What is remote sensing and what is its importance in agriculture?

Remote sensing is a technique that has been gaining new markets and applications in recent years. This technology aims at representing and collecting data from a certain region on the earth’s surface without the need for direct contact, that is, the data is collected in an aerial and distant manner. In this way, all information is obtained through high-performance sensors and instruments.

Source: View of Earth taken during ISS Expedition 59. Earth Science and Remote Sensing Unit, NASA Johnson Space Center

Remote sensing consists of the treatment, storage and analysis of collected data, in order to better understand the phenomena existing on the monitored surface.
This technique is capable of revealing geographic and even historical data on natural spaces, such as the distribution of forest areas and the advance of deforestation in a given region.
This technology can also be used to monitor the growth of urban areas and monitor the most diverse plantations and agricultural crops, among numerous other functions.

Source: View of Sudan taken during ISS Expedition 63. Earth Science and Remote Sensing Unit, NASA Johnson Space Center , 2021

How does remote sensing work?

The sensors used in this technology collect data by detecting the energy reflected by the earth’s surface. These modern sensors can be mounted and used in satellites, planes, helicopters and are currently being widely applied in drones, which have enabled great results. Sensors used for remote sensing can be of two types: active or passive.

Source: Artist rendering of Astranis microGEO Satellite. Astranis Space Technologies, 2021.

Passive sensors respond to external stimuli, that is, existing information. They collect energy that is reflected or emitted by the Earth’s surface. The most common source of passively detected radiation is the reflection of solar radiation. The other type, active sensors, use internal stimuli to collect surface data. For example, a laser cannon sensor that projects the rays onto the surface and calculates the time it takes the rays to bounce off the earth and return to the sensor. The information received by the sensors is treated in complex algorithms or integrated systems that generate images and data according to the user’s needs.

Remote Sensing Applications

This technology allows for diverse applications in various areas and provides numerous advantages. The most common uses of remote sensing are:
• Coastal applications: monitor bank changes, control sediment transport, map the coast and prevent erosion.
• Marine applications: monitoring ocean circulation, measuring water temperature and wave height. The data helps to improve the management of marine resources.
• Risk mapping: control of hurricanes, erosions and floods. It is possible to assess the impacts of natural disasters and create strategies for prevention.
• Agricultural applications: crop monitoring, growth control, pest detection and many others.

Source: Central-eastern Brazil, by Copernicus Sentinel-2A satellite. Here we can see a large, flat plateau blanked with fields benefiting from rich soils and an apparent abundance of water, before falling off into a green, hilly valley (left). The straight lines in the image are roads, such as the highway running in a nearly straight line from the centre-top to bottom of the image.
The area is particularly known for soybean production. The country’s soybean output has increased by more than 3000% since the 1970s, and Brazil is the second largest global producer of soybeans after the US.
Other crops in this area include corn, coffee and cotton.
A distinctive feature in this image is the circles – mainly at the centre. These shapes were created by a central-pivot irrigation system, where a long water pipe rotates around a well at the centre of each plot. The varying colours show different types of crop, or different stages of growth.
The two-satellite Sentinel-2 mission is designed to monitor changing lands, including crop type and health. While the first satellite has been in orbit since 2015, its Sentinel-2B twin was launched on 7 March. Together, the satellites will provide new images of Earth’s land surfaces every five days.
AuthorESA / Copernicus Sentinel-2A

Remote Sensing in Agriculture

Remote sensing technology has great potential when applied in the agricultural sector. Through integrated sensors and systems, it is possible to obtain various information, such as:

• Planted area estimation: through the images it is possible to estimate the entire extension of the plantation, being able to control and monitor the growth of the planted area.
• Survey of the number of plants in a given area: using images as a basis and applying modern algorithms, it is possible to know the amount of existing plants, detect areas of lower density and optimize the planting.
• Plant and crop health: through the different colors of the plants in the images, it is possible to see those that are not developing as they should and also those that lack water and certain nutrients.
• Detection of pests in the plantation and bottlenecks in the production process: as well as in monitoring the health of plants, through coloring the images, you can find pests and places of low production, allowing you to avoid significant drops in production.

Source: Images from the Sentinel-2A satellite from February to October 2016 show the changing landscape in Spain’s Brazo de Este natural park and around the city of Los Palacios y Villafranca.Part of the Guadalquivir river basin, the area pictured has a rich agriculture with crops including rice, watermelon, pepper, cucumber, tomato and quinoa. In this animation we can clearly see changes in the fields as different crops grow at different rates, and are harvested in different seasons.
The Copernicus Sentinel-2 mission is designed to provide images that can be used to distinguish between different crop types as well as data on numerous plant features, such as leaf area, chlorophyll content and water content – all essential for accurately monitoring plant growth. European Space Agency, 2021.

Remote sensing in agriculture can be done in the most classic way, using satellites and planes. However, the cost of both is quite high, which has led farmers to look for more accessible technologies.

Remote sensing and drones

Currently, the use of drones in precision agriculture for aerial monitoring of plantations is widely used, as it is more accessible and flexible when compared to classical technologies.
These small unmanned aircraft have a great advantage, unlike satellites they can carry out images regardless of weather conditions.

Source: This photo shows a BQM-34 Firebee II drone being carried aloft under the wing of NASA’s B-52 mothership during a 1977 research flight. The Firebee/DAST research program ran from 1977 to 1983 at the NASA Dryden Flight Research Center, Edwards, California. NASA/Dryden Flight Research Center, 2021.

In addition, drones allow use whenever necessary, unlike satellites that can only be used for crop monitoring only according to availability. Remote sensing is one of the technologies that have been applied in precision agriculture. This modern way of managing plantations has provided productivity results never achieved before, and also enabling a reduction in several operating costs.

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