High-quality reference images are crucial for empirical model-based atmospheric corrections. The Taiwan Space Agency (TASA) has developed an approach that uses Surface Reflectance (SR) from Sentinel-2 as a reference for these corrections. To enhance efficiency, the selection and preparation of reference images must be automated. Therefore, a procedure for optimal reference image selection has been developed. This procedure includes three main steps: First, Setting the search criteria based on input images, such as acquisition date and geographic locations. Second, using remote servers to search for all available reference images within the given period and calculating cloud cover over land. Third, retrieving the top three cloudless reference images as candidates for atmospheric corrections. After applying atmospheric corrections, the result with the most Pseudo-Invariant Features (PIFs) will be selected as the final output.
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