Atmospheric Correction Methods for Optical Remote Sensing Imagery of Land ������������������������������������������������������������������������������������������������������������������
The optical part of the electromagnetic spectrum covers wavelengths from 100 nm to 1 mm. However, only a small part of the optical spectrum can be used for remote sensing from airborne and spaceborne platforms, because of the characteristics of the scattering, absorption, and emission of radiation by the terrestrial atmosphere. Figure 7.1 presents a typical atmospheric transmittance curve in those spectral regions that can be exploited with remote sensing techniques. Basically, there exist three large spectral intervals: 0.4-2.5 μm, 3-5 μm (mid-infrared or MIR), and 8-14 μm (thermal infrared or TIR). For technical reasons, the rst region is often split into the visible to near-infrared (VIS to NIR or VNIR; 0.4-1.0 μm; no detector cooling required) and short-wave infrared (SWIR; 1.0-2.5 μm; detector cooling required) regions. The main absorbing gases in the atmosphere are water vapor, ozone, carbon dioxide, and oxygen; the most variable gas in space and time is water vapor.