Understanding NDVI: Measuring Plant Vitality and its Limitations

What is NVDI?

NDVI is a calculation between the near-infrared light reflected by vegetation and the visible light. Healthy vegetation absorb more visible light and reflect more near-infrared light. 

What is NVDI used for?

What many do not know, is that NDVI was not designed to measure plant vigor. It was designed to simply detect living vegetation and distinguish it from other matter like rocks, soil, or dead vegetation. With that in mind, it isn’t hard to understand why as an index for measuring vine vigor, NDVI is loaded with potential errors and inaccuracies.

Inherent shortcomings of NDVI

One of the most important shortcomings of NDVI is its dependency on the time of day at which the aerial images are taken. Since NDVI does not correct for changes in solar incidence angle (the angle at which the sun shines on the leaves) NDVI produces vastly different results throughout the day.