An archaeology project that involved regular people doubled the number of known prehistoric barrows in the region in just four months. Over 6,500 volunteers have analyzed data acquired by the experts, supporting the accurate identification of approximately 1000 prehistoric burial mounds in the Netherlands.
Volunteers in archaeology
Archaeology has long been associated with the image of experts painstakingly digging at remote sites, meticulously uncovering fragments of human history. However, in recent years, the landscape of archaeology has been transformed by the inclusion of non-professionals—citizen scientists.
Citizen scientists have become increasingly important in various fields, contributing to areas where researchers need additional manpower. In ecology, they help track species populations and environmental changes, while in astronomy, they identify distant celestial objects and phenomena through large datasets. In medicine, citizen scientists participate in data collection for health studies, contribute valuable insight into public health trends.
For archaeology, this contribution is particularly relevant when it comes to the use of Lidar (Light Detection and Ranging) technology. Lidar is a remote sensing method that can detect subtle changes in landscape topography. It often reveals hidden archaeological features like burial mounds, ancient field systems, and more. Lidar data, while incredibly powerful, is challenging to interpret. Oftentimes, you have to manually look over kilometers and kilometers of data.
This is where Heritage Quest’s innovative approach comes into play: harnessing the interpretive potential of thousands of volunteers to classify archaeological features in Lidar images.
Heritage Quest
A burial mound, also known as a barrow, is an ancient structure that consists of an artificial hill of earth or stones built over a grave or a group of graves. These mounds were typically constructed to mark the burial sites of important individuals or communities, often during the prehistoric period. Barrows can vary in size and design, with some being simple, low mounds, while others are larger and more complex, sometimes containing multiple burials or burial chambers.
In 2018, the Heritage Quest project was launched to harness the power of citizen scientists to detect barrows on Lidar imagery of the central Netherlands. With minimal training, volunteers were tasked with identifying features such as mounds and Celtic fields across thousands of small image tiles.
Every tile was analyzed by at least 15 volunteers to reduce errors. Over 2000 volunteers participated in the initial mapping of the Veluwe, classifying nearly 400,000 tiles. Then, the subsequent Utrechtse Heuvelrug phase saw even greater participation with 4,572 volunteers analyzing over 300,000 tiles.
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“While the volume of data exceeded our expectations, we faced a key challenge common to large citizen science projects: how reliable are the detections made by volunteers?” states lead author of the research, Quentin Bourgeois from Leiden University.
How good are citizen scientists?
Obviously, there’s always a concern about citizen science because the data is generated by non-experts. In this case, the Lidar images in Heritage Quest were prone to “noise” — inaccuracies due to misinterpretation of natural features as archaeological objects.
To test the reliability of the citizen scientists’ work, the Heritage Quest team conducted ground-truthing: they physically went to the areas identified as promising by volunteers. Field teams visited 380 consensus locations, where they used coring tools to take samples from potential barrow sites. This process revealed that about 59% of the locations identified by the volunteers were indeed ancient burial mounds.
The results, says Bourgeois, are exciting.
“Citizen science works! We found a direct correlation between the number of volunteers identifying a potential archaeological object and its likelihood of being a prehistoric burial mound.”
“What would have taken professional archaeologists years to accomplish was achieved in a matter of months thanks to the combination of lidar technology and citizen participation”, the researcher adds.
Interestingly, the accuracy of the classifications increased dramatically with higher levels of volunteer consensus. When seven or more volunteers agreed on the presence of a barrow, the probability of it being correct rose to 75%. With an inter-user agreement of 12 or more, the accuracy skyrocketed to 85%. These results demonstrate that even though the volunteers were not trained archaeologists, their collective insight was highly reliable, especially when their observations converged.
Why this is so important
For starters, the project is important in itself — it uncovered a lot of prehistoric activity that wasn’t known previously. It will likely give archaeologists work to do for years and years. With a new map of potential barrow sites, local governments and heritage organizations will also have the information they need to protect these ancient monuments. The discovery of previously unrecorded barrows allows for better planning to ensure these sites are preserved amidst modern development pressures like agriculture and urbanization.
But perhaps the most important impact is creating new ambassadors for science.
The Heritage Quest experience shows that involving the public in archaeological research can yield high-quality results while fostering a deeper appreciation for local heritage. Many volunteers became advocates for the protection of archaeological sites in their regions, engaging in further local initiatives to promote the preservation of prehistoric landscapes.
“I’m blown away by how many previously unknown burial mounds the volunteers helped uncover”, concludes Bourgeois. “I knew we were working in an important area with many traces of a prehistoric landscape still preserved, but I never expected to find so much so quickly! But for me the most amazing outcome is seeing the passion the volunteers had for our research! They have now become vocal advocates for the preserved traces of prehistoric landscapes in their region.”
The study was published in the journal Antiquity. https://doi.org/10.15184/aqy.2024.127
