Laser Scanning the Great Tombs of the Boyne Valley

Marcus sets up the instrument to begin a 360° scan of the chamber and passage of Knowth East, collecting an astonishing 500,000 data points approx. per second.

As one of Ireland’s foremost heritage landscapes, the great neolithic passage tomb complexes of Newgrange, Knowth and Dowth, collectively known as Brú na Boinne, attract hundreds of thousands of visitors every year. The chamber within Newgrange, the most famous of Ireland’s many passage tombs, welcomes a steady stream of tourists who crouch and shuffle single file up the long passage, literally rubbing shoulders with some of the finest megalithic art in Western Europe.

In the 5,000 or so years since it was first constructed, the settling of the mound’s layered bulk had caused many of the uprights lining the passage to lean and tilt inwards, making parts of the passage difficult to negotiate. This was remedied during the excavations and renovations led by Prof. Michael J. O’Kelly between 1962 and 1975 so that today the chamber is readily accessible. At Knowth and Dowth however, the chambers remain largely out of reach for most visitors due to a mixture of structural obstacles, site management and safety concerns.

At Knowth East, the passage orthostats nearest the chamber lean in so heavily that the only route through is on hands and knees along a wooden plank. At the time of the chambers discovery in 1967, the excavator, Prof. George Eogan, actually entered by crawling above the passage orthostats, eventually managing  to reach the chamber floor below by lowering himself down along the two metre high portal stones.

The situation is not much different at Dowth North, here the only means of access to the passage is a rather claustrophobic and uncomfortable crawl down a 20 metre long souterrain that was probably constructed between the 9th-11th centuries A.D. The lighting fixtures that had been installed decades ago are now flooded and defunct, the chamber now lies in damp and eerie silence.

With the sophisticated technology and expertise offered by a team from the York Archaeological Trust however, it is hoped that ‘virtual visits’ may be offered in the future through the medium of 3D virtual reconstructions and interactive ‘fly through’ videos of these unique and remarkable sites. The incredible level of detail and realisitic textures captured in this project will also allow researchers, whether within Ireland or abroad, to continue to study and analyse the construction and decoration of the tombs from their desks.

Over several days in May 2012, Dr. David Strange-Walker and Marcus Abbott meticulously scanned, photographed and logged GPS co-ordinates for both Knowth and Dowth in an exciting project organised in conjunction with UCD. Dr. Steve Davis of the School of Archaeology in UCD was one of the main co-ordinators of the project and both he and David were interviewed inside the chamber of Knowth for a piece on RTÉ News, broadcast on the 15th May:

Phillip Bromwell of RTÉ meets the team at Knowth.

I was delighted to be given the opportunity to meet the team and check out the work going on within the chambers of Knowth and Dowth and am very much looking forward to seeing the results of the surveys and scans, particularly the megalithic art. Having firsthand experience of how difficult it can be to record and in some cases even access the sheer number of decorated stones, it will be very interesting to see how technological advances along with the talent of people like Marcus and David can bring this collection of some of Europe’s finest pre-historic carvings to life for everyone to enjoy.

In the meantime, below are some images from my short visits to see the team in action. This was of course a very challenging environment to work in. Not only are there extremely low light levels within the chambers, but due to the scale of  the project it was not exactly practical to stop the work in progress and set up some atmospheric environmental portraits, not to mention the need to regularly find the nearest hiding place and sit still for several minutes while the scanner was collecting data! All of the shots therefore were taken handheld at exceptionally low shutter speeds mostly combined with very high ISO settings to increase the sensitivity of the camera just to avoid blurring as Marcus and David went about their various tasks.

Marcus secures the scanner to its low-level base where the passage meets the chamber in Knowth East.

It’s very much a case of ‘watch your head’ and ‘watch your step’ in the eastern chamber at Knowth.

Marcus checks the location and visibility of the targets which will allow the different scans to be combined later with sophisticated software.

The large basin stone in the rear chamber, Knowth East.

Marcus checks the settings on the scanner before it begins a 360° scan of the chamber and passage.

David Walker sets up the camera to capture the texture and colour of the surfaces that have been measured by the laser scanner.

The scanner set up in the right hand recess of the main chamber of Dowth’s northern passage.

The chamber in Dowth North is normally in permanent total darkness, the lighting arrangements are ‘bring your own’.

The very talented Marcus Abbott (left) and David Strange-Walker pictured in the eastern chamber of Knowth.

For more information on laser scanning and past projects using similar techniques, the wonderful website of the Nottingham Caves Survey project is very much worth a browse. Other exceptional case studies are featured on Marcus Abbott’s site. Special thanks are due to Dr. Steve Davis for arranging access for both myself and the team over the ten day period and particularly to the OPW for their time and co-operation in facilitating the work.

Bealtaine at Beltany Stone Circle, Co. Donegal

The beginning of May and official summertime was marked in more ancient times by the fire festival of Bealtaine. Bealtaine falls close to the astronomical cross-quarter day, half way between the equinoxes and the solstices. It is known to have been celebrated from at least medieval times and marked a time of reckoning when rents and debts were due and workers and servants were hired for the season ahead. Its significance in more ancient times is more obscure. The actual astronomical cross-quarter day this year falls on the 5th of May however the festival in the modern calendar is fixed on the 1st.

Beltany Tops stone circle sits on a hilltop in Co. Donegal, not far south from the village of Raphoe. 60 or so stones remain from what was likely to have been a contiguous kerb-like circle around a raised platform 45m in diameter. It also features two outlying stones. It probably pre-dates the ‘Celtic’ calendar festivals by several thousand years, however we cannot be certain that people in the Neolithic or Bronze Age did not have a similar calendar or festivals.

Various astronomical alignments have been claimed to exist at the circle, however the most intriguing is the Bealtaine sunrise, possibly marked by a triangular stone whose inward face is covered in cup-marks (small round depressions hammered or ground out of the surface of the stone and the most common form of prehistoric rock art). Around the cross-quarter day the sun rises directly behind this stone, as can be seen in the title photo of this post. The name ‘Beltany’ also happens to be an anglicisation of ‘Bealtaine’, adding another interesting layer of association.

The above photos were taken on a perfect sunrise on the actual cross-quarter day in May 2007. The sunrise is now partly blocked by nearby trees but the effect is still quite spectacular to witness as the first limb of the sun peeps through the branches directly behind the cup-marked stone which is pointed, almost like a target.