UAV Sensor Sensibility

From thousands of feet in the sky to a hundred feet off the ground, the sensors and payloads carried by unmanned aircraft systems (UAS) of all sizes to gather data and complete missions are what make them far more than planes without pilots.

The ability to lighten and miniaturize electronics while providing a high degree of accuracy and precision for a multitude of applications ranging from surveying to surveillance to sense-and-avoid means that UAS are becoming more capable every day.

FLIR Systems Inc. and RIEGL USA Inc. both offer versions of their sensors for the small UAS (sUAS) market.

“People in UAS have wanted thermal imaging for years,” says David Lee, marketing manager for FLIR Systems which makes sensors that see heat rather than light. In May last year, FLIR released its Vue sensor for sUAS operators. It was followed more recently with the improved Vue Pro, which offers onboard recording and in-flight control.

Two years ago, RIEGL introduced its VUX1 LiDAR sensor that was small enough and light enough to mount on an unmanned system while remaining well under the U.S. Federal Aviation Administration (FAA) 55-pount limit for sUAS. James Van Rens, RIEGL USA CEO, says the LiDAR system which sends out small pulses of laser light to generate 3D maps is accurate to within two millimeters at low level and a few centimeters up to 25,000 feet in altitude.

Headquartered in Wilsonville, Oregon, FLIR has been in business since 1978 and is the world’s largest manufacturer of thermal imaging sensors. Until last year, Lee says the public was probably most likely to see images on the TV show “Cops” shot from police helicopters equipped with FLIR sensors. 

The early FLIR systems were large and heavy because they had a small number of detectors that had to scan very fast, requiring cryogenic cooling. Today, Lee says FLIR uses uncooled sensors with its Lepton long-wave imaging technology, which enables the sensors to be lighter, but more complex. With only two moving parts, Lee says they can run continuously for years without failure. According to FLIR, their cameras are ten times less expensive than traditional thermal cameras.

Some of the most common applications for FLIR sensors include search and rescue, firefighting, precision agriculture, security surveying and inspections of roofs, cell towers, substations and power lines. 

“We’re getting the third dimension into the mix and seeing things from above,” Lee says. “The main reason to put a FLIR sensor on a UAS is to position a sensor in 3D space.”

He estimates that 95 percent of FLIR’s customers have a specific problem they’re trying to solve or business opportunity in mind when they purchase a thermal imaging sensor.

For example, one customer is looking to start a business inspecting solar panels. Another is using FLIR sensors to check whether irrigation systems on golf courses are operating properly and yet another is looking at sugar beet piles to make certain the stored crops aren’t fermenting, which is visible as generated heat.

“The people who continually surprise me are our customers and the innovative ways they find to use our sensor,” Lee says.

According to Van Rens, the advantage of LiDAR is not only its precision, but also its ability to take accurate measurements in adverse environments and complex urban areas. In addition, it can map through vegetation and water-absorbed soils.

Using LiDAR-equipped UAS to inspect electrical transmission towers and power lines enables them to perform a task that can be dangerous for manned helicopters.

“This application is one that a lot of power line companies and people involved in transmission industry are interested in having UAVs do,” he says.

Referring to a LiDAR image of an electrical transmission line, Van Rens pointed out the areas in which an electrical utility could gain valuable information, which included trees encroaching on the right of way, sagging power lines and the connecting guide wire at the tower tops which can show overall system stability.

RIEGL has adopted a somewhat different approach from other sensor manufacturers by developing and selling its own UAS platform, the RiCOPTER.

“Our customers told us they didn’t want to put an expensive sensor up in the air on a handmade system,” Van Rens says. “RIEGL came out with its own turnkey system to give people confidence.”

Designed for professional surveying missions, RIEGL’s octocopter is equipped with an integrated VUX-1 LiDAR sensor, an inertial measurement unit (IMU), a global navigation satellite system (GNSS) and can also carry two additional digital cameras if needed.

While demonstrating the RiCOPTER at a radio-controlled aircraft show, Van Rems says a hush fell over the crowd as the UAS took off because it sounds like no other unmanned aircraft. He describes it as a multi-purpose tool capable of carrying a variety of sensors to reliably perform such applications as construction, road and railroad surveying, corridor mapping, pipeline inspections and precision agriculture.

One of the sensor trucks of the large UAS world is the General Atomics MQ-9 Predator B flown by U.S. Customs and Border Protection (CBP) from the National Air Security Operations Center (NASOC) at the Grand Forks (North Dakota) Air Force Base. The agency also flies the Predator B along the Mexican border from sites in Sierra Vista, California, and Corpus Christi, Texas.

“The ‘S’ in UAS is a system, so the aircraft itself is only part of the system,” says David Fulcher, deputy director of the northern border facility.

A former U.S. Navy aviator who now flies manned aircraft and the Predator B—known as the Reaper by the U.S. Air Force—for CBP, Fulcher explains that more than any other aspect of this large UAS, it’s the sensors that provide the greatest asset to law enforcement.

“It’s an aerial surveillance platform,” Fulcher explains. “It carries the electro-optical and infrared camera system, as well as a ground radar system.”

Fully loaded, a Predator B can weigh up to 10,000 pounds. Designed for endurance, not speed, the UAV can remain airborne for more than 30 hours flying near its service ceiling of 50,000 feet. However, Fulcher says CBP’s certificate of authorization (COA) with the FAA limits the Predators’ altitude to between 18,000 and 28,000 feet. The COA allows the agency to fly up to 100 miles south of the Canadian border in an area stretching from Washington State to Michigan.

