The more efficiently and safely farmers can work, the better it is for our food supply—and Unmanned Aircraft Systems (UAS) are playing a huge role in improving productivity and ensuring the food we eat is indeed safe. China-based XAG is among the companies working to develop services and solutions that make smart farming possible, and that includes deploying drones for crop protection.
Before UAS, farmers typically sprayed crops using backpacks, tractors or manned aircraft, said Justin Gong, vice president of XAG. Of course, each of these methods comes with its own limitations and risks. Backpack spraying leads to high levels of chemical exposure and the associated health risks to the sprayer. Tractors can crush crops as they spray, hurting the farmer’s profitability. Manned aircraft are limited by the availability of airport facilities and can be expensive, making it especially difficult for smaller farms to use them.
“Agricultural production safety has been an increasing concern and a more precise, efficient, economic solution is desired,” Gong said. “UAS and other intelligent agricultural devices provide precise, smart and efficient solutions for farmers around the world. We want to help farmers reduce chemical usage by at least 30% and water consumption by 90%, while using less labor for the same amount of work.”
The XAG P30 Plant Protection UAS is designed to provide those smart farming solutions, but before it could, designers had to overcome a number of challenges that impacted positioning accuracy. They were able to do that by using a Global Navigation Satellite System (GNSS) receiver from NovAtel. The receiver is designed to support a dual-antenna, high-precision, RTK solution for navigation.
Typically, UAS rely on a barometer to detect altitude, GPS for positioning and a compass for heading direction, Gong said. The problem? None offer the level of precision needed for crop spraying.
Environmental conditions affect the barometer and its accuracy, while GPS positioning deviation could be as much as one to 20 metres, making it difficult to meet the precision requirement for agriculture. The Earth’s changing magnetic field can interfere with the compass, and that often results in plants being sprayed more than once or not being sprayed at all.To overcome these challenges, XAG began testing their custom receiver in 2015.
"There were lots of problems that needed to be solved in the UAS plant protection area at that time,” Gong said. “The compass was easily interfered with, triggering frequent accidents. GPS positioning precision fluctuated greatly with time so autonomous flight couldn’t be realized and surveying data couldn’t be reused. That’s why we decided to turn to RTK positioning.”
The company offers a robust RTK solution with high fix availability and reliability to maximize production, as well as configurable reliability levels for variable environments. RTK delivers fast initialization times and position accuracy over a variable range of usable baseline lengths, with independent quality checks indicating whether a fixed position solution was verified. This ensures a higher level of robustness and a more reliable position solution, which is key for plant protection applications. And the two-independent onboard GNSS RTK antennas give the drone the ability to identify its nose direction without a compass, making it possible for it to operate in an environment with magnetic interference.
“We chose to collaborate with NovAtel for its product performance stability,” Gong said, and “its good reputation internationally.”
XAG applied the high-precision GNSS receiver to the plant protection UAS. This NovAtel solution was one of the best modules available at the time, Gong said. They also used the module in the RTK Base Station.
Integrating the RTK module onto the platform provided the precise positioning and heading direction information needed to make crop spraying a successful application.
“We also used micro-metre wave radar, optical positioning and a visual obstacle avoidance system as assisting methods,” Gong said. “By doing all this, we are able to refine our UAS positioning accuracy down to centimetre grade, which is adaptable to a much wider range of terrains compared to other products in the market. We are now able to conduct precise plant protection operations on hills, terrace fields, orchards, vineyards, grassland, and of course, on plain vast farmlands.”
A Closer Look at the UAS
While NovAtel’s GNSS RTK high-precision navigation system provides the accuracy the fully autonomous drone needs to successfully complete agricultural missions, it also comes equipped with a variety of built-in sensors customized for crop spraying scenarios, Gong said.
Acceleration sensors and gyroscope solve for aircraft attitude angles, while visual sensors are used for obstacle avoidance. Radar provides precise altitude detection and the flowmeter enables the UAS to precisely spray crops as it’s flying overhead. A speed sensor is used on the atomizing plate of the spraying nozzle and another sensor monitors current voltage to estimate battery capacity for flight operation. The GPS/BeiDou/GLONASS satellite systems provide precise spatial orientation, and a temperature and humidity sensor monitor the environment as the system performs missions.
When GNSS RTK or GPS is interfered with, the optic positioning module is activated automatically to assist with the localization of the UAS, ensuring reliable operation no matter the time of day. The system has the ability to use Cloud RTK flying mode, so there’s no need to install a GNSS RTK base station in areas that have cellular network coverage.
Featuring carbon and aluminum composite technology, the drone is designed to fly in harsh weather conditions, which is key for crop spraying applications.
While UAS are an important part of smart farming, they’re not the only technology XAG is working on to bring more efficiency to the agricultural industry. Many of these solutions, including field navigation and autopilot technologies, also need RTK precise positioning, Gong said.
“We started by developing our own products that meet the needs of farmers,” Gong said. “But we did not simply sell the equipment. Instead, we built our plant protection team to provide service to the farmers. This not only enables the farmers to use an advanced technology, but it also reduces the hassle of buying expensive equipment that might be a bit too sophisticated for them to learn at the beginning.”
The Future of Farming
Since 2016, RTK has been the key technology in XAG’s UAS navigation, but there have been some challenges along the way, Gong said. With the increase in users, low probability problems have gradually occurred, including errors in heading, tracking and loss of contact with the satellite. When these types of issues come up, XAG works closely with NovAtel to resolve them, ultimately improving the product.
Through smart farming and products like the XAG P30, they aim to make farming more sustainable. The company’s technologies not only reduce chemical and water consumption, they also ensure food security, increase food productivity and improve food safety—and NovAtel’s precision navigation solutions play a large role in making that happen.
“As we gradually gain market share in China, we are educating the farmers and more young talents about the latest agricultural technology at the same time,” Gong said. “By building up a comprehensive understanding about our solutions for the farmers, we gradually gain recognition in the market. People now see there’s another way of making the plant protection process very efficient and smart. As a result, they build up confidence in the technology. Eventually, the mindset of the whole agriculture industry will change as more people adapt to the products and solutions we provide."