Filed under: Commentary, Guest Blogger, News, On Location, Technology | Tags: ancient footprints, photogrammetry, Preservation
Sarah Duffy, PhD is a Postdoctoral Research Associate at the University of York in the Department of Archaeology. In May of 2013, after a series of storms, ancient footprints were revealed on a beach near Happisburgh (pronounced “Hays-boro”) on Britain’s east coast in Norfolk (see a 6-minute video). The footprints were fragile and washing away a little day by day. Sarah was called to the site by Dr. Nick Ashton, Curator of Palaeolithic and Mesolithic collections at the British Museum, to document it. Here is our interview with Sarah about this dramatic discovery.
CHI: Sarah, can you tell us how you got involved in the project and what you found when you arrived?
Sarah: It really came down to good timing and an opportune meeting of research colleagues. When the footprints were discovered, I had just begun working with Dr. Beccy Scott at the British Museum on a project based in Jersey called “Ice Age Island”. Beccy and my partner, Dr. Ed Blinkhorn, another early prehistoric archaeologist, have collaborated for many years, and he introduced us. During the week of the discovery, Beccy happened to be at a research meeting with Dr. Nick Ashton and suggested that he get in touch with me about the Happisburgh finding.
The next day, I received a call from Nick who asked if I would be able to take a trip to Norfolk to record some intertidal Pleistocene deposits at Happisburgh. Having just completed my PhD thesis (a “dissertation” in US currency), I was up for an adventure and ready to take on the challenge, and so I was on a train to the southeast coast two days later.
My first plan of action was to figure out how on earth you pronounced the name of the site! The next step was to figure out what equipment I would need to have available when I arrived. This proved somewhat challenging, as I had never visited the Norfolk coast, and it seems quite humorous in hindsight that one of the pieces of kit I requested was a ladder.
All of this said, the urgency to get the site photographed became clear when I showed up one very rainy afternoon in March. Standing on the shore, I felt very privileged to have been invited to record such an important set of features, which disappeared within only weeks of their discovery by Dr. Martin Bates.
CHI: What were your goals in the project and why did you choose to shoot images for photogrammetry? Can you tell us a little bit about your approach?
Sarah: Since I wasn’t sure what to expect when I reached the site, I took both photogrammetric and RTI kit materials with me. I intended to capture the 3D geometry of the prints with photogrammetry and subtle surface relief with RTI. However, when I arrived, both the weather and tidal restrictions limited the time we were able dedicate to recording. I therefore focused my efforts on photogrammetry, which proved a flexible and robust enough technique that we were able to get the kit down the cliff side in extremely challenging conditions and capture images that were used later to generate 3D models.
Based on the looming return of the tide and the amount of time required to prepare the site, our window of access was quite small. While I took the images, aided by Craig Williams and an umbrella, the rest of the team battled the rain and tide by carefully sponging water from the base of the features. As mentioned, I originally intended to capture images from above the site using a ladder. However, as the ladder immediately sank into the wet sand, I was forced to find other means of overhead capture: namely Live View, an outstretched arm, and umbrella. There was just enough time to photograph the prints, loosely divided into two sections, using this recording approach before we had to retreat back up to the top of the cliff (and to a very warm pub for a much deserved fireside pint!).
CHI: When you got back to your office, how long did it take you to process the images, and what software did you use?
Sarah: Originally, I used the Standard Edition of PhotoScan by Agisoft, later returning to the image set in order to reprocess it with their Professional Edition. PhotoScan’s processing workflow is relatively straightforward, and the time required to generate geometry is somewhat dependent on the hardware one has access to. The post-processing of the images was by far the most time-consuming component of the processing sequence. Since the software looks for patterns of features, there was a substantial amount of image preparation that needed to be completed first, before models could be produced. For example, rain droplets on the laminated surface that contained the prints needed to be masked out, as well as the contemporary boot prints that accumulated in the sand that surrounded the site throughout the image sequence.
CHI: How were the 3D models you produced used by the other archaeologists involved with the site?
Sarah: Once the models had been generated, the rest of the team, including Nick Ashton, Simon Lewis, Isabelle De Groote, Martin Bates, Richard Bates, Peter Hoare, Mark Lewis, Simon Parfitt, Sylvia Peglar, Craig Williams, and Chris Stringer, wrote the paper on the results. Nick Ashton and Isabelle De Groote closely analyzed the models of the prints in order to study size, movement, direction, and possible age of the early humans who might have created these features. Isabelle later worked with the 3D printing department at Liverpool John Moores University in order to have one of the digital models printed.
CHI: Since the footprints were washed away, your images are the best record of the site that exists. Are the 3D models accessible? What will you do to preserve this material?
