From Unmanned Systems Magazine: Lower barriers to entry spur multispectral sensor use



Accessible, actionable multispectral imaging has been decades in the making. With a wide range of imagined applications still yet to be discovered, multispectral imaging promises to change the future of — and possibly disrupt — any number of fields and industries.

For example, researchers at the U.S. National Academy of Sciences have used multispectral infrared sensors to map out blue pigment in paintings, making identifying artworks, as well as evaluating the condition and authenticity of the work, potentially less invasive and more efficient.

And then, there are more practical applications for multispectral imaging, from analyzing food to determine safety, to analyzing crime scene evidence, to managing and analyzing wildfire firefighting. But some practical and growing applications are connected to agriculture, ecosystem research, and wildlife and ranch management.

As the cost of the multispectral imaging has decreased, more farmers, scientists and fieldworkers are investing in unmanned aircraft and taking advantage of applications that make gathering data beyond the visible spectrum possible. Multispectral images might reveal evidence of alarming trends such as the spread of disease among crops or animals, an infestation of invasive insects or plants, or signs of poaching or predator activity.

According to Thompson Rivers University in Canada, the school’s Dr. John Church has partnered with Southern Alberta Institute of Technology and Golden BC’s Kingsclere Ranch to work under an “Idea to Innovation” grant from the Natural Sciences and Engineering Research Council.

The three-year grant will support Church, an associate professor of science and the British Columbia Innovation Chair in Cattle Industry Sustainability, as he explores new methods for detecting cattle on the range.

“This project is unique in that it allows for better management of all ranch assets,” he explains. “Past management techniques have been more of an art rather than a science, and we hope to change that.”

Joined on the project by Associate Professor of Geography Dr. David Hill, the team will use UAS to create large aerial photomaps that producers can use to make land management decisions. Combined with radio frequency identification tagging, the researchers hope UAS will help ranchers find and identify individual animals in their herds.

Jeff Braisher of Kingsclere Ranch Ltd., says, “BC ranchers collectively manage vast tracts of both private and public land, so having access to tools that enhance our ability to manage this land is what really attracted me to the project.”

Restoration Ecologist Dr. Holly Jones uses drones for complementary purposes in her research at Northern Illinois University, where she serves as an assistant professor in the Department of Biology and the principal investigator at the Jones Lab in the Institute for the Study of Environment, Sustainability, and Energy. She and five other researchers recently won a climate innovation competition sponsored by French drone maker Parrot and Switzerland’s Pix4D, which creates professional, geo-referenced maps and models from aerial imagery.

Focused on applicants who integrate UAS into long-term environment-related research, the competition awarded technology and equipment grants of hardware and software to researchers around the world.

Jones is using the Parrot Disco-Pro AG, an all-in-one, multi-purpose drone package, in her lab’s research on a 4,000-acre restored prairie. She hopes to gather more precise, less subjective data across a greater share of the prairie land.

“What I notice is that there’s a lot of ecological variety happening over a larger scale that might not be caught when we’re measuring over a much smaller scale,” says Jones.

The Jones Lab is investigating how bison impact the ecosystem, the difference in impact between controlled fire and wildfire, and the effect of wetter spring seasons on plants.

“It’s a well-known rule that if the spring after you plant is a wet season, it is more productive … in the next spring after you plant in the fall, if you get a really nice rainy year, those plants are known to have more diversity,” she says. “We know the weather is likely to shift up here so we can look at how that might impact productivity.”

Her goal is to help prairie restoration ecologists determine whether to change a species planted in a given year and learn how climate conditions might affect those decisions. And, because bison can have a varying impact across large areas, she’s exploring how bison are impacting that plant activity as well as small mammals.

Weighing 28 ounces, the Parrot Disco-Pro AG has a range of up to 1.2 miles and a battery life of 30 minutes. The drone has cut the Jones Lab team’s flying time in half, taking just two weeks to cover 15 sites that measure 200 feet square each. Until now, Jones used the 3D Robotics’ 3DR Solo, which performs well but has a battery life of only 15 minutes and flies more slowly, limiting the size of the area that could be surveyed during flights.

The Disco-Pro features a reinforced fuselage that accommodates an agriculture package featuring the Parrot Sequoia multispectral imagery solution, which uses GPS and automatically records lighting conditions and images in four spectral bands: green, red, red- edge and near infrared.

Its autopilot is compatible with the Pix4Dcapture, an application that allows users to create flight plans for capturing image data and produces geo-referenced maps and models post-flight in desktop or cloud software. Flight plan options include polygon, grid, double-grid, circular and free flight, and the software has the capacity to set multiple plans within one project. Users can plot mapping parameters via mobile app on smartphones and tablets, and live-stream footage via the drone’s front camera. App subscribers are then able to download images online and retrieve them onsite or later. Pix4Dcapture is also compatible with several DJI models, including the Phantom 4.

Multispectral ecology

On the other side of the world, Dr. Lluís Brotons is senior researcher at Spain’s InForest Joint Research Unit at the Centre Tecnològic Forestal de Catalunya, a public consortia formed by local and regional European governments and the University of Lleida. His expertise is at the intersection of unmanned aircraft and ecology studies.

“The main objectives of the InForests UAV service are to narrow the distance between this technology and research carried out in our fields of expertise, and also to strive for future development,” says Brotons, who received a Parrot-Pix4D grant as well. The center was an early adopter of drones in ecology research, and launched InForest in 2015. It operates a small fleet of mostly DJI Phantom 2 and Phantom 3 units, with the Phantom 3 equipped with Parrot Sequoyah RGB and infrared multispectrum sensors.

Brotons says fewer barriers to entry are boosting the potential of UAS as a multipurpose remote sensing platform.

“We have used these technologies to identify and characterize the level of infestation at high resolution, given their ability to capture high resolution images at below-cloud low altitudes with virtually off-the-shelf miniaturized sensors and availability of software that can handle processing of large spatial datasets,” Brotons says.

With multispectral imaging, the center has used UAS for large-scale  applications such as forest fire analysis, as well as small-scale applications to map vegetation at the tree line.

For the grant, Brotons is focusing on monitoring the impacts of pests in Mediterranean forests. His team is combining mid-resolution satellite imagery with images gathered at tree level.

Defoliation has typically been assessed with satellite imagery, but that can fall short on both quality and quantity, he says.

“Multispectral data, to be acquired via specific near- infrared cameras, should allow advances in the mapping and monitoring of pine processionary moth defoliation assessments — specifically by allowing a much better comparison across images taken in different locations and at different times,” he says.

Pine processionary moths, or PPM, are some of the most destructive species that damage pine and cedar trees in Europe and other parts of the world.

Conducting field inventories is expensive, whether on foot or plane, and sometimes teams don’t end up gathering the required quantitative data, making the use of drones idea, as they can save time and money. While he says the resolution from UAS images isn’t as high as some other methods, Brotons appreciates what he receives in return.

“Multispectral cameras have richer spectral information that provides critical data, especially in analyses of vegetation changes,” he says.

While the use of UAS for in ecological research is still fairly new, Jones has identified an item on her wish list that would move her work forward and help capture more data about the prairie, saying, “I would love a hyperspectral.”

However, the cost of a hyperspectral equipment is roughly $10,000, and beyond her budget. So, for now, the Jones Lab will stick with multispectral sensors as the team continues to incorporate UAS into its research and the profession discovers increasing numbers of applications.

Below: Dr. Holly Jones works with a drone to study a 4,000 acre prairie. Photo: Parrot

Dr. Holly Jones works with a drone to study a 4,000 acre prairie. Photo: Parrot