Radiometric calibration with SNAP

• Download a Sentinel-2 Level 1C tile from ESA's Copernicus Open Access Hub web service as a compressed zi file: Downloading Sentinel-2 images.
• Start SNAP Desktop.
• File --> Open Product.... Browse to the zip archive or drag and drop the file from the Windows file explorer into the SNAP tab Product Explorer.
• Optical --> Thematic Land Processing --> Sen2Cor Processor --> Sen2Cor 280
• Specify the Processing Parameters:

A first run will be made with 60m pixel resolution (takes ca. 5-10 minutes). Topographic normalization is activated with DEM correction: TRUE. For DEM directory specify a folder where dem files are stored.

• Check Display execution execution report on. Run...
• Compare Output Product with Original Product. Mark the Original Product Name in Product Explorer Right Click Open RGB Image Window --> Sentinel-2 MSI Natural Colors. OK. Repeat for the Output Product.
• Window --> Tile horizontally
• Check View --> Synchronize Image Cursors and View --> Synchronize Image Views. Zoom and Pan.
• Activate a map view by clicking into the canvas of the Original Product. Click Mask Manager tab on the right.
• Check the mask layers opaque_clouds and cirrus_clouds in the Mask Manager.

• Click into the map canvas of the Ouput Product. Click Mask Manager tab on the right.
• Check the mask layers scl_cloud_shadow, scl_cloud_medium_proba, scl_cloud_high_proba, scl_thin_cirrus in the Mask Manager.

• For second run choose in Processing Parameters: Spatial Resolution: 10 (m). Be patient, processing takes some time ...