Thanks to researchers at the University of Illinois, an underwater GPS method has been developed. The technique uses polarization information of underwater light, collected by a specialized camera. Polarization is a method to describe the orientation of wave oscillations.
The team found that collected wave polarization patterns were consistently fluctuating, which contrasted biologists’ current theories. Upon further investigation, they found the sun’s relative position at the time of the data collection was the cause. With this in mind, underwater polarization patterns were used to help estimate the sun’s elevation angle and heading, which could generate GPS coordinates based on the recording’s exact date and time.
“We tested our underwater GPS method by pairing our bio-inspired camera with an electronic compass and tilt sensor to measure the underwater polarization data at a variety of sites around the globe, depths, wind conditions, and times of day,” says Viktor Gruev, University of Illinois professor of electrical and computer engineering, and leader of the study. “We found that we can locate our position on the planet within an accuracy of 61 km.”
The camera, dubbed the Mantis Cam, focuses on light refraction as it passes through the water’s surface and bounces between particles and water molecules. Judging by its moniker, the camera design was inspired by the mantis shrimp, a marine crustacean known for its elaborate visual systems.
The team believes the technology will help underwater navigation for both robots and humans, using visual cues from polarized light.
“We could use our underwater GPS method to help locate missing aircraft, or even create a detailed map of the seafloor,” says Samuel Powell, graduate student and co-author of the research. “Robots swarms equipped with our sensors could provide a low-cost means of underwater remote sensing—it would certainly be more cost-effective than current methods.”
In addition, the GPS system can further the knowledge of marine migratory behavior.
The full details are published in the article, “Bio-inspired polarization vision enables underwater geolocalization,” in the journal Science Advances.