I read that this expression in only for Bio optical model, therefore if someone don’t want to use Bio Optical Model, it isn’t necessary to set TSM factor and CHL factors. Is that right?
I’m trying to use empirical approach. I’m using the values Rhown folder for my further process (BandMath).
The bio-optical model is used to calculate the iops and the concentrations. In any case, if you only want to work with the water leaving radiances, you do not need to modify any exponent. What do you mean by empirical approach? Do you want to extract your own concentrations (chl) using reflectances? I do not understand what is your final goal.
In C2RCC you can have (normalized) water leaving radiances, remote sensing reflectance, or both. Each type of AC (C2RCC normal o extreme nets) will give you slightly different results, the models are trained with different datasets. You must find the one that is best on your area depending on your water type. best approach is to derive them all and compare with in situ data.
Thank you for your explanation.
Sorry for being not professional. I wanted to use the water leaving radiance after atmospheric correction to calculate Chl-a concentration, which at the end will be used empirical relationship between the indicator value and
the in-situ measurement.
What you seem to obtain is this relationship between your index and the chl value. The higher the chl content, the higher the value of your index (I used C2RCC normal). If you have this relationship with all three AC methods, I do not see anything wrong.
Hi Ganjug,
you wrote that you would like to have an empirical approach. But nevertheless, did you also look into the conc_chl bands of your processed products? They provide you the chlorophyll concentration based on the bio-optical model. I processed your dates with C2X-COMPLEX (most suitable for your lake, i guess) and looked at the conc_chl values. Except one date, they look quite ok compared to the in-situ data.
Also for your empirical approach, I would advice to use C2X-COMPLEX for the Atmospheric correction.
In terms of masking invalid pixels: also take into account the IDEPIX_CIRRUS_SURE flag/mask and IDEPIX_CLOUD_SHADOW. Another good flag is ‘Cloud_risk’ , though it is often too strict.
hope this helps,
Kerstin
Hello everybody,
For a study project I am trying to compute a chlorophyll concentration of the biggest sweet water lake in the Netherlands. My problem is that after realise the C2RCC tool the result gets black (or like 0 result). I am using the Sentinel2 L1C product, resampled to 10 metres. I tried two opcions with diference in parametres in ‘Salinity’: first with 0.0001 and the second time with the default value of it, but the result does not change. I am only an image of 1 date.
Does anybody knows what could be the cause of the error (see image below)?
I just tried it and got a result. But I have only resampled to 20m to speed up the process. I’ve used the default values and disabled some output variables like uncertainties.
I’m not aware of a tool using S2 L2A for water retrieval.
The L2A contain land surface reflectances and not water leaving reflectances. Therefore, it is not good to use them.
That’s also the reason processors like C2RCC start from L1C. Often there is a close relation between AC and water retrieval.
Other possibilities than C2RCC are Acolite and Polymer:
Could you please guide me?
If I have to retrieve Turbidity and clorophyll from water. Which process should I follow?
Should I work on L1C Or L2A? and what will be the further process?
You should use L1C as input. Afterwards you need to use one of those processors I have mentioned.
Which one I can’t say. The quality of the results can be different depending on your region.
I can’t provide a general guide. The usage and configuration of each is different.
Personally, I would say use the C2RCC, because I’m involved in the development.
I would suggest that you look into the respective help pages and try which one works for you best.
sure, you can use C2RCC for creating commercial products.
But it would be nice if you give the C2RCC Team some credits. For example, that you say somewhere that you have used C2RCC. You can cite it like this: ESA SNAP C2RCC Processor v{USED-VERSION},https://c2rcc.org
Replace {USED-VERSION} by the latest version you have used for your processing.
