1. Energy Electromagnetic Interactions by atmosphere
All radiation is detected by satellite remote sensing systems through the atmosphere with a certain distance or path length. Tesebut path length can vary in length. In the photography of the space generated from solar radiation that passes through two thick full-time Earth's atmosphere on its journey from the source of radiation to the sensor. In addition, a thermal sensor which detects the energy emitted by objects on Earth, over a distance in the atmosphere is relatively short. Differences in distance traveled, atmospheric conditions, the wavelength used and the amount of signal energy that affects the sense of total variation in the atmosphere.
Influence of the atmosphere varies greatly depending on the intensity and spectral composition of radiation available to a satellite remote sensing system. This influence is caused by the scattering mechanism (scattering) and absorption (absorption) atmospheric.
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Figure 3. Scattering (Scattering) and Resapan (Absorption)
2. Energy Electromagnetic Interactions with Earth's Surface
Energy part of the object on the surface of the earth will be reflected, absorbed, or transmitted by applying the law of conservation of energy. In the law of conservation of energy can be expressed as the reciprocal relationship between the three types of interaction energy, as follows:
E1 (l) = ER (l) + EA +ET (l)
E1 = energy of the object
ER = the reflected energy
EA = energy absorbed
ET = energy of the transmitted
The equation above is an energy balance equation that shows the interrelationships between the mechanisms of reflection, absorption and transmission. From the above equation there are 2 (two) things:
- Part of the energy reflected, absorbed and transmitted will vary depending on the type of material and conditions of earth objects. Of these differences, allowing us to distinguish different objects in an image.
- With different wavelengths, for the same object the energy reflected, absorbed and transmitted will likely differ, as a result, these spectral variations will produce a visual effect of color. For example: the object is blue when the object is much to reflect the spectrum of blue, green when many reflect the green spectrum, and so on. So that the visual interpretation by eye can use the spectral variation in the magnitude of the reflected energy to distinguish between different objects.