Scholarly record

USING METADATA OF SATELLITE IMAGES AND CARRIED OUT AN ATMOSPHERIC AND TOPOGRAPHICAL CORRECTION

George Tasionas

Abstract

Aim of this paper is the usage of metadata satellite images to accomplish an atmospheric and topographical correction of these images. The atmospheric correction is since there are particles in the atmosphere that scatter solar radiation, so that the receiver records together with the reflected radiation from the target and the result from the scattering in the atmosphere, with the result that the target in the image is brighter than it is. There are several ways to estimate the atmospheric correction, the most important are: (a) the use of black targets, (b) radioactive transfer-based atmospheric methods, (c) using black targets that absorb in specific spectral bands. In data obtained from remote sensing, topographical corrections are particularly important to overcome the alterations, such as shadows. These topographical changes occur mainly on rough ground because the sun-turning side receives peak reflection values, while the opposite minimum values. These alterations lead to inaccurate classification of soil classes due to different topographic angles. In general, the DEM based techniques are divided into 3 categories: 1) The first class includes Lambertian topographic correction approaches. 2) The second category includes non-Lambertian approaches. 3) The third category includes Empirical Approaches. Corrections should be applied to a reflection image before further analysis is performed. The basic steps followed during topographical normalization are: Calculation of topographical variables, Selection of sampling areas with a similar type of ground cover, Regression-correlation between the brightness values of these areas and of topographical variables, Smoothing the image and Assessment of the final result.

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