.png)
Vegetation indices are calculated using a combination of two or more eflectance bands from satellite imagery.
What are reflectance bands? Well, you first need to understand how the human eye perceives color. Why do oceans appear blue, and leaves green, etc.? In fact, everything on Earth reflects back radiation, which is light energy, at different wavelengths. Some of these wavelengths can be perceived by the human eye as colors. Other wavelengths can be seen by certain animals, cameras, or special sensors. Satellites are equipped with these sensors and can detect some specific wavelengths through reflectance bands.
The bands in the first zone are in the visible wavelength spectrum (RGB: red, green and blue) and provide information on leaf pigmentation , which is useful in determining the growth stage of a crop and can be a basic indicator of crop health.
The near-infrared (NIR) wavelengths in the second zone are a great way to identify healthy growing plants by detecting chlorophyll, which is a more direct representation of plant productivity.
Bands in the shortwave infrared (third zone) provide information on the water content of the plants, as well as biochemical components in the leaves.
For more than 30 years, NDVI (Normalized Difference Vegetation Index) has been the reference index in agriculture. It combines visible and near infrared bands to provide information on canopy density and greenness. NDVI is a great starting point for understanding crop growth during a growing season, making it the "go-to" VI for many agricultural users.
Older satellites could record NDVI at 30 meters resolution, and more recently at 10 meters. In recent years, there has been a race to provide NDVI maps at the highest resolution possible, as if this was the ultimate solution. However, this is not necessarily the only possible solution. Higher resolution provides more accurate information. But instead of trying to see more by zooming in with the same index, why not change the measuring tool? Depending on your application, other indices may be a better fit.
The following is a selection of vegetation indices (VIs) relevant to today's agriculture. They are divided into two categories: vegetation indices for crop performance and vegetation indices for crop productivity.
These indices provide information on the actual physical condition of plants, including coloration, density, and water content.
While color and density are certainly related to productivity, the following indices are better suited to estimate yield and provide information on the biochemical status of the plant.
Of the nearly 250 indices available from Sentinel-2 alone, Europe's most widely used Earth observation satellite, more than 130 can be useful for vegetation monitoring. So which index is best suited to your farm? Well, that depends on several factors. For example:
In the platform xFarm you will find all the vegetation indices listed in this article and get the best solution for your farm. Satellite data is updated every 5 days, so you can make decisions based on the most up-to-date information. Not only can you constantly monitor your crops, but you can also take advantage of the various applications of the indices, including creating prescription maps directly on the platform.
.svg)
