01-02-2013, 12:01 PM
Atmospheric Interfrences in Remote Sensing
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Introduction
The sun is the source of radiation, and electromagnetic radiation (EMR) from the sun that is reflected by the earth and detected by the satellite or aircraft-borne sensor must pass through the atmosphere twice, once on its journey from the sun to the earth and second after being reflected by the surface of the earth back to the sensor. Interactions of the direct solar radiation and reflected radiation from the target with the atmospheric constituents interfere with the process of remote sensing and are called as “Atmospheric Effects”.
What is EMR ?
Electromagnetic radiation consists of an electrical field (E) and a magnetic field (M). Both of these fields travel at the speed of light ©. Different kind of electromagnetic radiation can be distinguished by wavelength and frequency.
Scattering
Atmospheric scattering is the unpredictable diffusion of radiation by particles in the atmosphere.
Three types of scattering can be distinguished, depending on the relationship between the diameter of the scattering particle (d) and the wavelength of the radiation .
Rayleigh Scattering
It occurs when atmospheric particles' diameters are much smaller than the wavelength of the incoming light.
It is common high in the atmosphere.
Radiation with shorter wavelength is easier to be scattered .
Atmospheric Windows
The wavelength ranges in which the atmosphere is particularly ‘Transmissive’ are referred to as “atmospheric windows”.
Those wavelengths that are relatively easily transmitted through the atmosphere.
Atmospheric windows are present in the visible part μm) and the infrared regions of the EM spectrum.
Refraction
The proportions of energy reflected, absorbed, and transmitted will vary for different earth features, depending on their different material type and condition.
These features permit us to distinguish different features on an image.
[attachment=49199]
Introduction
The sun is the source of radiation, and electromagnetic radiation (EMR) from the sun that is reflected by the earth and detected by the satellite or aircraft-borne sensor must pass through the atmosphere twice, once on its journey from the sun to the earth and second after being reflected by the surface of the earth back to the sensor. Interactions of the direct solar radiation and reflected radiation from the target with the atmospheric constituents interfere with the process of remote sensing and are called as “Atmospheric Effects”.
What is EMR ?
Electromagnetic radiation consists of an electrical field (E) and a magnetic field (M). Both of these fields travel at the speed of light ©. Different kind of electromagnetic radiation can be distinguished by wavelength and frequency.
Scattering
Atmospheric scattering is the unpredictable diffusion of radiation by particles in the atmosphere.
Three types of scattering can be distinguished, depending on the relationship between the diameter of the scattering particle (d) and the wavelength of the radiation .
Rayleigh Scattering
It occurs when atmospheric particles' diameters are much smaller than the wavelength of the incoming light.
It is common high in the atmosphere.
Radiation with shorter wavelength is easier to be scattered .
Atmospheric Windows
The wavelength ranges in which the atmosphere is particularly ‘Transmissive’ are referred to as “atmospheric windows”.
Those wavelengths that are relatively easily transmitted through the atmosphere.
Atmospheric windows are present in the visible part μm) and the infrared regions of the EM spectrum.
Refraction
The proportions of energy reflected, absorbed, and transmitted will vary for different earth features, depending on their different material type and condition.
These features permit us to distinguish different features on an image.