Small Unmanned Aircraft and archaeology – why now?

In 2015 the Castle Studies Trust and the Morecambe Bay Partnership worked together to record the remains of Gleaston Castle in Cumbria. By using an unmanned drone to photograph the castle we were able to reach every part of the building. Below is an excellent explanation from Museum of London Archaeology’s Dr. Peter Rauxloh of how this technique works. It was originally published on MOLA’s blog.

Archaeologists have known about the benefits of investigating archaeology from an aerial perspective for more than 150 years, arguably longer, but the day-to-day use of aerial survey in MOLA’s work has been hampered by cost.

The model drone was a very popular Christmas present last year; a clear indication that cheap aerial photography has arrived. The big innovation from the perspective of archaeological aerial survey is the arrival of affordable digital photogrammetric software and automated flight control.

Photogrammetry is the practice of taking measurements from images. It is based on the fact that the position of an unknown point in 3D can be calculated if it is viewed from at least two other known points. This is the principle of triangulation, as important to map makers in the 17th century, as it is today.

The software in question uses the principle of photogrammetry and applies it to the processing of digital images to create 2D orthomosaics and 3D models. In essence, the traditional technique of aerial photogrammetry used a small number of high quality images taken with expensive specialist cameras from real aircraft, on which a small number of common points were identified between adjacent images. The new method uses a large number of images, taken with a standard consumer grade digital camera from cheap aerial platforms and is able to identify thousands of common points between images. Thus the technique tightly locks together overlapping areas to create robust orthogonal mosaic and highly detailed 3D models.

The amount of overlap required between images in order to create robust models is very high, typically 75-85% between each successive image. This means that 85% of one image must still be visible in the next image, but how does one ensure that critical degree of overlap is maintained?

Typically an aerial survey will be flown in a grid, much like a tractor ploughing a field, and each successive image needs 75-85% overl ap with its predecessor. Moreover once it has turned and starts to fly back over the site, it must also get 60-70% overlap between the images on each leg. For small survey areas the aircraft is flown manually since it is easy to ensure the area is well covered with images,  but it is far more difficult to maintain the required consistency on a large site.  This is why MOLA use an autopilot and have it follow a flight plan.

A flight plan is a group of 3D coordinates or waypoints between which the aircraft navigates using its on-board GPS. To position these waypoints so the images overlap a number of variables need to be balanced. These include the camera’s field of view, frequency of image capture and the desired flight height and the speed of the aircraft. These in turn need to be considered against the size of the area to be flown and how long the aircraft can safely stay in the air.

Below you can fly round the model of Gleaston Castle.

Gleaston Castle
by aerial-cam
on Sketchfab

Bringing Pleshey Castle’s history to the public

Betrayal, intrigue, fire, a king arresting one of his men, and the richest man in England. In 850 years Pleshey Castle has seen it all.

The village and castle owe their existence to Geoffrey de Mandeville who founded both in the 12th century. At the height of his power he was the richest man in England apart from the king, but lost it all when he was accused of being a traitor. Pleshey was owned by his descendants (though in the hands of the king) before it passed to the Bohun family by marriage. It remained with them until 1380 and in 1419 Pleshey Castle became part of the Duchy of Lancaster. Because of the Duchy’s ownership we have detailed accounts of building work in the 15th century. By 1559 the castle stood empty, and now survives as some very impressive earthworks.

Throughout its history the castle was remodelled several times – sometimes to improve the accommodation, at least once to repair fire damage, and once because it had been partly demolished. Excavations between 1972 and 1981 led by S.R. Bassett tried to shed light on this complicated history. Unfortunately this important work never saw the light of day. Notebooks and context sheets were left in the archives, out of reach of all but the most determined until now.

Our tour group in the outer bailey
Our tour group in the outer bailey

Patrick Allen and Nick Wickenden are leading the efforts to get the results of the excavation published. The Castle Studies Trust have funded the creation of detailed drawings showing the work. They provide an invaluable visual reference, and show how parts of the castle have developed.

Earlier this month we visited the castle with some of our donors. As well as exploring the castle it was a chance for donors to talk to trustees and see first-hand how valuable the charity’s work is.

Crossing the moat surrounding the castle you get an idea of how impressive the site is. The motte at the heart of Pleshey is an impressive 17m tall while the ramparts are nearly 5m high and cut you off from the outside world. You can still see where the chapel was excavated and a section was cut through the rampart.

Pleshey is privately owned so if you want to visit you have to arrange it in advance. This is typically of the sites we work with, and we give donors the opportunity to look round. Patrick and Nick gave us a tour, explaining the colourful history of the site and what they were doing to publish the excavations. Behind the scenes, the illustrations complemented the research and helped understand the phasing of the site.

It can take years for excavations to be fully processed and reach the stage where the results are ready for the general public. Sometimes that stage is never reached making it much more difficult for people to access information. Because of your donations we’re bridging the gap.

We’re looking forward to seeing the final results!

To keep informed about the Trust’s activities sign up to our newsletter.

Grants are now open!

