Wildlife conservation is one use for small, civil uncrewed plane techniques (UAS) that's seldom listed among the many marquee purposes for the know-how, such orthomosaic mapping, industrial inspection, and emergency response, to call a number of, but it has the potential to make vital contributions to environmental preservation.
That’s what I discovered when June Stephens, an ornithologist submitting a paper to the nationwide convention of the North American Ornithology Society, contacted me about utilizing a drone to doc an osprey nest. This appeared like a straight-forward mission I might knock out in lower than an hour of flying, however that was earlier than she defined that she needed to construct a 3D mannequin of the nest and, by the best way, the birds had put in radio jamming gear round their house.
CAN YOU HEAR ME NOW?
Okay, so the birds didn’t truly rig up jammers round their nest, however they did the subsequent neatest thing: they construct it proper on prime of a cellular phone tower. Previous to this task, I had by no means flown a drone close to a cell tower—a deliberate selection on my half. I knew that UAS have been used to conduct tower inspections, however I wasn’t conscious if any particular gear or precautions have been required to do it safely. Additionally, for years I’d heard second- and third-hand studies from different pilots of drones malfunctioning or falling out of the sky close to cell towers.
That struck me as being completely believable. Each UAS and mobile networks depend on radio alerts to perform, and it is sensible that a transceiver able to conveying lots of or hundreds of simultaneous phone calls and wi-fi knowledge connections might simply overwhelm the comparatively weak management, video, and telemetry transmissions that join a drone to its pilot.
With that in thoughts, I started my due diligence to find out whether or not or not this mission could possibly be flown safely. I started with an Web search, which revealed that neither mobile voice nor knowledge connections use the identical 2.four GHz frequency as most drones, together with the DJI Phantom four Professional+ I had chosen as my main plane for the mission. Nevertheless, for those who assume I’m going to make a flight security determination based mostly on what Google tells me, you then haven’t been paying consideration.
So, I headed out to the mission website with my UAS and a spectrum analyzer. Utilized by radio frequency engineers, electronics technicians and drone race organizers, a spectrum analyzer is principally a radio receiver that may decide up radio emissions throughout a variety of frequencies. It gained’t allow you to see or hear what these emissions are transmitting, however it is going to allow you to decide their relative power and see exactly what radio bands they occupy.
To start with, I took a studying on the base of the tower, to confirm what I had learn on-line. The alerts blasting out of the cell tower have been touchdown like artillery shells throughout the drone’s working frequencies, however with out scoring a direct hit. To date, so good.
Subsequent, I drove about half a mile away from the tower and deployed the spectrum analyzer once more, which revealed the alerts from the tower have been a lot diminished. I then powered up the Phantom and its floor management station and noticed a outstanding spike rise within the 2.four GHz vary—grossly overmatching the alerts from the tower.
Lastly, I drove again to the bottom of the tower and put all of it collectively: powering up the Phantom so I might see the transmissions from the mobile community and the plane aspect by aspect. The alerts from the 2 sources stretched out side-by-side on the spectrum analyzer’s show, however didn't instantly overlap.
With rising confidence that Google had not steered me incorrect, I started a collection of cautious check flights, waiting for any abnormalities within the plane’s efficiency, however I noticed none.
A UNIQUE CASE
Persuaded that the mission could possibly be carried out safely, I adopted up with ornithologist June Stephens, to seek out out extra about her objectives.
“Principally, we need to take a look at the supplies osprey use to construct their nests, in addition to how they're constructed,” she stated. “Additionally, ospreys will sometimes abandon their nests, and drones is perhaps helpful to assist us work out why.”
Throughout our dialogue, June jogged my memory that she hoped to assemble a 3D mannequin of the nest utilizing photogrammetry methods. I’ve used Pix4D and DroneDeploy to do some primary modeling: akin to stockpile estimation in an area quarry. Nevertheless, I wasn’t even positive that these kinds of instruments might be utilized to one thing as small and detailed as a chook’s nest.
I reached out to my colleague at Embry-Riddle Aeronautical College, Dr. Joseph Cerreta, to debate the likelihood. Joe is a nationwide professional within the area of photogrammetry and 3D modeling utilizing UAS, so I figured he would have the ability to reply my questions. It turned out that not solely wouldn't it be potential, however he was prepared to play an lively position within the course of: creating a flight plan for me to seize pictures of the nest and processing them in Pix4D to supply the mannequin.
“This can be a distinctive case, as a result of we’re making an attempt to seize one thing 100 ft off the bottom, however the identical rules apply right here as they do in different photogrammetry purposes,” he stated.
“We have to keep a constant distance between the goal and the plane, and guarantee enough overlap between particular person photographs to assemble the mannequin.”
In contrast to each earlier photogrammetry mission I had flown, this is able to not merely be a matter of defining an space to be mapped, setting a ground-sample distance and letting the plane fly from waypoint to waypoint as I stored watch to make sure the security of operations. Joe ready a diagram defining a collection of orbits I would wish to carry out across the tower utilizing the “Level of Curiosity” function within the DJI Go app.
To make sure constant knowledge, he advised I make use of the intervalometer constructed into the app, in order that the digital camera would routinely seize a picture each two seconds. Whereas I knew this was going to be a bit of tougher than a standard waypoint-driven mission, however I nonetheless figured the plane can be doing a lot of the work.
