NDGI

The NDGI operator algorithm computes the Normalized Difference Greenness Index from a given product.

The NDGI results from the following equation:

NDGI = (((lambdaN - lambdaR) / (lambdaN - lambdaG)) * G + (1.0 - ((lambdaN - lambdaR) / (lambdaN - lambdaG))) * N - R) / (((lambdaN - lambdaR) / (lambdaN - lambdaG)) * G + (1.0 - ((lambdaN - lambdaR) / (lambdaN - lambdaG))) * N + R)

, where:

The bands are:

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

and the coefficients are:

- l is the Canopy background adjustment coefficient
- lambdaN is the NIR wavelength used for NIRvH2 and NDGI coefficient
- lambdaR is the Red wavelength used for NIRvH2 and NDGI coefficient
- lambdaG is the Green wavelength used for NDGI coefficient

NDGI-Flags

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

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