The RI4XS operator algorithm computes the SPOT HRV XS-based Redness Index 4 from a given product.

The RI4XS results from the following equation:

RI4XS = pow(R , 2.0) / pow(G , 4.0)

, where:

The bands are:

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

Also the processor computes an additional flags band called 'ri4xs_flags' with the following bit coding:

Bit Position	Description
Bit 0	The computed value for RI4XS is NAN or is Infinite
Bit 1	The computed value for RI4XS is less than -1 (minus one)
Bit 2	The computed value for RI4XS is greater than 1 (one)