The normalized difference vegetation index (NDVI) is a standardized index allowing you to generate an image displaying greenness, also known as relative biomass. This index takes advantage of the contrast of characteristics between two bands from a multispectral raster dataset—the chlorophyll pigment absorption in the red band and the high reflectivity of plant material in the near-infrared (NIR) band.
Extremely low or negative values represent areas with no vegetation at all, such as cloud, water, or snow. Very low values represent areas of little to no vegetation, such as concrete, rock, or bare soil. Moderate values represent areas of shrubs and grassland. High values represent forest areas and lush vegetation.
The default equation used to generate the output is as follows:
NDVI = ((IR - R)/(IR + R)) * 100 + 100
This results in a value range of 0 to 200. This value range fits within an 8-bit data structure, which can easily be rendered with a specific color ramp or color map.
If you need the scientific NDVI pixel values (-1.0 to 1.0), click the Add Function button on the Image Analysis window to apply an NDVI, or you can open the Image Analysis Options dialog box, click the NDVI tab, and then check Scientific Output.
To visualize the result with a color ramp, click the NDVI button on the Image Analysis window, or you can use the Colormap function with one of the NDVI color ramps.
The input multispectral raster.
Visible Band ID
Specifies the band ID that represents the red part of the electromagnetic spectrum.
Infrared Band ID
Specifies the band ID that represents the near-infrared part of the electromagnetic spectrum.
Learn more about NDVI
The NDVI process creates a single-band dataset that mainly represents vegetation density and vigor. The differential reflection in the red and infrared (IR) bands enables you to monitor density and relative vigor of vegetation growth using the spectral reflectivity of solar radiation. Healthy vegetation commonly exhibits higher reflection in the near-infrared wavelength range than in the red wavelength range. When leaves are water stressed, diseased, or dead, they become more yellow and reflect significantly less in the near-infrared range. Infrared wavelengths are absorbed by clouds, water, and snow, and reflected similarly as the red band by rock and bare soil. The negative values represent clouds, water, and snow, and values near zero represent rock and bare soil.
An NDVI is often used worldwide to monitor drought, monitor and predict agricultural production, assist in predicting hazardous fire zones, and map desert encroachment. The NDVI is preferred for global vegetation monitoring because it helps compensate for changing illumination conditions, surface slope, aspect, and other extraneous factors (Lillesand 2004).
The default equation for NDVI is as follows:
NDVI = ((IR - R)/(IR + R))
- IR = pixel values from the infrared band
- R = pixel values from the red band
This scientific index outputs values between -1.0 and 1.0, which represents vegetation density and vigor. Negative values are mainly generated from clouds, water, and snow, and values near zero are mainly generated from rock and bare soil. Very low values (0.1 and below) of NDVI correspond to barren areas of rock, sand, or snow. Moderate values (0.2 to 0.3) represent shrub and grassland, while high values (0.6 to 0.8) indicate temperate and tropical rainforests.