Corgarff Castle and Elgin Cathedral

It’s been almost 2 weeks since my fieldwork trip to the Highlands – a 4-day survey whirlwind through several locations in the North of Scotland, including Inverness, Elgin, Fortrose and Corgarff. Most of my time was spent laser scanning Corgarff Castle – together with HES colleagues from the Fort George office and Li Sou from Historic England. Corgarff is a very special site: a striking white garrison tower surrounded by star-shaped walls, located at the edge of Cairngorms National Park. The location is very remote, but the views were stunning.

One of the highlights of the trip was certainly my return to Elgin Cathedral. Elgin was my first field project with the Digital Documentation team and provided the material for my very first post on this blog (see Elgin Cathedral QTVR). The objective was to photograph the interiors of the two towers of the Cathedral in order to produce a new set of QTVR panoramas – documenting the spaces after the installation of the new interpretation suite. We used the same set-up as before (Nikon D810 mounted on survey tripod using nodal ninja) with a few improvements (HDR photography using 5 brackets instead of 3, plus remote shutter release to eliminate movement). The system worked really well and we managed to finish the job in a few hours with great results. The only (slight) downside of this process: 5 brackets for every angle (3 rotations plus ceiling shots) resulted in approx. 150 images for each location (in RAW and JPG) = a lot of storage space. However, the quality of the final panoramas definitely justifies the file sizes!

I have already processed the raw photos in Photomatix to create the HDR images, which I’m now stitching together in PTGui to produce the panoramas. I’ve been using only RAW photographs for processing and exporting uncompressed TIFs, which doesn’t seem to add much to processing time, but really makes a difference to the quality of the final product.

My visit to Elgin was a great chance to finally see the stone collection properly displayed in the brand new exhibition, after a year of conservation work – which took place literally next door to our office in Edinburgh, in the HES Conservation Centre. The dark purple display stands were a perfect choice for showcasing the stones. The effigy of the bishop is one of the highlights of the collection – the light projection system used to display the colour scheme onto the stone is brilliant.

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Colour scheme projected onto the stone effigy.

Once the QTVRs are completed, my next project will be to process all the laser scan data from Corgarff Castle and Fortrose Cathedral. I’ve already imported all the data into Cyclone using the Auto-Align function, with moderate success (it gets confused by repeating geometry such as staircases with sometimes “interesting” results). However, auto-align can be a great tool for quickly checking results at the end of each day on the field – when there is still a chance to go back and fill in any gaps.

Laser scanning Kinneil House

A few months ago, the Digital Documentation team spent 2 days in the Kinneil Estate near Bo’ness. There were several reasons for this visit; one of them was to collect data (laser scanning and GNSS) in the area of the Roman fortlet for a PhD research project on the Antonine Wall.

The other reason for the visit was to laser scan Kinneil House itself for the Rae Project, our programme of digitally documenting all of HES’s properties in care. I was sadly not involved in scanning the House, which has some incredible Renaissance wall paintings and really is worth a visit. I was, however, given the task of processing the data, registering the scans in Cyclone and producing the deliverables: TruViews and a set of orthoimages (plans, elevations and sections).

The project consisted of P40 scans with HDR imaging for the exterior, plus HDS6100 and Faro scans for the interiors (total around 60 scans). I registered the scans and then cleaned them in Cyclone to isolate the building, remove trees, people and occasional noise from the data. For the orthoimages, I experimented with different visual styles, to see which one would bring out more detail in the point cloud. In the end, for each view I exported the same ortho-TIFF with different visual styles (shaded and silhouette) and combined them in Photoshop. Here are some of the results:

The Hidden Landscape of a Roman Frontier is joint PhD programme between HES and Canterbury University. For more info see here or follow Nick Hannon @Hannon_Arch on Twitter.

The local charity group Friends of Kinneil have been very enthusiastic about our work on the site. You can follow their activities on Twitter @kinneil.

And, as always, follow Rae Project activity on Twitter #RaeProject.

A trip to York, and Lancashire, and London…

It has taken me a while to post this, but the last month has been really busy. So, recap of the past 3 weeks:

Week 1, a trip to York (and Lancashire, and London) on an intern exchange programme, hosted by Historic England’s Geospatial Imaging team. Li (who has already blogged about this -check out her blog here) is the Geospatial team’s CIfA placement and will be joining us this following week in Edinburgh (and Inverness, and Fortrose, and Elgin) for the second half of our exchange.

