OLCI retrieval processing reads the OLCI Level-1B images and annotations as well as ADFs characterising de-registration of the cameras. The images are transformed from the Level-1B grid to the original acquisition grid containing all the pixels, including those from overlapping areas with adjacent cameras.
An ortho-geolocation of the OLCI reference channel (Oq) is derived from the Level-1B ortho-geolocation information relating to a virtual OLCI channel. The radiometric units from OLCI measurements are converted to TOA reflectance or normalised radiance according to one processing parameter. The Ground Control Point (GCP) database is read and first rejection criteria of GCP are applied.
In addition, as the SYNERGY and VGT algorithms are defined to be applied only on Land, several tests are defined in this section to distinguish land pixels and discard ocean pixels from the processing. In particular, a Land/sea mask is applied with margins of several kilometres taken into account at coastlines. Note that this distinction ocean/land can be taken into account to include ocean pixels in global aerosol processing.