3D Laser Scanner Makes Haunting Works of Art

3d art, lidar — A 3D imaging technology called lidar is responsible for creating haunting images of people in the city Harar, Ethiopia. Lidar sends out pulses of laser light, which bounce off of surfaces and return to the device. The scans move slowly, so while lidar is ideal for imaging structures, images of moving objects and people are often blurred.

(Image credit: Charles Matz and Jonathan Michael Dillon)

Two historians on a mission to preserve historic structures in Ethiopia inadvertently turned a cutting-edge 3D scanning device into a tool for creating works of art.

Lidar technology uses pulses of laser light to map the contours of 3D surfaces and structures.

For example, 2D photographs can capture the major features of a landscape, but lidar reveals every dip, ditch and rise. It shows the full size of boulders, the depth of canyons. Some lidar technologies can see through foliage, and have been used to hunt for lost cities buried in the jungle. Similarly, 2D photographs of sculptures and frescoes lose an entire dimension of the art work — it would be like photographing a Van Gogh painting in black and white. [See More Amazing 3D Lidar Works of Art]

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The city of Harar, Ethiopia, is listed as a UNESCO world heritage site and is considered the fourth holiest city of the Muslim religion, after Mecca, Medina and Jerusalem. The city contains many historic structures, such as the five gates of Harar that once served as entrances to the city's different neighborhoods. But the gates were built out of mud brick in the 1500s, and today are crumbling, along with many other pieces of the city's historic architecture.

The lidar technology used by Matz and Dillon is based on a simple idea: a device about the size of a microwave sends out individual pulses of laser light. A pulse hits a surface, bounces off it and returns to the box. The detector in the box measures the time it took the pulse of light to return, or it's time of flight. The time of flight of each pulse is what the software then uses to determine how far away an object is, which helps build a 3D map of the structure. [Images: One-of-a-Kind Places on Earth]

"Harar is off the beaten track and in a remote part of eastern Ethiopia," Matz wrote in an email. "It is a market crossroads in an agricultural region. It is ancient still in its mannerism and exchanges." The areas of Harar visited by Matz and Dillon often hosted markets where people were selling food and goods out of stalls, or off blankets on the ground. Each morning, a group of governorate personnel would arrive and clear people out of the area that Matz and Dillon were surveying.

In the images that the team captured, the people are blurry and often look as though they were sketched with vertical pencil lines — the shapes of their bodies are apparent, but their features are lost. Each lidar scan takes about 9 seconds, and two to three scans are needed to get a 3D map. If a person moves before the lidar device is done collecting the light, the laser pulses will bounce off their faces or bodies multiple times, so that multiple reflections are captured by the device and added to the image. It gives the impression of movement and impermanence, set against the buildings, which look steady and unmoving.

Harar is a colorful city: the buildings are painted in bright blues, while the women wear vibrantly colored fabric in yellows, reds and purples. But in the lidar images, these bright colors stand out against smooth, unnaturally black backgrounds. This is where the laser pulses have traveled out into space and never encounter a surface to bounce off of, so the machine receives no data about those areas. In the final images, it looks as though the city sits on the edge of an abyss. [In Photos: World Heritage Sites Dazzle with Culture & Beauty]

"[Lidar] technology hasn't quite developed where it can accumulate this information quickly because the data sets are very dense. We're talking gigabytes and gigabytes of information," Matz said. Big budgets can buy faster computer processors, but for many users, the high data output is prohibitive. Matz draws a parallel between lidar's current state and the state of early optical photography, when the technology also required very long exposure times. As lidar technology becomes faster, Matz thinks it will become more commonly used for artistic and aesthetic applications.