A problem exists when applying a set of ground training signatures determined under one atmospheric condition to the same area under another atmospheric condition. Sometimes the training signatures need to be adapted to the atmospheric condition of the subject area before classification. Other times the radiance measurements of an area with variable atmospheric conditions need to be adjusted to a common atmospheric condition before classification.
In order to describe the effects of the atmosphere on the ground-reflected radiance measured by the LANDSAT-1 satellite, a radiative transfer model was developed. The model is a combination of a doubling I model, which describes the effects of molecular and aerosol scattering in the atmosphere, and a scaling-approximation absorption model which takes into account the gaseous absorption due to oxygen, ozone and water vapor in the LANDSAT-1 spectral region.
The model indicates that atmospheric effects can be approximated by linear transforms. The transform shows that the atmosphere always degredes the albedo difference but not necessarily the color difference. Signature transformations of Lambertian surfaces due to changes in the atmospheric condition can be determined.
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