Radiometric calibration and atmospheric correction of sentry 2 L1C multispectral data using sen2cor

esa （ESA） Only sentinels have been released 2 Number （S2） Of L1C Level multispectral data （MSI）,L1C Level data are orthophoto images that have been geometrically corrected , No radiometric calibration and atmospheric correction . meanwhile ,ESA Also on the S2 L2A Level data are defined ,L2A Level 1 data mainly includes the bottom layer reflectance data after radiometric calibration and atmospheric correction （Bottom-of-Atmosphere corrected reflectance）, But this L2A Data needs to be produced by users according to their needs , So ,ESA Special production has been released L2A Level data plug-in Sen2cor. at present ,SNAP Yes Sen2cor Our support is not good , It's hard to be there. SNAP Call directly Sen2cor, therefore , Here's an introduction sen2cor Command line configuration steps . Of course ,L2A Level data also includes some other products , Such as aerosol thickness （Aerosol Optical Thickness, AOT）、 Atmospheric water vapor （Water Vapour Map, WVM） etc. . Want to know more about S2 Product data at all levels 、 as well as Sen2cor The plug-in , See the following link , Those who are not interested can skip directly .

Software download link ： Data download link

• S2 User's Manual ：https://sentinel.esa.int/web/sentinel/technical-guides/sentinel-2-msi/products-algorithms

• Sen2cor：http://step.esa.int/main/third-party-plugins-2/sen2cor/

How to implement the specific algorithm is not what we care about , Interested to find the relevant user manuals and technical reports , Only the implementation steps are given here ：

1. First , download SNAP The platform and Sen2cor plug-in unit ：SNAP It is recommended to download the latest 6.0 edition （http://step.esa.int/main/download/）, This is mainly used to view S2 data ;Sen2cor download 2.4 Independent installation version .

2. SNAP Just install it directly ;Sen2cor After decompression （ The folder name is ：Sen2Cor-2.4.0-win64）, Put it in your own user folder , Such as ,C:\Users\Administrator\AppData\Local, Then double-click to run L2A_Process.bat file .

3. open Windows The command prompt comes with （Command Propmt, CMD）,Win10 CMD On the start menu “Windows System ” Next . then , stay CMD Enter into Sen2cor In the path of , Such as ：cd C:\Users\Administrator\AppData\Local\Sen2Cor-2.4.0-win64. after , Enter the command ,L2A_Process --help, If the following results are returned , And there are no mistakes , Explain that your installation is OK .

C:\Users\Administrator\AppData\Local\Sen2Cor-2.4.0-win64>L2A_Process --help

usage: L2A_Process.py [-h] [--resolution {10,20,60}] [--sc_only] [--cr_only]

[--refresh] [--GIP_L2A GIP_L2A]

[--GIP_L2A_SC GIP_L2A_SC] [--GIP_L2A_AC GIP_L2A_AC]

directory

Sentinel-2 Level 2A Processor (Sen2Cor). Version: 2.4.0, created: 2017.06.05,

supporting Level-1C product version: 14.

positional arguments:

directory Directory where the Level-1C input files are located

optional arguments:

-h, --help show this help message and exit

--resolution {10,20,60}

Target resolution, can be 10, 20 or 60m. If omitted,

all resolutions will be processed

--sc_only Performs only the scene classification at 60 or 20m

resolution

--cr_only Performs only the creation of the L2A product tree, no

processing

--refresh Performs a refresh of the persistent configuration

before start

--GIP_L2A GIP_L2A Select the user GIPP

--GIP_L2A_SC GIP_L2A_SC

Select the scene classification GIPP

--GIP_L2A_AC GIP_L2A_AC

Select the atmospheric correction GIPP

4. then , hold Sen2cor Storage path of （C:\Users\Administrator\AppData\Local\Sen2Cor-2.4.0-win64）, Add to the environment variable of the system , Specific steps ： My computer → Right click 、 attribute → Advanced system setup → Choose environment variables →Path→ edit 、 newly build , You can add ; The purpose of this , To run in whatever Directory ,Windows The system can find Sen2cor plug-in unit .

5. Download a scene S2 L1C data （ It is recommended to use Internet Download Management download , Fast and uninterrupted ）, decompression ; then , stay CMD in , Switch to the folder where your data resides , Such as ：cd G:\s2-gucheng（ Not familiar with CMD Of , Remember to use first G: Cut to G disc ）; here , You can be in CMD in , according to Sen2cor Grammar requires （ See cmd Help information given ）, Enter the processing command , The grammatical structure is basically ：L2A_Process+ Data relative path + Optional parameters , Such as ：L2A_Process S2A_MSIL1C_20171005T030551_N0205_R075_T50SLJ_20171005T031513.SAFE --resolution=10 --refresh; Of course , You can also be in CMD Any directory , Input the absolute path of the data file for processing , Such as ：L2A_Process G:\s2-gucheng\S2A_MSIL1C_20171005T030551_N0205_R075_T50SLJ_20171005T031513.SAFE --resolution=10 --refresh.

6. then , Just wait anxiously Sen2cor Let's make it slowly , Select all three resolutions , About half an hour . The production of L2A Level data , and L1C The data is in the same folder , The naming rules and data storage methods are the same , The file name only puts MSIL1C Update to MSIL2A.

7. stay SNAP open L2A data , You'll find that , a L1C data ,L2A The multispectral curve of becomes normal . If , You are not used to it. SNAP, And there is no up-to-date ENVI5.4, You can build your own multispectral data .

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