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Uncovering the Past: How LiDAR Technology is Revolutionizing Archaeology

Introduction

Mapping and history have been entwined since the first came to be. Maps have allowed humans to expand and record their exploration. Pushing the boundaries of territories and countries and recording the expansion of humans in history. Now, mapping and history converge again in modern times with the use of modern LiDAR mapping to uncover new archeological discoveries.

LiDAR Explained

LiDAR stands for light detection and ranging. It works similarly to echolocation in animals but with light waves rather than sound waves. A transmitter, usually strapped to the base of a helicopter or aircraft, emits pulses of lightwaves and then records the time it takes for those lightwaves to return to the transmitter.

This information is then used to generate a three-dimensional rendering of the survey site. These lightwaves are able to penetrate vegetation and record a clear image of the ground beneath.

(a) Point cloud in X-ray visualization; (b) point cloud in elevation visualization; (c) Mesh model. Source: https://www.researchgate.net/figure/a-Point-cloud-in-X-ray-visualization-b-point-cloud-in-elevation-visualiz ation-c_fig7_367344616

The data from the transmitter is recorded as a point cloud with millions of three-dimensional coordinates. Unwanted, noisy points that may disrupt the model are then filtered out. Specialized algorithms convert the coordinates into a continuous surface or mesh, by connecting all the points. After constructing the initial mesh, touch-ups are done to add colour and texture. The result is a 3D mesh that accurately represents the scanned environment or object.

Applications in Archeology

This technology has been profound in the field of archeology. Areas in remote, densely forested or otherwise inaccessible areas are now able to be mapped in a matter of days. This has expanded the number and locations of archeological sites.

An aircraft can be flown over a forest area that would normally have taken days to reach, and use the lightwaves to penetrate the vegetative cover and record the ground underneath. This can reveal features like buildings, streets, and remnants of civilization.

Finding a Lost Mayan City

LiDAR was responsible for helping to find a lost Mayan city in the Mexican jungle. A PhD student stumbled upon a  LiDAR scan done for environmental monitoring while doing research. He used archeological processing methods on the data and an ancient city the size of Edinburgh, Scotland was revealed.

The city was named Valeriana, after a nearby lagoon. The mesh model showed pyramids, sports fields, causeways, districts and amphitheatres. LiDAR made the discovery of such a large site possible. What would have once taken years of hiking, mapping and vegetation removal is able to be done in an afternoon.

A map of where the city was discovered compared to a 3D mesh map removing the vegetation to reveal the ruins underneath. Source: https://www.bbc.com/news/articles/crmznzkly3go

This does come with its own challenges, in differentiating man-made shapes from natural shapes. To do this, shape, pattern and spatial organization must be analyzed, often done using trained AI.

Man-made structures often have straight lines, sharp edges, regular shapes (such as rectangles, circles, or paths), and structured alignments. Natural shapes, on the other hand, have irregular, organic shapes and smoother transitions, as well as randomness in placement (such as clustered rock formations or tree canopies).

LiDAR can reveal subtle changes in elevation, such as terracing, ditches, or level areas that may indicate human activity. Natural landforms tend to have gradual slopes and irregular contours. These methods, along with knowledge of local geology, help determine what exactly archeologists are looking at when viewing mesh models.

Conclusion

Using light waves emitted from a transmitter flown over a site, archeologists are able to strip away vegetation to ground level and make a three-dimensional rendering of a site. This has broadened the field of archeology and allowed archeologists to explore sites that would otherwise not be accessible or be extremely lengthy to explore. LiDAR opens
up the doors to historical discovery, allowing us to add new pages to our history books and expand our knowledge as a society.

References

https://education.nationalgeographic.org/resource/lidar-and-archaeology/
https://www.bbc.com/news/articles/crmznzkly3go
https://www.theguardian.com/us-news/2023/feb/23/lidar-technology-archeology-radical-thinking
https://www.researchgate.net/figure/a-Point-cloud-in-X-ray-visualization-b-point-cloud-in-elevation-visualization-c_fig7_367344616

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