaging

2009 ◽  
Vol 36 (11) ◽  
pp. 998 ◽  
Author(s):  
Fumiki Hosoi ◽  
Kenji Omasa
Keyword(s):  
Leaf Area ◽  
Seasonal Change ◽  
Lidar Data ◽  
Area Density ◽  
Cloud Data ◽  
Vertical Leaf ◽  
Leaf Area Density ◽  
Different Seasons ◽  
Lad Estimation ◽  
Autumn And Winter

Seasonal change of vertical leaf area density (LAD) profiles of woody canopy broad-leaved trees (Zelkova serrata [Thunberg] Makino) was estimated using 3D portable scanning light detection and ranging (LIDAR) imaging. First, 3D point cloud data for the canopy were collected using a portable LIDAR in spring, summer, autumn and winter. For data collection, the canopy was evenly scanned by the LIDAR from three positions 10 m above the ground. Next, the vertical LAD profile in each season was computed from the LIDAR data using the voxel-based canopy profiling (VCP) method. For the computation, non-photosynthetic tissues were eliminated using the LIDAR data obtained during winter. Influence of leaf inclination angle (LIA) on LAD estimation was corrected by LIA data measured by a high-resolution portable scanning LIDAR. The resultant profiles showed that LAD values tended to increase at the upper canopy from spring to summer and decrease at the middle and lower canopy from summer to autumn. Moreover, LIDAR-derived LIA distributions were compared among different seasons. LIA showed an even distribution in spring but changed to a planophile distribution in summer. In autumn, the angles in the <30° class decreased and those between the 30 and 40°classes increased.

scholarly journals Estimating cover fraction from TLS return intensity in coniferous and broadleaved tree shoots

Silva Fennica ◽  
2021 ◽  
Vol 55 (4) ◽  
Author(s):  
Daniel Schraik ◽  
Aarne Hovi ◽  
Miina Rautiainen
Keyword(s):  
Leaf Area ◽  
Laser Scanning ◽  
Forest Canopy ◽  
Point Clouds ◽  
Laser Beams ◽  
Experimental Calibration ◽  
Area Density ◽  
Leaf Area Density ◽  
Calibration Measurement ◽  
Lidar Return

Terrestrial laser scanning (TLS) provides a unique opportunity to study forest canopy structure and its spatial patterns such as foliage quantity and dispersal. Using TLS point clouds for estimating leaf area density with voxel-based methods is biased by the physical dimensions of laser beams, which violates the common assumption of beams being infinitely thin. Real laser beams have a footprint size larger than several millimeters. This leads to difficulties in estimating leaf area density from light detection and ranging (LiDAR) in vegetation, where the target objects can be of similar or even smaller size than the beam footprint. To compensate for this bias, we propose a method to estimate the per-pulse cover fraction, defined as the fraction of laser beams’ footprint area that is covered by vegetation targets, using the LiDAR return intensity and an experimental calibration measurement. We applied this method to a Leica P40 single-return instrument, and report our experimental results. We found that conifer foliage had a lower average per-pulse cover fraction than broadleaved foliage, indicating an increased number of partial hits in conifer foliage. We further discuss limitations of our method that stem from unknown target properties that influence the LiDAR return intensity and highlight potential ways to overcome the limitations and manage the remaining uncertainty. Our method’s output, the per-beam cover fraction, may be useful in a weight function for methods that estimate leaf area density from LiDAR point clouds.

scholarly journals Influence of Tree Canopy Coverage and Leaf Area Density on Urban Heat Island Mitigation

2021 ◽  
Vol 13 (13) ◽  
pp. 7496
Author(s):  
Atefeh Tamaskani Esfehankalateh ◽  
Jack Ngarambe ◽  
Geun Young Yun
Keyword(s):  
Leaf Area ◽  
Urban Areas ◽  
Tree Canopy ◽  
Urban Trees ◽  
Urban Heat Islands ◽  
Daily Maximum ◽  
Area Density ◽  
Leaf Area Density ◽  
Urban Heat ◽  
Cooling Effects

Urban heat islands (UHI) are a widely documented phenomenon that adversely increases urban overheating and, among other effects, contributes to heat-related mortalities and morbidities in urban areas. Consequently, comprehensive UHI-mitigating measures are essential for improving urban microclimate environments and contributing to salutogenic urban design practices. This study proposed urban cooling strategies involving different tree percentages and leaf area densities in a dense urban area during the summertime in Korea. The cooling effects of sixteen various combinations of proposed scenarios based on common urban tree types were studied via in-situ field measurements and numerical modeling, considering both vegetated and exposed areas. It was observed that by changing the characteristics of the leaf area density (LAD) per plant of our vegetated base area—for instance, from 4% trees to 60% trees, from a low LAD to a high LAD—the daily average and daily maximum temperatures were reduced by approximately 3 °C and 5.23 °C, respectively. The obtained results demonstrate the usefulness of urban trees to mitigate urban heating, and they are particularly useful to urban designers and policymakers in their efforts to minimize UHI effects.

scholarly journals STUDY ON INDIRECT ESTIMATING LEAF AREA DENSITY

2006 ◽  
Vol 71 (603) ◽  
pp. 111-117
Author(s):  
Ai KADAIRA ◽  
Harunori YOSHIDA ◽  
Daisuke MURAKAMI ◽  
Mamiko ITOU
Keyword(s):  
Leaf Area ◽  
Area Density ◽  
Leaf Area Density

Effect of sward structure of two tropical grasses with contrasting canopies on light distribution, net photosynthesis and size of bite harvested by grazing cattle

1982 ◽  
Vol 33 (2) ◽  
pp. 187 ◽  
Author(s):  
MM Ludlow ◽  
TH Stobbs ◽  
R Davos ◽  
DA Charles-Edwards
Keyword(s):  
Leaf Area ◽  
Growth Regulators ◽  
Light Distribution ◽  
Trimethylammonium Chloride ◽  
Tropical Pastures ◽  
Area Density ◽  
Tropical Grasses ◽  
Bite Size ◽  
Leaf Area Density ◽  
Grazing Cattle

Our aim was to determine whether increasing the sward density of tropical pastures, for the purpose of enhancing the size of bite harvested by grazing cattle, would reduce yield by affecting light distribution andcanopy photosynthesis. The growth regulators (2-chloroethy1)trimethylammonium chloride (CCC) and gibberillic acid (GA) were used to alter the leaf area density of the tussock-forming grass Setavia sphacelata and of the sward-forming grass Digitaria decumbens. GA increased plant height, the length of stem internodes, and the size of bite harvested by cattle. On the other hand, CCC decreased canopy height, and increased leaf area density and bite size. The variation of leaf area density, investigated experimentally by using growth regulators (5-25 m-1) and theoretically by simulation modelling (5-40 m-1), had no significant effect on either leaf or canopy photosynthetic characteristics. Hence we believe that there would be a negligible reduction in yield of these tropical grasses if their leaf area densities were increased up to a value of 40 m-1, which exceeds those of temperate pastures. Such increases in leaf area density may increase animal production from tropical pastures where bite size limits daily intake of forage. The agricultural implications of the findings are discussed.

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