Sen2Cor Frequently Asked Questions

[Sen2cor_dev_team]

Frequently Asked Questions

This page summarises the Sen2Cor Frequently Asked Questions raised within the forum and external communications. This page will be kept up-to-date

1) L2A_GIPP important information

Please be aware that a new installation of Sen2Cor 2.x does not replace the L2A_GIPP.xml that is located in the existing destination folder (e.g. C:\Users\username\Documents\sen2cor\2.x).
Please be sure that the L2A_GIPP.xml is up-to-date with the Sen2Cor Version you are using.
Please use the command line --GIP_L2A path_to_the_L2A_GIPP.xml to force the use of the chosen L2A_GIPP.xml

2) Configure DEM

Since the release of Sen2Cor 2.2, Digital Elevation Maps can be used for two purposes:
Improvement of the scene classification and improvement of the terrain correction.
The usage of a DEM is not set by default. It has to be set manually in the L2A_GIPP.xml
Sen2Cor 2.11 now fully support the Copernicus DEM.
Please refer to the Section 2.2.8 of the Sen2Cor Software User Manual

3) Configure ESA CCI

The ESACCI-LC for Sen2Cor data package is prepared for users of Sen2Cor version >= 2.5 who want to benefit from the last improvements of Sen2Cor Cloud Screening and Classification module.
This auxiliary data information is used in Sen2Cor to improve the accuracy of Sen2Cor classification over water, urban and bare areas and also to have a better handling of false detection of snow pixels.
Please refer to the Section 3.1.2 of the Sen2Cor Software User Manual.

Users of Sen2Cor version 2.10 (and up) should download the new monthly snow condition files derived from ESACCI from the following location: ESACCI-LC-L4-ALL-FOR-SEN2COR-2.10.tar.gz
and follow the instruction in the Software User Manual.

4) Radiometric offset

Since PB 04.00 (25/01/2022) a radiometric offset has been introduced in order to preserve/provide negative radiometric values.
For these recent products, please be sure to perform the correct conversion when moving from Digital Number (DN) to Surface Reflectance (SR):
L2A_SR = (L2A_DN + BOA_ADD_OFFSET) / QUANTIFICATION_VALUE
L2A_SR = (L2A_DN - 1000) / 10000 for PB 04.00 and 05.09
Please refer to the following link (section: Level-2A processing): Processing Baseline - Sentinel Online

5) Updates from latest Processing Baselines (PB)

Updates brought by new Processing Baselines have been frequent during the Copernicus Sentinel-2 mission lifetime.
New PBs may introduce changes in the resulting products that has to be considered.
Please refer to the following page to be up-to-date with past and recent implementations: Processing Baseline - Sentinel Online

6) Long string path in Windows

We are aware of a problem that may occur in Sen2Cor during processing on Windows machines when using long path pointing to the L2A destination folder.
An error in finding/writing a folder/file in the Sen2Cor Post-Processing may be the culprit of this behaviour
We recommend to keep the path_lenght for the input and output directories below 90 characters

7) LINUX, error on linked library during installation

We were aware of a Segmentation Fault message during the Sen2Cor installation of version 2.11 within some Linux Distributions:
Configuring…
./pkgsetup: line 46: 4013 Segmentation fault “$INTERPRETER” “$PATCHELF_EXE” “–set-rpath” “$OUT_DIR/lib” “$lib_file” > /dev/null 2>&1
./pkgsetup: line 46: 4019 Segmentation fault “$INTERPRETER” “$PATCHELF_EXE” “–set-rpath” “$OUT_DIR/lib” “$lib_file” > /dev/null 2>&1
…

There are two known outcomes for this error message:
1 The installation proceeds and a message ‘Congratulations, Installation successful…’ appears. In this case the previous error message can be ignored
2 In other more recent Distributions of Linux, the installation could fail (e.g. Ubuntu 22.04)

A new updated Sen2Cor package as been released on 27/04/2023 and is available at Sen2Cor v2.11 – STEP, as indicated in the related news. This package solves the installation issue.

8) Dev_environment not supported.

In previous versions of Sen2Cor (up to 2.10) a Developer environment was described in the SUM and a YML file was provided. This is not supported anymore.
We will update the users if this information will be again available for future versions of Sen2Cor.

