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Selecting a Drone for Crop Scouting

 

The drone market targets many different customers, including agricultural professionals. Drone videos and photography allow for a different perspective of the field and have the potential to uncover in-season production issues that scouting may miss. Assessment of crop fields can be made quickly when flying 200-400 feet above the crop. However, the cost of a drone can vary widely, and without experience, choosing the best option is probably difficult for most farmers and consultants. University of Delaware Cooperative Extension has flown a variety of drone types and has some suggestions for early adopters.

A quadcopter with 4 propellors and a rotary with six.
Figure 1. A quadcopter (left) versus a rotary with six propellors (right).

1. Choose a Quadcopter

Rotary drones with four propellers (known as quadcopters) are the most typical drone sold. Compared to drones that mimic airplanes, quadcopters are easier to launch, land, and maneuver. Any rotary drone with more than four propellers is meant to carry a heavier load; these larger drones are a better choice for advanced users (Figure 1).

Two examples of handheld controllers made of a rough sturdy plastic.
Figure 2. Handheld controllers are easier to fly with than a cellphone application.

2. Not All Drones Come with a Controller

Some drones can also be maneuvered with an app on your phone, so the manufacturer may not include a hand-held controller. Based on experience at UD, hand-held controllers (Figure 2) allow better flight maneuverability than a cell phone application.

A handheld controller will have joysticks to maneuver the drone and possibly have buttons to allow the operator to take photos or request the drone fly back to the takeoff spot. Controllers may also connect to your cellphone or tablet to take images. If you find a cheaper version of the drone online, be careful to make sure it still comes with a controller (Figure 2).

3. Make Sure the Drone Comes with a Photo or Video Camera

It may seem obvious that a drone would be equipped with some type of camera, but a picture on a website may be misleading. Check to make sure that a camera is included with the drone package, or you may have to purchase the camera separately at an added cost. It will be difficult to scout crops without a camera. For some drones, the camera is integrated into the drone and cannot be removed, while other drones may have a gimbal or fixed camera mount.

Quality becomes important depending on the end user goals. A scout may prefer a higher quality camera to share photos with customers. However, many high-quality cameras are meant to produce videos, which may not be necessary for crop scouting. You do not need a multispectral camera to scout crops, so do not waste your money.

Four examples of mounted cameras shown side by side. The two on the right have mounted cameras while the two on the right have a rotating gimbal that allows for additional directional viewing.
Figure 3: Mounted cameras that face the same direction during the flight (a,b) are not useful for scouting as those on a rotating gimbal (c,d) that you control form the ground.

4. Gimbals are Optional, but Helpful

A gimbal allows for movement of the camera to scan a field left to right, front to back, and straight down. With a gimbal, the camera can be moved while the quadcopter hovers in a stationary position or during flight. We recommended purchasing a drone where the camera moves independently from the drone with a gimbal. Drones that are more expensive may already have a camera/gimbal combination (Figure 3d), while others will require you to purchase a gimbal separately (Figure 3c).

5. Does the Drone Connect to a Phone or Tablet?

Scouting will be more productive if the camera is sending images or live feed directly to your cell phone or tablet. While cellphone connectivity may not be listed as a feature, a photo of the controller with a cellphone attached is a good indicator that they will connect (Figure 4).

For your cellphone to properly connect to the drone, there must be an associated phone application. Check the specifications for software (as a downloadable app) to fly the drone from the manufacturer or a third party. Many popular drone flight apps for android or apple devices can work with several manufacturers.

An iPhone attached to a partial controller.
Figure 4: Controller connected to cellphone.

6. What are the Safety Features?

The drone should come with a global positioning system GPS, which can assist with finding the drone during an emergency landing, or facilitate a function called return to home (RTH). For RTH, the drone will return to the takeoff point with the push of a button if the takeoff point was marked with GPS. A drone should also engage the RTH function if contact with the controller is lost or the battery is dying.

Obstacle avoidance is important for RTH, and it will be up to the drone pilot to make sure the path is clear. However, some drones may also come with infrared sensors that can help avoid larger obstacles, such as trees or homes. It is not recommended to rely on these sensors alone; use common sense when engaging RTH.

While not necessarily a safety feature, check and see how the drone will operate under different weather conditions. The top concern is winds, which can vary considerably over the course of the day. We experience particularly high wind speeds during spring, and a stable drone would be helpful instead of planning around low wind conditions.

7. Signal Range

Many drones connect to controllers through WiFi signals and can lose contact when flown too far. Some drones may only maintain signal 200 feet from the takeoff point, while others may reach between 3,000 feet to 5 miles. Look to the listed technical specifications before purchasing; if none are listed be wary. Drones must be kept within line of site, so a 5-mile signal range is unrealistic. However, agronomists scouting fields should expect to need at least a half-mile (3,000 feet) to get the most out of scouting. In one direction, 3,000 feet could potentially cover 120 acres (Figure 5). An additional issue may arise in populated areas, where home WiFi signals may override and cut off contact with your drone. If the drone has a RTH function, it may automatically engage when signal is lost, which should reduce the issue of WiFi interference.

A map showing The distance from a building to the end of two fields - a distance of about 0.5 miles, or 3000 feet (yellow line).
Figure 5: The distance from the building to the end of the fields is about 0.5 miles, or 3000 feet (yellow line). The fields within the black dotted line represents about 120 acres.

8. Battery Life May Determine the Total Acreage Scouted

Signal distance and battery life will determine how many acres can be scouted during a single flight. The estimated battery life of any drone is probably longer than a pilot will achieve. Drones with more propellers, cameras, and WiFi will drain batteries faster. While many quadcopters may advertise 25 to 30-minute flight times, the reality may be closer to 15 minutes. If you include return time for a safe landing, it may leave about 10 minutes for scouting. This is also another reason to have RTH as an option. When the low battery is indicated, selecting RTH can be a safe way to bring the drone back the fastest. Practice will make any drone operator more efficient when scouting fields and allow for increased productivity.


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