Views from the sky
By Carolyn King
To map a field, the UAV flies over a field in parallel passes and takes photos at regular intervals.
Photo by Janet Kanters.
Does using an unmanned aerial vehicle (UAV) make sense for your crop operation? UAVs, also called drones or unmanned aerial systems, are available as fixed-wing types, like little airplanes, or rotor types, like little helicopters. They are catching the attention of Prairie crop growers and specialists who want to see how well they work for crop scouting and field mapping, and how the costs compare to the benefits.
UAVs for weed and disease issues
In Alberta, a project is underway to evaluate the use of UAVs to generate field maps to help in making decisions on weed and disease management. Dr. Chris Neeser, a weed research scientist with Alberta Agriculture and Rural Development (AARD), is leading the project. He wants to develop a set of procedures for acquiring and processing high-resolution UAV imagery and to assess the usefulness and economics of this tool.
To map a field, the UAV flies over the field in parallel passes and takes photos at regular intervals. Imagery software is then used to stitch all the photos together to create a map of the whole field.
The fixed-wing UAV used in Neeser’s project is a prototype developed and flown by Jan Zalud of JZAerial in Calgary. Neeser says, “It can fly for about 15 to 20 minutes before you have to change the battery. That is just enough time to map a quarter section, taking about 120 images per quarter and flying at an altitude of about 600 feet.”
A small digital camera is attached under the UAV’s wing. The camera’s filters have been modified to capture near-infrared light. “Instead of the red, green, blue spectrum, we get the near-infrared, green, blue spectrum,” explains Neeser. “Vegetation reflects near-infrared wavelengths better than the other wavelengths, so it allows you to do NDVI (normalized difference vegetation index) mapping.”
Healthy plants reflect more near-infrared light than stressed or dead plants, so NDVI maps can be used to evaluate factors like plant stress due to disease, drought or low available nitrogen. So, with proper interpretation and analysis, the maps could help with decisions on variable rate applications of inputs.
Neeser explains that because the photos were taken from a height of 600 feet, the imagery has a resolution of about six centimetres to the pixel; that is, each image pixel covers a 6 cm by 6 cm area on the ground. So the UAV imagery can show things like crop rows and any seeding errors in those rows, but not the individual leaves on a plant. Problems that occur fairly uniformly across a field are hard to detect on the imagery, but patchy problems, like a patch of weeds or diseased plants, are easy to see.
“To detect greater detail, the UAV could fly lower. But it would take longer to get coverage of the whole field, longer to analyze the imagery, and more processing power. So it’s a trade-off,” he says.
In co-operation with several southern Alberta crop growers, the UAV was flown over 12 fields and six crop types in 2014. In the coming months, Neeser will be analyzing the maps, comparing them to what was actually happening on the ground, called “ground-truthing,” and evaluating the costs and benefits of using UAV imagery.
The project is funded through the Alberta Crop Industry Development Fund, with funds from the Alfalfa Seed Commission, Alberta Pulse Growers Commission, Alberta Wheat Commission, Western Grains Research Foundation, Alberta Canola Producers Commission and Potato Growers of Alberta.
In Manitoba, Rejean Picard, farm production advisor with Manitoba Agriculture, Food and Rural Development (MAFRD), has been trying out a DJI Phantom 2 quadcopter (a helicopter-type UAV with four rotors).
He has been using the Phantom 2 for freestyle flying, guiding it as it flies over the field. “Because it’s freestyle flying, it’s very quick to start and fly and collect imagery and be back to the operator in minutes.” The UAV’s camera is a GoPro model that can take still colour images and HD video.
“A UAV gives you that eye-in-the-sky perspective, so you can see much more of the field than you can standing at ground level. I also like that you can collect pictures of a field over time to see how things change, and you have a permanent record of what the field looked like at different times of the year,” he notes.
Picard especially likes his system’s ability to receive live images while the drone is flying. “With the live on-screen display, you can see what the camera is seeing. For example, if the field is wet so you can’t drive through it, and you want to see the extent of water damage or flooding in the field, then the live images allow you to do that.”