There are two key dates for the charity over the next few months: 1 September and 15 December. The first marks the opening of our grants process. It is the start of the journey to understanding our history better. Applications close midway through December.

In that time we get to find out what people have been planning. After that comes the decision process which shapes what we do next year.

Our decision is informed by a panel of experts who have worked on castles across England, Ireland, Scotland, and Wales. Their broad experience means we’re ready for just about any project which comes our way. We focus only on sites which aren’t managed by major heritage organisations. That way we can maximise how effective our work is, as these sites are unlikely to get attention otherwise.

You can help us by sharing the news that our grants are open. If you know a heritage group working on a castle, or some industrious soul with a passion for castles let them know about us. We offer up to £5,000 which can cover work like a digital reconstruction or a laser survey.

Want to learn more about previous grants or looking for inspiration? Read our grants page for details of projects from 2014 and 2015.

4 Castles to Visit this Month

Every year historic buildings across England, Northern Ireland, Scotland, and Wales open to the public for free. It is a great excuse to go out and visit some castles. You can find out more details online. Here are four places we find interesting.

Mugdock

Mugdock Castle in Scotland. Photo by Ryan Woolies, CC-BY-NC-ND 2.0.
Mugdock Castle in Scotland. Photo by Ryan Woolies, CC-BY-NC-ND 2.0.

A nine-mile drive from Glasgow, Mugdock Castle was built in the 14th century and converted into a mansion about 500 years later. The Grahams who lived there until the 20th century were an influential Scottish family. Visitors can walk round the gardens which were laid out in the Victorian period and the ruins of the castle.
Mugdock Castle is open from 10am to 4pm on Saturday 12th and Sunday 13th September.

Carrickfergus

Carrickfergus Castle, Northern Ireland. Photo by Andrew McCoubrey, CC-BY-NC-ND 2.0.
Carrickfergus Castle, Northern Ireland. Photo by Andrew McCoubrey, CC-BY-NC-ND 2.0.

John de Courcy began building Carrickfergus Castle on the coast in 1177 and more than 800 years on it is one of the best preserved Norman castles in the country. When looking round, try to imagine the gatehouse being twice as tall. It was shortened in the 16th century when the castle was adapted to use cannon.
Carrickfergus Castle is open from 10am to 5pm on Saturday 12th and Sunday 13th September.

Dolbadarn

Dolbadarn Castle by Sian Monument. CC-BY-NC-ND 2.0.
Dolbadarn Castle, Wales. Photo by Sian Monument, CC-BY-NC-ND 2.0.

Dolbadarn Castle was built by Llywelyn the Great, Prince of Gwynedd, in the 13th century. The round tower is typical of Welsh design. Its close link to the Welsh princes meant that when Edward I invaded and built his own castles, timber from Dolbadarn was used to build the castles as Llywelyn’s castle was partially demolished.
Dolbadarn Castle is open from 11am to 4pm on Sunday 6th September with tours every hour.

Guildford

Guildford Castle, England by tps58. CC-BY-NC-ND 2.0.
Guildford Castle, England. Photo by tps58, CC-BY-NC-ND 2.0.

At Guildford Castle you have a royal palace, a great tower possibly built by King Stephen in the 12th century, and gardens. You can climb to the top of tower which sits on top of a mound. There’s a chapel inside with old graffiti. On the outside you can see where an extra floor was built on top of the tower.
The castle is open from 10am to 5pm on Saturday 12th September.

Ballintober: a palace castle in a border territory

County Roscommon’s Ballintober Castle was probably built by Richard de Burgh, Earl of Ulster, in the early 14th century. It changed hands several times, but from 1381 it was under the control of the O’Conor family. After nearly being attacked in 1642, the castle was abandoned as a residence and the elements have left Ballintober as a ruin. The O’Conor family still own the castle today.

Despite Ballintober’s storied past and impressive ivy-clad remains, it was not investigated by archaeologists until 2008 and 2009. When Niall Brady applied to the Castle Studies Trust for funding in 2013 the project to survey the castle offered the chance to push forward our understanding of the castle.

Though the castle now lies in ruins, parts of it stand up to 4m high (13ft). Ballintober Castle is rectangular, measuring 73.8m by 80.5m (242ft by 264ft). There is a tower at each corner, and on the east side the entrance is flanked by two further towers. The polygonal corner towers are thought to emulate the design of Edward I’s Caernarfon Castle in Wales. As well as being a military structure, emulating the most powerful of royal castles, Ballintober was a residence. Its comfortable accommodation revealed by the fireplaces marked it as a palace castle.

Ballintober is a ‘keepless castle’ which means it does not have a great tower such as the one seen at Trim Castle (Ireland) or Dover Castle (England). Instead it relied on its outer walls. There are a few castles like Ballintober. Richard de Burgh also built Ballymote as a keepless castles around the same time.  Just 18km (11mi) to the south-east of Ballintober is Roscommon, which may have provided the template for Ballintober. It was built decades earlier in 1269 on behalf of Henry III. Ballintober is the largest keepless castle in Ireland, and is more than twice the size of Roscommon despite its royal patronage.

