GNDVI Algorithm Specification |

### GNDVI

The Green Normalized Difference Vegetation Index algorithm was developed by Gitelson et al. (1996).
The authors verified that GNDVI was more sensible than NDVI to identify different concentration rates of chlorophyll, which is highly correlated at nitrogen.
The use of green spectral band was more efficient than the red spectral band to discriminate nitrogen.

The GNDVI results from the following equation:

GNDVI = (IR_factor * near_IR - green_factor * green) / (IR_factor * near_IR + green_factor * green)

### GNDVI-Flags

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

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