As one ag industry expert put it, using a drone on the farm is like being able to see your field from a 10,000-foot altitude, but also being able to zoom in to two inches above the plants. Growers are increasingly discovering that drone mapping is an invaluable tool, both for its ease of use, and for its many applications on the farm.

Odds are you’ve seen one of these red and green maps and heard the term NDVI—but you still might have a lot of questions about how to use it.

Let’s start with the basics. Healthy plants reflect a lot of near infrared (NIR) and green light and absorb a lot of red light. Vegetation indices interpret the amount of light captured across different wavelengths in order to increase the contrast in your map and highlight variability in a way that corresponds to plant health or stress.Different vegetation indices were developed with different purposes and for different camera or sensor types. NDVI (Normalized Difference Vegetation Index,Rouse et al., 1973) is one of the oldest and most well-known indices, and it’s intended to be used with NIR imagery.

What this means is that if you want to use the NDVI index for true NDVI, you need a NIR camera.