3D images displayed at museum enhance general public's understanding of Great Wall

Visitors watch a video about the Great Wall at an exhibition on the research and digital achievements on the Great Wall at the Tianjin Museum in north China's Tianjin municipality on Feb. 12, 2023. (Photo/Xinhua)

Over more than four years, Chinese researchers have used digital technology to obtain information of the Great Wall, capturing more than 2 million images that cover 90 percent of the artificial walls along the Great Wall.

An exhibition on the research and digital achievements on the Great Wall which opened in February 2023 at the Tianjin Museum in north China's Tianjin municipality revealed more secrets of the Great Wall.

The 3D models displayed at the museum can help the public better see the structures of the Great Wall.

"Do you see this small hole in the Great Wall? When people look at it, they may think it is a damaged area along the Great Wall, but actually it is not," said Li Zhe, a member of the research team at Tianjin University, who pointed at a picture of the Great Wall on display at the museum.

Li said that with the help of artificial intelligence (AI) and a database they built that contains 3D images of the Great Wall, researchers spotted many such "holes". Then they carried out field inspections and found out that the "holes" are actually the secret doors of the Great Wall.

The research team of Tianjin University has identified over 130 physical remains of secret doors in the Great Wall since the end of 2018, when a project of collecting 3D images of the Great Wall kicked off.

Li said the design of the secret doors shows the wisdom of ancient people, adding that the structure of each secret door is unique based on the local terrain.

"For instance, one secret door could guarantee smooth operations of horse trading activities in ancient times by keeping horses on one side of the door and businessmen on the other. This door could prevent horses from attacking humans," Li said.

Li said that the project enables the public to realize that the Great Wall is actually a system, and it stretches like rays. Previously, researchers didn't obtain enough information about the Great Wall or organize the information in a systematic manner over technological reasons, and with the help of the database and AI, they can make progress in this respect.

According to Li, previously, an average of eight representative pictures could be acquired by inspecting one kilometer of the Great Wall, and during this project, researchers can get about 300 pictures from various angles by covering the same distance.

Li's research team started to use ultra-low-altitude drones to boost their ability to acquire data of the Great Wall since 2004. The drones can carry surveying and mapping devices, including cameras and radars, to obtain detailed information such as the structures and hidden facilities in the Great Wall.

"It is crucial to build a digital archive of the Great Wall. As the research proceeds, I realize that the Great Wall is a valuable cultural heritage for Chinese people and even the whole mankind," said Li, adding that "We should use our professional knowledge to supplement explanations of the Great Wall from the perspective of architecture, and combine the knowledge with archeological achievements to know about the Great Wall more comprehensively."