Enjoy this article written by Michael ‘Bhodi’ Rodgers


During the summer of 2019 four undergraduate students and I travelled to Ferns to document Ferns castle, St Edans cathedral, and St Marys abbey using two Leica 3D laser ‘LiDAR’ scanners.  For the uninitiated 3D laser scanners calculate the distance between the scanner and points on an object by calculating the time it takes for a laser pulse to leave the scanner and reflect back from the object’s surface. This calculation is used to determine the exact X, Y and Z location of the point that was just scanned.

The scanners used at Ferns can reach out to 270m and record a million points per second!  The scanners also have photographic cameras used to take digital photographs from the scanner location. These colour photographs are then used to assign a colour value to each of the scanned points, giving the resulting data photorealistic colour.

Figure 1 Ferns 3d Scanning at Ferns Castle with Michael 'Bohdi' Rodgers

Figure 1: Laser scanning in tight spaces. The laser scanner cannot see the area beneath itself. Putting it on a small tripod reduces the size of the circle that cannot be “seen” by the scanner.

Completed laser scans creates a truly three-dimensional picture, called a point cloud, of the scanned object or monument providing an extremely detailed conservation record which, amongst many other uses, allows for the creation of architectural renderings, site monitoring for structural stability, a guide for required construction works and/or as a guide for reconstruction in the case of unexpected future damage.

For example, an extreme example of the potential of 3D scanning was the 2019 fire at Notre Dame Cathedral in Paris – a conservationist’s worst-case scenario! Fortunately, in 2010 3D laser scanning was undertaken at the cathedral, with the resulting scan aiding in reconstruction efforts by providing detailed and measurable documentation of architectural elements destroyed by the fire.

At Ferns we began our scanning at the castle, the focus of our research; this scan was intellectually challenging due to some site specific features, not least the tight space between the east wall of the castle and the wall along the adjacent property line. Typically we would scan a castle wall from 10-20 meters away, but here we were just 2 meters distant!

The bottom room of the southeast tower was also very dark and we needed to use headlamps and hand-held lights to brighten things up. The laser scanner doesn’t need the extra light, it can scan in full darkness, but the photographs we take to colour the resulting scan do need enough light to be sufficiently exposed.

Figure 2: Scanning the outside of the cathedral.

Figure 2: Scanning the outside of the cathedral at Ferns.

Recording the castle took dozens of scan locations and once done we moved the scanners down the sidewalk to the cathedral and abbey. All of our data is captured while working in a local grid system so that every scan is properly aligned with the next scan. This meant moving our scanner carefully with survey gear down the busy Ferns sidewalk. The students did a fantastic job aligning all of our scan locations, some 95 in total, with extremely high precision.

So now that we have these historic features recorded what comes next. First, just having the high resolution data means that these buildings are digitally preserved, so, as stated, these data might come in handy in the future to assist in any needed conservation works. My students and I are also creating a web-based viewer that supports a digital tour of the sites.

Many historic sites have areas that are inaccessible due to safety issues or they are inaccessible due to the need for a visitor to climb stairs. Additionally, people without the current financial means to visit a site in person can still visit virtually, and a virtual tour might inspire one to find a way to visit in person in the future!

Figure 3: Laser scanning point cloud of St. Mary's Augustinian Abbey with the cathedral in the background.

Figure 3: Laser scanning point cloud of St. Mary’s Augustinian Abbey with the cathedral in the background.

Our web-based viewer is in its first version where one can use their web-browser to look around inside each of the rooms of the southeast tower of the castle. You can also look around the outside, and we are working towards adding the ability to walk down the sidewalk to visit the cathedral and abbey. Our viewer also works with WebGL enabled devices such as certain tablets and virtual reality devices so that you can take an immersive tour of Ferns from virtually anywhere.

For monre information see https://clas.ucdenver.edu/rogers-lab/ or consult Chapter 13 of the upcoming Uncovering Medieval Ferns book.

Acknowledgment of Support

This blog is number eight of a ten-part series entitled ‘Discovering Medieval Ferns’ which has been funded by the ‘Rediscovering Ancient Connections – The Saints (Ancient Connections)’ Project.

Ancient Connections Logo for Discovering Medieval Ferns blog series

Ancient Connections’ is an ‘inter-reg’ cross-border arts and heritage project linking Pembrokeshire and north Wexford, which strives to revive the ancient links between these communities, allowing them to rediscover their shared heritage and trade knowledge, experience, and skills.

‘Ancient Connections’ have also funded a major academic volume, also entitled ‘Discovering Medieval Ferns, upon which this blog series is based.

Discovering Medieval Ferns Book Cover 2023

This volume, which includes fifteen papers from an interdisciplinary team of twenty+ scholars, aims to highlight the remarkable history and archaeology of medieval Ferns, focusing on intriguing discoveries from recent excavations and research programmes.

The volume, which is the most complete picture to date of the origins and evolution of medieval Ferns, will be published by Four Courts Press later in 2023.

The logos of EU and Welsh bodies involved with Ancient Connections that have supported the excavation at St Mary's