Rayleigh Correction Error


#1

Hi ,

 All the fellowing questions only about MERIS 

 I have been used the function 'Optical -> Rayleigh Correction' with 'Compute Rayleigh optical thickness bands  ' and 'Compute bottom of Rayleigh reflectance bands' checked, than an error got form the process .(fig 1)
I used the software BEAM  which has the same function of 'MERIS Rayleigh Correction' could get a well result.
The Test Data I have been uploaded.

 Where I will find the function of the model of  'Case- 2 Regional Process'  in SNAP

Sincerely
Tanks for your answer


#2

I guess you are using an older version of SNAP/S3TBX. The ‘dem_alt’ error has been fixed a while ago.
You can update your installation by going to Help -> Check for Updates

The old C2R is not available in SNAP anymore. But it has a successor. It is called C2RCC.
For SNAP version 5.x you need to build it on your own. If you want to do so, you can follow the instruction on the GitHub Repository.
In version 6 it will be integrated by default. It is already in the BETA version which can be downloaded here.


#3

Thank you very much. :slight_smile:


#4

dear marpet : slight_smile:
I read the snap engine api doc, and read the examples of python.
I have no idea about the method using gpt() by python with c2cc.
Could you show me a small demo with python? Maybe only code with java?
thank you!
tsai


#5

The attached script reads a product, invokes the C2RCC for OLCI and write the result.
You need to define the parameters as you need them. For defaults just add nothing to the HashMap.

I have not tried to run the script. So it might have some small issues but it should make it clear how to invoke C2RCC

snappy_c2rcc.py (550 Bytes)


#6

:+1:Thanks for your kindness and sincerely help. it’s very helpful. :slight_smile:


#7

We can say that the rayleigh correction operator is slightly different for example from the resampling operator, I have tried it without knowing about the need of writing the product before actually being able to visualize any band but I noticed this difference is that write? I mean the resampling operator comes from GPF, the rayleigh one is indipendent from that.


#8

You can do the Rayleigh correction also with GPF.

GPF.createProduct('RayleighCorrection', ...)

#9

I read your words many times to understand the true meaning.
Before I use the snap to model ‘c2rr’ , I have been code the ‘acolite_win_20170113.0’ to get Rrc result of the S2A and Landsat8 .


#10

yes, I saw the script, but after replying to your previous post :slight_smile: I had followed the same approach used for the subsetting operator but in the Rayleigh case it is not the best one.


#11

wonderful!
I accept your advice, and I 'll try your method.

Thanks marpet ~ :blush: