Retrieval of three-dimensional tree canopy and shade using terrestrial laser scanning (TLS) data to analyze the cooling effect of vegetation

Kong, Fanhua; Yan, Wei-jiao; Zheng, Guang; Yin, Hui; Cavan, Gina; Zhan, Wenfeng; Zhang, Ning; Cheng, Liang

doi:10.1016/j.agrformet.2015.11.005

Cited by 111 publications

(49 citation statements)

References 61 publications

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“…The mean annual temperature is 15 °C, with a mean daily maximum temperature of 31 °C between June and August. Between 1951 and 2016, Nanjing experienced 127 summer heat wave events, defined as three consecutive days when the daily maximum temperature equals to or exceeds 35 °C [16,41]. Per capita public green space in Nanjing has increased rapidly since the implementation of Urban Green Space System (UGSS) planning in 1997, from 8m 2 to 15m 2 in 2014.…”

Section: Experiments and Methodsmentioning

confidence: 99%

“…(2) Point density of 3DPC of green façade (PD 3DPC ) Three-dimensional greening quantity (i.e., the spatial volume formed by the stem and leaves of a plant) is an important parameter to evaluate the ecosystem service benefits of green infrastructure [16]. Given the limited ability of traditional methods to precisely quantify this parameter, few studies have investigated the relationship between vegetation mass and cooling effect of green façades at a fine scale [12], although previous studies have identified a strong influence of vegetation mass on cooling performance for tree canopies [16,23].…”

Section: Plant Characteristicsmentioning

confidence: 99%

“…However, few scientific investigations have quantified this cooling effect at a high spatial resolution within individual walls, because it is difficult to acquire temperature data and vegetation characteristics at such a fine scale [12,18]. With the development of LiDAR-based sensing techniques, the use of terrestrial laser scanning (TLS) to quantify plant characteristics such as LAI, plants thicknesses, and density has grown rapidly [7,16,23,35,43]. To date, TLS has mainly been used to measure structural tree or forest canopy parameters; little research has been conducted on climbing plant characteristics of green façades [2].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Cooling effect of direct green façades during hot summer days: An observational study in Nanjing, China using TIR and 3DPC data

Yin

Kong

Middel

et al. 2017

Building and Environment

Self Cite

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Highlights• Direct green façades (DGFs) are being applied to buildings in high density cities.• A new methodology to evaluate DGFs' fine-scale cooling effect is presented.• DGF enables 4.67 and 8.03 °C maximum surface temperature reduction compared to bare wall at overall and pixel scales.• DGF cooling effect is most obvious around midday and significantly decreases at night.• Surface temperatures of DGF exhibit significant spatial variations at pixel scale. AbstractThermal regulation is a key ecosystem service provided by direct green façades (DGFs), as vegetated walls absorb short wave radiation, reduce solar re-radiation from hard surfaces, and provide cooling due to shading and evapotranspiration. Few studies have investigated the correlation between the cooling effect of DGFs and vegetation characteristics at a fine spatial and temporal scale. This paper presents a new methodology to evaluate the cooling effect of DGFs related to fine-scale plant characteristics for hot summer days using thermal infrared (TIR) and three-dimensional point cloud (3DPC) data, through a case study conducted at the Executive Office Building on Nanjing University's Xianlin Campus, China. Results show that daily mean DGF surface temperature is significantly lower than the average bare wall surface temperature, with a maximum reduction of 4.67 °C. The cooling effect of the DGF is most obvious during midday (10:30 h to 16:00 h) and significantly decreases at night. At the pixel scale, the DGF exhibits a significant spatial variation of surface temperatures, which may be closely related to the DGF's canopy structure. Among the four vegetation indices acquired based on 3DPC data, the percentage of green coverage and the cooling effect of the DGF exhibited a linear relationship, while plant thicknesses, point density, and volume of the green façade were power function distributions. Incoming solar radiation and air temperature are the dominant independent variables in cooling effect and surface temperature fitting models. Our findings can guide DGF design to cool the thermal environment more effectively and to enhance building energy savings.

