QGIS: Creating an NDVI Image in QGIS

  • Software: QGIS 3.34.x
  • OS: Any

There are many ways to make an NDVI image but we’re going to walk through QGIS to do this one. What is NDVI? Normalized Difference Vegetation Index (NDVI).

For this I downloaded a 4 band image from the USGS that covers part of Georgia (United States).

Here is the image in Color:

The Image in CIR – Color Infrared).

Open the Raster Calculator by going to Raster (top Menu) -> Raster Calculator. WHen you open the Raster Calculator you’ll see the 4 bands for this image. The raster bands listed correspond to 1 for Red, 2 for Green, and 3 for Blue and 4 for CIR.

So the formula is simple: Infrared – Red/Infrared + Red. Be sure at the top of the Raster Calculator to set a output tiff or set the output to be virtual (On the fly raster). Your formula will look like this:

When completed you’ll have a new raster (Gray Band) that will have Values between 0 and -1. Typically mine fall between -1 and 1.

Symbolize your raster appropriately. In this case the more red means healthier/growing vegetation. This imagery was flown in early spring so the pine will be bright red while grasses will fall more to light red to gray.