Google experts divulge ocean mapping secrets

There has been widespread interest in how Google collects its ocean data

Google has released further details on the accuracy of Google Earth 5.0, which now traces the ocean floor and includes surface data from marine experts.

The release follows speculation that Google Earth had helped in the discovery of a grid of 'streets' in the ocean thought to be the lost city of Atlantis.

Google has denied the Atlantis reports, but widespread interest in how Google collects its ocean data has prompted the company to call in two of its experts to explain more.

Walter Smith, from the National Oceanic and Atmospheric Administration, and David Sandwell, from the Scripps Institution of Oceanography at UC San Diego, explained in a blog post that the lines were "ship tracks" stemming from a process known as echo sounding, which maps strips of sea floor under ships by measuring the time it takes for sound to travel from the ship to the sea floor and back.

Google also gains a picture of the ocean by measuring the water surface using satellite-based radar. For example, the ocean is higher when there are large underwater mountains, the scientists said.

However, Smith and Sandwell admitted that large discrepancies in the ocean data still remain, and said that Google's map of Mars is about 250 times more accurate than the map of the ocean.

To gain a perfect picture, the whole ocean would have to be mapped with ships, which would cost around $2bn (£1.4bn), according to a US Navy study.

"That may seem like a lot of money, but it's not that far off from the price tag of, say, a new sports stadium," Smith and Sandwell concluded.