BREMERHAVEN, Germany, Aug. 15, 2013 — An IR camera has been turned into a tool for automatic whale detection onboard the research vessel Polarstern
, designed to detect whales by their spouts during times of loud industrial noise.
Regulatory authorities request mitigation measures for the protection of marine animals when in the close vicinity of loud activities, such as pile driving during wind farm construction, or the use of airguns when searching for oil and gas. One such measure involves monitoring the surrounding seas and turning off the equipment when whales approach; that task, however, is easier said than done.
After coming up for air, an Antarctic mink whale is descending underneath the sea ice of the Weddell Sea. Mink whales are the biggest winter inhabitants of the Antarctic sea ice. They measure up to 10 m in length and weight up to 10 metric tons. Nevertheless, they belong to the smaller members of the family of plankton-feeding baleen whales. Courtesy of Mario Hoppmann, AWI.
“Whoever has looked at the sea for any length of time knows how quickly the eyes get tired and concentration dwindles,” said Dr. Daniel Zitterbart, a physicist at the Alfred Wegener Institute (AWI) for Polar and Marine Research. “In addition, we cannot look in all directions at the same time, and at night we virtually see nothing. Therefore, it has been difficult, especially at night, to spot whales near vessels or marine platforms.”
As a result, Zitterbart and his colleagues from AWI’s Ocean Acoustics Lab have spent the last four years trying to find a way to continuously monitor the surrounding seas for whales. The answer was found in advancing Rheinmetall Defence Electronics’ FIRST Navy IR camera into a tool for automatic whale sightings.
The FIRST Navy thermal imager is installed in Polarstern’s crow’s nest at a height of about 28 m above water on a highly stabilized platform (white base). The sensor head (green) rotates at 5 rps. In the crow’s nest the wind often blows at gale force strength due to the ship’s superstructure, while the temperature plummets to –30 °C, presenting high demands to the system. Courtesy of Lars Kindermann, AWI.
“The thermal imaging camera is located at 28 meters height in Polarstern’s windy crow’s nest,” Zitterbart said. “The thermal sensor is so sensitive that it detects differences in temperature of less than a hundredth of a degree Celsius. The whale spout, which, at least in subpolar and polar regions, is significantly warmer than the sea surface, appears as light grey or white fountains on these images.”
The video stream is processed by a software suite developed by Zitterbart able to detect and examine the whale spouts.
“A whale spout is bright on the thermal image and then becomes darker again in a very specific pattern,” he said. “Our software divides each of the recorded images into 31,600 little snippets, which are individually examined for differences in brightness. Subsequently, the computer decides whether snippets exhibiting significant contrast change bear the characteristic features of a whale spout. This way we can also spot those animals that have emerged for only a very short breath of air.”
The IR camera system spins around its own axis five times per second and takes an IR photo of the whale every 0.2 s. This way the system can create very detailed photo sequences of a whale spout like this one and is able to automatically analyze the records for the typical color pattern of a whale spout. Courtesy of Daniel Zitterbart, AWI.
Direct comparisons during one of the expeditions showed that the thermal imaging camera recorded twice as many whales near the vessel than scientists did when trying to spot the animals with binoculars.
“The key strength of our system lies in the fact that we can locate large whales such as blue, fin, right and grey whales around the clock, especially at night, with great accuracy, allowing for a better protection,” said Dr. Olaf Boebel, head of AWI’s Ocean Acoustics Lab and co-author of the study. “Whenever an animal is detected by the system, appropriate safety measures are implemented.”
Following the successful test of the technology and its ability to operate in inclement weather, Zitterbart is already working on a system extension.
“We now have a second, normal camera coupled to the infrared camera system,” Zitterbart said. “It automatically shoots photos of each whale detected by the IR system. This way, we can determine its species to collect data on the size and distribution of their respective populations.”
This thermal imaging whale detection also provides location and distance data for each whale, allowing AWI scientists to track the animals and explore their behavior.
The work appeared in PLOS ONE
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