Learning to fly his quadcopter took some practice, especially to land it without damaging the rotors. Picard says it can fly for about 20 minutes before the battery needs to be recharged, and it can operate in wind speeds up to about 40 kilometres per hour. “It is GPS-driven and designed to hover. With the GPS, it will find and maintain its position, within a certain range [even in breezy conditions].” The UAV weighs about one kilogram.
“The costs for my unit include the UAV itself with the gimbal (the supporting arm that holds the camera), which is about $1,000. The camera is another $400. The live on-screen display is about $400 to $500. So the total cost would be between $2,000 and $2,500, tax included. For that you get an effective entry-level UAV for growers,” he notes.
One of the tools Picard has been playing with recently is imagery analysis software called Assess, which costs about $300. “The still images that I collect with my UAV are distorted somewhat because the camera uses a wide-angle lens. But, by using the software and knowing the field’s size, I was able to differentiate the different colours in the images, such as thinner patches versus thick green patches. And I was able to determine fairly closely what proportion of the field had a thin plant stand, which could be drowned-out spots or a knoll where there is little growth,” he explains. “So with other tools, a person can use even this basic UAV effectively.”
Geo-referenced mapping and scouting
Jeff Kostuik, a diversification specialist with MAFRD, has been experimenting with a fixed-wing UAV. He says, “We run a small applied research farm here [at Roblin] with the Diversification Centres in Manitoba, and we’re always looking for different ways of gathering data. I thought being able to fly the drone on a regular basis would be a good fit for what we’re doing. But more importantly, I wanted to figure out how using a drone might fit for regular farmers, would it be worth the cost, and how would they get a return on investment.”
He is using one of senseFly’s earlier introductory models called the swinglet CAM. “We’re able to fly our UAV only if the wind is under 20 km/h, but senseFly’s newer models perform quite well in winds up to 40 to 45 km/h. Depending on weather conditions like wind speed and temperature, ours will stay in the air from 10 to 20 minutes; newer models can stay up longer.”
Kostuik’s system costs about $20,000 to $25,000. It has GIS (geographic information system) capability so it can create geo-referenced imagery for precision farming uses. It can provide regular photos, as well as near-infrared and NDVI imagery. It weighs about 0.5 kg.
He says the swinglet CAM is extremely easy to fly. “The computer does all the work for you. You do pre-flight programming for exactly what you want. The resolution you want will determine how high it will fly and the amount of [photo overlap between passes]. Then you just shake the drone three times to start the motor and throw it into the wind. It automatically flies your programmed route. When it’s done, you basically hit ‘come home’ on the computer, and the plane lands within about 15 metres of where you are.”
He notes, “You can view the pictures individually once the plane lands – you just take the SD [memory card] out of the UAV and put it into your laptop to view them. But to stitch all those photos together to get a map of the entire field takes a few hours.”
To Kostuik, the most obvious use for UAV technology is crop scouting, especially when it is difficult to walk or drive into a field. On the images that Kostuik is obtaining, it’s easy to see things like crop rows, lodging, weed patches and cutworm-damaged areas.
However, he emphasizes that the NDVI images need to be ground-truthed to be sure they’re interpreted correctly. “We’re finding that you still can’t beat boots on the ground. A drone can be a tool in the toolbox, but it is not something that you can rely on [by itself] to tell you what is going on in the field,” says Kostuik.
On the plus side, he says UAV imagery is great for targeted on-the-ground scouting.
UAVs and the bottom line
UAV technology is pretty cool, but will it improve your bottom line? “You need to look at the costs and the type of information the drones can glean from the field and then how you’ll deploy that information to make more informed business decisions,” says Nevin Rosaasen, a research economist with AARD. “At the end of the day, it’s how you leverage it to put more dollars in your jeans.”
One consideration is how the costs and benefits of UAV imagery compare with other ways to get information about your fields. Compared to satellite imagery and conventional air photographs, UAV imagery has advantages like higher spatial resolution, better timeliness and the ability to tailor the data collection to a specific site. Compared to boots on the ground, UAV imagery provides quick, easy access to the whole field and helps improve the efficiency of on-the-ground scouting. On the other hand, there’s the cost of purchasing and repairing the UAV system, the time to learn to use it, and the time to operate it and analyze the imagery.
The time needed to learn how to fly a UAV varies; some are easy to learn and others are a little more complicated. All UAV operators must follow Transport Canada’s air safety requirements (see sidebar).