My week with Historic England was busy, packed with site visits (amazing Rievaulx Abbey and Mount Grace Priory), an SfM photogrammetry session at English Heritage’s archaeology store in Helmsley, a laser scanning survey of Bellmanpark lime kilns in Clitheroe, and finally a day trip to the Natural History Museum in London. I had the chance to participate in field work as part of the team, both in Helmsley (photographing a 19th century curiosity for SfM photogrammetry with Li), and Clitheroe (survey for structural monitoring of the historic lime kilns using P40 laser scanner and TST ). Having experience with the techniques and equipment from my own internship in Digital Documentation, it was great to see how the Geospatial team use the same technology to tackle similar problems. I’ve left York full of new ideas and keen to try them out in future projects.

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Which brings me to the end of the week, when I was so lucky to be invited to Historic England’s visit to the Natural History Museum Research Labs in London. We spent the day touring the Imaging and Analysis labs and hearing about the amazing research that takes place there. I could probably write an entire post about this, but for now just 2 words (or 5): SEM photogrammetry. Dramatic pause. Also, confocal microscopy, CT scanning, 3D modelling. It was an absolutely fantastic experience and a perfect ending to my week with Historic England.

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During the last 2 weeks, most of my time has been spent working on a BIM model of the Palace at Edinburgh Castle. This subject definitely deserves its own post, so stay tuned. The building has undergone many phases of development and alterations, which have resulted in an extremely complex structure – geometrically, but also functionally. Creating a BIM model for this type of building is not straightforward, even with the advantage of having a complete point cloud as a basis for modelling.

Having had the opportunity to follow this project all the way from laser scanning on site to data processing and registration and now to modelling in Revit, I can see that creating a BIM model for the Palace will be a great asset for in-depth understanding of the structure, the way the building works, and the way it has changed over time. The model is being developed in-house by HES and requires the coordination of different teams and disciplines. Eventually, when both structural and M&E information is added to the architectural model, we will have a complete picture of this building from a single source – probably for the first time ever. More on the Palace BIM project to follow within the next few weeks.

The Palace block, Edinburgh Castle. Screenshot of the point cloud in Recap.

 

2nd SEAHA Conference, Oxford

I have arrived back in Edinburgh after spending  2 fantastic days in Oxford at the 2nd International Conference on Science and Engineering in Arts, Heritage and Archaeology (SEAHA). I had the pleasure of listening to some great speakers during the 8 sessions on topics ranging from Imaging and the Environment to Digitisation. The conference also offered a great range of breakout sessions: my choices were a tour of the conservation department at the Ashmolean Museum led by Mark Norman and a heritage tour of Oxford by Professor Heather Viles.

 

Part of the conference was also a poster session, where I participated with a poster on 3D moisture mapping. Using Skelmorlie Aisle in Largs as an example, I combined 2D image data from microwave moisture meters with 3D point cloud data from laser scanning using the functionalities of Leica Cyclone software. This method of presenting image-based data enables much clearer communication of scientific data, such as moisture levels, and in some cases can aid interpretation of the results. The same workflow can be applied for thermal (IR) images and other image-based data. In fact, the application of both thermal and moisture data to the Skelmorlie Aisle point cloud (in different areas, of course) is the next step of the project.

My poster has been included in the book of abstracts, which can be found as a PDF on the SEAHA website.

3D moisture mapping: combining image-based data and 3D point clouds

Sofia Antonopoulou, Historic Environment Scotland

3D moisture mapping is a collaborative project between the Digital Documentation and Science teams at Historic Environment Scotland, which aims to develop a method for analysing and presenting the environmental behaviour of historic buildings by combining different datasets. In this case, environmental information in the form of 2D moisture maps is overlain on 3D geometric data from laser scanning. The resulting datasets retain the colour-coded environmental information (moisture levels) with the spatial accuracy of 3D laser scans, thus creating a metrically accurate 3D model of the environmental condition of a building. This can be used as a tool for analysis, interpretation, and presentation of image-based environmental data for the purpose of informing conservation decisions. The case study focuses on Skelmorlie Aisle, a 17th century chapel in Largs, Scotland. The Science Team at Historic Environment Scotland have been regularly monitoring and analysing the environmental conditions inside the chapel, collecting data on temperature and moisture levels. In the case study, the data from microwave moisture meters (2D moisture maps) are combined with laser scan data (3D point clouds) captured by the Digital Documentation Team. The methodology developed for 3D moisture mapping can also be applied for other image-based information, such as thermal imaging.

The SEAHA conference was an incredible opportunity for me to listen to some really interesting presentations and find out more about current research on heritage science. I was able to chat to some very knowledgeable people about all things heritage, be inspired by them, and get insight and ideas on a variety of issues – even potentially finding solutions to some practical (digital documentation) problems, but more on that to follow…

For a full account of what went on at the conference, follow the SEAHA blog here.

