Geologists from the University of Sydney have discovered that a 26km-wide island that can be seen on charts and maps does not in fact exist Reuters

For more than a decade it has featured on the world's maps. Viewed from Google Earth, Sandy Island appears as a dark, tantalising sliver, set amid the shimmering vastness of the Pacific Ocean.

But when marine scientists arrived at the island in the Coral Sea off Australia they were in for something of a shock: it didn't exist. Where there was supposed to be a sandy outcrop complete with palm trees, a few coconuts and maybe a turtle there was merely blue undulating water.

The Australian scientists, led by Maria Seaton, a geologist at Sydney University, had embarked on a voyage to study plate tectonics. They spotted that the enigmatic island lay along their route.

But there were several puzzling discrepancies: though the island appeared on the Google Earth map, there were no images of it.

It had also featured for the past 12 years on the usually reliable world coastline database. But there was no sign of it on their sea chart.

Dr Steven Micklethwaite, a crew member from the University of Western Australia, recalled: "We went upstairs to the bridge and found that the navigation charts the ship uses didn't have it.

"And so at that point we thought: Well, who do we trust? Do we trust Google Earth or do we trust the navigation charts? "

The scientist added: "This was one of those intriguing questions. It wasn't far outside of our path. We decided to actually sail through the island ... Lo and behold there was nothing! The ocean floor didn't ever get shallower than 1300 metres below the wave-base. There's an island in the middle of nowhere that doesn't actually exist."

Micklethwaite told the Sydney Morning Herald that the ship's captain was nervous about running aground and proceeded cautiously as they made their "un-discovery". "We all had a good giggle at Google as we sailed through the island. It was one of those happy circumstances in science. You come across something somebody has never noticed before."

The scientists would now send the correct data to the authorities to get the world map fixed, he said.

The non-discovery took place during a 25-day expedition by Australia's Marine National Facility, on board its RV Southern Surveyor research vessel. Had the island existed it would have belonged to France, since its location near the archipelago of New Caledonia is in French territorial waters. (If real and emphatically Gallic, it would presumably have been called Île de Sable, rather than the less than inspiring Sandy Island.)

Speaking on Thursday, Danny Dorling, president of the British Society of Cartographers, said it was not surprising that the error had crept in. "You can't create a perfect map. You never will," he said. "Our current world map is a collection of highly accurate satellite maps and some of the oldest data collected from Admiralty charts."

The mistake would have been surprising if the location had been a busy shipping lane or populated area, Dorling said. "The Coral Sea is in the middle of nowhere."

Humans have been making maps for thousands of years. They probably predate writing. (The earliest – a cave painting 30,000 years old – shows some early humans in a rectangle.) According to Dorling, maps serve two purposes: one practical, to help us navigate and find our way around; the other existential, to give us a sense of perspective, and to define our place on a large and ever-changing planet. "It gives you a sense of identity," he said.

Dorling also said that in the case of Sandy Island it was probably human error that had led to its creation. Charts were, after all, originally compiled by sailors using a watch and measuring longitude, with ancient sailors travelling by the stars. Far from being fixed, the world map is mutable too: with new islands and archipelagoes appearing following volcanic eruptions, and others disappearing in the same way.

The cartographer said it was just possible that Sandy Island – now a non-island, according to its Wikipedia entry – would have the last laugh.

"It's unlikely someone made this island up. It's more likely that they found one and put it in the wrong location. I wouldn't be surprised if the island does actually exist, somewhere nearby."

Isles of wonder

Atlantis

The legendary island has been the subject of discussion and parody since ancient times. According to Plato, Atlantis sank into the ocean "in a single day and night of misfortune". This was 10,000 years ago. No-one has been able to find it since. Numerous locations have been suggested: the Mediterranean, the middle of the Atlantic, Turkey, Crete, Bolivia, Peru, Mexico and southwestern Andalusia. Despite its enduring appeal, scholars can't agree if Atlantis really ever was a naval power, or a historical fiction dating back to earliest times.

Laputa

Invented by Jonathan Swift, Laputa is a flying island or rock that features in Gulliver's Travels. Its residents use magnetic levitation to manoeuvre the island in different directions. Laputan society is divided between the educated - who practice maths and astronomy - and servants. A tyrant is in charge; he crushes his enemies by landing on them.

San Serriffe

Less famous, perhaps, than Atlantis but no less worthy, San Serriffe is a fictional island nation created by journalists at the Guardian. The nation was invented as an April Fool's Day spoof in 1977; a description of it ran over 10 pages and appeared to fool some people. San Serriffe was located in the Southern Ocean (not far from Sandy Island, relatively speaking) Its inhabitants were called the Flong; for many years the autocratic General Pica was its ruler; happily, it later became democratic.