Using Drones in Agriculture and Natural Resource Management

This article will discuss some of the applications of unmanned aircraft systems (UAS) or unmanned aerial vehicles (UAV), often referred to as "drones" for agriculture and natural resource management. These devices are also known as Remotely Piloted Aircraft Systems (RPAS), although this internationally accepted term is reserved for scientific literature. A drone may be either fixed-wing or multi-rotor systems and may be flown manually or configured to fly fully autonomously. In the US, drones are regulated by the Federal Aviation Administration (FAA).

While flying drones has become a popular hobbyist activity, their value to agriculture and natural resource management lies in their capability to carry multiple sensors, including powerful digital cameras, multispectral sensors, thermal sensors, and advanced laser mapping systems. This technology could save time and money by providing valuable management information to farmers and/or natural resource specialists. For example, it is possible to fly a drone multiple times during a growing season to observe the effect of fertilization, irrigation, and terrain relief on crop yields with high accuracy and at a lower cost than other methods. Each year, new drones with improved sensors, higher endurance, and affordable prices are being released.

What is your drone budget?

A basic drone for agricultural purposes will likely cost in the range of $700 to $1200. More advanced level systems run from $1500 to $2500 and higher. Generally, the more advanced the guidance and control system and additional sensor technologies, the higher the price. Sophisticated systems in the realm of $20,000 to $50,000 are now being used routinely in natural resource management. There are cheaper drones on the market, but these drones are not equipped with Global Navigation Satellite Systems (GNSS). A GNSS is comprised of multiple satellites orbiting the Earth in a fixed trajectory that are used to provide high-precision spatial location information.

There are various GNSS that include Global Positioning System (GPS, US), Galileo (European Union), and Glonass (Russia). A drone can use one or multiple satellite systems to improve its positioning accuracy, although it is not necessary for a drone to collect data from all the systems to function efficiently.

What to Consider when Buying a Drone

Introductory drone

•  Ability to acquire information from at least two GNSS (for instance, GPS + Galileo).
• A digital camera with a minimum of 20 megapixels.
• Minimum flight time of 25 minutes (ideal with no wind).

 More advanced drone

• Ability to acquire information from at least two, ideally three satellite systems (for instance, GPS + Galileo + Glonass).
• A digital camera with 20 to 48 megapixels.
• Autonomous flights (pre-program altitude, speed, Area of Interest-AOI boundary, etc., prior to flight).
• Minimum flight time of 40 minutes (ideal with no wind).
• Anticollision sensors or obstacle avoidance system.
• Operating temperature 14°F-100°F.

Additionally, the budget should include funds for additional batteries, spare sets of propellers, and digital storage cards for imagery/data. You should also consider getting a hard case to protect your drone (Figure 1). Many companies sell bundle kits or packages with additional accessories. The above bullet lists are general and additional features should be explored depending upon your specific needs.

If you are interested in purchasing a drone but have more questions reach out to regional drone associations that can provide information about local regulations and events so the farmer can be better informed about the opportunities and limitations of the drone technology. One such organization in Pennsylvania is the Pennsylvania Drone Association. Additionally, there is the American Society for Photogrammetry and Remote Sensing (ASPRS). This society has a directory of drone pilots per state in the US. It is highly recommended to use the resources described above to gain a basic knowledge about drones to determine if they might help improving any crop management operation before purchasing an expensive drone.

Rules and Regulations

If you would like to fly a drone for agricultural purposes on your own property, you will need to register your drone at the FAA FAA register a drone web page. In this case, you would not need to be a commercially licensed pilot, since you are using your drone on your property, and you will be solely benefit.

If you are expecting to receive any type of payment or compensation of any sort for your flights, you will need a Part 107 Remote Pilot Certificate. To become a certified pilot, you must pass the Part 107 Remote Pilot Knowledge Test. The test evaluates your knowledge of basic safety rules and controlled airspace restrictions. There are many free resources on the web to study for the test (more detailed information can be found Study Resources). Once you have passed the test, you will receive a certificate number and the FAA will send you a Remote Pilot License. This license will expire in 24 calendar months, and it can be updated online at no cost.

 In general terms, you should be aware of the following basic rules:

• Register your drone on the FAA website
• Do not fly a drone at night
• Do not fly a drone over people
• Do not fly a drone over 400 ft above ground level (AGL)
• Do not fly a drone at excess speeds
• Do not fly a drone with wind conditions greater than 15 mph
• Do not fly a drone in the rain
• Do not fly under the effects of alcohol or any substance that might influence your performance as pilot
• Get familiar with local norms and laws pertaining to drone operations.

Special Considerations

There are some areas where you are not allowed to use a drone, even with a commercial license like flying over military bases or airports. This is a basic security measure that must be followed. An airport is restricted airspace - an area with limited access for drone flights.

Around restricted air space there are varying levels of security. Imagine a circle that surrounds an airport. The closer one gets to the center, the airport, the more restrictive the area will become. The center of the circle is called a zero-feet area, which means no recreative nor commercial drone flights are allowed (Figure 2). If one moves from the center to other areas (referred to as quadrants) without the zero-feet area restriction, it is possible to receive an FAA authorization to perform the flight under specific altitudes. For instance, if you would like to develop your flight over a quadrant with the number 100, that means that you only can fly under 100 ft AGL. For more information about the quadrants in your area.

