|
The atmospheric radiation correction plays an important role in
the preprocessing of remote sensing images. After a long
period of researching and developing, there are some well-
developed packages, such as LOWTRAN 7 and 5S, which are good in
calculating the atmospheric transmittance. In general, some
packages require the input parameters, like visibility, asymme-
try factor, phase function, ozone content...etc., but they can'
t be acquired quantitatively by users. For this reason, the
precision of the computed atmospheric transmittance is often
poor. The purpose of this research is to estimate the
visibility quantitatively. Aerosol extinction, Rayleigh
extinction and gases absorption cause the main variation of the
atmospheric transmittance. But only the aerosol extinction is
related to the variation of visibility. In order to estimate
the visibility, those effects that are indifferent of the
variation of visibility must be eliminated from the calculation
of atmospheric transmittance. By using some wide-band models
to do so, the visibility can be estimated from the aerosol
extinction. Thereafter, accompanied with the observed
visibility, one can compare it with the theoretical results to
diagnose the characteristics of individual models. The
precision of using visibility to describe the detail of aerosol
is limitted. Nevertheless, as the input parameter for the
packages mentioned above, the estimated visibility in this
study is reliable and acceptable.
|