The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Andres Kuusk - One of the best experts on this subject based on the ideXlab platform.
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a two layer Canopy Reflectance model
Journal of Quantitative Spectroscopy & Radiative Transfer, 2001Co-Authors: Andres KuuskAbstract:Abstract A computationally efficient Canopy Reflectance model is developed. A typical two-layer Canopy of forest understory communities is addressed in the model where a geometrically thin layer of vegetation of different structure and/or optical properties is under the main layer of Canopy. The model allows to calculate Reflectance spectrum in every given direction for the spectral range 400–2500 nm . The model calculations show that the use of effective Canopy parameters in a homogeneous Canopy Reflectance model may cause significant biases in estimated Canopy Reflectance.
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Validation of a Markov chain Canopy Reflectance model
International Journal of Remote Sensing, 1997Co-Authors: Andres Kuusk, Bruno Andrieu, Michaël Chelle, F. AriesAbstract:Abstract The Markov chain Canopy Reflectance model (MCRM) by Kuusk (1995 b) has been tested versus the ray tracing model on two different computer maquettes of field crops (Barley and Beet), and on the field data collected in the frame of the Franco-English Collaborative Reflectance Experiment in 1989 and 1990 on sugar-beet plots. Separate comparisons of single and multiple scattering components of the MCRM and the ray tracing procedure demonstrated good agreement of the models. Inversion of the MCRM on field data returned good estimates of LAI in the range LAI 0.1-4 using nadir Reflectance data in three SPOT and two Landsat TM channels. The estimated chlorophyll content was well correlated to the measured one, although underestimated to some extent. The use of directional data at 45 zenith angle and four azimuth angles improved the estimates of both the LAI and the chlorophyll content. It also permitted the estimation of additional parameters of the Canopy structure (leaf size, LAD, the Markov parameter).
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A computer-efficient plant Canopy Reflectance model
Computers & Geosciences, 1996Co-Authors: Andres KuuskAbstract:Abstract Two analytical models of vegetation Canopy Reflectance are combined. The new model considers the diffuse and specular reflection of optical radiation on leaves, the Canopy hot spot and nonlambertian soil. Diffuse fluxes are treated in a four-stream approximation. An elliptical distribution has been used for leaf inclination. Comparisons of the models demonstrate a good agreement. The FORTRAN-77 code of the model can be used in MS-DOS and UNIX environment. A complete set of algorithms of the new model is appended.
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a markov chain model of Canopy Reflectance
Agricultural and Forest Meteorology, 1995Co-Authors: Andres KuuskAbstract:Markov properties of stand geometry are incorporated into an analytical multispectral Canopy Reflectance model. The correlation of leaf positions in adjacent layers significantly influences the gap probability in a stand and, consequently, the Canopy Reflectance (CR) and its angular distribution. The sensitivity analysis demonstrated that the effect is greatest on the angular distribution of multiply scattered radiation. Validation of the new CR model that considers the Markov stand geometry demonstrated an improved agreement between model calculations and measured directional Reflectance distribution of near infrared (NIR) Reflectance for barley and soybean stands. As a consequence, inversion of the new model in the NIR spectral region and in two spectral bands simultaneously allowed significantly better estimation of the leaf area index of a stand than the Nilson-Kuusk model which assumes a Poisson stand geometry.
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a fast invertible Canopy Reflectance model
Remote Sensing of Environment, 1995Co-Authors: Andres KuuskAbstract:Abstract Taking advantage of positive features of the Nilson-Kuusk and the SAIL Canopy Reflectance (CA) models, a new fast CR model has been developed. The new model considers the diffuse and specular reflection of shortwave radiation on leaves, the Canopy hot spot, and nonlambertian soil. Diffuse fluxes are treated in a four-stream approximation. An elliptical distribution has been used for leaf inclination. Comparisons of the models demonstrate a good agreement. The complete set of algorithms of the new model is appended.
Chunjiang Zhao - One of the best experts on this subject based on the ideXlab platform.
