Water Detection by Sentinel 3

Hi dear
I am new in Sentinel 3 usage. I have to flood detect by sentinel 3 images.
Could somebody help me in this field?
Could I use just the LQSF masks for water detection?
If not, is there any processor or product for water detection by S3, like Fmask and Sen2Cor forS2?
Why did somebody use C2RCC separately? I think it is done on L2 products.

I’m not sure if the flags of OLCI are sensitive enough for flood detection, because flooded land has still a land characteristic in the spectrum. And you would also need some value to compare against it to decide if the pixel is flooded or was always water.
How they are defined is described here on page 17: Sentinel-3 OLCI Land User Handbook - Sentinel Online (esa.int)
C2RCC is used to detect the constituents of the water, not the water itself.
Idepix relies on the provided flag information of the L1C product and additional static maps. In general, Idepix is simlar to Fmask it classifies the pixels.

What you can do is to compute the NDWI2 (Optical / Thematic Land Processing / Water Radiometric Indices), put a threshold on it e.g. 0.6 and if this is higher and the flag says the pixel should actually be land then you might have a flooded area.
As static information to compare against you could also use the Fractional land/water Mask (Raster / Masks).

In general, using sentinel-1 for flood detection would be better.
If you search in our Tutorials for ‘flood’ you will find some information.

1 Like

Thank you very much for your complete answer.

Dear Marco Peters
Your last respond really help me to not to be confused in Sentinel 3 usage. Your opinion is the reality but I am doing research so I have to know the algorithm details of the processes.
I found a good report about water detection by S3 which illustrates the differences between S3 water mask, SRTM BEAM and CCI WB methods by S3 (SENTINEL 3 – LAND-WATER MASK: A new MERIS/ATSR land/water, inland water, coastline and intertidal mask at 300m resolution in S3 format, http://dx.doi.org/10.13140/RG.2.2.16553.31840).
I found STRM BEAM processor in Idepix/OLCI Preprocessing algorithm. However, I could not find CCI WB processor or its algorithm.
My questions are:
-What is the Idepix (S2/MSI and S3/OLCI) Algorithm in detail? (I only found it uses a NN)
-What is the SRTM BEAM algorithm?
-What is the CCI WB Algorithm?
Is there any ATBD for that three processes(similar to sen2Cor (S2PAD-ATBD-0001))?
(Some useful links could solve my issue.)
I really appreciate your help.

This report is from a colleague of mine Is currently not in the office. Probably on Wednesday he will be back.

For Idepix is no exhaustive documentation available. The algorithm depends on the sensor. For OLCI a NN is used, for S2 MSI not. Also, for OLCI not only a NN is used. Other techniques are used in combination with the NN.


some more information regarding your question.
You can find some (very limited) information in the SNAP about IdePix.

This presentation might give you more insight:
IdePix - Identification of Pixels

Regarding the “SRTM BEAM algorithm”. This is documented here.

BEAM is the predecessor of SNAP.

The CCI water body mask is described here: Remote Sensing | Free Full-Text | Compilation and Validation of SAR and Optical Data Products for a Complete and Global Map of Inland/Ocean Water Tailored to the Climate Modeling Community (mdpi.com)