How do we measure crops health from space?


The process of precision agriculture can seem daunting at first, but in reality, it provides a very simple way to achieve better results. Precision agriculture equipment indeed does nearly all the work for a farmer and requires a minimal effort to enjoy a much better quality yield for a less cost. But how exactly do we examine the quality of the crops and provide farmers with the precise nitrogen recommendations?

How exactly does it work?

Strangely enough, the process of healthier plants production actually begins in space. In order to unravel how the quality of crops can be measured from such a far distance, it is first important to understand that everything on our planet from objects to plants and humans, has a specific spectral signature. In our day-to-day lives, we only use a tiny part of the electromagnetic spectrum called Visible Spectrum. Our eyes detect electromagnetic radiation, process it and create our vision of the world. Any object that reflects red light in the visible spectrum appears red to us, an object reflecting green light will look green and so forth.

In the same way that electromagnetic radiation enables us to differentiate between objects, we can differentiate between crops by looking closely at their spectral signatures that are shown on the satellite pictures. Plants are made up from biomass, which is largely composed of such elements like carbon, hydrogen, and oxygen. However, during certain periods of the growth of a crop, it utilizes different kinds of nutrients. A deficiency of any of them emits a special spectral signature that can easily be detected and measured.

Satellite image: vegetation index of a field in Southern Sweden (June, 2017)
Satellite image: vegetation index of a field in Southern Sweden (June, 2017)

How do we get the data about the field?

Here, at Vultus, we primarily utilize data from NASA and ESA space programs. With these sources, we receive data 2-3 times a week on every piece of land across the globe at a resolution of 10m. It is extremely important to us that the quality of this data would be as high as possible, as it allows us to deliver the most accurate nitrogen recommendations to the farmers. To ensure the maximum precision, we perform several layers of correction and calibration of the data - during this process we mostly fix any distortion of the satellite images that could be caused by earth's' atmosphere.