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Effect of Vertical Distribution of Crop Structure and Biochemical Parameters of Winter Wheat on Canopy Reflectance Characteristics and Spectral Indices
IEEE Transactions on Geoscience and Remote Sensing, 2020Co-Authors: Chunjiang Zhao, Heli Li, Pingheng Li, Guijun Yang, Xiaohe GuAbstract:Vertical heterogeneity of the Canopy is being increasingly recognized in remote estimates of vegetative properties. Given the current limited knowledge of this issue, this paper investigated the effects of different vertical distributions of crop structure [e.g., leaf angle (LA) and leaf area index (LAI)] and biochemical parameters [e.g., chlorophyll a and b content $(\text{Chl}_{{a}+{b}})$ and water content $(W_{c})$ ] on Canopy Reflectance and vegetation indices (VIs). A recently developed multiple-layer Canopy Reflectance model (MRTM) was tested for winter wheat and used to run a simulation analysis of different Canopy scenarios. The results showed that the MRTM performed well to model winter wheat Canopy Reflectance with regard to spikes and vertical distributions of leaf properties. The vertical profiles of LA and LAI influenced Canopy Reflectance at almost all wavelengths, whereas the vertical profile of $\text{Chl}_{{a}+{b}}$ mainly affected Reflectance in the visible region, and that of $W_{c}$ only affected Reflectance in the near-infrared region. Changes in vertical distribution of the LA resulted in clear variations in VIs related to the LA, LAI, and $\text{Chl}_{{a}+{b}}$ estimates. The vertical LAI and $\text{Chl}_{{a}+{b}}$ profiles mainly influenced the VIs related to the LAI and $\text{Chl}_{{a}+{b}}$ estimates. The $W_{c}$ vertical profile primarily affected the VIs used to estimate crop water properties. The sensitivities of the VIs were mainly associated with the spectral responses and penetration characteristics of the bands they used. These findings suggest that the sensitivity of VIs to the vertical distributions of crop parameters should be considered when establishing models for remote crop monitoring.
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Effect of Vertical Distribution of Crop Structure and Biochemical Parameters of Winter Wheat on Canopy Reflectance Characteristics and Spectral Indices
IEEE Transactions on Geoscience and Remote Sensing, 2017Co-Authors: Chunjiang Zhao, Heli Li, Pingheng Li, Guijun Yang, Xiaohe GuAbstract:Vertical heterogeneity of the Canopy is being increasingly recognized in remote estimates of vegetative properties. Given the current limited knowledge of this issue, this paper investigated the effects of different vertical distributions of crop structure [e.g., leaf angle (LA)] and leaf area index (LAI)] and biochemical parameters [e.g., chlorophyll a and b content (Chla+b) and water content (Wc)] on Canopy Reflectance and vegetation indices (VIs). A recently developed multiple-layer Canopy Reflectance model (MRTM) was tested for winter wheat and used to run a simulation analysis of different Canopy scenarios. The results showed that the MRTM performed well to model winter wheat Canopy Reflectance with regard to spikes and vertical distributions of leaf properties. The vertical profiles of LA and LAI influenced Canopy Reflectance at almost all wavelengths, whereas the vertical profile of Chla+b mainly affected Reflectance in the visible region, and that of Wc only affected Reflectance in the near-infrared region. Changes in vertical distribution of the LA resulted in clear variations in VIs related to the LA, LAI, and Chla+b estimates. The vertical LAI and Chla+b profiles mainly influenced the VIs related to the LAI and Chla+b estimates. The Wc vertical profile primarily affected the VIs used to estimate crop water properties. The sensitivities of the VIs were mainly associated with the spectral responses and penetration characteristics of the bands they used. These findings suggest that the sensitivity of VIs to the vertical distributions of crop parameters should be considered when establishing models for remote crop monitoring.
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Identifying Crop Leaf Angle Distribution Based on Two-Temporal and Bidirectional Canopy Reflectance
IEEE Transactions on Geoscience and Remote Sensing, 2006Co-Authors: Wenjiang Huang, Jihua Wang, Chunjiang ZhaoAbstract:The effect of crop leaf angle on the Canopy-reflected spectrum cannot be ignored in the inversion of leaf area index (LAI) and the monitoring of the crop-growth condition using remote-sensing technology. In this paper, experiments on winter wheat (Triticum aestivum L.) were conducted to identify the crop leaf angle distribution (LAD) by two-temporal (erecting and elongation stages) and bidirectional in situ reflected spectrum and the Airborne Multiangle Thermal Infrared (TIR) Visible Near-Infrared (VNIR) Imaging System (AMTIS) images. The distribution characters of the leaf angle for different LAD varieties were expressed using the beta-distribution function and the SAILTH radiative transfer models. The proportion of the leaf angle in 5deg angle classes (from 5deg to 90deg) for erectophile, planophile, and horizontal varieties was dominated by 75deg, 55deg, and 35deg. The different LAD varieties had a similar Canopy Reflectance in 680 nm (red) and 800 nm (near-infrared band) at the erecting stage, while they had significant differences at the elongation stage. The ratio of the Canopy Reflectance of 800 nm at the erecting stage [R800(B)] to the Canopy Reflectance of 800 nm at the elongation stage [R800(A)] was used to identify the different LAD varieties through the selected two-temporal Canopy Reflectance. A method based on the semiempirical model of the bidirectional Reflectance distribution function (BRDF) was also introduced in this paper. The structural parameter-sensitive index (SPEI) was used in this paper for crop LAD identification. SPEI is proved to be more sensitive to identify erectophile, planophile, and horizontal LAD varieties than the structural scattering index and the normalized difference f-index. We found that it is feasible to identify horizontal, planophile, and erectophile LAD varieties of wheat by studying two-temporal and bidirectional Canopy-reflected spectrum
Xiaohe Gu - One of the best experts on this subject based on the ideXlab platform.
