Also find sen2corr with too high NDVI Values, now that are available in GEE I share a plot in a grape-vineyard in Chile; crop coefficient models tell us that calculated Kcb (crop basal coefficient) should by in 0,7 to 1,2 range so this stills in range after conversion from NDVI… but the change is major (20% to 30% higher). so I was loking for a clue about, any?
I was guessing 3 theories:
1.- its just right… nothing to do
1.- LUTs that are used in sen2cor algth., for aerosol,atmosphere, ozone, etc are not locally calibrated for Chile, and this region (Coquimbo) in particular, wich is a thing because heres where many of the biggest optical telescopes are instaled because of low atmospheric moisture… the change also ocurrs near the coast.
2.- The Dark vegetation pixel found in this arid to semiarid region is not black enought so the algth. tends to light out the B8 bands… but the change ocurrs also in southern forest zones.
the documentation is here: https://step.esa.int/thirdparties/sen2cor/2.4.0/Sen2Cor_240_Documenation_PDF/S2-PDGS-MPC-L2A-SUM-V2.4.0.pdf