Hi @gaetano
Hopefully for you, a LAI processor has just been developed for SNAP, for Sentinel-2 data, and will be available in the upcoming 4.0 release. It is named “Biophysical Processor”, and computes several biophysicl variables : LAI, Cab, Cw, fAPAR and fCOVER.
The algorithm is more precise than what you can derive from NDVI, and actually consists in a neural network which inverts PROSAIL simulations.
Cheers,
Julien