Tag Archives: photogrammatery

Adventures in Digital

Hello, my name’s Rose and I’m a student at University College London, where I’m studying for an MA in Digital Humanities. As part of my course I spent ten weeks completing a placement at the BPMA, working with Martin, the Head of Digital, and Rachel, the Digital Media Manager.

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One of the main projects I worked on involved creating 3D models of items from the museum collections using photogrammetry, which I wrote about previously. I’d already learnt a little about the techniques involved, and this project gave me some valuable practical experience putting those lessons into action. It was amazing to be given access to photographic equipment and modelling software, and to have the freedom to experiment with different techniques. I benefitted a lot from the Digital Team’s photography knowledge, and I’m very proud of the models our experiments produced! Check them out here: https://sketchfab.com/postal

3D model of Stamp Snake. You can manipulate the model here: https://sketchfab.com/models/8c78b277cb0c4b2c9a3901970c94e2f4

3D model of Stamp Snake. You can manipulate the model here: https://sketchfab.com/models/8c78b277cb0c4b2c9a3901970c94e2f4

Another project involved digitisation work of a different kind, scanning historical maps and documents. A highlight was handling documents related to the sinking of the Titanic, and learning about the Post Office and Mail Room which were on board. This really made me appreciate how unique a resource the BPMA’s collections are.

I also digitised the negatives of maps depicting different postal routes; it was fun to take a small piece of film and digitise it to reveal the detailed and colourful illustrations it held. Digitisation can help preserve the museum and archive collections and make them more accessible; it’s exciting to think these images could help engage people in the story of Britain’s social and communications history.

Newly digitised map ready if needed for The Postal Museum!

Newly digitised map ready if needed for The Postal Museum!

I really enjoyed my time at the BPMA as I was given the opportunity to develop so many new skills and to work on more projects than I have space to mention! I’m interested in seeing how digital technologies continue to play a part in the BPMA’s work, and especially in the new Postal Museum. My placement gave me a valuable insight into life in the museums and heritage sector, and I’m extremely grateful to everyone I met who took the time to talk to me about their role.

Experiments in Photogrammetry

Recently we experimented with producing a set of 3D models of items from the collection using a process called photogrammetry. Rose Attu, a Digital Humanities MA Student from UCL, who’s currently on placement at the BPMA, talks us through the process.

To create a 3D model a series of overlapping photographs of a single object are taken from different positions, and then a piece of software is used to triangulate the coordinates of each image and align them, reconstructing the whole object in 3D. With each shot, the digital camera also records metadata including the focal distance between the lens and the object; this enables the software to recreate the position the camera was in when each photo was taken.

Curator Emma Harper holding the stamp snake

Curator Emma Harper holding the stamp snake

The objects we chose were the prosthetic Postman’s Hand and the Stamp Snake. An object covered in a repeating pattern, or one without any distinguishing features at all, will affect the software’s ability to rebuild the depth of an object. Both these objects have plenty of distinctive features, so the software could detect the details from photo to photo and build accurate models without distortions.

Postman's prosthetic hand being photographed

Postman’s prosthetic hand being photographed

Our first object was the Postman’s Hand. Once it was in frame and in focus, and evenly lit to avoid shadows, we could begin the capture process. To capture our objects from multiple angles we used a turntable to rotate them through 360°. The turntable was also covered in a distinctive image, which gave the software more common points to identify. The turntable was edited out at a later stage, so that our final models were just of the hand and the stamp snake.

Stamp snake being photographed

Stamp snake being photographed

On average it took 30 photos to complete one rotation, after which the camera was raised for a second sequence capturing the object from a higher angle. For more consistent results we kept the camera settings the same until a rotation was complete, and used a tripod and remote shutter release to keep the camera static. We output the raw image data as a set of TIFFs and corrected the white balance, and then our images were ready to be transformed.

Based on the estimated camera positions and the details in the images, the software built a point cloud, which is essentially a 3D model made up of dots. It then added a more detailed polygonal mesh layer representing the object surface. The final step was to add the textures; because we photographed our objects in high resolution, even the tiniest details were visible on the final models.

Snapshot of the 3D model of the stamp snake. Manipulate the model on Sketchfab.

Snapshot of the 3D model of the stamp snake. Manipulate the model on Sketchfab!