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Effect of Vertical Distribution of Crop Structure and Biochemical Parameters of Winter Wheat on Canopy Reflectance Characteristics and Spectral Indices
IEEE Transactions on Geoscience and Remote Sensing, 2020Co-Authors: Chunjiang Zhao, Heli Li, Pingheng Li, Guijun Yang, Xiaohe GuAbstract:Vertical heterogeneity of the Canopy is being increasingly recognized in remote estimates of vegetative properties. Given the current limited knowledge of this issue, this paper investigated the effects of different vertical distributions of crop structure [e.g., leaf angle (LA) and leaf area index (LAI)] and biochemical parameters [e.g., chlorophyll a and b content $(\text{Chl}_{{a}+{b}})$ and water content $(W_{c})$ ] on Canopy Reflectance and vegetation indices (VIs). A recently developed multiple-layer Canopy Reflectance model (MRTM) was tested for winter wheat and used to run a simulation analysis of different Canopy scenarios. The results showed that the MRTM performed well to model winter wheat Canopy Reflectance with regard to spikes and vertical distributions of leaf properties. The vertical profiles of LA and LAI influenced Canopy Reflectance at almost all wavelengths, whereas the vertical profile of $\text{Chl}_{{a}+{b}}$ mainly affected Reflectance in the visible region, and that of $W_{c}$ only affected Reflectance in the near-infrared region. Changes in vertical distribution of the LA resulted in clear variations in VIs related to the LA, LAI, and $\text{Chl}_{{a}+{b}}$ estimates. The vertical LAI and $\text{Chl}_{{a}+{b}}$ profiles mainly influenced the VIs related to the LAI and $\text{Chl}_{{a}+{b}}$ estimates. The $W_{c}$ vertical profile primarily affected the VIs used to estimate crop water properties. The sensitivities of the VIs were mainly associated with the spectral responses and penetration characteristics of the bands they used. These findings suggest that the sensitivity of VIs to the vertical distributions of crop parameters should be considered when establishing models for remote crop monitoring.
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Effect of Vertical Distribution of Crop Structure and Biochemical Parameters of Winter Wheat on Canopy Reflectance Characteristics and Spectral Indices
IEEE Transactions on Geoscience and Remote Sensing, 2017Co-Authors: Chunjiang Zhao, Heli Li, Pingheng Li, Guijun Yang, Xiaohe GuAbstract:Vertical heterogeneity of the Canopy is being increasingly recognized in remote estimates of vegetative properties. Given the current limited knowledge of this issue, this paper investigated the effects of different vertical distributions of crop structure [e.g., leaf angle (LA)] and leaf area index (LAI)] and biochemical parameters [e.g., chlorophyll a and b content (Chla+b) and water content (Wc)] on Canopy Reflectance and vegetation indices (VIs). A recently developed multiple-layer Canopy Reflectance model (MRTM) was tested for winter wheat and used to run a simulation analysis of different Canopy scenarios. The results showed that the MRTM performed well to model winter wheat Canopy Reflectance with regard to spikes and vertical distributions of leaf properties. The vertical profiles of LA and LAI influenced Canopy Reflectance at almost all wavelengths, whereas the vertical profile of Chla+b mainly affected Reflectance in the visible region, and that of Wc only affected Reflectance in the near-infrared region. Changes in vertical distribution of the LA resulted in clear variations in VIs related to the LA, LAI, and Chla+b estimates. The vertical LAI and Chla+b profiles mainly influenced the VIs related to the LAI and Chla+b estimates. The Wc vertical profile primarily affected the VIs used to estimate crop water properties. The sensitivities of the VIs were mainly associated with the spectral responses and penetration characteristics of the bands they used. These findings suggest that the sensitivity of VIs to the vertical distributions of crop parameters should be considered when establishing models for remote crop monitoring.
C.c. Borel - One of the best experts on this subject based on the ideXlab platform.
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Principles of the radiosity method versus radiative transfer for Canopy Reflectance modeling
IEEE Transactions on Geoscience and Remote Sensing, 1992Co-Authors: S.a.w. Gerstl, C.c. BorelAbstract:The radiosity method is introduced to plant Canopy Reflectance modeling. The authors review the physics principles of the radiosity method which originates in thermal radiative transfer analysis when hot and cold surfaces are considered within a given enclosure. The radiosity equation, which is an energy balance equation for discrete surfaces, is described and contrasted with the radiative transfer equation, which is a volumetric energy balance equation. Comparing the strengths and weaknesses of the radiosity formulation with those of the radiative transfer formulation for Canopy Reflectance modeling, it is concluded that both methods are complementary to each other. Results of a sample calculation are given for a simplified Canopy model with 4000 leaves.