Laser scanning equipment at a castle
The laser scanning in progress at Ballintober.

Laser-scanners were used to record the standing structure and as a result we have a 3D point cloud which can be used to create accurate plans, elevations, and views. The survey took three days to complete in the field, followed by considerable time processing and interpreting.

It’s told us a lot about the castle. The south-west tower has a fireplace on the ground floor, and would have once had a fine timber vault. It may have housed a high-status hall. While it’s possible the south-east tower is the oldest as it is the smallest of the corner towers, the north-west tower was substantially redesigned in the 17th century. The arrow slits are wider than those found at Roscommon and Ballymote, and may be wider. This might suggest that comfort was a consideration in their design. There are signs of later adaptation, with gun loops being added to accommodate gunpowder weapons.

The survey also shows that Ballintober Castle is asymmetrical, with the entrance off centre. One possible reason is that the design changed to encompass a larger area or perhaps it stands on an earlier fortification.

Importantly, the survey has provided the foundations for further work. We are delighted to see further research at Ballintober, building on excellent recent work. From July to August this year Foothill College, California, ran a Summer Fieldschool at the Castle. ‘Castles in Communities’ is advertised on the Archaeological Institute of America website. Niall Brady was one of the fieldschool directors. We asked him how the excavations went:

“The CST-funded survey in 2014 was a very important precursor to starting the present work. The 2015 season went well. We focussed on questions associated with tracing missing lengths of the standing walls, rather than looking into the main interior. This was to give us some sense of the site’s stratigraphy, while also tackling obvious questions in a way that wouldn’t open a can of worms we couldn’t close. We also engaged the attention of a conservation engineer, who is now quite excited by what can be possible in future years, vis a vis conservation works on the standing remains.

“For the four weeks on site, the excavation results were good, showing 16th-century and later levels. We only really broke the ground surface in three discrete locations, and so look forward to going deeper and exposing medieval horizons next year. There was massive buy-in from the local community (the landowners and the villagers), who see the great potential that lies in our plans for the castle site and its living community about it.”

Excavations in the southeast corner tower, exposing phases from the castle's broad history. Photograph by Nialll Brady.
Excavations in the southeast corner tower, exposing phases from the castle’s broad history. Photograph by Niall Brady.

The work the Castle Studies Trust is not the end point of a journey, but a crucial stepping stone towards understanding medieval society.

For more information on Ballintober, read the full length report prepared by Niall Brady. Please donate so we can support more projects like the one at Ballintober.

Three years of the Castle Studies Trust

Three years ago this month, the Castle Studies Trust officially became a registered charity. A group of castle enthusiasts while visiting castles realised there is still so much we do not know about these fascinating structures, even the basics of what they look like, let alone what they were used for and how they developed over centuries. This, combined with continued long term cuts to traditional funding organisations the enthusiasts decided to do something to help and set up a the CST.

From the start there have been three key tenets of the Trust:

  • Being a new source of funding for such work and not taking monies from existing sources and thus reliant on public donations.
  • Focusing on sites not in the care of major heritage organisations such as Cadw. This means we concentrate on castles which are privately owned or run by trusts or local authorities where even less is known about this sites.
  • All results must be published within a set time frame (currently nine months) and freely available to the public.

The charity exists to push the boundaries of our understanding of castles. We are primarily a grant-giving body and are run entirely by volunteer trustees. Once we were set up fundraising began in earnest so we could support research projects. Enough was raised so that in late 2013 applications were opened. As luck would have it, we were able to support four grants that year, one in each of England, Ireland, Scotland, and Wales. It is an annual process and earlier this year we awarded our second set of grants to another two sites.

There are thousands of castles in the British Isles, built over hundreds of years and they are visited by millions of people every year. Some are very well understood. Many are in the care of national heritage organisations such as Cadw or the National Trust. But with so many castles there is always more to learn. That is why we feel we can make a real difference.

We work around castles which large heritage bodies might not have the resources for but have incredible potential. This year we are supporting two projects, one at Gleaston in Cumbria, and the other at Pleshey in Essex. Between them we have a site at risk of decay or even collapse and a castle which was the pride of one of the richest men in 12th-century England.

Aerial photo of Pleshey Castle. The castle consists of a grassy mound next to a kidney shaped enclosure, all surrounded by a moat. In the background is the village of Pleshey.
Pleshey is one of the grantees for 2015

Already we’re seeing the results from our first set of grants coming through. At one of the sites the work we supported has triggered further research supported by the Archaeological Institute of America. The Trust isn’t going to change our understanding of the Middle Ages overnight, but we can make an invaluable contribution and pave the way for more work.

The application process for new grants opens in September. We’re eagerly looking forward to see what projects are suggested.

Three years in, we’ve come a long way and in the future hope to support even more projects. With your support we can continue working at the cutting edge of our understanding. Help us do something exciting.

This new blog will be used to explain what the Castle Studies Trust does and the projects we support.