Active and passive microwave remote sensing of land主动和被动微波遥感的土地.pptVIP

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Active and passive microwave remote sensing of land主动和被动微波遥感的土地.ppt

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Active and passive microwave remote sensing of land主动和被动微波遥感的土地

PASSIVE MICROWAVE TECHNIQUES FOR HYDROLOGICAL APPLICATIONS by : P. Ferrazzoli Tor Vergata University Roma, Italy ferrazzoli@disp.uniroma2.it CLASSIFICATION OF REMOTE SENSING INSTRUMENTS Based on physical processes CLASSIFICATION OF REMOTE SENSING INSTRUMENTS: Summary Active Passive Optical/UV Lidar Radiometer Microwave Radar Radiometer PASSIVE SYSTEMS: the emission process Background: every surface, at T0 K, emits electromagnetic power PASSIVE SYSTEMS: the emission process at microwaves Brightness: Black body brightness: Brightness temperature (definition): Microwave emissivity: PASSIVE SYSTEMS: the emission process Reciprocity Reflectivity: R(f, θ,φ)= Pr / Pi (reflectance) Absorbivity: A(f, θ,φ) = Pa / Pi = 1- R(f, θ,φ) (absorbance) Kirchhoff (reciprocity) law: e(f, θ,φ) = A(f, θ,φ) Pi Pa Pr Horizontal polarization Vertical polarization depends on volumetric soil moisture (SM) is a roughness factor SOILS Important for applications: εr is stongly influenced by moisture. Real and imaginary parts of soil permittivity as a function of volumetric soil moisture content (SMC) at 1.4 GHz (L band) Measured values (by Ulaby, Moore, Fung, 82) GENERAL PROPERTIES OF EMISSIONFROM NATURAL MEDIA Emissivity of flat surfaces vs. angle (computations) (by Ulaby, Moore, Fung, 82) Increasing moisture, ε increases, Reflectivity increases, Emissivity decreases BARE SOILS Emissivity vs. angle, L band (1.4 GHz) Ground based measurements (by Ulaby, Moore, Fung, 82) moisture Constant roughness, Moisture variations BARE SOILS Emissivity vs. angle, L band (1.4 GHz) Ground based measurements (by Ulaby, Moore, Fung, 82) Constant moisture, Roughness variations roughness e1 = (1-?) [1- exp(- σev h sec?)] ? e2 = (1-?) [1- exp(- σev h sec?)] exp(- σev h sec?) rs e3 ?= es?