Strange low NDVI values with sen2cor 2.10.01

s2tbx sen2cor
#1

Good morning, since the end of January, when I calculate the NDVI from Sentinel 2 images, I get a value which is systematically about 0.1 points lower than the NDVI calculated from Landsat images and also than that calculated with the specific SNAP function.
I get this lower value both if I calculate the NDVI directly from Level 2 images and if I start from Level 1 images and apply sen2cor vers 2.10.01 to them.
Does the same happen to others of you? Can it be related to the new version of sen2cor?
Thanks
Matteo De Sancts

2 Likes
#2

Nobody is having the same problem?

#3

Hello, i think this problem is related to the 1k offset added since 25th January to all S2 data.
I guess this offset is not added to Sen2Core, there should be a specific option to enable.
Check this Sentinel-2 MSI Level-1c Band 10 values

Regards
Alessandro

1 Like
#4

Thank you Alessandro, it could be the reason of NDVI strange values…

1 Like
#5

It is the reason! Thank you again Alessandro!

#6

Dear user,

As indicated in point 4) of Sen2Cor FAQ, a radiometric offset has been introduced since PB04.00 that needs to be taken into account when converting L2A image Digital Numbers into L2A Surface reflectance.

Cheers,

@Sen2cor_dev_team

#7

Dear all,

I add the same problem of low NDVI values and I corrected the values (with a substraction of 1000) of the L2A bands red and nir output of sen2cor to get the good values of the indice.
However I am a bit disapointed with the SCL bands : since 25-01-2022, I only have 8 and 9 for this band (clouds with high or medium probability).
Are you aware of that ?
The shift of 1000 must be apply on the L1C bands before running sen2cor on it ?
Thanks for your answer.
Aline Déprez

#8

Dear @deprezal,

Thank you for your message.

We provided an answer to the issue your are facing in post shift-of-1000-in-s2-reflectance-since-25-01-22

We hope you find the answer useful.

Cheers,
@Sen2cor_dev_team