EVALUATING ATMOSPHERIC CORRECTION METHODS USING ASTER IMAGE

This research presents an evaluation of two atmospheric correction (AC) methods applied to ASTER image. The aim of this study was to determine the most suitable atmospheric correction method for ASTER satellite images by evaluating different methods of AC. The ASTER images used in this research were acquired in October 2004, over Kangankunde, an area with rare earth elements deposit found in Balaka district of Malawi. The study also used laboratory USGS ASTER resampled spectral reflectance library data.
In this research, FLAASH and Log residual AC methods were applied to ASTER image. The results of the AC methods were compared separately with each other. Then the comparisons were done with laboratory USGS ASTER resampled spectral reflectance library data. Lastly, band ratio technique was used to map different mineral groups at the study area.
From the results, FLAASH AC method was found to be a better AC method for mineral exploration and mapping. The log residual method, appeared to miss some specific absorption features as it could generalize much in terms of reflectance. Each of the AC methods did show some unknown features at different wavelengths which are recommended for further investigation. Mineral maps produced by band ratio techniques showed some small differences in mineral abundances as well as, spatial distributions. The comparisons were affected by unavailability of some datasets such as field data to show correlation between the image corrected data and field data through scatterplots. We expect this research to contribute its value to the understanding of potential issues and sources of errors in processes of AC and image analysis techniques and the selection of suitable AC method for aster image. Overall, we found that the FLAASH method is a better AC method than the log residual method.