# 3.4.3.7. Sentinel-3¶

Sentinel-3

This tab allows for the conversion of Sentinel-3 images (OL_1_EFR) to the physical measure of Top Of Atmosphere reflectance (TOA), or the application of a simple atmospheric correction using the DOS1 method (Dark Object Subtraction 1), which is an image-based technique (for more information about conversion to TOA and DOS1 correction, see Image conversion to reflectance). The following ancillary data are required for conversion: instrument_data.nc , geo_coordinates.nc , tie_geometries.nc .

Once the input is selected, available bands are listed in the metadata table.

WARNING: Sentinel-3 bands are reprojected to WGS 84 coordinate system using a sample of pixels from the file geo_coordinates.nc . For the best precision you should use the official SNAP tool (see http://step.esa.int).

## 3.4.3.7.1. Sentinel-3 conversion¶

• Directory containing Sentinel-3 bands : open a directory containing Sentinel-3 bands; names of Sentinel-2 bands must end with the corresponding number; ancillary data required for conversion must be in the same directory;
• Apply DOS1 atmospheric correction: if checked, the DOS1 Correction is applied to all the bands;
• Use value as NoData : if checked, pixels having NoData value are not counted during conversion and the DOS1 calculation of DNmin; it is useful when image has a black border (usually pixel value = 0);
• Create Band set and use Band set tools: if checked, bands are added to the active Band set after the conversion; also, the Band set is processed according to the tools checked in the Band set;
• Add bands in a new Band set: if checked, bands are added to a new empty Band set after the conversion;

• RUN : select an output directory and start the conversion process; only bands listed in the table Metadata are converted; converted bands are saved in the output directory with the prefix RT_ and automatically loaded in QGIS;