Although the sensor systems on the Predator make it well suited for patrolling low-population areas, Fulcher says there’s a misconception that the UAS operates as an all-seeing eye in the sky. To catch smugglers and those trying to enter the U.S. illegally, it’s first necessary to determine where to look.

Noting that all the sensors deployed on the CBP’s Predator UAS are also deployed on its manned aircraft, Fulcher says, “The radar systems predominantly cue the camera. The cameras are pretty small with a narrow field of view. So you have to know what you’re looking for in order to be able to see it on the camera.

“It can’t do wide-area collection at the same time,” he continues. “When you point and focus the camera, you can pick out things like a group of smugglers coming across the border. You can tell how many there are. You can tell that they’re carrying backpacks.”

But what the cameras can’t do is differentiate between a male and a female, identify a particular make or model of vehicle or read a license plate.

“There’s a lot of discussion about UAS technology, but aerial surveillance is not a new technology,” Fulcher says. “We’ve used radars and cameras in law enforcement for decades now. The new technology is the fact that there’s nobody on the aircraft and it has increased endurance.”

One of CPB’s latest sensors is called VaDER (Vehicle and Dismount Exploitation Radar). Originally developed by Northrup Grumman’s Electronic Systems for the military, it uses synthetic aperture radar which is capable of seeing tire tracks and footprints. It is not yet in use along the Canadian border.

“One of the key features of synthetic aperture radar is that every pixel is very precisely located based on the way the radar generates the image,” Fulcher says.

He describes the process of “cuing up data” to determine where Border Patrol agents should search for clues by helicopter or on foot.

“We can take a picture, go back and take another picture later of the same thing and run a computer algorithm to determine what has changed in those two pictures,” Fulcher says. “We can start to develop patterns to allocate resources.

“Smugglers tend to use the same routes until they’re caught,” he explains. “Movement is one of the keys to smuggling that we try to exploit with the radars. The ground moving target radar is installed on all of our Predators, which can pick up vehicle traffic. In the areas that there is smuggling, we can pick up the vehicles, the direction of travel, and the size and speed of the vehicle as its moving.”

The objective is to stay ahead of drug smugglers—who Fulcher says are becoming increasingly sophisticated—by pushing sensor detection beyond the borders and intercept them before entering the U.S.

“We use all these pieces of equipment to accomplish our missions,” he says. “Predominantly, our mission set is border security.”

In the realm of sUAS sensors and payloads, necessity can become the mother of invention. When Stephen Burtt, CEO of Aerial Technology International (ATI), took the company’s UAS to precision agriculture shows to demonstrate them to farmers they were impressed. However, one question frequently came up: Can you use them to scare off birds?

“I must have heard this question a hundred times at one trade show,” he recalls. “It started as a joke and became more real as more people asked for it.”

Based in Wilsonville, Oregon, ATI began working three years ago with the agriculture industry of the state’s Willamette Valley. Burtt discovered that farmers were quite serious about the nuisance of birds decimating such high-value crops as grapes and blueberries.

Ground-based sound systems have long been available to farmers, but Burtt says they eventually lose their effectiveness as the birds become accustomed to their locations. Another solution is having a falconer bring in a predatory bird to fly over fields. It works, but at $800 an hour, it’s an expensive way to frighten birds, Burtt notes.

Early this year, ATI introduced the Raptor Module for its line of AgBOT UAS, a sonic emitter payload that enables the aircraft not only to mimic the calls of 20 different birds of prey, but also duplicates their flight patterns. 

“The response has been overwhelming,” Burtt says. “The people who have wanted this are ecstatic. Farmers have been spending millions of dollars on different deterrents. I have a feeling this will be a valuable tool in the bag.”

ATI’s experience in precision ag has taught the company a valuable lesson in trying to meet the market’s needs. The ability to switch out sensors and payloads in the AgBOT UAS to accomplish a variety of missions provides farmers with a flexible and useful tool, Burtt says.

For example, Burtt says the company originally attempted to support a wide variety of sensors and platforms that sometimes didn’t work well together. Now they outsourced their sensor and data analytics to Micasense Inc.

“Our mission now is to provide support and training,” Burtt explains. “We deal with each client personally and give them enough training to be successful.”

UAS sensors aren’t always related to gathering data and images. In the case of LeddarTech, a Canadian supplier of detection and ranging systems in Quebec City, Quebec, their sensor technologies use light pulses to provide navigation and collision avoidance capabilities to sUAS.

“This enables drone operators to execute precise flight missions while protecting their equipment and making it safer for people on the ground,” says Michael Poulin, LeddarTech’s director of product management.

“We commercialize modules developers can integrate into their products and systems,” he adds. “We have services to develop custom solutions by integrating circuits into core components developers can use.”

Some of the company’s customers are using its sensors as altimeters for automated landings, as well as terrain-following flight operations and collision avoidance. Poulin says that for structural inspection applications, the sensor enables the UAS to maintain a constant distance from the structure by creating a detection bubble around the drone.

The key is a signal processing core within LeddarTech’s integrated circuits, which means the drone itself doesn’t need to handle much of the processing load, according to Poulin. Some of these same technologies are being used for automotive applications developed by LeddarTech and are currently in use with major auto manufacturers.

“We’re planning to be more visible in the UAS market,” Poulin says. “We want to be a significant player in sense-and-avoid solutions for the drone market.”

Fulcher sees improvements in sensors as a bright spot in moving UAS technology forward.

“As the sensor systems continue to improve faster than the aircraft, we no longer have to change the aircraft to change sensor systems,” he concludes.

Author: Patrick C. Miller
Staff Writer, UAS Magazine
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