9) The Version of Sen2Cor used for processing a L2A can be found in:

• the L2A_Quality.xml file within the L2A_Product\GRANULE*TILE_NAME*\QI_DATA\ (Since Version 2.10 or PB 04.00)
  e.g.: <report gippVersion=“02.11.00”…
• the MTD_MSIL2A.xml, e.g.:
  <GIPP_FILENAME type=“GIP_L2ACSC” version=“21003”>S2__OPER_GIP_L2ACSC_MPC__20220121T000003_V20220125T022000_21000101T000000_B00</GIPP_FILENAME>
  <GIPP_FILENAME type=“GIP_L2ACAC” version=“21003”>S2__OPER_GIP_L2ACAC_MPC__20220121T000004_V20220125T022000_21000101T000000_B00</GIPP_FILENAME>
  Version = “Mmmpp” with “M”= major version, “mm” = minor version, “pp” = patch, e.g. version=“21003” stands for “Sen2Cor Version 2.10.03”

10) Product Definition

The L2A product content (e.g. bands list at different resolutions) follows the specification described in the L2A Product Definition Document (PDD) and in the L2A Input Output Definition Document (IODD).

11) Sen2Cor Documentation

Software User Manual (SUM), Software Release Note (SRN), Copernicus Sentinel-2 Level 2A Product Definition Document (PDD), Sentinel-2 Level 2A Input Output Data Definition (IODD)
can be found following the link: Sen2Cor download page.

12) User and Technical Guides for the Copernicus Sentinel-2 Multi-Spectral-Instrument (MSI)

Sentinel-2 MSI User Guide
Sentinel-2 Technical Guide

13) Sen2Cor Literature Review

Sen2cor related publications

14) When processing old S2 products (form 2015 to 2017)

Please consider using L1C products in SAFE compact format (since PB 02.04) that can be (re)downloaded from https://dataspace.copernicus.eu/

Please note that the L1C/L2A Collection-1 products will be available in Q1 2024 since the beginning of the Sentinel-2 mission (2016): L1C/L2A Collection-1 availability status

15) List of Sen2Cor command line options (see the -h output)

usage: L2A_Process.py [-h] [–mode MODE] [–resolution {10,20,60}]
[–datastrip DATASTRIP] [–tile TILE]
[–output_dir OUTPUT_DIR] [–work_dir WORK_DIR]
[–img_database_dir IMG_DATABASE_DIR]
[–res_database_dir RES_DATABASE_DIR]
[–processing_centre PROCESSING_CENTRE]
[–archiving_centre ARCHIVING_CENTRE]
[–processing_baseline PROCESSING_BASELINE] [–raw]
[–tif] [–sc_only] [–sc_classic] [–sc_cog]
[–cr_only] [–debug] [–GIP_L2A GIP_L2A]
[–GIP_L2A_SC GIP_L2A_SC] [–GIP_L2A_AC GIP_L2A_AC]
[–GIP_L2A_PB GIP_L2A_PB]
input_dir

16) Difference between PSD and Processing Baseline

PSD stands for Product Specification Document.
The latest (14.9) is available here : Sentinel-2 Products Specification Document (PSD) - Sentinel Online
PB stands for Processing Baseline.
Please refer to the following page for detailed information :Processing Baseline - Sentinel Online

The log message that appears when processing either Collection-1 L1C products (PB05.00) or recent L1C products (PB05.09):
" Product versions > 14.9 are not implemented yet.
Version 14.9 will be used by default, but warnings during validation might occur."
can be misleading as L1C products from Collection-1 (PB05.00) and with PB05.09 are both in line with Sentinel-2 Product Specifications 14.9 and therefore are fully supported by Sen2Cor version 2.11.

This message only appears because Sen2Cor did not know about Processing Baselines higher than 04.00 at the time of its release. It can be discarded when processing L1C products Collection-1 (PB05.00) and PB05.09.

17) L2A Naming convention and processing baseline

Sentinel-2 naming convention example:

S2B_MSIL2A_20230529T025529_N0509_R032_T50RMT_20230529T062606

MMM: is the mission ID(S2A/S2B)
MSIXXX: MSIL2A denotes the Level-2A product level
YYYYMMDDHHMMSS: the datatake sensing start time
Nxxyy: the Processing Baseline number (e.g. N0509)
ROOO: Relative Orbit number (R001 - R143)
Txxxxx: Tile Number field
YYYYMMDDHHMMSS: the product generation time

Note: L2A Products processed with Sen2Cor Toolbox will have by default a processing baseline number N9999 to distinguish them from operational products generated by the ground segment.

18) Sentinel-2 tiling system

The link to the kml file of the official Sentinel-2 tiling grid is available on the following page: Sentinel-2 Data Products