The result, North Korea Uncovered, is one of the most detailed maps of North Korea available to the public today. The small file, which can be installed on top of Google Earth, has been downloaded more than 47,000 times since an updated version was released last month. "We have portrayed things about which they are most proud and ashamed," Melvin said in an email interview.

Among the most notable findings is the site of mass graves created in the 1990s following a famine that the UN estimates killed about 2 million people. "Graves cover entire mountains," Melvin said. Also visible is the stark contrast between the living conditions of North Korea's elite and the general population.

The palaces housing dictator Kim Jong Il and his inner circle, clearly shown on the maps, contain Olympic-size swimming pools with giant waterslides and golf courses. Conversely, much of North Korea's population is reliant on foreign food aid, ironic given the authoritarian regime is built around the ideology of self-reliance.

Analysing the satellite maps allowed Melvin to plot the country's transport and electricity network, revealing that many towns have no power supply at all. Melvin and his team also believe they have discovered the Vinalon complex that has been connected with chemical warfare experiments. The project highlights the collaborative power of the internet, which allows disparate groups of amateur sleuths to work together to uncover state secrets and shine new light on previously hidden countries.

North Korea is of particular interest to diplomats, analysts and the public of late because the communist regime has ramped up its nuclear tests, launched a series of short-range missiles and threatened possible attacks on South Korea. Melvin said he notified two North Korean embassies of his project but received no response.

"This project is a terrific record of their 'revolution' so I would love to have more of their input for historical purposes," he said Melvin, who began the project as a way of mapping places in North Korea that he had visited, said he pored over books, maps, pictures and news reports to identify locations on the Google satellite map. But he received significant help from collaborators, some of whom have studied North Korea professionally. For instance, The Wall Street Journal reported that Joshua Stanton, a Washington attorney who has served in the US military in South Korea, identified one of the country's most notorious prisons, Camp 16, by combing the map for structures identified in sketches created by defectors.

A US senator then used Stanton's information to criticise North Korea's human rights record, saying "Google has made a witness of all of us ... we can no longer deny these things exist". North Korea's own publicity of the movements of Kim Jong Il have also been invaluable to Melvin. Media reports from the country allowed him to identify locations the dictator has visited, such as a hydroelectric dam and power station he toured in April.