Correção atmosférica em imagens Landsat do Estado da Paraíba.

Abstract

In this study we adapted an atmospheric correction model that filters the effect of molecular composition ("air") and aerosols on satellite images, transforming the radiance detected by the sensor in a reflectance at surface. The basic structure of the model consists of a two-layer scheme, the upper layer consisting only of the lower area formed by the planetary boundary layer containing aerosols. The model was applied to Landsat 5 TM images of two scenes in the state of Paraíba: one from the coast (João Pessoa) and another from the backlands (São Gonçalo). Planetary reflectances were calculated on typical targets (water, vegetation, soil, etc.) in the spectrum. using bands 1-5 and 7. The order of magnitude of the Optical depth of aerosols was evaluated from pyrelometric and pyranometric data of the region. Other aerosol parameters, such as simple albedo and asymmetry factor, were obtained from the literature. The model is discussed through sensitivity tests and comparison with published results. The tests showed a reliable behavior of the model in the face of variations of optical depth and aerosol types. From the application of the method to Landsat images it was observed that the corrections can reach a considerable fraction of the values ​​of the respective planetary reflectances in channels 1, 2 and 3. The method is simple and can be applied systematically to Landsat 5 TM images.