The NDBI operator algorithm computes the Normalized Difference Built-Up Index from a given product.

The NDBI results from the following equation:

NDBI = (S1 - N) / (S1 + N)

, where:

The bands are:

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

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

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