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Old Cities, New Discoveries: How LiDAR is changing Archeological Surveys

LiDAR (Light Detection and Ranging) is not a new technology; it has been around since the early 1960’s when a LiDAR-like system was introduced by the Hughes Aircraft Company. Like many technologies, LiDAR’s start was in aerospace with its first major applications being in the Apollo program. The astronauts on Apollo 15 used a laser altimeter to map the surface of the moon. Of course, LiDAR and laser technology have come a long way in the last 50 years.

We are seeing more applications using variations of the technology with each passing year. LiDAR has received attention in popular culture lately, with Elon Musk discussing its effectiveness for autonomous vehicle navigation, as well as Apple including a LiDAR Scanner on the latest iPad Pro model. Another relatively new and exciting use for LiDAR is in the surveying of large swathes of dense jungle in the search for ancient cities and settlements.

Ancient civilizations have always grabbed our collective curiosity, with explorers searching for lost cities for centuries. Archaeologists have been excavating these ruins and cities, from China to Egypt to Mexico and beyond. This is an arduous task, moving archaeological equipment and samples to and from far off places, especially when this unforgiving terrain includes some of the densest jungles on Earth.

Technologies have come along that have helped to alleviate some of the challenges faced, including improvements to transportation and artefact preservation – making the movement of findings out of the remote and humid sites much easier. For the most part, these famous sites are well discovered, and to make new findings teams must hike through thick, insect-infested, disease-bearing jungles. With modern clothing, immunizations, and repellents, exploration has become less deadly than years passed. However, it is still a tall task, which makes the latest advancements using LiDAR all the more exciting and important for improving this field of discovery.

Advantages of LiDAR and application to archeology

The main advantage LiDAR provides is that vast areas of the jungle can be surveyed in a short amount of time. The wavelengths of light transmitted by LiDAR range from ultraviolet, through the visible spectrum to the near-infrared, allowing the beams to penetrate through dense forest canopies and reflect the surface underneath. LiDAR has always been an effective tool for creating digital elevation models of the Earth’s surface.

However, with increased resolution, LiDAR can now be used to search for ancient cities and even outline overgrown structures through thick vegetation. LiDAR surveying of an area collects data that, with geospatial software, can be interpreted to provide new insight into the scale and sprawl of ancient settlements.

In 2010, after discovering that other airborne survey methods such as multispectral data or airborne radar weren’t yielding the results they had hoped for, anthropologist’s Dr Arlen Chase and Dr Diane Chase decided to try a LiDAR survey of the area surrounding the ancient Mayan site of Caracol, Belize. The LiDAR survey showed that the settlement sprawled across a much wider area than previously thought.

The Chase’s then came up with a revised proposal for the population of the large Mayan city, now estimated to have had a population of 115,000 at its peak. Their survey led to a new approach to archaeology in places where traditional have limited effectiveness. Since then, LiDAR has provided important insight and discoveries in various other archaeology projects around the world.

LiDAR Surveying in Cambodia

In 2015, LiDAR surveys in the areas surrounding the Angkor Wat temple in Cambodia revealed “multiple cities between 900 and 1,400 years old beneath the tropical forest floor, some of which rival the size of Cambodia’s capital, Phnom Penh.” This study, led by Australian Dr Damian Evans, covered an incredible 1,901 square kilometres making it the largest airborne survey ever undertaken in an archaeological project at the time.

These previously unknown settlements led researchers to conclude that the civilization had a much denser and larger population, even suggesting that these “cities would have constituted the largest empire on earth at the time of its peak in the 12th century.” The survey discovered large infrastructure systems extending great distances from what was previously thought to be the main settlement of Angkor. As Michael Coe, an expert from Yale University says, “I think that these airborne [LiDAR] discoveries mark the greatest advance in the past 50 or even 100 years of our knowledge of Angkorian civilisation”.

An aerial image highlighting the areas involved in the airborne survey around Ankor Wat.
After a 2012 LiDAR survey produced discoveries around the Angkor Wat temple, Dr Damian Evans returned in 2015 for a larger survey of the area surrounding the main settlement. Sourced from: The Guardian

LiDAR Surveying in Guatemala

A project spearheaded by the PACUNAM Foundation has surveyed more than 2,100 square kilometres of dense jungle in the Maya Biosphere Reserve using LiDAR. Their findings revealed 60,000 previously unknown Mayan structures throughout the area. Not only does this provide new sites for archaeological endeavours, but it also changes the way researchers are thinking about the Mayan civilization.

Settlements are becoming larger and they are discovering vastly more sophisticated infrastructure between areas, suggesting that “this entire region was a settlement system whose scale and population density has been grossly underestimated”. Thanks to LiDAR surveying, experts are now suggesting the population of the region at its peak could have been 10-15 million people, a dramatic increase from previous estimates of 5 million. The next phase of this 3-year PACUNAM LiDAR Initiative includes the eventual survey of an incredible 14,000 square kilometres of the Guatemalan lowlands.

The LiDAR survey revealed more than 60,000 previously unknown Maya structures that were part of a vast network of cities, fortifications, farms and highways. Source: Wild Blue Media/ National Geographic

Looking to the future

With the successful results of these surveys, it seems as though an important new tool has been added to archaeologist’s repertoire. As PACUNAM intends to continue their large survey of the Guatemalan rainforest, it will be interesting to see what other important discoveries are aided by LiDAR and remote sensing technologies. The incredible scale and precision provided by LiDAR in these densely forested remote regions of the globe are proving invaluable and revolutionary for researchers. It is an exciting time of discovery aided by modern applications of LiDAR, who knows what will be revealed next.

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