Desde hace unos a\u00f1os, un grupo de investigadores estadounidenses y australianos desarrollaron una c\u00e1mara especial inspirada en los ojos del camar\u00f3n mantis que puede ver los patrones de polarizaci\u00f3n de las ondas de luz, que penetran en el mar. Eso significa que la c\u00e1mara de inspiraci\u00f3n biol\u00f3gica puede detectar c\u00f3mo los patrones de polarizaci\u00f3n de luz cambian una vez que la luz ingresa al agua y se desv\u00eda o se dispersa. Esos investigadores ahora se dan cuenta de que pueden usar esos patrones de polarizaci\u00f3n submarina para deducir la posici\u00f3n del sol y usar eso para determinar la ubicaci\u00f3n geogr\u00e1fica de la c\u00e1mara.\u00a0<\/p>\n
![\"Photograph](\"https:\/\/spectrum.ieee.org\/image\/MzA0MjIyMQ.jpeg\")
A diving trip to the Great Barrier Reef may have unlocked a new way to build a GPS-like\u00a0sensor that works underwater. The device is based on recent scientific understanding of how marine animals sense their geolocation\u00a0based on the signature polarization\u00a0patterns of light entering the water.<\/p>\n
A few years ago, U.S. and Australian researchers developed a special camera inspired by the\u00a0eyes of mantis shrimp<\/a>\u00a0that can see the polarization patterns of light waves, which resemble those in a rope being waved up and down. That means the bio-inspired camera can detect how light polarization patterns change once the light\u00a0enters the water and\u00a0gets\u00a0deflected or scattered.<\/p>\n Those researchers now realize that they can use those underwater polarization patterns to deduce the sun\u2019s position\u2014and use that to figure out the location of the camera itself.<\/p>\n Current limitations in the cameras and\u00a0software mean that the underwater GPS method is only accurate to\u00a0within about 60 kilometers (km). That seems like a huge error range, but it\u2019s still fairly remarkable considering the size of the Earth\u2019s oceans, which each cover tens of millions of square kilometers. The research is detailed in the 4 April 2018 issue of the journal\u00a0Science Advances<\/a><\/em>.<\/p>\n \u201cWe can improve this method by using better cameras and developing new machine learning algorithms to refine the position estimates,\u201d\u00a0said\u00a0Viktor Gruev<\/a>, an electrical and computer engineer at the University of Illinois at Urbana-Champaign.\u00a0\u201cI believe in a very short time, we will have accuracy of less than 1 km.\u201d<\/p>\n Traditional GPS technology based on radio signals from satellites cannot work under the sea, because radio signals do not travel well underwater. By comparison, Gruev and his colleagues demonstrated how the light polarization method for underwater geolocation can\u00a0work\u00a0at depths of as much as 50 meters below the surface.<\/p>\n Their results were especially unexpected because many marine biologists have generally believed that light traveling through water is polarized only from a horizontal viewing direction. That would make it extremely difficult to get useful geolocation\u00a0information from analyzing the\u00a0sunlight filtering down through the ocean depths.<\/p>\n But biologists also know that many marine animals, like many terrestrial animals or birds,\u00a0seem to have polarization-sensitive eyes that can be used to hunt or navigate underwater.<\/p>\n Gruev points out that earlier conclusions about polarization patterns were based in large part upon incomplete measurements and incomplete mathematical models of the underwater environment. The camera has shown that polarization patterns in\u00a0light from the sun can be detected and measured from many different angles.<\/p>\n![\"A](\"https:\/\/spectrum.ieee.org\/image\/MzA0MjI2MQ.jpeg\")
During a diving field trip to the Great Barrier Reef, Gruev and his colleagues noticed that the background polarization patterns seemed to be changing in the underwater environment depending on the time of day and viewing direction.<\/p>\n