Could anybody describe how actually L2NOMINAL mode works in MACCS processor? Does it use the same tiles processed for the previous dates as the supplement information? Or does L2NOMINAL mode mean that a composite image for the same date is built and the information from surrounding area is used?
I want to know is it still separate processing procedures for different tiles and it differs from L2INIT mode only by utilizing information from the previous dates? And how this information can enhance the accuracy of atmospheric correction?
The nominal mode is used whenever a previous L2A product is already created for the exact same tile. For the first products of the season, MACCS will always use the INIT mode (as there are no previous L2A). So basically, MACCS is using the previously created L2A tile/product for improving the accuracy of the atmospheric correction. About the internal details of how MACCS is doing this, you can ask Olivier Hagolle from CESBIO (maybe you could find additional information here: http://www.cesbio.ups-tlse.fr/multitemp/?p=6203).