 Details on earliest known marine navigation tool revealed by scanning technology at WMG, University of Warwick 
 
 Late fifteenth-century astrolabe - used by mariners to measure the altitude of the sun – recovered from Portuguese explorer ship which sank in 1503 
 
 - used by mariners to measure the altitude of the sun – recovered from Portuguese explorer ship which sank in 1503 Pioneering scanning analysis and 3D imaging revealed invisible navigational markings, proving the identity of the object 
 
 Details of the earliest known marine navigation tool, discovered in a shipwreck, have been revealed thanks to state-of-the-art scanning technology at WMG, University of Warwick. When the team found the object, no markings were visible – they believed it was an astrolabe, but they could not see any navigational markings on it. Enter Mark Williams, a professor at Warwick who used "pioneering analysis and 3D imaging" to reveal hidden "etches around the edge of the object, each separated by five degrees." “Usually we are working on engineering-related challenges, so to be able to take our expertise and transfer that to something totally different and so historically significant was a really interesting opportunity.” 
 
 The astrolabe is a bronze disc, which measures 17.5cm in diameter, and is engraved with the Portuguese coat of arms and the personal emblem of Don Manuel I, the King of Portugal from 1495-1521. It is believed to date from between 1495 and 1500, and was recovered from the wreck of a Portuguese explorer ship which sank during a storm in the Indian Ocean in 1503. Media playback is unsupported on your device Media caption Divers uncover 500-year-old Vasco da Gama fleet treasure 
 
 David Mearns, from Blue Water Recovery, who led the excavation and is the author of The Shipwreck Hunter, told the BBC: "It's a great privilege to find something so rare, something so historically important, something that will be studied by the archaeological community and fills in a gap." "It was like nothing else we had seen and I immediately knew it was something very important because you could see it had these two emblems on it," he told the BBC.
– The world's earliest known navigational tool used by Vasco da Gama's fleet was discovered in a shipwreck off the Oman coast, NPR reports. Called a marine astrolabe, it's believed to date from 1495 to 1500. Unlike the Game of Thrones intro astrolabe, sailors used this one to figure out where they were on the high seas. It was found in the wreck of the Esmeralda, part of the Portuguese explorer's armada. Da Gama, who discovered the first sea route from Europe to India, was returning home from his second trip there when he left some ships in the Indian Ocean to "disrupt maritime trade," meaning pillage. Several of the ships sank during a fierce storm in 1503. The Esmeralda was discovered in 1998. Since excavations began in 2014, University of Warwick researchers have recovered 2,800 artifacts, the jewel of the cache being the astrolabe, a bronze disc measuring 7 inches in diameter. Emblems depict the Portuguese coat of arms and the personal stamp of King Dom Manuel I. "It was like nothing else we had seen, and I immediately knew it was something very important because you could see it had these two emblems on it," team leader David Mearns of Blue Water Recoveries tells the BBC. "It's a great privilege to find something so rare, something so historically important." At first, the team wasn't 100% sure it was an astrolabe, but laser scans revealed navigational marks around the edges every 5 degrees, which sailors would have used to calculate their location by measuring the sun's position above the horizon at noon. (A ship that sank in 1BC may hold priceless treasures.)