On the day of the mission, I might uncover that this was not the case. However first, we needed to watch for a break in Oregon’s dreary winter climate, and it turned out that we have been dealing with one other constraint: Daddy osprey was coming house quickly, and he doesn’t like drones getting up in his crib.
PLANNING AND EXECUTION
“Ospreys mate for all times,” June defined. “Through the winter, they migrate right down to South America. The male returns in April to wash up and put together the nest, and the feminine joins him a couple of weeks later.”
She added: “It’s necessary to fly this mission earlier than the male arrives, in order that we don’t scare him away, and in addition in order that he doesn’t turn into aggressive towards the drone.”
Lastly, the climate forecast confirmed a number of days of overcast skies, with out rain, in the course of the upcoming week. I want to fly photogrammetry missions on cloudy days, in order that the exhausting shadows created by direct daylight don’t intrude with the meeting and rendering of the completed product.
The potential for radio frequency interference apart, this mission was uncomplicated from a planning perspective. The research website was situated in Class G airspace with a ceiling at 700 ft above floor degree (AGL). Since I might be flying inside 400 ft of the cell tower, which itself was 100 ft tall, the laws beneath 14 CFR Half 107 allowed me to fly to a most altitude of 500 ft AGL—though this was merely some extent of trivia since Dr. Cerreta’s flight plan didn't name for something approaching that altitude.
The METAR from Aurora State Airport, the closest reporting station to our location, reported wonderful visibility, no wind and an overcast cloud layer at four,300 ft AGL. I tuned my hand-held aviation radio to Aurora’s tower frequency, to reinforce my situational consciousness of crewed plane working within the neighborhood, however there wasn’t a lot exercise all day, and none in our quick neighborhood. The osprey was nowhere to be seen.
I took a deep breath and put my thumbs on the sticks, sending the Phantom aloft. Previous to this mission, I had scant expertise with the Level of Curiosity functionality constructed into DJI’s drones, so I had taken a while to apply at a park close to my house. That have made it clear to me that this flight wouldn't be as straightforward as I had first imagined.
With Level of Curiosity enabled, the united statesdid a very good job of retaining the digital camera aimed on the goal, however not an ideal job, which means that I needed to gently experience the yaw on the left stick to ensure it stayed exactly within the middle of the body. Likewise, sustaining the exact altitude that Dr. Cerreta needed together with the space to focus on required fixed consideration.
Briefly, what I had first imagined can be a tedious mission largely reliant on automation turned a few of the most intense and demanding flying I've ever executed. It didn’t assist that the operation began with a scare: Dr. Cerreta needed the primary collection of photographs taken under the nest, wanting up at it. Nevertheless, the Phantom’s digital camera refused to tilt any larger than the horizon. After a second of panic, I found that this restrict was managed inside the DJI Go app, put in place to maintain amateurs from photographing their very own propellers, presumably.
Having flown the mission to one of the best of my means, I transferred the ensuing pictures to Dr. Cerreta, at that second three,000 miles away in Daytona Seashore, Florida.
MAKING SENSE OF IT ALL
Processing the info would entail much more effort than capturing it had. The issue was that, along with the cellular phone tower and the nest perched on prime of it, I had additionally captured the encompassing neighborhood and an area highschool. If the pictures have been fed into the photogrammetry software program of their entirety, it will try and render all of these background parts, possible obscuring the info concerning the nest that we had got down to mannequin.
“It’s essential for us to masks that background info out of the mannequin,” Joe defined to me. “I’m in a position to try this instantly in Pix4D by way of a course of that they name ‘carving.’ Principally, I'm going by way of and spotlight the background in a collection of photographs, carving out the cell tower and the nest.”
My coronary heart sank: I had captured greater than 200 photographs in the course of the mission, so it might take weeks of full-time work to excise the background from every of them. Thankfully, Pix4D is sufficiently clever to study from a subset of photographs which parts to discard and which to retain. Joe ended up having to hand-carve 30 of the pictures, a course of that took about 20 hours.
“Pix4D did a superb job of constructing the 3D mannequin after I chosen the background that we needed to carve away,” he stated.
As for June Stephens, she was thrilled with the completed product, which offered a singular perspective on the nest.
“On the North American Ornithology Society nationwide convention annually, we've got a monitor dedicated to rising know-how,” she defined. “Drones have been used to review nesting conduct earlier than, particularly within the arctic, the place they have been used to rely tern nests.”
Nevertheless, utilizing a drone to review the construction and composition of a person nest was breaking new floor within the subject, June stated.
“On this case, we discovered by learning the 3D mannequin that these ospreys want to make use of willow for his or her nest,” she stated. “They like to make use of lifeless limbs which range in measurement, they usually additionally add some grasses and chickweed as padding. I used to be stunned to see that the nest additionally offered habitat for smaller birds, who constructed their very own nests within the decrease a part of the construction.”
For me, this mission demonstrated that it takes a staff to get outcomes, with every individual bringing their very own skills and expertise to bear. June had outlined our objective based mostly on her information of ornithology, and regardless that he was on the opposite aspect of the nation, Joe had successfully decided the maneuvers that may be required to perform it and processed the ensuing knowledge.
Although I used to be the individual with my thumbs on the sticks flying a troublesome mission with unfamiliar technical challenges, on reflection, I feel that I obtained the straightforward half.
TEXT AND PHOTOS BY PATRICK SHERMAN
The submit Mission Profile: 3D Mapping An Osprey Nest (On a Cell Tower!) appeared first on RotorDrone.