The NMDI operator algorithm computes the Normalized Multi-band Drought Index from a given product.

The NMDI results from the following equation:

NMDI = (N - (S1 - S2)) / (N + (S1 - S2))

, where:

The bands are:

- N is the NIR band
- S1 is the SWIR 1 band
- S2 is the SWIR 2 band

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

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