We were surprised with how little effort and technology it took, and the results were fantastic!  For our set-up we used:

  • Lazy Susan turntable with a nonrepeating pattern on it
  • Digital SLR camera and tripod
  • Light box or tent
  • Studio lights or some source to help get rid of shadows
  • Photogrammetry software – we used Agisoft which was great and you get a 30 day free trial

Have a go yourself– we would love to see your models!

– Rose Attu

Exploring 3D technologies at the BPMA

The last 12 months have been exciting for the Digital team here at the BPMA. Our Share Academy/London Museums Group funded project, From Vault to View, which partnered us with Mona Hess from UCL’s Civil, Environmental and Geomatic Engineering Department, has given us both a lot to do and to think about. The project has now come to an end, but it has increased the knowledge we now have of 3D technologies, and encouraged us to do much more.

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George V Die for striking leads. 1½d postage British Empire Exhibition, 1925

The aim of the project was to test different methods of capturing objects in 3D. Working with our little-viewed objects, Mona tried a variety of techniques to see what would produce good 3D models and what wouldn’t. The objects chosen posed real challenges: many were made of bright metals, which makes them difficult to capture using laser scanning or photogrammetry techniques; some were complex shapes, such as a flintlock pistol; while others had such a lack of detail making them difficult to measure and recreate as 3D computer models.

So what did we get out of it? Before the project we knew very little about how 3D

imaging worked. We felt the buzz around these technologies, such as 3D printing, but had little idea of how these things were created or how they might be used. All we really knew was that we had a rich treasure of 3D objects that no-one could really access physically in a satisfactory way.

By the end of the project, the BPMA had purchased photogrammetry software which has enabled us to try 3D imaging for ourselves – and the results are extremely promising. These techniques can be learnt by our staff and employed to create 3D models of items in the museum collection for exploration by the public.

This new-found knowledge, though still fairly elementary, has given us confidence to explore other uses for 3D imaging. In December 3D experts, ScanLab Projects, spent a week scanning the work depot, platforms and tunnels of Mail Rail which we will be opening to the public in 2016 as part of our plans for The Postal Museum. The results are truly astounding and we hope to show them in the near future.

Scanner capturing Mount Pleasant platform

Scanner capturing Mount Pleasant platform

Beyond all this, the project has given us an opportunity to revisit the objects and see them afresh. Although we weren’t able to obtain good 3D models of objects such as the large printing plates and the rollers, we did get excellent images of a number of dies using a technique known as Reflectance Transformation Imaging [RTI]. We also obtained an excellent laser-scanned 3D model of the Machin cast of Queen Elizabeth II – a truly unique and iconic object. The fruits of these experiments will eventually be made available via our website and online catalogue as we integrate the technology.

Plaster head of HM the Queen made by Arnold Machin for new definitive issue of stamps, third version (POST 118/5373)

Plaster head of HM the Queen made by Arnold Machin for new definitive issue of stamps, third version (POST 118/5373)

-Martin Devereux, Head of Digital

From Vault to View: Scanning trials

It’s been an exciting month for those involved in our 3D digitisation project, as it moved into the trial stages. A while back we shared what objects we selected for the scanning. A couple of weeks ago, Mona Hess, the project’s 3D digitisation specialist, visited the BPMA to undertake trials of low-cost scanning and photogrammatery techniques. 

In conjunction with our Conservator, Krystyna Koscia, Mona tested the application of a cyclododecane spray – a substance which, when applied to objects, makes them easier to digitise with a laser–scanner.

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Cyclododecane spray applied to test objects.This substances evaporates shortly after application and makes the object easier to scan with a laser.

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Mona applies the Cyclododecane spray to test objects as Krysia looks on.

The main event of the day was the photographing of a large printing plate against a target background, from which photogrammetric measurement will be taken to create a 3D map of the plate. You can find out more about photogrammetry and other techniques we will be using in this post. The plate was also scanned using a low-cost laser scanner, to obtain a rough geometry of the plate itself. Other objects were also photographed and scanned, including a die, an embossing die, a slogan die and a roller.

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Martin examines the plate.

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Mona standing on a stool for photogrammetry imaging.

You can check out the preliminary 3D model of the plate online now, and manipulate the model. We promise that the final results will be more detailed!

Trials continue in May, when Mona will be using the laser-scanner at UCL to scan other key objects from the collection.

-Martin Devereux, Head of Digital