And the best part is they could do it all from the comfort of their armchairs, without shouldering the costs of travelling to Afghanistan and the threats posed by gangs of Taliban militants. Before Thomas's project there was only one known site in the Registan desert region of Afghanistan and the last time a researcher visited the area was in the 1970s. Using Google Earth, Thomas's team have managed to catalogue 450 sites in the area, dating back centuries if not millennia.

"Even in the 70s when it was possible to go to Afghanistan it was quite a tribal area, quite an inhospitable area ... and to be quite frank there are easier areas to work than in the middle of the desert," Thomas said. In Google Earth's satellite images of the Registan, which lies on the border between the Helmand and Kandahar provinces, Thomas and his team found deserted villages, camp sites, small fortresses, cemeteries, reservoirs and underground water channels. This month, Thomas presented a poster containing detailed new plans of the citadel of Bust to the World Archaeological Congress in Dublin, Ireland. Bust was the tenth to twelfth century Ghaznavid dynasty's winter capital and stretches over seven kilometres along the Helmand river.

French archaeologists worked on the site in the 40s and 50s but the sheer scale of the remains meant large areas went unsurveyed, Thomas said. "Only 130 of the 1286 known archaeological sites [in Afghanistan] have plans," Thomas said.

"A lot of the sites are in very remote areas. They haven't been excavated properly or even visited in detail, so what we've done is we found that about 250 of those sites fall within high resolution areas in Google Earth, and we've been focusing on the medieval sites and drawing plans based on the Google Earth images." Thomas said although archaeologists had leapt on Google Earth for use in their lectures and visual presentations, they had been lazy about using the potential data it contains for research. While many archaeologists buy highly detailed satellite images of areas they are studying for hundreds of dollars, Google Earth is free and has built-in measurements, making it far easier to sketch plans.

"The most important aspect of the work is that we'll be able to go to the Afghan archaeological institute and say these are the sites in this area, if you've got guys down there you can either go and visit them or you can at least start thinking about trying to protect them," Thomas said.