Sarah: Coverage of the footprints, including excerpts of the digital models that I generated and the 3D printout, can be viewed at the Natural History Museum exhibit in London, Britain: One Million Years of the Human Story, which closes September 28th. Findings from the analysis have also been published in PLOS ONE, an open-access, peer-reviewed scientific journal.
As mentioned, when I visited the site last March, I had hoped to undertake a RTI survey. Although conditions on the day of recording did not permit multi-light capture, I have since been able to generate virtual RTI models that reveal the subtle topography of the prints. An excerpt of one of these models can be viewed on my website.
Additionally, the research team, in collaboration with the Institute of Ageing and Chronic Disease at Liverpool, are currently working on extracting further information from the image set. Findings from this work will be made available in the future. Once analysis is complete, the images and resulting models will be archived with the British Museum.
CHI: Thank you for your time, Sarah, and what a great story!
Sarah Duffy has been collaborating with Cultural Heritage Imaging (CHI), including taking CHI’s training in Reflectance Transformation Imaging (RTI) and working with the technique since 2007 while she was a graduate student in Historic Preservation at the University of Texas at Austin. Sarah authored a set of guidelines for English Heritage on RTI. During her doctoral work, she also began to apply her imaging skills in the area of photogrammetry.
We often get asked why we set up CHI as a nonprofit. I can understand the question, because we are doing some pretty high-tech projects, and we work with a number of famous institutions whose names people recognize, perhaps making us seem grander and better endowed than we really are.
My background is in computer science, and I worked in software product development for years. At some point I had decided I wanted to apply my skills to “make the world a better place.”
Mark had similar leanings. His background was in philosophy and studio arts, primarily sculpture. He began looking into 3D modeling and laser scanning in the late ’80s, and by the mid-1990s he was teaching the subject. I had a minor in sculpture and ceramics. We both loved history, art, and archaeology. We had met in 1983 and married in 1989. By the late ‘90s, digital cameras were coming into play, and structured light scanning technology was becoming available for 3D capture.
Mark and I got fired up. We started seeking out people who worked in archaeology or museums to better understand their needs. Our first questions were: What did they wish to do that they couldn’t do in the field? Could the emerging imaging technologies help them in research and creating access to more cultural material?
Over time, and as we learned more, the seeds of CHI took root in us. By 2002 we began to imagine how existing and emerging technologies could be used to create robust, powerful, low-cost tools to document cultural heritage objects and collections. And so we formed Cultural Heritage Imaging.
Today, well over 10 years after we started our nonprofit, we remain committed to fostering the improvement, availability and adoption of these documentary tools. We see them as “democratizing technology,” because our vision is founded on making cultural and natural science techniques and materials available to people all over the world.
Many of our collaborations are only possible because we are a nonprofit. “Pulling on the same oar” for humanity’s benefit is a powerful reward. Our nonprofit status is attractive to top researchers and organizations who are drawn to work on and contribute to saving history. These experts are sometimes willing to help for very little money, and occasionally they even raise their own grant funding. Our open source approach is inclusive and allows others to add new features to the tools, moving the whole community forward.
The downside of this commitment to openness is there is a constant need to raise money, and much of the money we get is earmarked for specific purposes. It’s great to get funding for a project we want to do, like the National Endowment for the Humanities Start-up grant we recently received. However, many of the requirements of running the organization and fostering community growth are not covered by the grant funds.
Funding is critical! We get a lot of volunteer support, we work with students and professors, we get discount rates from many professionals. We are extremely grateful for this help and it makes an enormous difference. At the end of the day, we rely on the good graces of our donors to keep us, and the community, going.
Filed under: Commentary, News | Tags: Anna Ressman, cultural heritage imaging, Digital Imaging, Oriental Institute Museum, Reflectance Transformation Imaging, RTI, Technology, University of Chicago, visualization
Recently Anna R. Ressman, Head of Photography at the Oriental Institute Museum, University of Chicago, shared a compelling article with me, and now I’m sharing it with you.
Here is a link to the Oriental Institute newsletter (PDF), which contains the article entitled, “Behind the Scenes: Museum Photography at the Oriental Institute.”
Anna describes the process in which five very different artifacts are documented, each with a unique challenge. And yes, you guessed it, one of those artifacts was documented using the RTI highlight method.
Documentation of the Egyptian stele “was photographed with a method of computational photography called Reflectance Transformation Imaging (RTI).”
Anna concludes the section on RTI with these insights: “RTI files can be created in such a manner that pixel data is analyzed to show specular information rather than color data, which can reveal more information about the surface of the object than color data alone (figs. 3–4). As you can see, the inscriptions on the stele are much clearer in the specular-enhancement PTM image (fig. 3), even though the studio photograph (fig. 4) was taken using a macro lens under controlled studio lighting. The former may not be as aesthetically pleasing as the latter, but it reveals much more information than would normally be seen — and that is just a single image out of a series of forty-five.”
