Hello!
I am looking for a document explaining how the Sentinel 2 toolbox computes the vegetation variables, how is it validated and what is their accuracy. Do you know where I can find this?
Thank you
Chloe
the algorithms are given in the help section:
As we are talking about an index, validation is up to you 
These are some operations which (given that the data is calibrated) result in specific ranges which indicate different phenologic response. Neither can they be taken as the only truth, nor are their outputs valid for any case.
In terms of the NDVI you usually know what to expect (smaller than 0 at water areas). For the others, explanations are given in the papers which initially proposed them. There you will also find answers on how the index was empirically developed, what output is valid, at which regions it performs best and what limits could arise.
I agree that literature reference in the documentation of the different modules in SNAP would be helpful.
Thnak you very much!