The FAA has developed a system to manage the automated authorizations at any quadrant different than a zero-feet quadrant. This system is called the Low Altitude Authorization and Notification Capability (LAANC). The FAA provides a list of companies providing public LAANC services.

After you select the company of your preference, you register your name and add some basic information in the company's page to create an account, and then you may request an authorization. If all the information is correctly entered (AOI, date, time, pilot's information, drone information), the authorization will be provided immediately for any area different than a zero-feet quadrant. If you need to fly over a zero-feet quadrant, which is the most restricted area within a controlled airspace, you will need to communicate directly to the FAA to explain the objectives of your flight. This process might take several weeks, and the FAA might not accept your request.

It is a good practice to double check if your AOI is within 3 miles of an airport and if so, see the maximum allowed altitude you may fly a drone. When flying, you must have your license, a copy of the drone registration number, and written permission signed by the landowner, manager, or representative at hand when developing a flight to avoid any legal issue. Moreover, if you are planning to fly over an FAA controlled area, you must have a copy of the LAANC authorization. Depending upon the complexity of the flights, the FAA recommends having a person with you during the flight to help you monitoring the flight.

Once you have your Remote Pilot License and a basic understanding of the opportunities and limitations of this technology for your specific objectives, you might consider purchasing a drone. There are multiple options in the market for the agricultural and natural resources fields, and the final decision will be a function of the following considerations:

What type of information are you interested in acquiring?

While there are many expensive sensors on the market, most agricultural users only need a drone with a digital camera (sometimes referred to as a visual light camera or as an RGB camera) attached to it. The camera can be used to create two main products: an orthophoto and a digital elevation model (DEM) (Figure 3 and Figure 4 respectively).

An orthophoto is useful because you can determine distances and areas from a field. This information is valuable when planning farm operations such as the determination of areas for specific crops, the amount of fertilizer, and the minimum size of roads to move heavy machinery.

The DEM provides information about differences in elevation in a field. If you know the relief of your AOI like a pasture in terms of elevation and slope, you will be able to better target terrain and crop management operations such as material transport, machinery transit, and irrigation planning, etc.

Specialized software can analyze each image acquired by the drone and find common points among all the images. This is a highly demanding processing stage and for that reason you might need a powerful computer. Then, the software will "stitch" all the images to produce an orthophoto (sometimes called orthomosaic) (Figure 2) and a DEM (Figure 3).

All products will have some error, this is inevitable even for sophisticated, expensive drones. This error ranges between 10 meters to a few centimeters and it will depend on the accuracy of the drone’s global navigation satellite system. In this regard is important to mention that an error of 1 to 5 meters could be considered acceptable for agricultural or natural resources management. Errors of centimeters or millimeters are common in civil engineering.

Would you like to develop your own maps?

If you want to process the images yourself, it is important to have a high-end computer and the right software. The computer and software you select will dictate your ability to process images to obtain reliable products. Normally, the software companies will publish a list of basic-to-advanced hardware requirements. A basic computer configuration for drone images processing is comprised of a 4-8 core Intel or AMD processor of 2.0+GHz Central Processing Unit (CPU), Random Access Memory (RAM) of 16-32GB, and a dedicated Graphics Processing Unit (GPU) (for example GeForce or Radeon). A basic to advanced computer configuration that can process the information may cost $1,500 to $5,000. There is free software available, but it may be difficult to process many images (more than 200 or 300 images); there is also software that may cost $600-5,000 depending on the software selected which can be easier to work with. Luckily, there are tutorials to learn how to a) prepare a good flight, b) do the flight in an efficient and safe manner, and c) process your images using both free and licensed software.

If you are uncomfortable with making the maps but would like to fly the drone, there are companies that can develop products as orthophotos or DEMs using the drone images for you. To do this, you fly the drone, collect hundreds of images of an AOI, and then send a copy of all the images to a company for further processing. After three to five days, you will receive a copy of the digital products, like an orthomosaic and a DEM map. In general terms, the processing time and the final costs will depend on the size of the AOI.

It is also possible to hire the whole process out, this will require hiring a licensed pilot and a processing analyst. Oftentimes the pilot might provide the processing services too. Hiring a pilot in the US to do just the flight or survey, generally costs $150 to $300 per hour. Again, the image processing should be considered as a separate service.

The costs provided are approximations and might vary depending upon:

•  The time on the field.
• The extension of the AOI.
• The complexity and risks of the flight (presence of tall trees, buildings, power lines, etc.).
• The experience of the pilot and the map processing company.
• The accuracy of the final products. If you need very accurate products, the pilot might need to develop a ground survey to improve the accuracy of the final products, which will increase the final cost.
• The type of sensors to be used (only visual light versus multispectral and/or thermal).

The evolution in drone technology is promising and each day, new developments and products are being introduced for agriculture and natural resource management.