Normalized Difference Vegetation Index (NDVI) is a numerical indicator that is used for a visible and infrared band of electromagnetic spectrum.
In precision agriculture the tool NDVI is use for visible spectrum and adopted to analyze remote sensing measurement to access the weather, the target being observed.
Various band to band ratios or difference are used to produce information that can be used for precision agriculture.
How do you calculate NDVI?
NDVI, basically is a calculation of crop health or vegetation. Mathematically comparing Near Infrared (NIR) and Red light signals. That can help differentiate plant from non-plant and healthy plant from sick plant.
This index is a measure of the difference between Near Infrared and Red light reflected by the surface. Their difference is normalized by sum of these wavelengths.
NDVI always ranges from -1 to +1. But there isn’t a distinct boundary for each type of land cover. For example, when you have negative values, it’s highly likely that it’s water.
If you have NDVI value close to +1, there’s a high possibility that it’s dense green leaves and soil have NDVI value close to 0. This is measured by a device named as Greenseeker.
Use of NDVI:
Industry tools like drone mapping software make it simple for agronomists and farmers to benefit from NDVI by creating maps that convert the -1 to +1 scale into colors we can see and quickly evaluate.
Farmers and agronomists can use NDVI to see stressed crops at a farm up to 2 weeks before the human eye would be able to detect. Crops stress sooner in the NIR than they do in the visual spectrum.
So growers can identify diseases, pests, fungus, or arid conditions sooner, and then respond and make quicker decisions before the issues become an even bigger problem.
Overall, NDVI is a way to measure plant health. Healthy plants absorb most of the visible light while reflecting a large amount of the near-infrared light. Unhealthy plants do the opposite. NDVI is an extremely helpful tool to assess plant health, and understanding it is important.
Author: Ahmed Mukhtar
Department of Agronomy University of Agriculture Faisalabad