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An Interactive Model for Atmospheric Correction in Satellite Images,
INSTITUTO DE PESQUISAS ESPACIAIS SAO JOSE DOS CAMPOS (BRAZIL)
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The presence of the terrestrial atmosphere is a constant problem in satellite image classification. This paper describes a procedure to test quantitatively the performance of an atmospheric correction algorithm. This specific algorithm was developed at INPE, based on ONeils model. It is difficult to obtain a reasonable atmospheric model for Brazilian conditions, due to lack of aerosol data. The procedure consists of correcting two images of the desired scene, for different days, changing the aerosol optical depth, and comparing at selected areas, the contrast and the correlation between the images. For a better correction, the contrast improves, as well as the correlation. Based on the previous information, it is possible to select the proper aerosol optical depth. Care should be taken, however, since an exaggerated contrast improvement by itself or a good correlation alone are not sufficient. Using both criteria, a better judegement can be made. Scenes that have undergone considerable temporal changes, as those at different stages of a given crop, should be avoided. In order to make the interactive model practical, it was necessary to calculate quickly and interactively the atmospheric transmittance. This was done by means of a modified LOWTRAN program.
APPROVED FOR PUBLIC RELEASE