Saying goodbye to Oxford on Wednesday with a walk around the city centre (and a rather long visit to Blackwell’s on Broad Street) brought me back in front of the Sheldonian Theatre to have a last look at the Emperor Heads. Until next time Oxford.

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One of the Emporor Heads outside the Sheldonian Theatre in Oxford. Apparently, no one knows exactly who or what they are meant to be. My favourite theory is that they represent a history of beards. This guy at least looks pretty Greek to me…

3D and 4D Digital Monitoring of Sea Defences at Skara Brae

A while ago, I was asked by the Climate Change team at Historic Environment Scotland to write a short article on the work we did at Skara Brae this April, to be featured in the HES Climate Change blog. The blog is a great resource on various topics relating to the effects of climate change on the historic environment.

The article explained how laser scanning is being used to monitor the condition of the protective sea wall that has defended the Neolithic village for more than 80 years. In light of growing concern for the effects of climate change on coastal heritage, our work on the site is of particular importance in ensuring the long-term survival of Orcadian heritage.

The blog article was also a good opportunity for me to produce images from the database, which is still being processed. For more details on our work at Skara Brae, please read the article here.

3d moisture mapping at Skelmorlie Aisle

The 3D moisture mapping project is an attempt to develop processes for better visualisation and understanding of microwave moisture data, used to analyse dampness and water ingress in historic buildings. A newer version of the method was the subject of my presentation at the HES Conservation Research Showcase event last month. This version of the process involves mapping orthographic moisture maps of different surfaces (floor and interior elevations) directly onto point cloud data using Leica Cyclone. It is a reasonably quick and reliable method for applying colour-coded moisture data onto the point cloud, which can then be used as a basis for renderings, animations, etc. More details on the process to follow…

Coastal erosion monitoring at Skara Brae, Orkney

I have just returned to Edinburgh after an adventurous 4-day fieldwork trip to Skara Brae in Orkney, using laser scanning to determine the degree of coastal erosion on the Bay of Skaill around the neolithic settlement. To do that, a 3D survey of the site is conducted every 2 years and the data compared to determine the changes in the position and shape of the sand dunes forming the edge of the coast.

 

Due to limited time on site (and adverse weather conditions) 2 teams were working at the same time on the beach using the Leica P40 and C10 scanners and survey control using traverses and GPS. The C10 was used to scan the top of the dunes on the east of the village, in a traverse tying to scans along the beach (see photos).

 

The weather was not in our favour (low temperatures and high winds), but the work was completed in time. The data is being processed at the moment and the comparison with the 2014 scans will reveal the degree of erosion on the coastline.

Edinburgh Castle Palace Scan2BIM

March was a very busy month for the Digital Documentation team. Much of our time has been spent laser scanning the Palace block at Edinburgh Castle for a scan-to-BIM case study by Historic Environment Scotland. The idea is to create an BIM or AIM (asset information model) of the Palace block to be used for the subsequent management of various aspects of the building’s function.

Laser scanning is the primary method of survey for the building fabric (architectural elements), but it will be supplemented by additional surveys. The laser scanning survey is guided by the Asset Information Requirements document, which specifies areas of interest/priority and required levels of detail per category. The goal is to achieve 100% coverage of both exterior and interior spaces.

According to the AIR document, some of the least “glamorous” areas of the building, such as boiler rooms, electrical cupboards, switch rooms, and attic spaces have a higher priority for the model than some of the high-profile exhibition areas for example. This means that a lot of our time on site has been spent crouching inside tiny cupboards and boiler rooms surrounded by pipes and cables. These areas tend to be confined spaces full of equipment, difficult to navigate (or even to set up the scanner) and usually need a lot of scans to get good coverage and avoid shadows or data voids. Although we do not have to scan every last surface inside a boiler room, the AIR document makes it clear that at least the general dimensions and position of all equipment will need to be visible in the resulting point cloud.

In this project, multiple scanners have been used. The Leica P40 produces clean, crisp data with considerably less noise over great distances, but is very difficult (or impossible) to set up inside any of those tight cramped spaces. Therefore, all the cupboards, boiler rooms, switch rooms, etc were scanned with a Faro Focus 3D, which has a much shorter range and produces noisy data, but is significantly smaller, a lot lighter, and can easily fit inside any of those spaces. The same scanner was used in the attics, which were accessible through a folding ladder and generally very tight spaces, difficult to navigate when carrying any sort of equipment. Using the Faro proved very successful in those areas (on a photographic tripod or sitting directly on the floor).

Laser scanning an attic at Edinburgh Castle Palace with a Faro Focus 3D. Ghostbusters uniform to be worn at all times, as per the risk assessment report. 

Registration of the data has been progressing along with the field work. More on that to follow very soon…