NDVI Algorithm Specification |

### NDVI

The Normalized Difference Vegetation Index algorithms exploit the strength and the vitality of the vegetation on the earth's surface.

The spectral signature of wholesome vegetation shows a abrupt rise of the reflection level at 0,7 µm, whereas land without vegetation, according to the type of surface, has a continuous linear course. So much more active the chlorophyll of the plants, so much bigger is the boost of the reflection level at the near infrared (0,78 - 1 µm). Beside the determination between of the vegetation and other objects it allows to detect the vitality of the vegetation.

The NDVI results from the following equation:

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

In the area of red the incoming solar radiation won´t be extensively absorbed by the pigments of the mesophyll inside the folios, primarily by the chlorophyll. In the area of the near infrared in contrast the bigger part of the incoming radiation was reflected. The NDVI composes a measurement for the photosynthetic activity and is strongly in correlation with density and vitality of the vegetation. The normalizing reduces topographic and atmospheric effects and enables the simultaneous examination of a wide area.

### NDVI-Flags

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

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