Sen2Cor is a processor for Sentinel-2 Level 2A product generation and formatting; it performs the atmospheric, terrain and cirrus correction of Top-Of-Atmosphere Level 1C input data. Sen2Cor creates Bottom-Of-Atmosphere, optionally terrain and cirrus corrected reflectance images; additional, Aerosol Optical Thickness, Water Vapour, Scene Classification Maps and Quality Indicators for cloud and snow probabilities.
When you download Sentinel-2 Level-1C data you first need to unzip it. Sen2Cor can not read zipped products like SNAP. The input for Sen2Cor must be the original downloaded unzipped Level-1C product, no processing can be applied before running Sen2Cor. In Snap you can go to Optical -> Thematic Land Processing -> Sen2Cor
In the I/O Parameters we need to click on … next to the product name and navigate inside of the first product folder ( .SAFE suffix). Then, open the MTD_MSIL1C.xml file. In the Processing Parameters tab change the resolution to “ ALL” and select “Display execution output”. Click Run .
At the moment there is a bug when restricting the processing to only single resolution (e.g 10 m) it will fail.
Once finished, a new product will be created in your input folder. You can load it by going inside the product folder and opening the MTD_MSIL2A.xml in SNAP.
There are many parameters that you can change in the operator. If you want to know what they are you should download one Level-2 product available for your area (should be available globally since the end of 2018) and then unzip to folder and navigate to GRANULE à <’name of your granule’> à AUX_DATA there open the GIP_TL.xml file (just double click and it will open in browser window). There you can find all the parameters used to generate the product in Sen2Cor and what they are as well as the available values.
It is also possible to run Sen2Cor in command line. In terminal type “L2A_Process -h” to learn the correct syntax and inputs.