NDPI Algorithm Specification |

### NDPI

The Normalized Difference Pond Index algorithm was developed by J.P Lacaux & al., (2006).
The NDPI makes it possible not only to distinguish small ponds and water bodies (down to 0.01 ha), but also to differentiate vegetation inside ponds from that in their surroundings

The NDPI results from the following equation:

NDPI = (mir_factor * middle_IR - green_factor * green) / (mir_factor * middle_IR + green_factor * green)

### NDPI-Flags

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

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