LibGrid

# NDVI

The NDVI, the Normalized Difference Vegetaton Index, is a measure for bioactivity.

It builds on the fact that a healthy vegetation with active photosynthesis absorbs light in the red spectrum but almost no light in the near infrared spectrum (see spectrum on the right). In contrast to that, barren land and water surfaces do not exhibit this characteristical absorption and absorb light more uniform across the spectrum. The non-uniformity of the absorption, that is the NDVI, is measured by the following formula:

$\displaystyle{ NDVI = \frac{nir-red}{nir+red} }$

Typical values range from −0.1 for no bioactivity over 0.2–0.5 for average to 0.5–0.8 and higher for an increased photosynthetic activity.

The merger application (as introduced on the PanSharpening page) supports the calculation of the NDVI as an option. To compute the NDVI from the Landsat nir (channel 40) and red (channel 30) bands, we use the following command line:

grid/merger nir.tif red.tif ndvi.tif