LONDON (REUTERS) - For experts in the field of ocean mapping, it is no small irony that we know more about the surfaces of the Moon and Mars than we do about our planet's sea floor.

"Can you imagine operating on land without a map, or doing anything without a map?" asked Dr Larry Mayer, director of the United States-based Centre for Coastal and Ocean Mapping, a research body that trains hydrographers and develops tools for mapping.

"We depend on having that knowledge of what's around us - and the same is true for the ocean," he told the Thomson Reuters Foundation.

With their deep craters and mountain ranges, the contours of the Earth beneath the waves are both vast and largely unknown.

But a huge mapping effort is under way to change that.

The United Nations-backed project, called Seabed 2030, is urging countries and companies to pool data to create a map of the entire ocean floor by 2030. The map will be freely available to all.

"We obviously need a lot of cooperation from different parties - individuals as well as private companies," said Ms Mao Hasebe, project coordinator at the Nippon Foundation, a Japanese philanthropic organisation supporting the initiative.

"We think it's ambitious, but we don't think it's impossible," he added.

The project, which launched in 2017, is expected to cost about US$3 billion (S$4.1 billion). It is a collaboration between the Nippon Foundation and Gebco, a non-profit association of experts, which is already involved in charting the ocean floor.

The end result would be greater knowledge of the oceans' biodiversity, improved understanding of the climate, advanced warning of impending disasters and the ability to better protect or exploit deep-sea resources, said Ms Hasebe.

A CENTURY OF ADVANCES

So far, the biggest data contributors to Seabed 2030 have been companies - in particular Dutch energy prospector Fugro and deep-sea mapping firm Ocean Infinity. Both were involved in the search for Malaysia Airlines jet MH370, which disappeared in 2014.

But mapping the oceans goes back much further, said Dr Mayer - to 1903, when Prince Albert I of Monaco was the first to do it comprehensively.

The rudimentary method involved tossing overboard a "hunk of lead at the end of a rope" to plumb the depths.

Technology evolved after World War II to using echo sound reflections, but that produced only a "blurry picture", said Dr Mayer.

Today, high-tech multibeam echo sounders transmit a fan of acoustic beams from a ship, which ping back depending on the depth and topography of the ocean floor. That creates data points, which can be converted into a map.

"With advanced sonar technology, it really is like seeing. I think we've come out of the era of being the blind man with the stick," said Dr Robert Larter, a marine geophysicist at the British Antarctic Survey.

"We can survey much more efficiently - and, not only that, but also in much greater detail," he said, adding that the work was painstaking.

"The ocean's a big place!" he said.

The advent of new technology such as underwater drones and robots is also speeding up the mapping process.

A global competition hosted by energy giant Shell - the Shell Ocean Discovery XPrize - is also under way, offering US$7 million to teams that can develop technologies to conduct ocean exploration autonomously, rapidly and to a high resolution.

A team from Seabed 2030 has reached the final stages of the competition, with an idea based on remotely operated robots working in extreme depths to map territory independently.

CHANGING TIDE

Exploring Earth's final frontier will do more than satisfy scientific curiosity - it should bring economic benefits too.

More than 90 per cent of the world's trade is carried by sea, according to the International Maritime Organisation, a UN body, making safe navigation a key motivator for mapping.

"If a ship runs aground, it's a terrible day for the economy, it's a terrible day for the environment and it's a bad day for the captain too," said Dr Mayer.

Seabed 2030's map would have other benefits, experts said - in a warming world, it would provide a better idea of sea levels as ice melts and, importantly, warn about impending tsunamis that could devastate coastal communities.

They said it would also help the so-called "blue economy", as countries and companies seek to protect or exploit deep-sea resources - from exploring for oil and gas to installing wind farms or laying fibre-optic cables for the Internet.

That is predicted to become more important in the coming years, according to the Organisation for Economic Cooperation and Development. It expects the ocean economy to contribute US$3 trillion to the world economy by 2030, up from US$1.5 trillion in 2010.

POLITICAL RIFTS

Some parts of the oceans - the east coast of the US, and areas around Japan, New Zealand and Ireland - are relatively well mapped, experts said. Others, including the West African coast or that off the Caribbean, remain largely blank.

The introduction of the 1982 UN Convention on the Law of the Sea, an international treaty, allowed countries to determine their continental shelves and exclusive economic zones - legitimate territorial claims off their coasts.

It also spurred a rush to map and claim land, said Dr Larter.

"That's the biggest land grab in recent history," he said.

For Mr Julian Barbiere of Unesco's Intergovernmental Oceanographic Commission, it would be a "paradox" if, after collaboration at a scientific and technical level to share data, countries used that knowledge against one another in geopolitical spats.

"There are already tensions in some parts of the world, and one of the reasons is access to resources," he said.

Some countries, he added, are reluctant to give up strategic proprietary data to the Seabed 2030 project, largely due to national security concerns or in areas with sensitive geopolitical tensions, such as the South China Sea.

"There is already a lot of data which is sitting there, not being released. We hope to change attitudes and really get countries to contribute," Mr Barbiere said.

The next phase of the project, he said, is to encourage data donors and crowdsourcing - not just from exploration vessels, but also from cargo ships, recreational sea-users and fishing boats.

"(It) goes back to this principle: The ocean is an international space by definition... part of the common heritage of mankind," he said.

Looking ahead, in a bid to meet the UN Sustainable Development Goal 14 - to conserve and sustainably use the oceans - mapping will take centre stage during negotiations due to be completed by 2020, as nations create a new, legally binding treaty to protect the high seas.

"There are so many benefits to knowing more about the ocean floor," Ms Hasebe said.

"Humanity as a whole would be able to benefit."

Correction: The article has been edited to correct the title for Ms Mao Hasebe. We are sorry for the error.