To Do: Migrate

Download this episode as an mp3 or subscribe via iTunes.

TRANSCRIPT INTRO: Welcome to the Preservation Technology Podcast. The show that brings you the people and projects that are advancing the future of America’s heritage. I’m Kevin Ammons. And today we join NCPTT’s Jeff Guin as he speaks with Carla Schroer of Cultural Heritage Imaging. The non-profit organization recently used a PTT Grant to hold a workshop on 3D digital rock art documentation and preservation.

Guin: Carla, Thanks so much for being on the podcast. Why don’t you just start by telling us about your organization, Cultural Heritage Imaging.

Schroer: Cultural Heritage Imaging is a non-profit organization that’s based in San Francisco, and we drive both the development and the adoption of practical digital imaging solutions for people that are passionate about saving humanity’s legacy. And so we do that by working with museums and archeologists and sites to help them develop imaging technology. And we also collaborate with technical organizations to help develop technology and methodology.

Guin: What are some of the other organizations you work with?

Schroer: So we collaborate with a lot of people in all of our projects, and for this particular project, we just had a tremendous group of collaborators. We worked with the National Museum of the American Indian, which is part of the Smithsonian, the Presidio Archeology Program and a couple of archeologists from U.C. Berkeley — Meg Conkey and Ruth Tringham. And on the technology side, we had support from one of the senior researchers at Hewlett Packard Labs, computer graphic researchers at Princeton University, and also the University of California Santa Cruz. So that was our primary group of folks and then the number-one group I want to bring out, who co-taught the workshop with us, were photogrammetry experts at the Bureau of Land Management National Operations Center in Denver. And that is Tom Nobel and Neffra Matthews, who have been doing photogrammetry for a very long time. It was great to have their expertise on the project as well.

Guin: Let’s step back for a minute and discuss how you came up with the idea for the workshop.

Schroer: We’ve been working for some time with a number of technologies, but one of the key technologies is called Reflectance Transformation Imaging or RTI. And RTI is a really great technique for bringing out very fine surface details of an object. Reflectance Transformation Imaging allows you to create a very detailed model of the surface of an object, and you do that by taking a sequence of digital photographs with a light in different positions around the object. And then that’s processed on the computer to a new type of image that generates the surface information based on how the light reflects off of the object. And so once you have it in the computer, you can dynamically relight the object from any angle as well as apply some mathematical enhancements to bring out very fine surface details that could be difficult or even impossible to see with the naked eye.

We have used it successfully in a couple of different rock art sites, and we have presented some of our work at the American Rock Art Research Association Conference. There was a lot of interest among the rock art community in this technology. So that combination, with us putting together some training programs a little more focused in the museum community, really just brought this idea together. But we also included photogrammetry. And photogrammetry is a technique where you take overlapping images, and from those overlapping images, you can generate 3D points in space. And we brought in experts in photogrammetry from the Bureau of Land Management National Operations Center that have been using photogrammetry for really more than a decade on a lot of different projects, including rock art. So it was great to have them involved. Right now we can shoot a Reflectance image and a photogrammetric sequence of a rock art panel and get two different results. One of the future directions we’d like to do is put those two together so that you can have the reflectance image together with the 3D model of the surface. And we have some early research that is very promising in that area.

Guin: Tell us about how the workshop went.

Schroer: First, let me talk a little more broadly about the project. The project really has two components. So the first component was the workshop, and we held that in July. And then the second component, which we are working to complete right now, is to develop materials to be freely available on the web. So more focused on do-it-yourself kinds of materials, to make people aware of the technologies, see how it can be used and to start trying it themselves. So the first component, the workshop, we put out the word through various sources. Meg Conkey is the currently the president for the Society of American Archaeology. She gave out fliers at their last conference, and then various people we had met from different sources and we put out a call and an application process. And we were able to fill the workshop. We had 14 participants plus the instructors for the two full days that it went. It was pretty intense. We were covering an awful lot of material in two days.

The first day we spent a lot of time just showing people examples of results both with photogrammetry and with the reflectance imaging, and going through what it takes to shoot the stuff. So the people from Cultural Heritage Imaging did the reflectance imaging part and the BLM folks did the photogrammetry part. And we walked through what it actually takes to shoot the stuff. And then the second day, the focus was more on actually shooting some objects. So we had set up to work outside and to work with some material and to give people the chance to actually be part of actually shooting the material and then looking at the results. We also spent a little bit of time talking about where this technology is, where we see it going in the future; kind of what’s upcoming. And we had a tremendous conversation that was led by Michael Ashley with the participants to really get a lot of feedback about what are our barriers for adopting this technology in the field, how did folks see it being used. It was really great to have the technical people and some of the target audience really share what makes it valuable, what’s getting in the way and actually we are making a podcast of that discussion that’s going to be available as part of the materials that we are going to be producing.

Guin: Tell us about some of those conversations that you had during the workshop, especially about the future of this technology.

Schroer: We had a great mix of folks. The people who came were largely in the rock art field. We had people from all over the U.S. and a couple from the U.K., as well, but we also included some people on the technology side, including a researcher, a professor from U.C. Santa Cruz, who’s been helping develop some of the technology. And so that was really useful to create some conversations around both sides of that. We also had some folks interested in using the technology not specifically for rock art, but a little more broadly for other kinds of material. And, in one case, for early American grave stones, which obviously has a lot of shared qualities with rock art.


So, in terms of the future work, the technology today is something people can learn to do themselves with off-the-shelf digital cameras. You need a good tripod, you need a few things to get it done, and you need to learn how to shoot an image sequence. And then there is free software that you can get that will allow you to process it and look at the results for the reflectance imaging.


