What does the difference in file names mean?

Optical Toolbox
#1

I downloaded sentinel2 image from google earth engine. When I calculated NDVI in snap, I found that the NDVI rates are different on the same day.
For example 20200227T021631_N214 , 20200227T021631_N9999 have different NDVI rate.
NDVI rate of 20200227T021631_N214 which has Min:-0.415, Max:0.893
NDVI rate of 20200227T021631_N9999 which has Min:-0.425, Max:0.992

Does anyone know why it have difference NDVI rate?

#2

Although this is probably not related to SNAP, wouldn’t it be easier to compute the NDVI in the Google Earth Engine directly and download this instead?

#3

What if you look at the histogram of the inputs? Are the min and max also different?
This would explain the differences in NDVI.

If Google follows the naming convention of ESA than the N-number indicates the Processing Baseline number:
Nxxyy: the PDGS Processing Baseline number (e.g. N0204)
User Guides - Sentinel-2 MSI - Naming Convention - Sentinel Online - Sentinel (esa.int)

The baseline numbers are listed here:
Processing Baseline - Sentinel (esa.int)
A number 9999 does not exist.
Maybe this is invented by Google?

#4

I think N9999 changed from L1C so when I use sentinel data, I choose first original L2Adata. If I don’t have L2Adata , I change L1C to L2A then L2A data which have N9999.

#5

Hello @yoonseonguk

The N9999 identifier was put in place for Sen2Cor 02.08.00 to identify products generated by Users in standalone mode, and therefore discriminate them from the same product produced by the PDGS.
Before with previous version 2.5.5 it was only replicating the L1C baseline number.

Cheers

Jan

S2 MPC Operations Manager

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