Remote sensing for resources development and environmental management: Remote sensing for resources development and environmental management

Damen, M. C. J.

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Multivolume work

Persistent identifier:: 856342815

Title:: Remote sensing for resources development and environmental management

Sub title:: proceedings of the 7th international Symposium, Enschede, 25 - 29 August 1986

Year of publication:: 1986

Place of publication:: Rotterdam; Boston

Publisher of the original:: A. A. Balkema

Identifier (digital):: 856342815

Language:: English

Additional Notes:: Volume 1-3 erschienen von 1986-1988

Editor:: Damen, M. C. J.

Document type:: Multivolume work

Volume

Persistent identifier:: 856343064

Title:: Remote sensing for resources development and environmental management

Sub title:: proceedings of the 7th international Symposium, Enschede, 25 - 29 August 1986

Scope:: XV, 547 Seiten

Year of publication:: 1986

Place of publication:: Rotterdam; Boston

Publisher of the original:: A. A. Balkema

Identifier (digital):: 856343064

Illustration:: Illustrationen, Diagramme

Signature of the source:: ZS 312(26,7,1)

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: Damen, M. C. J.

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: 3 Spectral signatures of objects. Chairman: G. Guyot, Liaison: N. J. J. Bunnik

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: The canopy hot-spot as crop identifier. S. A. W. Gerstl, C. Simmer & B. J. Powers

Document type:: Multivolume work

Structure type:: Chapter

s forest frared film 3 0T predicts I as a ly. As ror ssume that e uniformly dependently n addition, ice of the imptions, we i the layers itributed in ise can be he distance ; the leaf iresent here ibution of lorizontally diam.) dz + dz (3) where, since the probability is azimuthally independent, we have represented the solar zenith and view angles as scalar quantities 52 and S2 , respectively. Here, L is the thickness of the canopy, p = d(LAI)/dz, and r 5 i/| tan(S2)-tan^ 0 ) | . If L is less than r, L r z f r Z 1 p(z) exp - pdu 4 exp - £<^du r When p is independent of height in the canopy, P(2,a 0 ) = \ |ex P (H> r exp(-2pr)-exp(-2pL) exp(-pz)exp (-£!!) V 2r ' dz (5; Analytic Model for HOT SPOT -100 -75 50 -25 0 25 50 75 100 View Angle (Degree) Figure 6. Analytic two-dimensional model of hot-spot for solar zenith angles from 0 to 60 deg. Here, pL = LAI. The integral in eqn. (5) can also be expressed in terms of error functions. For values of S equal to zero or equal to Q q , this expression reduces to l-exp(-LAI) or l/2(l-exp(-2LAI)), respectively. These results are identical to those obtained from eqs. (1) and (2) by taking the limit as c (= LAI/L) tends to zero. The expressions for P(*S2,S2 0 ) given by eqs. (3) and (5) are functions of the canopy variables p, i and L and the angles S2 and Q q . P(S2,S2 Q ) is independent of the height of the observer above the canopy. Using eqn. (3) the effect of varying the canopy and angular variables can be studied. Figure 5 shows the effect of varying the solar zenith angle. The maximum probability is independent of solar zenith angle and occurs when the view angle is in the retro-direction. For normally incident radiation the probability is symmetric about the retro-direction; however, this is not true for other incident directions. This effect is due to the stronger correlation between illuminating a leaf and being able to see an illuminated leaf for view angles closer to zero degrees. Figure 6 depicts the influence of leaf length i on P(S2,S2 0 ) for leaf lengths from 1 to 15 cm. Increasing only the leaf size, increases the size of the holes in the canopy; and consequently, it increases the angle over which both the incident and reflected radiation can use the same hole. This increased correlation between the incident and reflected radiation produces a broader hot-spot, as is evidenced in Fig. 6. These simplistic models do not take into account any transmittance through the leaves or any multiple Analyt ic Model for HOT SPOT -100 75 -50 -25 0 25 . 50 75 100 View Angle (Degree) Figure 5. Analytic two-dimensional model of hot-spot for leaf lengths from 1 to 15 cm. scattering. Both effects are important tor plant canopies, especially in the near-infrared wavelength region. Therefore, we developed a theoretical model to include mutual shading of leaves within a plant canopy in our multiple scattering radiation transport code 6 . The model also takes into account the vertical profiles of leaf size, leaf area index and leaf angular distribution. A shading function is derived, which gives the percentage of the reflected radiation intensity as a function of the angle relative to the sun direction. The computed angular distribution of the reflected solar radiation above the canopy thus contains the hot-spot effect and can be used as input for atmospheric radiative transfer calculations to obtain the radiation distribution above the atmosphere, which simulates the signal measured by a 1 satellite. Initial results indicate that hot-spot characteristics remain almost invariant to atmospheric perturbations in the visible and near-infrared wavelength regimes 7 . REFERENCES 1. G.H. Suits, 1972. Remote Sensing Envir. 2, 117. 2. R. Greenler, 1980. Rainbows, halos, and glories, Cambridge Univ. Press. 3. B. W. Hapke, 1968. Planet. Space Sci., 16, 101. 4. K. Lumme, 1971. Astroph. Space Sci., 13, 219. 5. N.J.J. Bunnik, W. Verhoef, R.W. deJongh, H.W.J. van Kasten, R.H.M.E. Geerts, H. Noordman, D. Ueni, and Th. A. de Boer, 1984. Proc. of 18th Int. Symp. Rem. Sens. Envir., Paris, France, Vol. II, 1033-1040. 6. S.A.W. Gerstl and C. Simmer, 1986. Remote Sensing Envir., august issue 7. C. Simmer and S. A. W. Gerstl, 1985. IEEE Trans. Geosci. and Rem. Sensing, Vol. GF.-23, No. 5, 648. Note, equations (3) through (5) are valid only when the observer is in the principal plane. Extensions of these results to other observation directions are easily obtained.

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