Cusick was taking a break from work, standing on a platform along the Brooks River in Alaska’s Katmai National Park and preserving a world-famous spot for watching bears, as the giant mammals ventured out into the water to catch and fish. I loved going down. Otis was a few hundred feet away, standing relatively still.
Cusick, who works for the National Park Service’s Alaska Regional Office, creates maps and trains people on GPS and use of scanners in the field. He typically uses a laser scanner—specifically, a terrestrial lidar scanner—to measure the volume of stationary objects such as buildings and gravel piles in the park. It’s a $70,000 industrial-grade device that sits on a heavy tripod. That evening, Cusick aimed at Otis, and took a scan.
Lidar is short for “Light Detecting and Ranging” and is probably best known for its use in autonomous vehicles. A lidar scanner sends out millions of pulses of infrared light and measures how long it takes them to return after hitting an object like Otis. These measurements form a point cloud that can be used to construct a three-dimensional map of the object.
Within seconds, Cusick was able to pinpoint what looked like Otis’ rear on the tablet attached to the scanner. Computer software later processed the scan, creating a 3-D model that could be used to determine the width of the bear’s back.
Cusick was excited; He didn’t think his experiment would work.
“I was like, ‘Wow, I got a comeback – I can measure Otis’ butt here! He recalled this week to Granthshala Business with a laugh.
It may seem easy to use a scale to weigh a bear, but it is impractical in the wild, where it can be chewed. (Plus, you’ll have to lure the bears to a scale and have them stand for about 11 seconds or so.) In the spring, wild bears can be weighed by biologists who fly by by helicopter to the bears. Let it cool, push it into a trap, and lift it through a pulley system. But, apart from its infiltration, the method may not be possible in the fall, when the bears have grown fat for the winter.
“One big, big advantage of this method is that it’s non-invasive; we don’t have to capture the animals,” said Lindsey Mangipen, an Anchorage-based polar bear biologist for the US Fish and Wildlife Service. “It’s also logistically less challenging for us.”
Estimating bear weight with lidar is much less disruptive, although it is still a very complex guessing game. For example, scan takers are only able to capture part of the bear, because there is no way to place the scanner on the other side of the river, Cusick said. To compensate for this, they can cut the bear’s scan in half and double the volume of the more complete body part to estimate the bear’s total volume. And while a 3-D scan can be used to determine a bear’s volume (how much space it takes up in three dimensions), it doesn’t estimate anything about its density, which would help figure it out. It is necessary to do how heavy it is.
To get a good estimate on density, which can vary from bear to bear based on gender, bone composition, time of year, and many other factors, Cusick spoke to biologists who study the animals. They thought it would be reasonable to estimate that a bear is composed of 60% water and 40% fat, so he and his colleagues used those percentages in 2019 and 2020, from scanned volumes, to tease out weight estimates. did. For many bears in Katmai.
The overall process required several people, Cusick said: One person scans while another verifies the identity of the bear, for example. Weight estimates, which can be made with multiple scans for a bear, are made independently by different people and compared.
It’s currently impossible to know how accurate this method is, but Mangipen is hoping to validate the scanning technique by partnering with zoos to scan captive polar bears whose weight is known as they step on the scales. Can be trained to keep. Those known weights can be compared to the weights obtained from 3-D scans of the bears.
While it would be impossible to know for sure which bear is actually the fattest this year, Cusick thinks the 747 looks once again the biggest.
“We all have our favourites,” he said. “The anthropomorphism here is strong enough.”
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