Corgarff Castle is the former noble residence of the Forbes clan, and during the Jacobite Rebellion, it was used as an army base by Redcoats. It sits in a dramatically isolated location in rural Aberdeenshire (see cover image for views from its doorway!). It has a distinctive star-shaped perimeter wall, and as part of Historic Environment Scotland’s Rae project, the entirety of the Castle’s interior and exterior was laser scanned over two days.
I helped out on the second day of scanning, working with HES’ team of Mike Jack and Sofia Antonopoulou, to fill in areas where more detail was needed using the Leica HDS 6100 laser scanner.
I also used a Nodal Ninja (right) to take overlapping photographs that can be digitally stitched into a 360⁰ image. The one I used was specially calibrated to be complementary with the Leica 6100 laser scanner, so the high definition imagery can be overlain onto the scans generated in the same position.
I greatly enjoyed taking views of the surrounding countryside, and watching the Castle’s current residents (nesting families of swallows), swoop around while we continued with our survey.
This post is about one particular use of laser scanner point clouds collected in the field. After several scans are acquired and are correctly georeferenced, using a total station, GPS or other systems, plan and elevation drawings of the scanned features can be drawn in CAD. Using the Bentley Pointools plugin for AutoCAD 3D, it is possible to display sections through the scan data in the vertical or horizonal plane (x and y axes). This appears onscreen as a thin line of the point cloud, which can be traced as polylines to generate CAD drawings of building plans and elevations, with details of faces and sections where necessary.
The great advantage of using this techique is that the onsite data acquisition is far faster than taking measurements by hand, and the data can be later exported back in the office. So it was that I worked with laser scan point clouds (scanned using the Faro Focus 3D) and a photogrammetric 3D model (processed in Photoscan) of the Monk’s Oven and Pump House at Calder Abbey , a site I have never visited, in order to produce elevation and plan drawings using CAD. Special thanks to David Andrews for his patient tuition in this!
These are the plans and elevations of the Pump House that I drew, with additional corrections and editing by David. (All images and drawings: copyright Historic England).
From 15th-17th February 2016, I surveyed and recorded historic graffiti and carvings across the site of Carlisle Castle using the Leica P40 Scanstation, photography and video recording (Canon 5D Mk ii) for SfM photogrammetry. Most of the carvings found are located inside the keep, and I do recommend a visit – keep your eyes peeled and you realise there is graffiti all over the castle, as the red sandstone is a very soft material (though you must certainly refrain from adding your own..!).
Most of the carvings are of medieval and post-medieval date, many of which have never been systematically recorded before. Quite a few of the medieval carvings allude to allegiances with powerful families and rulers. Coat of arms and heraldic symbols are very common, especially in the so-called prison room on the keep’s second floor. The “prisoners’ carvings”, as they are commonly called, depict crests connected to Richard III, who for a time was Warden of the March, including his personal symbol, the white boar, the white Yorkshire rose, as well as symbols connected to the influential Dacres (scallops) anad Percys (fetterlocks), who were his allies.
The original medieval oak door to the “prison” room also has carvings, but has never been fully analysed, so I took this opportunity to laser scan and photograph it for the production of 3D models.
Some graffiti dates to the 19th century and were created by soldiers. One piece on the keep’s second floor clearly states the graffiti artist belonged to the 55th Westmorland Regiment, which amalgamated with the 34th Cumberland Regiment to become the Border Regiment in 1881.
Lastly, a fascinating example of historical recyling can be seen inside D’Ireby’s Tower, where a Roman altar stone had been reused in the medieval period as a door lintel! I took photographs of the altar to be processed into a photogrammetric model.
Once this data is all processed, I hope to analyse the detail and quality of the 3D models generated, to see which method and settings are most suitable for future recording of similar historical carvings. It was great to see how intrigued visitors were in the work. I hope this will provide a digital means for people to view these carvings that can be difficult to access physically.
Last December, I was tasked by the curatorial team at English Heritage to study a badly eroded panel on the walls of the outer gatehouse (also known as D’Ireby’s Tower) at Carlisle Castle.
The 13th century tower forms the core of the present tower dating to 1378-83, by John Lewyn, which has been altered and restored in the 19th and 20th centuries. On the front of the tower is the barbican, where a blank stone panel is situated below crenelations added in 1819. The panel is heavily weathered, however, it has been suggested by various authors and illustrators that it once depicted a coat of arms, potentially of Richard III, who was Warden of the West March prior to becoming king (Summerton 2008), or the family crest of the Dacres, a dominant family of the area in the 16th century (Wills 2015).
With the help of Geospatial Imaging officer David Andrews, we laser scanned the panel, and I’m currently comparing the results of this with the photogrammetry I have been processing from photos taken on 15th February on a scaffold on site. I’m aiming to produce a research report with the complete results of this analysis by the end of my placement.
Summerson, H. 2008. English Heritage Guidebook:Carlisle Castle, English Heritage, London
Wills, H. G. 2015. The Best Kept Secrets of the Western Marches, Arthur H. Stockwell, Devon