GVI - Normalized Difference Vegetation Index

The basic index for measuring the 'greenness' of the earth's surface is the Normalized Difference Vegetation Index (NDVI), which is basically a calculation of the differences between AVHRR channels 1 and 2. A reasonable estimation of the density and coverage of green vegetation can be determined by measuring how green the earth's surface is.

Regions on display include North America, South America, Alaska, Europe, Asia,
British Isles, Africa, and Oceania.

NDVI values range from -.1 to .703 and are unitless. Values greater than .1 generally denote increasing degrees in the greenness and intensity of vegetation. Values between 0 and .1 are commonly characteristic of rocks and bare soil, and values less than 0 sometimes indicate clouds, rain, and snow.

NOTE: Low values of NDVI do not necessarily denote lack of vegetation. For example, during the winter months deciduous forests may appear more orange than green.