Hello everyone,
Processing Sentinel 3 OLCI ocean colour products (CHL_NN), we observed a difference in the “quality” of the maps obtained from Sentinel 3 A and Sentinel 3 B L2 WFR. The pixels in Sentinel 3B seem to be doubling, creating an effect of elongated pixels. The images below show an example of the chlorophyll map of the same date and area obtained with Sentinel 3 B and A.
We also observe this behaviour in the RGB images obtained from the L1 EFR (example below).
Has someone found the same problem? Can someone give an insight? Thank you in advance
Maybe @TomBlock could help you.
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Good morning SoutoCeccon,
could you please post the exact names of the products that you used to create the images. So that I can possibly reproduce the behaviour.
Thank you,
Tom
Good morning, and thank you for your reply,
The products I used to create the images are as follows with the AoI in Baia Verde (Italy):
Chlorophyll:
*S3A_OL_2_WFR____20210626T092009_20210626T092309_20210627T215914_0179_073_207_2340_MAR_O_NT_003.SEN3
*S3B_OL_2_WFR____20210626T084045_20210626T084345_20210627T202322_0179_054_064_2340_MAR_O_NT_003.SEN3
RGB:
*S3A_OL_1_EFR____20210827T091235_20210827T091535_20210828T132213_0179_075_321_2340_LN1_O_NT_002.SEN3
*S3B_OL_1_EFR____20210827T083318_20210827T083618_20210828T125411_0180_056_178_2340_LN1_O_NT_002.SEN3
I also report that I have observed this behaviour on other dates as well, such as:
2021/08/27
*S3A_OL_2_WFR____20210827T091235_20210827T091535_20210828T212934_0179_075_321_2340_MAR_O_NT_003.SEN3
*S3B_OL_2_WFR____20210827T083318_20210827T083618_20210828T212501_0180_056_178_2340_MAR_O_NT_003.SEN3
2021/08/19
*S3A_OL_2_WFR____20210819T092004_20210819T092304_20210820T213844_0179_075_207_2340_MAR_O_NT_003.SEN3
*S3B_OL_2_WFR____20210819T084047_20210819T084347_20210820T201543_0179_056_064_2340_MAR_O_NT_003.SEN3
Thank you very much in advance
Paola
Dear Paola,
sorry for the long wait time.
I have downloaded the first of the files that you listed “S3A_OL_2_WFR____20210626T092009_20210626T092309…” and checked with this file the behaviour.
I could reproduce your observation easily, both with SNAP 10 released as well as with the latest build. And I can also explain why this is displayed:
It is in the data. More prominent in the CHL_NN, but also in CHL_OC4ME data. These variables are stored with a precision of 8 bits, so - extremely poor resolution. I put a pin on a section that seems to have duplicated pixels, opened the raw NetCDF file and checked that location. Voila:
So, it’s not a bug, it’s really in the data.
Tom