The cost of UAVs varies quite a bit. “An entry-level recreational drone with two cameras, for instance, is as cheap as $350. For drones that provide more accurate information, with higher resolution photo and video images, you’re looking at a base entry of around $3,000 to $4,000,” says Rosaasen. Also, “some UAV parts can be costly if you have some crashes as you learn to fly it. And if your drone goes down in a fairly tall or dense crop, it can be tough to find.”
Systems with the GIS capabilities needed for precision farming applications are more expensive and require a greater time investment for imagery analysis.
“We’ve created a bunch of very nice photographs, but what does the imagery mean to the producer and how does he make money from that? I’m not a GIS specialist and all that is a steep learning curve for me,” notes Kostuik. “It’s more suited to people who are a little more advanced in precision farming and variable rate applications. You can generate a prescription map fairly easily and quickly, and it’s real-time as opposed to satellite imagery. Our imagery has about 6- to 10-cm pixel resolution, whereas satellite imagery has about 30-m pixel resolution, so ours is a lot more precise.
“If you have the ability to use those prescription maps, then this technology could to save you money. If you’re using it for crop scouting, it could save a little time, but not necessarily a lot of time.”
Kostuik thinks a higher-end system, like his $20,000-plus system, would be cost-prohibitive for an individual farmer to purchase, but it could make economic sense for an agronomist who is providing precision farming services for a number of clients.
Neeser has a similar view. “I can see crop consultants using this as one of their tools to collect information about their clients’ fields. They would need to import the UAV images into a GIS program and overlay those over images with other information, like yield maps, fertilizer application maps, soil maps and so on. In conjunction with all the other information, the UAV imagery could be valuable to help make better decisions, as they accumulate several years of these images and see the differences depending on what crops are grown,” he says.
“But combining the UAV imagery with GIS would require a substantial investment of time to learn how to do it, because it requires some specialized knowledge. And it takes time to get the images and analyze them. Also, there is a significant risk with this kind of equipment; it could crash, for instance.”
Neeser expects UAV use in agriculture to continue to increase. “It is rapidly developing technology, so it looks like we’ll see UAVs being used more and more in the future.”
Rosaasen says the use of the technology provides a lot of opportunity to revolutionize the way crops are produced. “Thinking out to 2025 or 2030, drones could be delivering small shots of fertilizer or a specific herbicide to individual plants. We have all the tools to do that; we just haven’t put it all together in a complete package yet. I think producers will find innovative ways to deploy this technology faster than analysts can speculate on how it might be used. If there’s a way to make a dollar, farmers will figure out how.”
Operating your UAV safely and legally
Anyone operating a UAV in Canada must follow the rules set out in the Canadian Aviation Regulations and must respect all federal, provincial/territorial and municipal laws related to trespassing and privacy.
Until recently, use of a UAV for work purposes, including things like crop scouting, required a Special Flight Operations Certificate (SFOC) from Transport Canada. However, in November 2014, Transport Canada brought in two exemptions that simplify small UAV operations.
Under the new exemptions, an SFOC is no longer required for work use of UAVs under 2 kg and certain operations involving UAVs under 25 kg. However, operational limitations apply to both these exemptions (for example, restrictions related to flying height, distance from aerodromes, and type of airspace in which the UAV operation is taking place). Anyone wishing to operate a UAV outside of these limitations must still obtain an SFOC. In addition, the exemptions apply only to operations within visual line of sight. This means the pilot or his visual observer must maintain visual contact with the aircraft, without any aid such as binoculars, to maintain control and decisively see and avoid other aircraft or objects.
Transport Canada is also simplifying the application process and reducing the time it takes to issue SFOCs for larger UAV operators.
“We’re trying very hard to give UAV users the easiest possible access to being able to operate, while balancing that with the need to make sure things are safe for people on the ground and people in the air,” says Martin Eley, director general of Civil Aviation at Transport Canada. “So we’re encouraging people to understand and live up to their responsibilities and become familiar with the basic rules of the air, because UAV operators are sharing the air with people in larger aircraft.”
Visit Transport Canada’s website (www.tc.gc.ca) for more details on flying your UAV safely and legally.