Normalised Difference Vegetation Index (Hardisky, Klemas, and Smart 1983).

This index is a reflectance measurement that is sensitive to changes in water content of plant canopies. The NDII uses a normalized difference formulation instead of a simple ratio, and the index values increase with increasing water content.

The index formula is defined as:
( B8 - B11 ) / ( B8 + B11 )