Using the NDVI button on the Image Analysis window

Using the NDVI button computes the normalized difference vegetation index (NDVI) from a multispectral image or two selected image layers. The NDVI is a standardized index allowing you to generate an image displaying greenness (relative biomass). This index takes advantage of the contrast of the characteristics of two bands from a multispectral raster dataset—the chlorophyll pigment absorptions in the red band and the high reflectivity of plant materials in the near-infrared (NIR) band.

1. To view the Image Analysis window, click Windows on the main menu and click Image Analysis.
2. If you are selecting a multiband dataset, you can specify which band will be used for the red and infrared inputs by doing the following:
   1. Click the Options button on the Image Analysis window.
   2. Click the NDVI tab.
   3. Change the inputs for the Red Band and Infrared Band.

      By default, the Red Band is 3 and the Infrared Band is 4. You may need to look at the metadata for your imagery to determine which bands to use. If, for example, you have a three-band color infrared image, the Infrared Band may be 1 and the Red Band may be 2.

   4. Optionally, check Use Wavelength.

      This option will attempt to identify the correct bands to use if the wavelength information is in the dataset. If not, then the band numbers will be used.

   5. Optionally, check Scientific Output.

      The Band Arithmetic function will be used instead of the NDVI function, since the Band Arithmetic function will output values between -1.0 and 1.0. Whereas, the NDVI function will scale the values to a range of 0–200, which can easily be rendered with a specific color ramp or color map.

   6. Click OK.
3. Click a multiband raster, mosaic dataset, or image service layer in the Image Analysis window.
4. Optionally, select two single-band raster, mosaic dataset, or image service layers in the table of contents.
5. Click the NDVI button .

   The output is added as a temporary layer to the table of contents. By default, a color map renderer is applied using a color map where green represents vegetation, unless the Scientific Output option is checked.

   By default, the NDVI operation adds at least two functions to the temporary layer: the NDVI function and the Colormap function.

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