Dear Mr marpet,
I am wondering to retrieve chlorophyll content from sentinel-1. Is that possible? or could you recommend some suggestion?
No idea. I doubt that this is possible. But I’m not a SAR expert. Maybe you ask in the S1TBX category. There should be some guys around who might be able to tell you if this is possible.
Hello,
I would like to analyze the chlorophyll and salinity in the sea from sentinel 2A data. Can you help with this?
Thanks in advance.
You can use the C2RCC algorithm to estimate Chlorophyll concentration from Sentinel-2 data.
Regarding the salinity data, you can have a look at the Copernicus Marine products (CMEMS). I think Sentinel-2 data is not a proper dataset to estimate salinity.
Federico
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Supset for origin image or resampled one ?
(i got the some - nothing for tsm and nothing for chl)
Dear Mr.Peters
I’m trying to use C2X processor. But first of all I need to set some parameters. I have the values of salinity, temp, ozone, Air pressure, Elevation of my study area, then I set them. I applied both C2RCC and C2X processor. C2RCC processed perfect. But some problem in C2X processing. The result of min values are minus. What should I do. Maybe should I change TSM exponent and TSM factor as you have shown above
I tried another way, then put the BandMath " if Valid_PE and (rhown_B4 < rhown_B5) then ((rhown_B5 - rhown_B4) / (rhown_B5 + rhown_B4)) else NaN" so. But the most of area are eliminated
Can you give me advice?
You should only change the TSM factor if you have them for your own area. Otherwise you can only guess.
Thank you for your reply.
I have no data of TSM factor. Can you tell me how i set it or how I can get this value for my study area?. For example my study area is located in Germany. in the default setting of C2RCC. the TSM factor is 1.06. Should I change it? maybe 1.72?
what about TSM exponent?
This is the formula for the TSM calculated by SNAP.
TSM = TSMfac * iop_btot^TSMexp
So, if you have TSM values of your lake, you can compare with the iop_btot extracted by C2RCC and recalculate the factor and exponent.
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Dear Abruescas,
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).
Is that right? or alternatively which output is able to use for empirical approach?I selected in C2RCC processor
Output normalized water leaving reflectance
Output irradiance attenuation coefficients
Output uncertenties
I mean alternatively which output is possible to use instead of Output of normalized water leaving reflectances in order to apply empirical approach.
I’ll be appreciate for your reply. Thank you
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.
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Dear Abruescas,
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.
Best regards
Gandolgor
Sure! I also should have read the post more slowly. Let me try with your scene and I will answer back to you as soon as possible.
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.
This is similar of what I found here (plot A):
Does it make sense?
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)?
Kind regards.
Hello HenkTol
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.
You have stored the target as BEAM-DIMAP, right?
Can you try with 20m too? Just to check if this works for you.
Hello marpet,
Thanks for the suggestion! Resampled to 20m it did work!
Kind regards,
Henk