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Principles Of The Radiosity Method For Canopy Reflectance Modeling
10th Annual International Symposium on Geoscience and Remote Sensing, 1990Co-Authors: S.a.w. Gerstl, C.c. BorelAbstract:The radiosity method is introduced to plant Canopy Reflectance modeling. We review the physics principles of the radiosity method which originates in thermal radiative transfer analyses when hot and cold surfaces are considered within a given enclosure. The radiosity equation, which is an energy balance equation for discrete surfaces, is described and contrasted with the radiative transfer equation, which is a volumetric energy balance equation. Comparing the strengths and weaknesses of the radiosity method and the radiative transfer method, we conclude that both methods are complementary to each other. Results of sample calculations are given for Canopy models with up to 20,000 discrete leaves. 16 refs.
Heli Li - One of the best experts on this subject based on the ideXlab platform.
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Effect of Vertical Distribution of Crop Structure and Biochemical Parameters of Winter Wheat on Canopy Reflectance Characteristics and Spectral Indices
IEEE Transactions on Geoscience and Remote Sensing, 2020Co-Authors: Chunjiang Zhao, Heli Li, Pingheng Li, Guijun Yang, Xiaohe GuAbstract:Vertical heterogeneity of the Canopy is being increasingly recognized in remote estimates of vegetative properties. Given the current limited knowledge of this issue, this paper investigated the effects of different vertical distributions of crop structure [e.g., leaf angle (LA) and leaf area index (LAI)] and biochemical parameters [e.g., chlorophyll a and b content $(\text{Chl}_{{a}+{b}})$ and water content $(W_{c})$ ] on Canopy Reflectance and vegetation indices (VIs). A recently developed multiple-layer Canopy Reflectance model (MRTM) was tested for winter wheat and used to run a simulation analysis of different Canopy scenarios. The results showed that the MRTM performed well to model winter wheat Canopy Reflectance with regard to spikes and vertical distributions of leaf properties. The vertical profiles of LA and LAI influenced Canopy Reflectance at almost all wavelengths, whereas the vertical profile of $\text{Chl}_{{a}+{b}}$ mainly affected Reflectance in the visible region, and that of $W_{c}$ only affected Reflectance in the near-infrared region. Changes in vertical distribution of the LA resulted in clear variations in VIs related to the LA, LAI, and $\text{Chl}_{{a}+{b}}$ estimates. The vertical LAI and $\text{Chl}_{{a}+{b}}$ profiles mainly influenced the VIs related to the LAI and $\text{Chl}_{{a}+{b}}$ estimates. The $W_{c}$ vertical profile primarily affected the VIs used to estimate crop water properties. The sensitivities of the VIs were mainly associated with the spectral responses and penetration characteristics of the bands they used. These findings suggest that the sensitivity of VIs to the vertical distributions of crop parameters should be considered when establishing models for remote crop monitoring.
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Effect of Vertical Distribution of Crop Structure and Biochemical Parameters of Winter Wheat on Canopy Reflectance Characteristics and Spectral Indices
IEEE Transactions on Geoscience and Remote Sensing, 2017Co-Authors: Chunjiang Zhao, Heli Li, Pingheng Li, Guijun Yang, Xiaohe GuAbstract:Vertical heterogeneity of the Canopy is being increasingly recognized in remote estimates of vegetative properties. Given the current limited knowledge of this issue, this paper investigated the effects of different vertical distributions of crop structure [e.g., leaf angle (LA)] and leaf area index (LAI)] and biochemical parameters [e.g., chlorophyll a and b content (Chla+b) and water content (Wc)] on Canopy Reflectance and vegetation indices (VIs). A recently developed multiple-layer Canopy Reflectance model (MRTM) was tested for winter wheat and used to run a simulation analysis of different Canopy scenarios. The results showed that the MRTM performed well to model winter wheat Canopy Reflectance with regard to spikes and vertical distributions of leaf properties. The vertical profiles of LA and LAI influenced Canopy Reflectance at almost all wavelengths, whereas the vertical profile of Chla+b mainly affected Reflectance in the visible region, and that of Wc only affected Reflectance in the near-infrared region. Changes in vertical distribution of the LA resulted in clear variations in VIs related to the LA, LAI, and Chla+b estimates. The vertical LAI and Chla+b profiles mainly influenced the VIs related to the LAI and Chla+b estimates. The Wc vertical profile primarily affected the VIs used to estimate crop water properties. The sensitivities of the VIs were mainly associated with the spectral responses and penetration characteristics of the bands they used. These findings suggest that the sensitivity of VIs to the vertical distributions of crop parameters should be considered when establishing models for remote crop monitoring.