Unmanned aerial vehicles (UAVs), more commonly known as drones, are in the news a lot lately. Whether they are causing a stir by hovering over the Eiffel Tower in Paris or zooming over a field recording sensor data, as these robotic flying machines proliferate, they are having an impact on a wide range of industries, including agriculture. Most drones have pilots on the ground, and many can also operate independently of their human masters. They come in all shapes and sizes—some are helicopters with four or more rotors, some are built more like miniature airplanes, and others resemble insects such as moths or dragonflies.

Since there are so many different types of UAVs, it would be cumbersome to go into great detail describing them all. However, we can put drones into several categories to make it easier to discuss them. First of all, we can categorize them by whether the machine is operating under remote control, such as a radio-controlled (RC) airplane or helicopter, or if it is operating autonomously. Most UAVs are not fully autonomous, but have features that allow them to navigate to a location or perform patterned flights. Remotely controlled drones have a pilot in charge at all times. Many UAVs can be switched between remote control and autonomous modes.

Another way to classify UAVs is either as fixed or rotary wing. Fixed-wing drones are much like RC aircraft, but with greater autonomous capability and, as is the case with agricultural drones, more on-board sensor systems. An example of the rotary type is the quadracopter (with four rotors), of which there are many varieties. Microdrones can be considered a third category characterized by diverse structures and theories of operation, often using an insect biomimicry approach.

Drones in the Fields

Airplanes have been used in agriculture since shortly after the end of World War I, when military biplanes began to be converted into crop dusters. Since then, crop dusting has been the most iconic use of aircraft for agricultural purposes. Despite the success of full-sized crop dusters, there are issues with them. They are noisy, require skilled pilots and, if not operated properly, they can waste product by spraying it in the wrong places. Airplanes fly fast and close to the ground, which doesn’t leave much room for error. And, nimble as they are, even helicopters cannot get too low over hilly, highly variable terrain. Enter the drone age.

For crop dusting, rotary-winged drones have a big advantage over full-sized aircraft because they can execute slow, sharp turns and hover close to the ground to provide tight coverage over a given area. Small crop-dusting drones can deliver pesticides or fertilizers accurately, but are not yet able to haul heavy loads. In Japan, mid-sized, remotely controlled helicopters have been spraying crops for years. These machines do not fly autonomously yet, but their small size allows them to do jobs their full-sized cousins cannot. A fleet of small rotary-wing drones could make short work of a large area if they work in tandem. Groups of drones operating this way are called swarms.

But what can drones do in fields besides perform the role of crop sprayer? Plenty, as it turns out. Companies offering UAV services to growers are proliferating. Some of the features currently available in a typical outdoor system include automatic takeoff and landing, automatic return home, GPS navigation, way point programming (specifying the points where turns are executed to fly a route), terrain following (useful in hilly terrain), time-lapse photography and video (live and recorded). Small UAVs are also capable of using a variety of sensor packages for map making, erosion monitoring, infrared analysis of chlorophyll and other analyses. Since drones can fly low, their cameras get unobstructed views that cannot be obtained any other way. Drones are relatively cheap to fly since they are so small and light. Many are electric, so they can be flown often to generate enough data to get a detailed picture of the progression of a crop over time.

Indoor Agridrones

Although the term drone conjures up images ranging from little quadracopters fabricated using 3D printers, to weaponized military machines, one doesn’t usually associate them with indoor use. As it turns out, UAVs may indeed have applications in the enclosed space of a greenhouse or other agricultural facility.

To work in confined spaces, a UAV must be small. While they are getting smarter all the time, drones are getting more compact as well. One area of active research when it comes to small aerial vehicles involves swarms. A swarm is a group of UAVs flying together in a coordinated pattern. Individual machines are aware of the positions, velocities and directions of other members of the swarm. Researchers at the University of Pennsylvania have demonstrated a swarm of three agricultural UAVs. Larger swarms of small UAVs could quickly inspect a large greenhouse crop.

Even without the need for swarms, miniature UAVs can still be useful. The most promising application is in crop monitoring. Camera drones are generally too big and heavy to safely operate around plants in an enclosed space, but there are numerous small systems in development. The MicroUAV Lab at Delft University in the Netherlands has developed lightweight machines with on-board cameras that fly with a flapping action. As soon as it is plugged in, the UAV can fly around a room in obstacle-avoidance mode. MicroUAVs may also find use in the precision application of chemicals when needed for pest management, or to collect samples from difficult-to-access locations.

Safety and Legal Status of Drones

Up until recently, the legality of flying a UAV depended on what you were doing with it. The US Federal Aviation Administration (FAA) had made it clear that commercial drone flights were illegal without approval. But in February 2015, the FAA released a set of proposed regulations that would “allow routine use of certain small unmanned aircraft systems in today’s aviation system, while maintaining flexibility to accommodate future technological innovations.”

That sounds pretty good, but many think the proposed rules are overly restrictive and don’t keep up with current technological innovations, let alone future ones. It remains to be seen if all line items in the proposed rules will make it into law, but some of the important provisions are:

  • Vehicle must weigh less than 55 lb.
  • Daylight operations only
  • Pre-flight check required
  • Maximum altitude of 500 ft. (higher altitudes available with approval)
  • Maximum speed of 100 mph
  • Line-of-sight operation only

Those rules seem reasonable to most people, but it is the restrictive requirements governing the operators that have caused the most chagrin. According to the FAA, operators would be required to:

  • Pass an initial aeronautical knowledge test
  • Be vetted by the Transportation Security Administration (TSA)
  • Obtain an unmanned aircraft operator certificate with a small UAV rating
  • Pass an aeronautical knowledge test every 24 months
  • Be at least 17 years old
  • Make the UAV available to the FAA for inspection or testing

Unfortunately, finalization of the new rules has been delayed and is now not expected to happen until 2017. In the meantime, likely responding to pressure from many sides, the FAA has loosened its process on granting exemptions while the rules are under review. This is providing some breathing room for the many companies hoping to get UAV businesses off the ground. Small UAVs, operated by their owners for recreational purposes, fall under hobbyist guidelines for radio-controlled aircraft, which state the vehicle must:

  • Weigh less than 55 lb.
  • Fly no more than 400 ft. off the ground
  • Keep three miles from any airstrip or airport
  • Remain in your line of sight at all times
  • Keep clear of people, animals, structures or anything else the UAV could harm
  • Keep out of restricted airspace
  • Not be used for business

So, can a farmer fly a drone over his own property to inspect it? Is that recreational or commercial use? It’s a gray area. Such operation could be interpreted as business use, taking it out of the hobbyist category, and would require an FAA exemption. Operating a drone indoors while workers are present could also be problematic.

In any case, the future of agricultural UAVs seems promising, if the regulatory framework can find a way to allow for expanded use while maintaining the safety of the people on the ground. The combination of robotics, GPS and UAVs will certainly have a significant impact on largescale agriculture. And as the technology develops, and if miniaturization advances at its current pace, it might not be long before these technologies become more common in indoor operations as well.