IPVI Algorithm Specification |

### IPVI

The Infrared Percentage Vegetation Index algorithm was first described by Crippen (1990).
Crippen found that the subtraction of the red in the numerator was irrelevant, and proposed this index as a way of improving calculation speed.
It is restricted to values between 0 and 1, which eliminates the need for storing a sign for the vegetation index values.
It also eliminates the conceptual strangeness of negative values for vegetation indices.

The IPVI results from the following equation:

IPVI = (IR_factor * near_IR) / (IR_factor * near_IR + red_factor * red)

or:
IPVI = 1/2 * (NDVI + 1)

where: NDVI = (IR_factor * near_IR - red_factor * red) / (IR_factor * near_IR + red_factor * red)

Conclussions:
- IPVI is functionally equivalent to NDVI and RVI, but it only ranges in value from 0.0 - 1.0
- IPVI eliminates one mathematical operation per image pixel which is important for the rapid processing of large amounts of data.

### IPVI-Flags

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

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