The SI operator algorithm computes the Shadow Index from a given product.

The SI results from the following equation:

SI = pow(((1.0 - B) * (1.0 - G) * (1.0 - R)) , (1.0 / 3.0))

, where:

The bands are:

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

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

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