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Section: Experiments and Methodsmentioning

confidence: 99%

Section: Plant Characteristicsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Cooling effect of direct green façades during hot summer days: An observational study in Nanjing, China using TIR and 3DPC data

Yin

Kong

Middel

et al. 2017

Building and Environment

Self Cite

View full text Add to dashboard Cite

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“…Small-leaved tree species tend to be more effective at cooling than larger-leaved species [12,13]. Therefore, the cooling effect and shading of plants is mainly determined by the canopy density, leaf arrangement, height, branch spread, bole height, solar radiation, and optical properties of the leaves [8,14,15].…”

Section: Introductionmentioning

confidence: 99%

Screening of Tree Species for Improving Outdoor Human Thermal Comfort in a Taiwanese City

Lin

Tsai

2017

Sustainability

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Tropical cities can use urban greening designs featuring trees that provide shade and cooling in hot outdoor environments. The cooling effect involves numerous tree characteristics that are not easy to control during planting design, such as the canopy size and the optical properties of leaves. Planting the appropriate tree species dominates the cooling effects and the human thermal environment. Based on environmental and plant data, including the tree species, crown diameter of trees, physiologically equivalent temperature (PET), and sky view factor (SVF) in an outdoor space, a series of hierarchical cluster analysis (HCA) procedures was implemented to identify the tree species that are appropriate for improving thermal comfort. The results indicated strong correlations between SVF, average crown diameter, and PET. SVF decreased as the average crown diameter increased. For the average crown diameter of trees in an area wider than 1.5 m, the cooling effect was especially dominated by the tree species. Therefore, 15 species were screened by HCA procedures, based on a similar cooling effect. These species had various cooling effects, and were divided into four categories. Tree species, such as Spathodea campanulata and Cinnamomum camphora, had the appropriate crown diameter and cooling effect for the most comfortable thermal environment.

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“…Moreover, different space partitioning methods and projection strategies, such as point quadrat analysis [17], voxelization of 3D scattered laser points [18], and different projection methods for transforming 3D PCD into 2D hemispherical photography images [19,20], were used to retrieve tree leaf area density and canopy LAI values; (2) Computer graphics and machine vision theory were also applied for point cloud processing. Many computer techniques, such as multi-angle photographs and combined multi-view stereo vision algorithms [21,22], have been used to produce high spatial resolution 3D point clouds of vegetation structure.…”

Section: Introductionmentioning

confidence: 99%

A Novel Approach for Retrieving Tree Leaf Area from Ground-Based LiDAR

Yun

et al. 2016

Remote Sensing

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Abstract:Leaf area is an important plant canopy structure parameter with important ecological significance. Light detection and ranging technology (LiDAR) with the application of a terrestrial laser scanner (TLS) is an appealing method for accurately estimating leaf area; however, the actual utility of this scanner depends largely on the efficacy of point cloud data (PCD) analysis. In this paper, we present a novel method for quantifying total leaf area within each tree canopy from PCD. Firstly, the shape, normal vector distribution and structure tensor of PCD features were combined with the semi-supervised support vector machine (SVM) method to separate various tree organs, i.e., branches and leaves. In addition, the moving least squares (MLS) method was adopted to remove ghost points caused by the shaking of leaves in the wind during the scanning process. Secondly, each target tree was scanned using two patterns, i.e., one scan and three scans around the canopy, to reduce the occlusion effect. Specific layer subdivision strategies according to the acquisition ranges of the scanners were designed to separate the canopy into several layers. Thirdly, 10% of the PCD was randomly chosen as an analytic dataset (ADS). For the ADS, an innovative triangulation algorithm with an assembly threshold was designed to transform these discrete scanning points into leaf surfaces and estimate the fractions of each foliage surface covered by the laser pulses. Then, a novel ratio of the point number to leaf area in each layer was defined and combined with the total number of scanned points to retrieve the total area of the leaves in the canopy. The quantified total leaf area of each tree was validated using laborious measurements with a LAI-2200 Plant Canopy Analyser and an LI-3000C Portable Area Meter. The results showed that the individual tree leaf area was accurately reproduced using our method from three registered scans, with a relative deviation of less than 10%. Nevertheless, estimations from only one scan resulted in a deviation of >25% in the retrieved individual tree leaf area due to the occlusion effect. Indeed, this study provides a novel connection between leaf area estimates and scanning sensor configuration and supplies an interesting method for estimating leaf area based on PCD.

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Retrieval of three-dimensional tree canopy and shade using terrestrial laser scanning (TLS) data to analyze the cooling effect of vegetation

Cited by 111 publications

References 61 publications

Cooling effect of direct green façades during hot summer days: An observational study in Nanjing, China using TIR and 3DPC data

Cooling effect of direct green façades during hot summer days: An observational study in Nanjing, China using TIR and 3DPC data

Screening of Tree Species for Improving Outdoor Human Thermal Comfort in a Taiwanese City

A Novel Approach for Retrieving Tree Leaf Area from Ground-Based LiDAR

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