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Introduction of Surface Scattering Modeling

Introduction of Surface Scattering Modeling. Importance of surface scattering Dielectric properties of Soil: Surface roughness properties: Surface scattering models 1) Small Perturbation Model 2) Physical Optical Model 3) Geometrical Optical Model 4) Integral Equation Model

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Introduction of Surface Scattering Modeling

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  1. Introduction of Surface Scattering Modeling • Importance of surface scattering • Dielectric properties of Soil: • Surface roughness properties: • Surface scattering models 1) Small Perturbation Model 2) Physical Optical Model 3) Geometrical Optical Model 4) Integral Equation Model • Validation of surface scattering model • Numerical Simulations

  2. Dielectric Properties of Soil Solid Material - 4.7 Water - frequency & temperature Soil - frequency, moisture, temperature, and texture Im DC Clay 80% & Sand 20% Clay 20% & Sand 80%

  3. Measurement of Dielectric Properties of Soil

  4. Surface Roughness Properties correlation function • Stationary Random Rough Surface • Description: • surface rms. Height • correlation length • correlation function Gauss Exponential 1/e

  5. Surface Roughness Measurement

  6. Surface Roughness Correlation Functions Surface Roughness Measurements at Washita Site • Characteristics: • Exponential function has higher frequency components Power spectrumFT surface profile or correlation function power spectral density function

  7. Small Perturbation Model pq = vv or hh is the fourier transform of the surface correlation function. Guass Exponential Validity Condition: ks < 0.3, kl < 3 & rms slope < 0.3

  8. Physical Optical Model is nth power of fourier transform of the surface correlation function. Guass Exponential Validity Condition: 0.05λ < s < 0.15λ, l > λ, & m < 0.25

  9. Geometric Optical Model rms slope - m Reflectivity Validity Condition: s > λ/3, l > λ, & 0.4 < m < 0.7

  10. Validity Regions of Classical Surface Backscattering Models

  11. Tradition Backscattering Models

  12. Measured Co-Polarization Ratio by Scatterometer

  13. Integral Equation Model (1) where kZ = k cos, kX = k sin, and pp = vv or hh, the symbol is the Fourier transform of the nth power of the surface correlation coefficient.

  14. Integral Equation (2) where, are the Fresnel reflection coefficients for horizontal and vertical polarization.

  15. Validation Experiment

  16. Comparing Models with Different Surfaces Smooth Surface 20° Mixed Surface 40°

  17. Comparing Models with Rough Surface 20° 40° 40°

  18. Comparing Models with Mixed Surface 40° 20°

  19. Comparing IEM Model with SIR-C & AIRSAR Measurements

  20. Polarization & Incidence Sensitivities to Soil Moisture • - - (VV*HH)^0.5 • ….. VV • ----- HH • 40° VV ------ 50° - - - - 30°

  21. Sensitivity to Surface Roughness n - - - 1 n ….. 1.2 n----- 1.4 • - - 50° • ….. 40° • ----- 30° 40° Co-function :exp n - - - 1 n ….. 1.2 n----- 1.4 L - - - 20 L ….. 15 L ----- 10

  22. Characteristics of Classical & IEM Surface Backscattering Models • Tradition models: Two independent functions • Dielectric and roughness • For SP & PO • co-polarization ratio HH/VV is independent of surface roughness and proportion to dielectric constant and incidence angle • For GO • Co-polarization ratio is unite • For IEM • Dielectric and roughness functions are not independent

  23. Problems in Roughness Measurements

  24. Simulation of Surface Roughness

  25. Effect of Multi-scale Surface roughness on Backscattering

  26. Summary on Surface Scattering Models • Surface roughness parameters are described by the surface auto-correlation function, rms height, and correlation length • Tradition surface scattering models (SP, PO, and GO) are outside of application range due to restrictions on surface roughness parameters • Recently developed IEM model has much wider application range for surface roughness parameters • Research is needed for better techniques to describe natural surface properties

  27. Outline of today’s talk • Importance of surface scattering • Dielectric properties of Soil: • Surface roughness properties: • Surface scattering models 1) Small Perturbation Model 2) Physical Optical Model 3) Geometrical Optical Model 4) Integral Equation Model • Validation of surface scattering model • Numerical Simulations

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