Red Edge Normalized Difference Vegetation Index (Gitelson and Merzlyak, 1994)
These indices make use of bands in the so-called “red edge”, which is a spectral area across the red and the NIR. These indices are sensing the “red edge”area where chlorophyll absorption is not so high, so they are not saturating as other indices using the red and the green visible bands.
The index formula is defined as:
(B8a - B5) / (B8a - B5)