When it comes to surveying historical sites, using classical archaeological methods can be slow and labour-intensive. As a result, an increasing number of archaeologists are turning to drone technology to more efficiently survey larger areas, and at better resolutions than satellite imagery can achieve. Iconem, an organisation that safeguards world heritage through digital technologies, did just that during a mission this summer.
In the Kurdish region of northern Iraq, history runs deep. And its ancient cities—such as Akre, which was formed in 1877—make it an archaeologist’s dream.
“Our mission was to scan Shanidar Cave, Deween Castle and a Zoroastrian settlement in Akre,” says Yves Ubelmann, founder and CEO of Iconem. “Satellite images are not sufficient for this work because they do not have a high enough resolution. Higher resolution photos taken with drones are much more accurate and are therefore much better suited to our detailed work.”
With help from Drone Adventures, a non-profit organisation that promotes the civilian use of drones, the team primarily used a senseFly eBee Plus drone to create the detailed 3D terrain models required to digitally reconstruct the sites.
“The eBee Plus was key to accurately capturing the mountainous terrain,” Ubelmann says. “It was able to follow the reliefs without us having to hike up the mountainside. It can also fly for an extended period of time, which allowed us to scan large areas in one flight. So, it saved us time and provided us with more detailed photos.”
[The drone] was able to follow the reliefs without us having to hike up the mountainside. It can also fly for an extended period of time, which allowed us to scan large areas in one flight…
Digital reconstruction by drone
The team used this fixed-wing aircraft for large-scale aerial mapping of the mission’s entire three sites. Then, small quadcopter drones were flown to capture oblique pictures of Akre. Finally, these datasets were completed with terrestrial pictures, taken with a camera on the ground. All these data were then merged using Pix4D photogrammetry software. The result: detailed digital replicas of the sites, spanning approximately 100 hectares, or one square kilometre, per site.
Deween Castle, which dates back to the 12th century, was especially interesting because it was built on top of a mountain, making it difficult to keep resolution consistent. The landscape and castle towers posed a challenge, but the team was able to achieve these different levels of detail in order to capture the castle in its current environment.
“The Zoroastrian site perched above the village is threatened by new urbanisation. It is crucial that we scan the site before it is lost.”
Many sites in the area are vulnerable to urban expansion, increasing the importance of documenting the site’s existing structure.
“Akre is transforming,” Ubelmann explained. “Many of its old buildings are being demolished and replaced with new concrete ones. The village is expanding and modernising. The Zoroastrian site perched above the village is threatened by this new urbanisation. It is crucial that we scan the site before it is lost.”
With classical archaeological methods, such as using a laser scanner, one reference point is typically documented every two square metres. However, Ubelmann says, “it is very difficult to capture a reference point every square meter. Aerial surveying is much faster and more precise. In only one hour we can scan a very large area. Plus, we can survey one reference point for every square centimetre, which is much more accurate than classical methods.”
Approximately 2-3 hours were dedicated to surveying each site, some of which were not accessible by foot due to their remote locations. In these cases, aerial surveying was therefore especially useful. An average of three eBee Plus flights were required per site: two high resolution flights to capture details, flown at a height of 45m, and another flown higher (130m above the site) to replicate the overall environment of the sites.
… the focus of the mission was to provide the resulting data to the international archaeological community for virtual exploration
“This mission showed how the eBee is crucial to rapidly scanning large areas,” Ubelmann adds. “It enables the user to work quickly and efficiently in difficult working conditions.”
Rather than physically digging for artefacts, the focus of the mission was to provide the resulting data to the international archaeological community for virtual exploration, part of a much larger project whereby Iconem is developing an online resource that will make 3D renderings available to archaeologists for research.
“Drone technology allowed us to quickly and thoroughly document these sites, laying the groundwork for continued documentation of cultural heritage. It is the first step in a project that will continue,” Ubelmann adds.