The NGRDI operator algorithm computes the Normalized Green Red Difference Index from a given product.

The NGRDI results from the following equation:

NGRDI = (G - R) / (G + R)

, where:

The bands are:

- G is the Green band
- R is the Red band

Also the processor computes an additional flags band called 'ngrdi_flags' with the following bit coding:

Bit Position	Description
Bit 0	The computed value for NGRDI is NAN or is Infinite
Bit 1	The computed value for NGRDI is less than -1 (minus one)
Bit 2	The computed value for NGRDI is greater than 1 (one)