Where we’re going is, we’re trying to raise money, and we have some proposals out to further that the software, to make it more robust, add features that people are asking for, and also to add, well, really, there’s this whole field called computational photography, which is based on taking image sequences and processing them for various kinds of results, and that field in computer graphics research is just taking off. So, there are a number of ways that the reflectance imaging we see going into the future can be married with techniques like photogrammetry or structured light scanning could be used with techniques that are being developed to capture more accurate color because the sensors in a standard digital SLR are not great at color accuracy.


And then also a proposal that we have out is to do something that we call “automatic rendering” that allows you to take these imaging sequences with light in different positions and generate technical drawings with very different drawing styles that the user can choose from. This data that’s collected, is the same kind of data that’s collected to do reflectance imaging. So we’re very excited about that because you can take a data set one time, process it two different ways and get two very different kinds of results depending on what questions you’re trying to answer or how you’re trying to present your information to others.


Guin: Are you involved with actually coding software?


Schroer: Our organization is small, and we collaborate. We have technical expertise and project management and a little bit of coding expertise, but by and large, the real software development is happening in university research groups that we partner with. We partnered with the National Research Council in Pisa, which has a team that is very focused on cultural heritage work, and has worked with us extensively on a project funded by the Institute for Museum and Library Services. There’s a team at the University of Minho in Portugal, and we’ve done some work with Warwick Digital labs. The tool I was just talking about, the automatic rendereing, that’s a project that we have proposed in conjuntion with Princeton University, so the primary code development would be happening at Princeton.

Guin: It seems like these things you’re developing could be used in other applications as well. For a larger audience beyond just archeology. Have you explored any of that? You’re in the “tech capitol of the world,” pretty much.

Schroer: Our focus is really about finding solutions that solve problems in the cultural heritage and natural sciences area, so we do have a focus on museums as well as on archeologists and archeological sites. There are potential other directions that people could go with some of these techniques, and where we’ve seen people doing other kinds of work we’ve tried to partner with them. One thing we’ve found is that a lot of the tools that are out there are either very early in the research phase so they’re not quite ready for people to do themselves, like the actual techniques and methodology aren’t well described or you have to be a propeller head to actually figure out how to do it.

And so what we try to do is figure out what of those things are really interesting, compelling and solve problems in the field, and how do we get those things developed and get them in people’s hands where they can do it them themselves. Because one of the core principles of our organization is that we are a “teach a person to fish” model. So for technology to get out there and really get used that helps in imaging, people have to be able to do it themselves. If they have to hire a specialist to do it, then only a very tiny fraction of the work that needs to get done will get done. If people can do it themselves and it fits in their regular work flow and it solves problems that they already face everyday, then we think it will get adopted and used. And so that is a real driving force for us for what we choose and what we try to get funded and how we try to develop it and get it in people’s hands.

Guin: How do you seek out those people who are good potential partners?

Schroer: What we did was we focused vary early on on people that were working on how to capture information about the real world from photographs. So that’s a fairly narrow band actually. And our president, who also operates as our chief technology officer, has been going to CIGGRAPH, which is the big computer graphics conference, for many years. And so really through just starting to make some relationships with people there; he was invited on a panel many years ago that opened some doors that talked to people additionally. So really looking for people in this field that also have an interest to applying it to cultural heritage or natural sciences. And what we found is that folks really want to collaborate. They really want to find ways that their work can get used in the real world, and the kinds of material that we are working with is really exciting to everybody. So the hard work initially was finding the right people that had the right background, but getting them excited about working with rock art or working with ancient ceramics or coins or whatever it is, that’s been the easy part.

Guin: Alright, well is there anything else you want to add about the project or maybe your future directions for Cultural Heritage Imaging?

Schroer: We are a small organization with a big vision, and how we do that is through collaboration and finding the right collaborators is really key. I have been talking a little bit more on the technology side, but we have really important collaborators on the cultural heritage side as well. So for us, all the projects need to have both sides represented. You don’t want to just build tools without having the users that you’re targeting them for involved and helping to influence them and so forth. So we are getting close to posting the materials from this project and then we got kind of a related project grant from the Samuel H. Kress Foundation to develop materials specifically for the museum conservation audience that are based on the reflectance imaging.

And so we are partnering with the Fine Arts Museums of San Franciscoon that one. We are going to be shooting some objects from their collection, and interviewing their conservators about specific conservation issues and how they see these tools helping them solve conservation issues with the materials. So we are continuing to do training and trying to spread the word — that’s one side. And then the other future direction is trying to bring in the funding to try to do the related tools — the adding these features that we have been talking about — marrying this kind of technology with photogrammetry and 3D. And there is just a whole range of possibilities out there and lots of great people that are willing to work on it if we can get the funding institutions to give us support. And we do have a couple of big proposals that are out there right now.Guin: Carla, thanks so much for being on the podcast.
Schroer: Well thank you very much for the opportunity.

OUTRO: And that was Jeff Guin interviewing Carla Schroer. If you’d like to learn more about this project, you can access the podcast shownotes at the National Center for Preservation Technology and Training website. That’s at That’s it for this edition of the Preservation Technology podcast. Until next time, goodbye everybody.

Related Links:
CHI-NCPTT Grant Project Page
CHI-NCPTT Grant Photos on Flickr

National Center for Preservation Technology and Training
645 University Parkway
Natchitoches, LA 71457

Email: ncptt[at]
Phone: (318) 356-7444
Fax: (318) 356-9119