3D Visualization for Archaeology and Open Educational Resources (OER)

By Chris Givan (JPPM Digital Education Coordinator) and Noah Boone (JPPM Digital Education Content Developer)

Photogrammetry is a technique for creating 3D models, which is increasingly common in cultural and research contexts. At Jefferson Patterson Park and Museum, we’ve been using photogrammetry to create models of archaeological sites and artifacts that may not be accessible to visitors or which may be of interest to folks for whom the park is inaccessible because of its location. Thanks to a project funded by an IMLS CARES Act Grant for Museums and Libraries, we’ve begun to provide photogrammetric models as Open Education Resources (OER) and are exploring how to replicate, at home or in the classroom, the experience of visiting archaeological sites or interacting with artifacts.

Photogrammetry software creates 3-dimensional data by analyzing photos taken at multiple angles around a subject. This can be done using a variety of programs, both proprietary (Agisoft Metashape, Reality Capture, etc) and free-and-open-source (Meshroom, MicMac, etc). This process requires a high degree of overlap between photos by moving the camera or subject in small increments, such as with small rotations on a turntable. The programs identify like points between these photographs and construct a 3-dimensional point cloud (below, left). This point cloud can then be further processed to create a 3-dimensional model that can be viewable and distributable for a variety of purposes (below, right).

Side-by-side comparison of a point-cloud, left, and a mesh, right, in Agisoft Metashape. The rectangles surrounding and overlapping the image are Agisoft’s estimation of where the camera was when a corresponding photograph was taken.

Photogrammetry is incredibly scalable and results are primarily dependent on camera equipment. This method can be used with drone photography for creating models of landscapes and buildings and macro-photography can even be used to create models of insects. Photogrammetry offers many exciting possibilities to look at things in a different light and look at things at angles or scales that would otherwise not be possible.

We’re using our models from photogrammetry in a number of ways. First, we will be making models available as resources for anyone with a use for them on JPPM’s SketchFab page. SketchFab is a website for hosting and sharing 3D models, which includes contributions from cultural institutions around the world. We particularly like SketchFab because museum accounts allow you to restrict downloads if dealing with artifacts or sites for which you have received permission to make the models viewable but not redistributable.

Below are two objects on SketchFab that we have scanned with photogrammetry. The model of the site known as Sukeek’s Cabin includes annotations, an additional benefit of using SketchFab that allows us to add educational content directly to models.

However, publishing on SketchFab does limit interactivity and we want to replicate some of the physicality of visiting sites or seeing artifacts up close. There are also practical limits to what can be included in annotations. To achieve more interactivity we’re using the service Genial.ly. SketchFab models can be embedded directly into Genial.ly “microsites” with rich media or additional interactivity. Below, we used photogrammetry to model an “alphabet plate” found at Sukeek’s Cabin. We’ve used Genial.ly to simulate another dimension of “handling” the object by encouraging viewers to reassemble 2D views of the fragments. Even though this additional interaction is 2-dimensional, it derives from photogrammetry of the plate. On an interesting note, we were able to do this by photographing the plate while it remained in its display at JPPM’s Visitor’s Center, and the interaction we’ve simulated is not actually possible in person given preservation needs.

To enable even more interactivity, we’re using Unity, a game engine for creating both 3D and 2D content. Unity is commonly used for indie games but its streamlined experience and support for computers, mobile devices, and web browsers makes it excellent for education–as does a large community of users and assets to help speed development. By shifting from SketchFab and Genial.ly, where we’re limited to either visualizing a model in 3-dimensions or simulating additional interactions with the model from 2-dimensional perspectives, Unity enables interaction with archaeological sites and artifacts from the first person perspective or with controllers that do a better job approximating the feel of an object.

In the video below, you can see a very early experience of “walking” around the Sukeek’s Cabin site here on park property. Despite the ghostly reconstruction (because parts of it are hypothetical or not known with confidence*), there is still a sense of hominess when inside and the stairs in the corner invite further exploration. In the distance, we have added a representation of the Peterson house. Newly emancipated, Sukeek and family were still living within sight of their former captor’s home. From the first person perspective, the house feels watchful–a feeling difficult to replicate in SketchFab or Genial.ly, missing from the site today, but true to the limits newly-freed families often found on their freedom.

