Normalized Difference Vegetation Index
What Is NDVI?
Essentially, NDVI is an indicator of vegetation health based on how plants reflect certain ranges of the electromagnetic spectrum.
To the human eye, a plant is green because the chlorophyll pigment in it reflects green waves and absorbs red waves.Cell structures in plants reflect the near-infrared (NIR) waves. So, when photosynthesis occurs, the plant develops and grows and contains more cell structures.
This means that a healthy plant—one with a lot of chlorophyll and cell structures—actively absorbs red light and reflects NIR. An unhealthy plant will do the exact opposite.
This relationship between light and chlorophyll is how we can use NDVI to tell differentiate a healthy plant from a diseased one. The NDVI index detects and quantifies the presence of live green vegetation using this reflected light in the visible and near-infrared bands.
Put simply, NDVI is an indicator of the vegetation “greenness” —the density and health—of each pixel in an aerial image.
What Can NDVI Tell Us About Plants?
As a plant canopy transforms from the depths of winter dormancy to late-summer maturity, its reflectance properties also change. NDVI can help you to keep track of this seasonal variation.
It’s important to know that the NDVI is an indicator of the plant’s health and not a way to diagnose a particular condition. It’s more a set of quantifiable clues on what is currently happening on the field for you to equip yourself with. Drought, disease, pests, or floods are among the many factors that could be affecting vegetation and in turn, its NDVI values.
Thus, conducting NDVI analysis can direct you on where to investigate further or do broader damage assessment if you already know which factors are influencing plant health.