Sen2Cor - workflow question: when to apply?

s2tbx sen2cor
#1

Dear all

I am building a mosaic. Should I apply Sen2Cor (atmospheric corrections) before or after ‘gluing’ the tiles together?

More info: Tiles are neighborhoods from S2 and acquisition is the same.
I am building the mosaic before applying Sen2Cor, since acquisition time is the same… I would like to have opinions.

Thanks !!

#2

Dear @Sara.Aparicio,

Sen2Cor plugin processes one granule at a time, even when a product with multiple granules is supplied (Sentinel-2 L1C products released before 6th December 2016). I did not try to perform atmospheric correction after granules mosaicing, and I do not know if mosaiced granules can be used as input for the atmospheric correction.

I would suggest to first perform atmospheric correction with sen2cor plugin and second mosaic the results together.

In order to avoid differences along granules borders (due to the parameterization of the Visibility value), and if it may fit your analysis needs, I advice you to set the ‘VIS_Update_Mode’ flag in ‘L2A_GIPP.xml’ configuration file to value ‘0’, as suggested in this post:

Hope to get opinions from other users too!

Federico

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#3

My approach for mosaics:

  1. sen2cor (bottom of atmosphere reflectance, L1C -> L2A)
  2. sen2three (cloud free images with a stack of L2A - L3)
  3. gdal_merge.py (create mosaics)

Cheers,
Andreas

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#4

Thanks for the feedback @abgbaumann and @FedericoF !

#5

is sen2three operational? It doesn’t work for me

#6

Hello Val

Yes, sen2three should work. Which datasets are you using (old or new data format)? What is the error you have?

But at the moment the public available version (1.0.0.) does not keep the georeferencing in the jp2 files. Because of that a further processing with gdal as I use it is not possible.

The developer is already working on the new version which will keep the georeferencing.

Cheers from your ‘neighbour’ organisation in Frascati (ESA/ESRIN),
Andreas

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#7

Hi Andreas,

thanks for the response. I’ll be careful not to start a discussion here about sen2three, since there’s a dedicated category.

Just to answer your question, I think I remember reading that the current version doesn’t work with the new file convention just yet. But even with the old convention, I’m getting an error many others seem to have experienced along the lines Object of type bool has no len().

And since there’s nothing really going on in the sen2three category, I’ve just assumed it’s not yet operational. But I might just look into it again and definitely look forward to the new release.

Best from Rome,

Val

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#8

Hello @FedericoF ,

please I have a problem with the atmospheric correction of an image of sentinel2,

I installed SNAP version 5 and Sen2cor 2.3.0, when I run sen2cor I receive the following error

sen2cor.png561×593 33.4 KB

can you help me ?? please

#9

Dear @ELHACHIMI,

I am not a Sen2Cor developer, so I do not know why you get this error.
If you select ‘scene only’ option you will get only the image classification, and not the atmospherically corrected image.

Maybe some of the Sen2Cor developers can help you replying to this post.

Federico

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#10

Dear ELHACHIMI,

you may not combine ‘scene_only’ option with 10 m resolution. Scene classification is not performed in 10 m resolution, only the atmospheric correction. Therefore, either set resolution to 20 m or run without ‘scene_only’ option.
Bdpg

1 Like
#11

Hi @bdpg

Thank you so much, now my problem is solved:slight_smile: