Leaf BRDF measurements and model for specular and diffuse components differentiation

Bousquet, Laurent; Lachérade, Sophie; Jacquemoud, Stéphane; Moya, I.

doi:10.1016/j.rse.2005.07.005

Cited by 212 publications

(129 citation statements)

References 15 publications

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“…Previous comparison between ASD contact probe and integrating spheres observed slightly smaller mean absolute differences than we did, indicating that factors such as the measurement geometry and design of the probe may influence the comparison [18]. Because leaf spectral BRDFs may vary between species [30], a contact probe is probably not the best choice for comparing spectral differences between species. However, it is well suitable for monitoring relative changes in reflectance and thus physiological status of plants in field conditions, which is where it is usually applied [8][9][10].…”

Section: Systematic Differences Between Methodscontrasting

confidence: 70%

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Evaluation of Accuracy and Practical Applicability of Methods for Measuring Leaf Reflectance and Transmittance Spectra

et al. 2017

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Leaf reflectance and transmittance spectra are urgently needed in interpretation of remote sensing data and modeling energy budgets of vegetation. The measurement methods should be fast to operate and preferably portable to enable quick collection of spectral databases and in situ measurements. At the same time, the collected spectra must be comparable across measurement campaigns. We compared three different methods for acquiring leaf reflectance and transmittance spectra. These were a single integrating sphere (ASD RTS-3ZC), a small double integrating sphere (Ocean Optics SpectroClip-TR), and a leaf clip (PP Systems UNI501 Mini Leaf Clip). With all methods, an ASD FieldSpec 4 spectrometer was used to measure white paper and tree leaves. Single and double integrating spheres showed comparable within-method variability in the measurements. Variability with leaf clip was slightly higher. The systematic difference in mean reflectance spectra between single and double integrating spheres was only minor (average relative difference of 1%), whereas a large difference (14%) was observed in transmittance. Reflectance measured with leaf clip was on average 14% higher compared to single integrating sphere. The differences between methods influenced also spectral vegetation indices calculated from the spectra, particularly those that were designed to track small changes in spectra. Measurements with double integrating sphere were four, and with leaf clip six times as fast as with single integrating sphere, if slightly reduced signal level (integration time reduced from optimum) was allowed for the double integrating sphere. Thus, these methods are fast alternatives to a conventional single integrating sphere. However, because the differences between methods depended on the measured target and wavelength, care must be taken when comparing the leaf spectra acquired with different methods.

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Section: Systematic Differences Between Methodscontrasting

confidence: 70%

“…It is known that leaf spectral BRDFs differ strongly from Lambertian [30] and that the measured reflectance factors therefore depend on view and illumination geometries. The reflectance factor of Spectralon is also dependent on view and illumination geometries [31,32].…”

Section: Systematic Differences Between Methodsmentioning

confidence: 99%

Evaluation of Accuracy and Practical Applicability of Methods for Measuring Leaf Reflectance and Transmittance Spectra

et al. 2017

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“…Presently, there are several mathematical models describing the optic properties of leaves and canopy [127][128][129][130][131][132] and connection of these properties with the content of photosynthetic pigments in leaves [133][134][135][136]. Detailed models of PRI, which include a description of the geometry and discontinuity of canopy and different depth penetrations of light into the canopy, are developed on the basis of these models [109,137,138].…”

Section: Discussionmentioning

confidence: 99%

Connection of the Photochemical Reflectance Index (PRI) with the Photosystem II Quantum Yield and Nonphotochemical Quenching Can Be Dependent on Variations of Photosynthetic Parameters among Investigated Plants: A Meta-Analysis

Sukhova

Sukhov

2018

Remote Sensing

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Abstract:The development of spectral methods of remote sensing, including measurement of a photochemical reflectance index (PRI), is a prospective trend in precision agriculture. There are many works which have investigated the connection between photosynthetic parameters and PRI; however, their results varied and were sometimes contradictory. For this paper, we performed a meta-analysis of works in this field. Here, only linear correlations of PRI with photosynthetic parameters-including quantum yield of photosystem II (∆F/Fm'), nonphotochemical quenching of chlorophyll fluorescence (NPQ), and light use efficiency (LUE)-were investigated. First, it was shown that the correlations were dependent on conditions of PRI measurements (leaf or canopy; artificial light or sunlight). Second, it was shown that a minimal level of the photosynthetic stress, and the variation of this level among investigated plants, can influence the linear correlation of PRI with ∆F/Fm' and NPQ; the effect was dependent on conditions of measurements. In contrast, the distribution of LUE among plants did not influence its correlation with PRI. Thus, the meta-analysis shows that the distribution of photosynthetic parameters among investigated plants can be an important factor that influences the efficiency of remote sensing on the basis of the PRI measurement.

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“…Therefore, considering only diffuse reflections is not appropriate when both diffuse and specular reflections exist. The Phong model is a bidirectional reflectance distribution function (BRDF) model [34,35]. It describes the way that a surface reflects light as a combination in both diffuse and specular forms and has found wide application in computer graphics and 3D model rendering.…”

Section: Specular Reflections and Highlight Phenomenonmentioning

confidence: 99%

Specular Reflection Effects Elimination in Terrestrial Laser Scanning Intensity Data Using Phong Model

Tan

Cheng

2017

Remote Sensing

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Abstract:The intensity value recorded by terrestrial laser scanning (TLS) systems is significantly influenced by the incidence angle. The incidence angle effect is an object property, which is mainly related to target scattering properties, surface structures, and even some instrumental effects. Most existing models focus on diffuse reflections of rough surfaces and ignore specular reflections, despite that both reflections simultaneously exist in all natural surfaces. Due to the coincidence of the emitter and receiver in TLS, specular reflections can be ignored at large incidence angles. On the contrary, at small incidence angles, TLS detectors can receive a portion of specular reflections. The received specular reflections can trigger highlight phenomenon (hot-spot effects) in the intensity data of the scanned targets, particularly those with a relatively smooth or highly-reflective surface. In this study, a new method that takes diffuse and specular reflections, as well as the instrumental effects into consideration, is proposed to eliminate the specular reflection effects in TLS intensity data. Diffuse reflections and instrumental effects are modeled by a polynomial based on Lambertian reference targets, whereas specular reflections are modeled by the Phong model. The proposed method is tested and validated on different targets scanned by the Faro Focus 3D 120 terrestrial scanner. Results imply that the coefficient of variation of the intensity data from a homogeneous surface is reduced by approximately 38% when specular reflections are considered. Compared with existing methods, the proposed method exhibits good feasibility and high accuracy in eliminating the specular reflection effects for intensity image interpretation and 3D point cloud representation by intensity.

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Leaf BRDF measurements and model for specular and diffuse components differentiation

Cited by 212 publications

References 15 publications

Evaluation of Accuracy and Practical Applicability of Methods for Measuring Leaf Reflectance and Transmittance Spectra

Evaluation of Accuracy and Practical Applicability of Methods for Measuring Leaf Reflectance and Transmittance Spectra

Connection of the Photochemical Reflectance Index (PRI) with the Photosystem II Quantum Yield and Nonphotochemical Quenching Can Be Dependent on Variations of Photosynthetic Parameters among Investigated Plants: A Meta-Analysis

Specular Reflection Effects Elimination in Terrestrial Laser Scanning Intensity Data Using Phong Model

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