An image of the ancient city produced by Lidar. An image of the ancient city produced by Lidar.

High-tech mapping reveals massive city

Lidar scanning shows ancient city in Michoacán as big as Manhattan

A high-tech laser mapping technique has revealed the full extent of a lost ancient city which had as many buildings as Manhattan.

The site called Angamuco is located half an hour’s drive from Morelia on the eastern edge of the Lake Pátzcuaro basin in the state of Michoacán and was built by the Purépecha people, who were rivals to the Aztecs.

The 26-square-kilometer site was first found in 2007 and archaeologists subsequently used a traditional “boots on the ground” approach to survey it, discovering about 1,500 architectural features over every square kilometer they covered.

But the team soon realized that mapping the whole area that way would take more than 10 years because of the site’s rugged terrain.

Instead, since 2011 a technique known as light detection and ranging scanning (Lidar) has been used to survey the area.

The system uses a rapid succession of laser pulses directed at the ground from an aircraft. Combined with GPS and other data, the time and wavelength of the pulses reflected by the earth’s surface create a precise three-dimensional map of the landscape, even if it is covered with dense vegetation.

Using the Lidar technique, researchers were able to establish that there are 40,000 building foundations built on ground that was covered by lava flow thousands of years ago.

An archaeologist at Colorado State University who led the project and presented the findings at a science conference in Austin, Texas, this week told the newspaper The Guardian that prior to the initial discovery the existence of the site was completely unknown.

“To think that this massive city existed in the heartland of Mexico for all this time and nobody knew it was there is kind of amazing,” Chris Fisher said.

The archeologist said that more than 100,000 people are believed to have lived in the city when it was at its peak between about 1000 AD and 1350 AD.

“[Its size] would make it the biggest city that we know of right now in western Mexico during this period,” Fisher said.

The site is about twice the size of the Tzintzuntzan, the Purépecha capital and main ceremonial center, which is also located on the edge of Lake Pátzcuaro.

The team that completed the scanning work also discovered that Angamuco has an unusual layout.

The site’s large structures, including temples and pyramids, as well as its open plazas are located in eight separate zones near the perimeter of the site rather than concentrated together in the center of the ancient city.

Road systems, garden areas where food was grown and ball courts have also been detected.

Lidar technology has previously been used to detect and map other archaeological sites in the Americas in countries including Guatemala, Honduras and Belize.

However, some indigenous groups and academics have said that claims that the use of Lidar technology has led to the discovery of a “lost city” is factually incorrect and smacks of colonial rhetoric.

A professor of Mesoamerican archaeology at University College London said the work the team has completed at Angamuco is impressive but added that Lidar cannot completely replace traditional archaeological methods.

“Ultimately we still have to get on the ground and then excavate,” Elizabeth Graham said.

So far, a team on the ground at Angamuco has verified over 7,000 architectural features that were detected by Lidar.

Source: The Guardian (en), El País (sp)

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