A user explores the virtual environment around the Sukeek’s Cabin site. The photogrammetric model is visible on the ground as are interactive hotspots. A “ghost” of the home can be toggled on and off to get a sense of what it would have looked like.

We use these results in Open Education Resources (OER): free and openly-licensed resources that encourage reuse and remixing. (For more information, see this explainer from the University of Maryland or visit our Provider Set on OER Commons for examples.) For OER, photogrammetry offers a way to present lots of information with each resource. Photos and videos preserve how an artifact or archaeological site looks from a limited set of views, but digital models can preserve how a subject looks from any point of view, even those that may not be practically accessible. Where photogrammetry excels as an educational tool, though, is in approximating being able to tangibly interact with an artifact or site. While most interactions still rely on 2D screens, the opportunity to move and manipulate 3D models within those 2D interfaces helps replicate some of the sense of holding an object. As AR/VR and 3D printers improve, having a 3D model of an artifact or site will only improve in educational effectiveness.

*In addition to the current staff at JPPM, we are indebted to conversations with Kirsti Uunila and Ed Chaney for guidance on how the cabin would have looked.

Revisiting a 19th-century Flea Glass from the Southern Dispensary

by Patricia Samford, Director of the Maryland Archaeological Conservation (MAC) Lab

Since the theme of Maryland Archeology Month 2021 is  “The Archeology of Healing and Medicine,” I thought it would be a great time to revisit a rudimentary microscope called a “flea glass,” which I first studied in a February 2017 Curator’s Choice piece. The monthly Curator’s Choice series highlights significant or unusual artifacts from the Maryland Archaeological Conservation (MAC) Lab collections, and a 19th-century flea glass from the Southern Dispensary in Baltimore qualifies on both counts.

“The eye of a human being is a microscope,
which makes the world seem bigger than it really is.”
– Khalil Gibran (1883-1931)

Nineteenth-century physicians often required more than just the naked eye to assist them in offering quality health care to their patients. Using magnifying devices, like this simple microscope, also called a flea glass, allowed them to gain a better view of wounds or conduct routine visual examinations of ears, eyes, and throats.

An example of a handled Flea Glass Dating to the Second Quarter of the Nineteenth Century.
(Source: https://www.worthpoint.com/worthopedia/simple-microscope-flea-glass-245822098)

Invented in the 1500s, flea glasses were used primarily for studying insects and other small life forms rather than for medical purposes—hence the name. A small, convex lens held nearest to the eye and a larger, flat lens at the opposite end of a short metal tube allowed for magnification ranges of 6x to 10x.

The lenses and iron fittings of a flea glass or similar simple microscope were recovered from a circa 1850-1870 privy excavated at the Federal Reserve site (18BC27) in Baltimore. This magnifying instrument may have been originally mounted on a stand. A medical use for this scientific instrument was assumed because the privy fill also contained a number of other artifacts relating to medical care, including a mortar and pestle, a salve jar, a pill tile, a leech jar, a number of medicine bottles, and a possible stethoscope.

Flea Glass or Simple Microscope from the Federal Reserve Site (Top and Side Views).
Photo by Nicole Doub, MAC Lab.

Documentary records indicate that the privy was located near the Southern Dispensary, a branch of the Baltimore General Dispensary. A dispensary supplied free medicine and health care for citizens who could not otherwise afford medical services. The Southern Dispensary, funded by charitable donations and a small appropriation from the city, was incorporated in 1847 and remained in operation until at least 1889 (Woods 1847; Register 1890). The dispensary offered both clinic and in-home health care (Polk 1888).

Simple Microscope Mounted on a Stand.
Similar instruments were illustrated as early as 1685 in Oculus Artificialis by Johann Zahn

With large populations living in close proximity, it was critical for cities to provide medical services. At various times during the eighteenth and nineteenth centuries, infectious diseases, including tuberculosis, cholera, yellow fever and smallpox, struck Baltimore (Mdmedicine 2017). Clinics like the Southern Dispensary played key roles in treating infected individuals and preventing widespread epidemics.

