Spectral Invariant Provides a Practical Modeling Approach for Future Biophysical Variable Estimations
<p>The framework of the spectral invariant properties (SIP) model on how to describe the radiative transfer process from spectral invariants, which are derived bfromcanopy structure parameters. Detailed descriptions of each item are in <a href="#sec2-remotesensing-10-01508" class="html-sec">Section 2</a>.</p> "> Figure 2
<p>The bidirectional reflectance factor (BRF) of the SIP model in the red (<b>a</b>) and near infra-red (NIR) bands with the solar zenith angle at 0° (<b>b</b>), 30° (<b>c</b>), 60° (<b>d</b>) in the orthogonal plane evaluated by the RAMI On-line Model Checker (ROMC) reference dataset (ROMCREF). “HOM11” is the number of the standard RAMI scene, “DIS” represents the discrete medium of the leaves, “ERE” represents the erectophile leaf angle distribution (LAD) type, and “OP” means the orthogonal plane.</p> "> Figure 3
<p>The scatter plots between the BRF of the SIP simulations and the RAMI reference values (ROMCREF) in the red and NIR bands in the orthogonal plane at the RAMI platform in <a href="#remotesensing-10-01508-f002" class="html-fig">Figure 2</a>. The root mean square (RMS) error and signal-to-noise (S/N) were directly calculated with the RAMI platform (<a href="http://romc.jrc.ec.europa.eu/" target="_blank">http://romc.jrc.ec.europa.eu/</a>).</p> "> Figure 4
<p>The input leaf/soil spectrum (<b>a</b>) and canopy-scale spectrum simulations by SIP and PROSAIL (<b>b</b>–<b>d</b>). VZA represents the view zenith angle. The leaf area index (LAI) is 1 (<b>b</b>), 3 (<b>c</b>) or 5 (<b>d</b>), respectively, LAD is erectophile, and the solar zenith angle is 0°. The other input parameters are the same as <a href="#remotesensing-10-01508-t001" class="html-table">Table 1</a>.</p> "> Figure 4 Cont.
<p>The input leaf/soil spectrum (<b>a</b>) and canopy-scale spectrum simulations by SIP and PROSAIL (<b>b</b>–<b>d</b>). VZA represents the view zenith angle. The leaf area index (LAI) is 1 (<b>b</b>), 3 (<b>c</b>) or 5 (<b>d</b>), respectively, LAD is erectophile, and the solar zenith angle is 0°. The other input parameters are the same as <a href="#remotesensing-10-01508-t001" class="html-table">Table 1</a>.</p> "> Figure 5
<p>The evaluation of the SIP model by the widely-used SCOPE model at different canopy structures, solar angles, and soil backgrounds. The list of variables and their ranges are in <a href="#remotesensing-10-01508-t002" class="html-table">Table 2</a>.</p> "> Figure 6
<p>The polar map of NIRv, (<b>a</b>) the directional area scattering factor (DASF) calculated without the removal of the soil (<b>b</b>), and DASF calculated after the removal of the soil (<b>c</b>). The LAI is 1, LAD is erectophile, and the solar zenith angle is 30°. The other input parameters are the same as <a href="#remotesensing-10-01508-t001" class="html-table">Table 1</a>.</p> "> Figure 7
<p>The scatter plot between NIRv or DASF calculated from total scene BRF without the removal of the soil (DASF<sub>t</sub>), with DASF calculated at the black soil condition (DASF<sub>bs</sub>). The LAI is 1, and the solar zenith angle is 30°. The other input parameters are the same as <a href="#remotesensing-10-01508-t001" class="html-table">Table 1</a> or <a href="#remotesensing-10-01508-f005" class="html-fig">Figure 5</a>.</p> "> Figure 8
<p>The reflectance simulated by the SIP model in the red band (<b>a</b>) and NIR band (<b>b</b>) at different mean leaf inclination angles (MLA) in the principal plane. The LAI is 1, and the solar zenith angle is 30°. The other input parameters are the same as <a href="#remotesensing-10-01508-t001" class="html-table">Table 1</a>.</p> "> Figure 9
<p>The NIRv simulated by the SIP model when the solar zenith angle is 50° (<b>a</b>), and when the solar direction coincides with the view direction for hot spot observation (<b>b</b>). MLA represents the mean leaf inclination angle. The LAI is 1, and other input parameters are the same as <a href="#remotesensing-10-01508-t001" class="html-table">Table 1</a>.</p> ">
Abstract
:1. Introduction
2. Model Description
2.1. BRF of the Vegetation-Soil System
2.2. Absorption of the Vegetation and fPAR
