In 2025, as in previous seasons, we again employed some targeted 3D photogrammetric capture for the excavation team. In collaboration with Eddie and Derek in the early season we created a series of 3D models of the major open trenches which display their progress through the excavation. This year at Glencoe there were three areas of concern which needed to be photo-modelled, and each posed their own special challenges.
First of these, the trenches comprising what we’ve decided to call the “kiln”, are arranged in an hourglass shape and combined with the extreme variance in trench depth would mean a fair amount of awkward posing to capture the right angles and shots, maximizing coverage and important details.
Often, in 3D capture we imagine the process as more automated or somehow uninfluenced by a recorder, but in the field, this is certainly far from true. A good photo model is best shot actively and with attention to small details. A good understanding of what the camera needs to see and how it needs to be seen are critical to tailoring your results in the software later and these are skills gained through practice and an understanding of the features you are intending to record.
The other two trench areas, the taxman’s house and the tenant’s house, posed less challenges in terms of positioning but were much larger, requiring more photographs overall to properly catch the arrangements of stones throughout the exposed features. For these models especially, the never-ending stream of water flowing through the turf and into the low portions of the trench became difficult to work around. In my case the help of some industrious students and a pair of very dirty sponges won the day. With their help I was able to quickly shoot the required images for the wet sections and their overlap before they again flooded, and while some water is visible in the final models, it’s well within a tolerance of usable imagery.
As always, the biggest challenge to conducting a 3D modelling session in the field is weather and time of day. Lighting conditions need to be bright enough that the camera is able to be used from the hip, and a steady Scottish rain or wind will destroy the ability to reconstruct surfaces well. Luckily for us the final day of excavation was perfect for photographing the trenches and the weather held out long enough to shoot each area thanks to students and the NTS volunteers coordinated cleaning efforts.
Back in the lab during post ex, these images can be processed using photogrammetry software to produce a fully 3D render of the trenches. Photogrammetry via SFM or Surface From Motion, leverages the ability for distances and geometry to be calculated by scanning multiple photos from a digital camera. The software we use looks at each picture and finds points that appear in several images automatically, this allows the program to create a 3D array of every position the camera was in in refence to the ground (what we’ve shot) and begin mapping the surfaces we are interested in.
Once it creates a 3D model or Mesh of the object, we can reuse the detailed photographic imagery to make a “texture” which is like a big 3D image quilt made up of all the best 2D images from our data stretched out and arranged over the 3D surface.
Combining these gives us an excellent and detailed 3D model of the whole trench! Lastly, leaving some measured objects like scale bars and ranging rods in the area being shot allows me to select points for these objects and tell the software how far apart these points are applying that scale to the whole model which is now 1:1 scale within about 3mm of accuracy in the worst spots.
We use these models in a few ways, first, these models are an excellent archive resource for the contexts that we expose. Being able to recall the exact imagery and manipulate a 3D rendering of features allows a lot of flexibility when archaeologists might return to study the context through its reports.
They also help to produce some scale corrected images of the plan and section views which are very helpful as comparative images to the drawn recordings made by archaeologists in the field. They also serve to recapture any view of the trench that might be helpful to use later in reports or presentations.
3D models also allow us to examine and archive very fine details of the contents of each trench as they are revealed as we have done with the finds in the “kiln”.
Lastly, carrying out 3D modelling on site and in the lab with artifacts allows us to create interactive displays and high-quality tactile teaching tools and examples for wider engagement with the public and new enthusiasts to Scottish archaeology. You can find a models of the Achnacon site from 2025 here, 2024 here and the Summerhouse of MacIain here.
– Dr Cole Juckette (University of Glasgow)
Leave a Reply