Pro surfer Sebastian Steudtner was on his board, bobbing in the waters off Nazaré, Portugal, when he saw a lone monster approaching, steadily growing as it rumbled closer.
“I knew it,” Steudtner, 37, remembers thinking.
As the driver, Alemão Maresias, took a looping route into the wave, Steudtner could see the lighthouse, town and beach.
“You don’t feel the size,” he added.
That memorable ride was in October 2020, and it took a full 18 months for the German surfer to learn just how big the wave actually was that day.
For Steudtner, going from the pounding waves off Portugal’s Silver Coast to the record books involved a complicated, exhaustive measurement process.
Despite technological advances, the process for accurately measuring big waves still involves scientific rigor and creativity.
“You want the largest ruler possible in the image and to validate its size,” said Adam Fincham, a University of Southern California associate professor of engineering who specializes in geophysical fluid dynamics and led the analysis of Steudtner’s wave.
While Jet Skis — which are used to tow surfers into the world’s biggest waves — are the gold standard because their size is known and does not change, they are usually not present during key moments of a surfer’s ride.
The standard Fincham and his colleagues from Scripps Institution of Oceanography at the University of California San Diego and the Kelly Slater Wave Company settled on this year was Steudtner’s lower leg, from his heel to his kneecap.
“That distance does not change since you can’t bend your lower leg,” Fincham said.
Sebastian Steudtner has made a name for himself chasing big waves.
The team asked Steudtner to measure that length, which effectively gave them a ruler for the image of the surfer’s ride.
The experts must study the image closely, accounting for distortions that might misrepresent the wave’s size. Different angles and camera lenses could muddle the process.
To account for how to correct the images, Fincham traveled to Nazaré and stood at the locations where photos and videos of Steudtner’s ride were captured, calculating the camera angles and the distance of the camera to the wave face.
With this information in hand, the analysis team used 3D modeling software to geometrically correct the photos and convert pixels to inches.
Since he began analyzing waves a few years ago, Fincham said, the science has evolved with a better understanding of camera parameters.
Asked about his assessment of the accuracy of their work, Fincham said, “That’s a difficult question,” and noted his team arrived at a number for which there was consensus.
“When you look for a record ... you need a number. You can’t say, ‘It was just about that,’ ” he said. “We’re comfortable with it.”
While some might still think of surfing as a carefree activity, Fincham said he and his team kept the stakes of big wave riding in mind during their work.
“These guys are risking their lives, and you have to respect that and take it very seriously,” he said.
While Steudtner’s ride is now authenticated by Guinness World Records, there are others who’ve claimed to have surfed even bigger waves.
But sometimes the photos and videos don’t support the claims, and other times surf officials and their teams of scientists study the evidence and find something lacking.
Given the difficulty of accurately measuring a wave’s size, the World Surf League limits the time-intensive process to rides that are honored at the annual Red Bull Big Wave Awards.
“No one’s saying this is the biggest wave ever surfed in the world,” Fincham said.
While Steudtner is proud to have the record, he does not see it as the most important part of his story.
“Being from Germany and Austria, I wasn’t meant to be a surfer. Anything that you can dream up and set your sight on, if you never give up and pursue it, you can reach it,” he said.
When next season approaches, he said, he will be ready for an even bigger bomb, though record-chasing is not what drives him.
“It sets me free,” he said of life on the water. “It’s like freedom.”
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