Introduction and History Electromagnetic Wave Propagation
Velocity Wavelength Attenuation Dispersion
Rocks, Soils and Fluids: Electrical Properties Magnetic Properties
Environmental Influences Heterogeneity, Anisotropy and Scale Radar Equation
Scattering: Reflection, Refraction, Diffraction
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Without scattering, there would be nothing for the radar to measure. With too much scattering, the radar data becomes uninterpretable noise. Desirable scattering comes from the target of interest. Unwanted scattering is called "clutter", a type of noise that results from the spatial size and shape distribution of heterogeneity. Scattering results when a propagating electromagnetic wave encounters a change in electrical or magnetic material properties in which the change occurs over a short distance compared to the size of the propagating wavelength in the material in the direction of propagation, but proceeds over a long distance compared to the wavelength in other directions. Short and long in this context depend upon the magnitude of the contrast and geometry (size, shape, orientation). A large contrast change (such as a metallic object buried in sand) causes significant scattering at smaller scales than a smaller contrast (such as a subtle density change in sand). A gradational contrast may or may not produce significant scattering depending upon the rate of change. Thus a sharp, thin capillary fringe in coarse grained soils will produce good scattering at the water table and a good reflector in ground penetrating radar data. A diffuse, thick capillary fringe in fine grained soils will produce little scattering and the water table may not be visible in ground penetrating radar data. Surface roughness and volumetric heterogeneity produce similar kinds of scattering. The difference between a snowball and an ice cube is a good example of volumetric scattering. They're both the same material in the same state, but the snowball has a grain size distribution comparable to light. This causes considerable scattering, so you cannot see through the snowball and it appears to be white.
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REFLECTANCE PHENOMENOLOGY AND MODELING TUTORIAL
Polarization Fresnel Reflection Snell Angle Stokes-Mueller Matrices Poincare Sphere
Antennas Coupling Near / Far Fields Waveguides Multipathing Resonance
Survey Design Contrast Geometry Resolution Depth of Investigation Orientation
Data Acquisition Data Processing Modeling Interpretation Uncertainty
Applications: Noninvasive Surface Borehole Airborne Satellite and Space