I am trying to do my own conversion of L1C images to L2A due to ESA’s long-term archive system. I’m using Sen2Cor v2.9 on a Linux system to convert my images. I’m finding that there is an odd geometrical relict that appears to be coming from inclusion of the DEM, even though the DEM is fine. I’m not sure how to fix or mitigate it. Does anyone have any suggestions?
I have confirmed this behavior is solely due to the inclusion of the DEM, not the added inclusion of ESACCI-LC.
What makes this doubly confusing is this behavior below is illustrated for 2019-03-04 for the specified tile, and it can also be seen with 2019-03-29 (S2B) and 2020-01-21 (S2A). Surprisingly, this was not seen for 2019-09-23 (S2A). I have no idea why.
Using the parameters set as noted below, I ran Sen2Cor on an L1C image with the SRTM DEM and ESACCI-LC add-on to create the L2A image, then I differenced that image with the L2A file directly from Copernicus. When I look at the differenced image, I saw odd geometry so I decided to look at the image bands on their own. Shown here are the 10m bands for My L2A conversion (the first panel shows my study points that I’m extracting values for).
Here are the same bands for the downloaded Copernicus L2A.
Note that though I’m only showing the 10m bands here, the behavior is consistent across the 20m and 60m bands as well (and also for AOT).
I double-checked the DEM file itself, which appears to be fine (this is
6_5x5_TIFs/srtm_56_08.tif). I can not upload extra media to this post because I am a new user.
- I downloaded the L1C imagery for T47RLH for 2019-03-04 from Copernicus via Google Earth Engine here.
- I also downloaded the L2A imagery for the same tile and date in order to compare results (see here for the download).
- DEM is the SRTM one downloaded as per the Sen2Cor v2.9 user guide, page 21 (I would link the user guide here but as a new user I am unable to put >2 links).
- I also downloaded the ESACCI-LC files and added to the correct folder as per the user guide, page 32.
- In the
L2A_GIPP.xmlfile, the following are set:
DEM_Referenceare both set to my DEM folder
Force_Exit_On_DEM_Erroris set to TRUE
- In the
L2A_PB_GIPP.xml, the following is set:
Baseline_Versionis set to 02.11 in order to match the same parameter in the
L2A_PB_GIPP.xmlfile from the Copernicus L2A image.
This is the direct command I used to convert the L1C image to the L2A image I used to create the pictures shown above, following the convention of the user guide page 35.
--GIP_L2A /path/Sen2Cor-02.09.00-Linux64/L2A_GIPP.xml(this is moved from default)