2.3. Canopy Radiation Transfer Terms by Spectral Invariant
2.4. Analytical Formula of Spectral Invariant by Canopy Structure
3. Materials and Methods
4. Results and Analysis
4.1. Evaluation in the RAMI Platform in Angular Space
4.2. Evaluation by the PROSAIL Model in Hyperspectral Space
4.3. Evaluation the fPAR by the SCOPE Model
4.4. Impact of Soil Effect on DASF Calculation
4.5. Impact of the Mean Leaf Inclination Angle on BRF and NIRv
5. Discussion
6. Conclusions
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
Nomenclature
bidirectional reflectance factor | |
contribution by vegetation with no interaction with the soil background | |
single scattering of the vegetation in BRF | |
multiple scattering contribution of the vegetation in BRF | |
single scattering contribution of the soil background in BRF | |
multiple scattering contribution between the vegetation and soil in BRF | |
leaf albedo at wavelength | |
bidirectional scattering coefficient | |
leaf area density | |
canopy height | |
directional gap fraction at the solar direction | |
bidirectional gap fraction | |
leaf projection function | |
leaf inclination angle | |
solar zenith angle | |
view zenith angle | |
clumping index at the zenith angle of | |
hot spot correction function | |
canopy directional escape probability in the upward direction of | |
canopy directional escape probability in the downward direction of | |
canopy hemispherical escape probability in the upward direction | |
canopy hemispherical escape probability in the downward direction | |
recollision probability | |
soil reflectance | |
the fraction of visible sunlit soil in view | |
canopy directional interceptance in the solar direction | |
canopy hemispherical interceptance under diffuse radiation illumination | |
canopy zero-order transmission in the solar direction | |
canopy zero-order transmission at the direction of under diffuse radiation | |
canopy zero-order hemispherical transmission under diffuse radiation | |
absorption by vegetation under isotropic diffuse illumination at bottom | |
albedo in the downward direction under isotropic diffuse illumination at bottom | |
canopy downwelling transmittance with black soil background | |
canopy upward transmittance with isotropic diffuse illumination at bottom |
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Variables | Values/Types | |
---|---|---|
Canopy structure | Leaf area index | 1 |
Leaf angle distribution | Erectophile | |
Solar-sensor geometry | Solar zenith angle | [0°, 30°, 60°] |
View zenith angle | 0°–75° | |
Relative azimuth angle | [0°, 90°, 180°, 270°] | |
Leaf optics | Leaf reflectance | 0.02 (Red), 0.50 (NIR) |
Leaf transmittance | 0.01 (Red), 0.45 (NIR) | |
Soil background | Soil spectrum | 0.15 (Red), 0.20 (NIR) |
Variables | Values/Types | |
---|---|---|
Fractional vegetation cover | [0.1–1] | |
Canopy structure | Leaf area index | [0.5, 1, 3, 5] |
Leaf angle distribution | Spherical, planophile, erectophile | |
Solar geometry | Solar zenith angle | [20°, 30°, 40°, 50°, 60°] |
Soil background | Soil spectra | Four SCOPE spectra |
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Zeng, Y.; Xu, B.; Yin, G.; Wu, S.; Hu, G.; Yan, K.; Yang, B.; Song, W.; Li, J. Spectral Invariant Provides a Practical Modeling Approach for Future Biophysical Variable Estimations. Remote Sens. 2018, 10, 1508. https://doi.org/10.3390/rs10101508
Zeng Y, Xu B, Yin G, Wu S, Hu G, Yan K, Yang B, Song W, Li J. Spectral Invariant Provides a Practical Modeling Approach for Future Biophysical Variable Estimations. Remote Sensing. 2018; 10(10):1508. https://doi.org/10.3390/rs10101508
Chicago/Turabian StyleZeng, Yelu, Baodong Xu, Gaofei Yin, Shengbiao Wu, Guoqing Hu, Kai Yan, Bin Yang, Wanjuan Song, and Jing Li. 2018. "Spectral Invariant Provides a Practical Modeling Approach for Future Biophysical Variable Estimations" Remote Sensing 10, no. 10: 1508. https://doi.org/10.3390/rs10101508
APA StyleZeng, Y., Xu, B., Yin, G., Wu, S., Hu, G., Yan, K., Yang, B., Song, W., & Li, J. (2018). Spectral Invariant Provides a Practical Modeling Approach for Future Biophysical Variable Estimations. Remote Sensing, 10(10), 1508. https://doi.org/10.3390/rs10101508