Be sure to download the complete article and check out the rest of the newsletter as well.
Anna R. Ressman is Head of Photography at the Oriental Institute Museum, University of Chicago, USA. Anna is also a freelance photographer and a fine artist.
[Photos by Anna R. Ressman/Courtesy Oriental Institute Museum, University of Chicago]
Filed under: News, Technology | Tags: 3D laser scanning confocal microscopy, Attic pottery, Contour line, Greek, Greek vase, Magna Graecia, Red-figure vase, red-figure vases, Reflectance transformation imaging (RTI), relief line, RTI, Vase painting
Entitled “Evaluation of the relief line and the contour line on Greek red-figure vases using reflectance transformation imaging and three-dimensional laser scanning confocal microscopy,” the article examines “…the relief and contour lines on a group of ancient Greek red-figure vases and vase fragments.”
Paula and Philip, both of the Worcester Art Museum in Worcester, Massachusetts, USA, describe how they deployed “… two surface examination methods – reflectance transformation imaging and three-dimensional laser scanning confocal microscopy” to “… characterize the lines and answer questions regarding tools, techniques, and production sequence used by Greek vase painters.”
Their work is interesting and empirical, with numerous examples that yield detailed observations about the tools and techniques used to create the decorative features on vases and vase fragments, with a particular emphasis on relief and contour lines.
Download the entire PDF:
Filed under: Commentary, News, Technology | Tags: Antikythera Mechanism, PTM, RTI
Tom is a long-time friend of CHI and has been an adviser and collaborator on many projects. Tom is best known as the co-inventor (with Dan Gelb) of Polynomial Texture Mapping (PTM) in 2001 while he was at HP Labs. PTM is the first form of Reflectance Transformation Imaging (RTI).
Tom has had a long research career in the fields of computer graphics and computer vision as demonstrated by his many published papers. He has frequently applied this work to cultural heritage material, most notably as part of the team that deciphered the Antikythera Mechanism. This groundbreaking work was featured in the NOVA documentary “Ancient Computer”
Filed under: Commentary, News, Training | Tags: glossary of terms, photographic terms, technical terms
Over the years we have received a lot of requests for a glossary of terms used in RTI, and we are happy to announce that a new “Glossary of Photographic and Technical Terms for RTI” is available on our website! It includes photographic terms you need to know for RTI, like “Depth of Field,” “Color Temperature,” and “Aperture.” Also included are technical terms from computer graphics and computer vision like “BRDF,” “Fitting Algorithm,” and “Phong Lighting Model.” We have included terms for file formats like DNG, XMP and TIFF, along with basics in multi-spectral imaging such as “Infrared” and “Ultraviolet-induced Visible Fluorescence Photography.” We also included terms related to keeping good process history in your RTI work, including “Digital Lab Notebook,” “ICOM-CIDOC,” and “Empirical Provenance.” We did our best to adapt the definitions for RTI users, and we also included a few notes and recommendations on photographic settings.
As always with our work at CHI, this project was a collaboration. Lots of folks offered terms they wanted to see defined, and some provided definitions. We especially want to thank Tom Malzbender for definitions for many of the technical terms; Yosi R-Pozeilov for sharing his extensive glossary of photographic terms; and technical writer Judy Bogart for pulling it all together. And finally, we had a wee bit of funding for this work from the Institute of Museum and Library Services, as part of a larger grant project in their 21st Century Museum Professionals grants. Much of the work was done through volunteer efforts.
If you value this kind of documentation, along with the free open source RTI software, please consider making a donation to help support it.
What an encouraging way to end 2013: our Annual Giving campaign raised almost twice as much as the previous year! Our donors’ continued support of Cultural Heritage Imaging (CHI) is both touching to us personally and vital to our mission.
Our donors’ gifts enable CHI to develop innovative digital imaging tools and practices and disseminate them to experts and students all over the world. Specifically, this financial support helps us complete software projects, like our recent release of the updated RTIViewer 1.1 and our update to RTIBuilder (coming soon). Donations also fill in the gaps in our funding so we can refine our training materials and develop new instructional programs. We are currently working on a new class in collecting high-quality, accurate, 3D models using a digital camera (stay tuned to learn more about that). CHI also engages in a variety of projects with museums and historic sites, and donor contributions allow us to keep our fees as low as possible for these projects.
In the long run, financial gifts support our many users around the globe who are working on cultural documentation in vital fields such as archaeology, computer imaging, museum and library sciences, natural sciences, and data archiving.
We are deeply grateful to our donors for their generosity.
–The CHI team