References

Bradbury, S.
1968 The Microscope Past and Present. Pergamon International Popular Science Series. Pergamon Press, Ltd., Oxford.

Mdmedicine
2017 Epidemics in Maryland. Website accessed January 13, 2017. http://mdhistoryonline.net/mdmedicine/index.cfm?action=epidemics

Polk, R. L.
1888 The Medical Directory and Register for Baltimore, Washington, Maryland and District of Columbia. R. L. Polk & Co., Baltimore.

Register
1890 Annual Reports of the Register of the City and the Commissioners of Finance. John Cox, Printer, Baltimore.

Woods, John W.
1847 The Act of Incorporation and By-laws, of the Southern Dispensary of Baltimore: Together with a List of Officers for 1847. Baltimore.

Zahn, Johann
1685 Oculus Artificialis Teledioptricus Sive Telescopium. Würzburg, Germany.

Summer in the Conservation Lab

By Rebekah Engelland, Maryland Archaeological Conservation Laboratory Intern

During my summer internship with the Maryland Archaeological Conservation Laboratory (MAC Lab), I learned much about the conservation of archeological materials. As a pre-program conservation intern looking at graduate schools, I knew very little about conservation practices. I first focused on the treatment of iron, spending time in the air abrasive unit (essentially a microscopic sand blaster), practicing on non-archeological iron that had corroded. Once I felt comfortable with the air abrasive unit, I moved on to iron from archeological sites that required conservation. The next step in treating iron is to remove the chlorides, one of the critical components to rust. Every week I had to check the amount of chlorides in six different containers as the salts were extracted from the artifacts and drawn into a caustic solution.

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Working on the Fifth Regiment Armory’s World War I Memorial in Baltimore

Following iron, I learned how to clean copper alloy artifacts, which involved using a scalpel under a microscope to remove soil and corrosion until I came down on a stable patina layer. I also cleaned white metal artifacts (tin, aluminum and lead) and applied a protective coating once no more soil or corrosion remained. For silver-plated items, I learned to use electrolytic reduction, an electrochemical technique, to help take off the outer layer of tarnish and limit the amount of polishing before I applied a protective coating of wax. Lead required a different approach, and I used electrolytic consolidation to reduce the corrosion on the surface of the lead artifacts.

Throughout the summer, I also had the opportunity to go out into the field and help on projects. MAC Lab Conservator Heather Rardin and I had the chance to see a laser cleaning demonstration at the Fifth Regiment Armory’s World War I Memorial in Baltimore, where the Conservation of Sculpture and Objects Studio, Inc. removed previous paint layers and dirt from both bronze and stone with a laser custom-built for conservation. One of the assistants let me try out the laser to clean a few feathers on one of the bronze eagles.

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Removing ship’s timbers at Alexandria’s historic waterfront

At the Alexandria, Virginia waterfront, MAC Lab Head Conservator Nichole Doub and I helped Alexandria Archaeology’s team with on-site conservation as they deconstructed a ship’s hull before an underground parking garage was built. The ship, along with two others, was deliberately sunk to be part of a late 18th century wharf. By the time I joined the project, the team was removing the ship’s timbers using a crane. Nichole guided the deconstruction process, making sure the team did as little damage as possible to the remains of the ship. We returned a couple days later and helped the team remove the ship’s keel, which I helped strap to the crane. It was incredible playing a small role in saving a part of Alexandria’s history.

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Cleaning statues in Prince Frederick

On another excursion, Heather and I went to the Prince Frederick courthouse and helped Howard Wellman Conservation LLC treat three statues. The marble and limestone bases were treated with a biocide and then scrubbed down. To coat the bronze statue, we used a blow torch to heat up the metal. Then we applied a protective layer of wax with the brush, heating it up more with the blow torch to remove the brush strokes. These treatments would protect the statues against both corrosion and biological growths, though they would need to be repeated every few years.

Over the summer I received an extensive education on archeological and object conservation from the amazing staff at the MAC Lab. This experience makes me feel much more prepared to apply to graduate conservation programs. I want to thank everyone at the MAC Lab for taking the time to teach me and making this a truly incredible internship.