Sen2Cor - How to run Sen2Cor in SNAP


#1

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.

sen2cor

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.


#2

Hello!

I have searched for the GIP_TL.xml file but there isn’t one at Sentinel 2 Level 2A (available since 2018) products. There is only a file named AUX_ECMWFT.

GIP_TL.xml file exists though at the Level2Ap (available since 2017) products along with AUX_ECMWFT.file.

The same issue is reported also here since Aug 2018 with no answer provided

I would like to ask the following:

1 . Were can we find the GIP_TL.xml file of S2 Level2A products ?

Can someone provide an indicative GIP_TL.xml for S2 Level2A products so as to see what are the procedure parameters?

2. Do Level2Ap and Level2A products have been produced via the same Sen2Cor proces s i.e. were the same parameters set during the Sen2cor processing?

3. Is there an adequate elimination of the terrain/topographic effect at L2A and L2Ap products? Will someone get products of better quality by setting different parameters while processing L1C products via Sen2Cor (besides of course the fact of using a different DEM) and producing its own L2A products?

4.1 I can see that Level2Ap process has taken into account a DEM file for the terrain/topographic correction to eliminate the terrain/topographic effect, right?

4.2 Is this the SRTM 90m dowloaded automatically during Sen2Cor process from http://data_public:Gddci@data.cgiar-csi.org/srtm/tiles/GeoTIFF?

4 .3 Are Level2A products produced using this specific SRTM 90m DEM too?

5 . Are the ESA CII layer available here http://maps.elie.ucl.ac.be/CCI/viewer/download.php

ESACCI-LC for Sen2Cor data package

54 tif files, zip compression - 5.1Go

Rem: includes LC maps, water bodies v4 and snow products

taken into account for the production of the products 2Ap and 2A? I don’t recognise any relevant footprint in the GIP_TL.xml file of L2Ap.

6. Do update versions of Sen2Cor produce better quality L2A products than the one already available for download from the Copernicus Hub?

Thank you for your time!

Best regards,

Anastasia