Archaeologists are increasingly able to make discoveries without getting their hands dirty, by scouring satellite images. Some techniques, like the one developed by Ur and Menze, are highly sophisticated. We have also seen in our previous post how a laser technology called Lidar was used to discover the ancient city of Mahendraparvata which is older than Angkor vat. But Google Earth is enabling archaeology to be carried out using a desktop computer.
In 2011, it was announced that almost 2000 potential archaeological sites had been found in Saudi Arabia using the virtual world map. “Every six months I read about someone else who has used Google Earth to find an archaeological site,” says Ur. “It’s a good thing, because as cities are growing and agriculture is intensified, it has a destructive effect on global cultural heritage. Methods like this have the ability to quickly document what’s there.”
Swapping trowels and maps for satellites and algorithms is enabling archaeologists to search thousands of square kilometres of land for lost towns and villages overnight. The technique relies on the fact that the mud bricks used to build homes in many locations leave their mark on the landscape in the form of ‘anthrosols’, which have a lighter appearance than natural soil. Several images of the same patch of land taken by the ASTER satellite, each focused on a different part of the electromagnetic spectrum, are used to pick out different characteristics of the anthrosols.
When data from these different wavelengths is combined using an algorithm, it provides an accurate prediction of whether an archaeological site lies beneath. In early tests using the method on a 23,000 square kilometre (14,300 square miles) area in northern Syria, 14,000 settlements were discovered. Buried in sand and soil over time, the villages date from the late Neolithic right up to the recent past. “In the past, we archaeologists worked on the ground and either studied small areas intensively or large areas with low intensity. We looked out the window of a Jeep to spot sites, and would only find the biggest settlements,” says Dr Jason Ur, the Harvard archaeologist behind the technique. “This new method combines the intensity of the small search with the wide coverage of a broad one.”
In this way, the outlines of towns and villages can be traced out. “The algorithm runs on powerful computers overnight,” says Ur, who developed the technique with MIT computer scientist Bjoern Menze. When the outlines of settlements are combined with an elevation map, an estimate of each village’s volume is generated. This gives an indication of its longevity, as villages would expand outward and upward as they grew. “I’m now planning a research project for Iraq’s Kurdistan region,” Ur says, “but the algorithm should work well in similar environments elsewhere, such as the Niger Valley and coastal South America.”