In modern agriculture, the utilization of advanced technologies has transformed the way researchers and producers monitor and manage their crops. Drones and satellites have emerged as two powerful devices, offering numerous advantages to agri-businesses, ranging from territory surveillance to mapping and crop health assessment. Aerial imagery collected through these systems provides valuable insights by capturing data from the sky, enabling reserachers and farmers to make informed decisions and optimize their agricultural production. In the last decades, drone and satellite imagery has brought about significant improvements in large-scale crop monitoring across the agricultural sector. In this post, we will explore and contrast the use of drone and satellite image analytics for monitoring agricultural production, highlighting their respective strengths and differences, and showing how they can combine together.

Drones VS Satellites: 2 systems that answer differents needs

Drones, on the first hand, also known as Unmanned Aerial Vehicles (UAVs), are small remote-controlled aircraft equipped with high-resolution cameras and other sensors like multispectral cameras or 3D sensor (LiDAR). They can fly at various altitudes and capture detailed imagery of agricultural fields and research trials. Drones offer flexibility and precision, as they can be deployed on-demand and they can fly over specific areas of interest in a fairly short period of time thanks to their portability and lightness.

Satellites, on the other hand, are orbiting spacecraft that continuously capture images of the Earth's surface. Satellites are equipped with powerful sensors too, even if they usually are compatible with fewer sensor types (no 3D sensors yet for instance). The high-resolution equipment enable satellites to provide wide-scale coverage and monitor large agricultural regions from high altitudes. Satellites offer the advantage of regular and systematic data acquisition, allowing for consistent monitoring of crops over time.

Comparing the difference between drones and satellites in digital phenotyping

Drone and satellite imagery has brought about significant improvements in large-scale crop monitoring across the agricultural sector; however, they differ in several key aspects:

• Data Quality: Drones capture high-resolution imagery, providing detailed information about crop health, pest infestations, and nutrient deficiencies. Satellite imagery, although offering broader coverage, has lower spatial resolution, limiting the ability to detect finer details (see Fig. 2).
• Price: Drones generally require a higher initial investment due to the cost of equipment, maintenance, and skilled operators. Satellite imagery, on the other hand, often involves subscription-based services or imagery acquisition fees.
• Results: Drones provide real-time data and immediate feedback, allowing farmers to make prompt decisions and interventions. Satellite imagery offers regular monitoring and broader coverage, providing a comprehensive view of larger agricultural regions over time. Analysing drone imagery can be more time-consuming, as it often requires on-site data processing or uploading data to cloud platforms. Satellite imagery, in contrast, can be readily accessed and analysed through specialized software platforms, reducing the time and effort required for data processing.
• Autonomy: Drones rely on human operators for flight control and some countries, such as the U.S., require operators to keep their drones in sight. On the other hand, satellites operate autonomously once they enter orbit, independently circling the Earth and gathering data which is then transmitted to ground stations.
• Environmental accessibility: Satellites, unlike drones, are not constrained by landscape specifics such as mountains or forests, making them capable of capturing imagery from nearly any spot, including remote or hard-to-reach destinations. Additionally, drones have limitations in coverage due to the risk of equipment loss and the need to fly within proximity to the controller, with their range dependent on battery capacity.
• Resolution and Weather Conditions: Drones can capture high-resolution imagery even in cloudy or overcast conditions, as they can fly at low altitudes, when Satellites may face limitations in precision mostly due to the distance with the canopy. However, flying drones in adverse weather conditions, including strong winds, can be challenging and potentially unsafe. On the other hand, satellites are not affected by “local” weather conditions, such as wind, as they operate from space, providing consistent image quality regardless of weather conditions.
• Scalability: Drones are particularly effective for monitoring smaller to medium-sized agricultural areas, as they offer localized and targeted data collection. Satellites, with their wide-scale coverage, and consistency are better suited for monitoring larger agricultural field and trials or tracking crop evolution and changes over time.

Combining the best of both worlds

These devices are different in their specifications but also in the assessment that they can give access to. Indeed, the sensors from a Satellite cannot capture the same thing as a Drone camera would since the proximity with the canopy and the sensor resolution are not the same, and in digital phenotyping, those parameters prevail while looking for research-grade plant assessments with deep granularity (like organ counting and classification or disease assessments for instance). But there are some traits that both devices can capture, like NDVI for example which is a vegetation index useful to estimate Vigor and Biomass, and in that case, creating data fusion with both devices and sensors helps accessing precise assessments that will give insights at different scales such as the field scale, the plot scale and even the plant scale when using high-resolution sensors.

In conclusion, drones and satellites have become indispensable tools for monitoring agricultural production. While drones excel in providing high-resolution, near real-time data for small to large plot trials assessments, satellites offer broader coverage and long-term monitoring capabilities for large-scale agricultural regions. Both options have unique value for plant phenotyping and as usual, the way you should pick either one or the other or both, should be driven by the assessments and outputs you wish to get, and by your field trial and project specifications as mentioned in the text above. By leveraging the strengths of both drone and satellite image analytics, agricultural researchers can make improved data-driven decisions, based on valuable phenotypic data and analytics, to optimize crop management practices and improve seed breeding and agricultural production globally.

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Sincerely,

Your Hiphen Team.
Topic delivered by Patrizia ZAMBERLETTI - Imaging Solutions Specialist @Hiphen.