Photographs into Models: Documenting the World Trade Center Ship

By Carrie Fulton

If you attend any archaeology conference or glance through recent issues of journals, you will quickly see the extent to which photogrammetric documentation has become a part of an archaeologist’s toolkit. Take a few photos, import them to software, and hit go. Violà! You now have digital models of your site or object. Ok, so the steps are slightly more detailed, but with new technology, the interfaces and steps to producing accurate models are getting easier and less technical.

The benefits of digital recording are massive: increased speed of recording, preservation of three-dimensional information, geo-referenced data, digital preservation of contexts that are destroyed through the process of excavation, and easy dissemination of information. How can this technology be used effectively? And are there drawbacks? If so, how can they be mitigated?

Let’s look at the excavation and documentation of the remains of a late 18th-century ship discovered during the construction at the World Trade Center site in July 2010.

Figure 1: Remains of the World Trade Center Ship looking from the stern towards the retention wall. (Photo: K. Galligan)

Since the ship was found in one section of an active construction site, we had to move quickly so the timbers could be removed and construction could continue. Approximately 32 feet of the ship’s stern (back end) remained. However, a modern retention wall bisected the ship and destroyed evidence for much of the forward half of the ship except for a very small section of the bow (forward end) of the ship that was uncovered in August 2011 when the other side of the wall was cleared.

To capture the relationship between timbers we used laser scanning, photographs, videography, and sketches. This enabled us to give each timber a unique identification so that upon disassembly we could keep track of each piece and reconstruct the in situ relationship. Once removed from the site, we had more time to analyze the timbers, but the next step in the preservation of the ship hadn’t been determined. We were faced with the question: How do we record each timber accurately and quickly? We settled on an approach that combined traditional methods for documenting timbers with recent advances in photogrammetry to create three-dimensional digital recordings of the timbers.

Figure 2: Making a 1:1 tracing of a frame. (Photo: D. Fulton)

Traditionally, nautical archaeologists record the dimensions by tracing the timbers in 1:1 reproductions or making scaled drawings of each face (Figure 2). The advantage of this approach is the close examination and documentation of each face, noting patterns in fasteners, tool patterns, and any biological growth that might be indicative of post-depositional processes. However, this method is extremely time consuming, and there is the possibility for dimensions to be distorted in tracing (due to parallax) or in condensing information into a scaled drawing.

For the best use of resources and time, we made 1:1 tracings of the two sides of the frames where the ceiling planking and the outer planking were attached. This allowed us to record the arrangement in nail patterns, which is crucial to answering questions about whether the ship timbers had been repaired. To document the curves of the frames that are difficult to render in two dimensions, we used photogrammetry to generate three-dimensional models. For all other timbers of the ship, we also used photogrammetry rather than tracings.

Each timber still had its own data sheet with notations for tool marks, measurements, marine growth, and any other information that might aid in the reconstruction of the ship and its life history. However, the timber is now preserved in a digital record as a three-dimensional model. Creating a model involved a three-step procedure:

Figure 3: Drew Fulton photographs a frame which was imported into PhotoModeler Scanner.

STEP 1: Photograph the timber. For the version of PhotoModeler Scanner in 2010, stereo pairs of photographs were taken from each side of the object, with the photographer maintaining a 45-degree angle between the object and the camera. To aid in linking the photographs together, computer generated and coded dots were placed around the timber. We used push-pins to mark nails and other features so that they could be easily spotted in photographs. This allowed us to maintain the high degree of detail afforded by the tracing method while decreasing recording time.

Figure 4: 3D model of a timber created in PhotoModeler Scanner.

STEP 2: Generate 3D data. The photographs were then used to create a 3D model in PhotoModeler Scanner by first creating cloud data of the timber and then transforming the cloud data into a triangulated mesh. This mesh recorded the curves of the timbers and was exported into the NURBS modeling software Rhinoceros.

Figure 5: Reconstruction of the small deck.

STEP 3: Render into a model. Using Rhinoceros, a 3D image was created and nails were added following the locations of preserved nails. From this model, individual drawings can be produced to link the timber to information from field notes and examination in the lab. Additionally, these individual pieces were combined digitally in Rhinoceros to reconstruct the ship, using the aid of data from the laser scan.

Figure 6: Reconstruction of a frame in Rhinoceros.

The emphasis for us was integrating three-dimensional recording techniques with traditional measuring and documentation techniques to quickly and accurately record the ship and enable analysis when access to the actual timbers may not be possible. On the one hand, it is easy to see the benefits: it’s a fast process in the field, it preserves and records curves very well, it facilitates collaboration and dissemination of information with digital files that can be easily shared. On the other hand, we tend not to think about the costs associated with it: digital cameras with high resolution files requiring terabytes of storage, the possibility of having corrupt hard drives, and long hours and tedious manual work to render the digital data into final forms. Most significantly, while advances in digital technology enable better documentation, will these advances make our early attempts obsolete? For example, the version of PhotoModeler Scanner that we used has already been updated, no longer requiring stereo-photographs. Using the photographs from the World Trade Center Ship, I am eager to try rendering models using newer versions of software to see what these changes might mean for our data. However, what would happen if I could no longer open the software used to access the data?

The power of photogrammetric techniques lies in their integration with traditional techniques, using them alongside measurements and drawings to record the archaeological data. While it’s a helpful tool, we still need to future-proof our data. From the 3D models, we can still produce standard drawings and take measurements. By supplementing recordings in the field and tape measurements, this redundancy can help catch errors in recording while producing a complete visual record of the object.

While moving forward with new technologies and digital recording procedures, are we at risk of advancing too quickly? Is there a risk that we will no longer have the computer programs or software to open these files and thus render our documentation obsolete? Or, is this a way of ‘future-proofing’ our data?

ACKNOWLEDGEMENTS

Archaeologists at AKRF, INC., Diane Dallal, Michael Pappalardo, Elizabeth Meade, and Molly McDonald, managed the excavation of the site for the Lower Manhattan Development Corporation (LMDC). The principle investigation of the ship was led by Warren Riess (University of Maine) and Carrie Fulton (Cornell University). Drawings were made by Kathleen Galligan. Drew Fulton (Drew Fulton Photography) photographed onsite panoramas and the timbers for photogrammetry. Timbers were initially stored at the Maryland Archaeological Conservation Laboratory and are now held in the Conservation Research Laboratory at Texas A&M University. The LMDC and the Port Authority of New York & New Jersey provided funding for this project.

Check out the other #TechWeek Posts:

Tech Week: Photography in Archaeology by Jonathan Libbon
Going Interactive Underwater by Drew Fulton
Preservation Photography: Roles and Rules by Karen Price

What the Tech…?!

A recent SHA Academic and Professional Training Student Sub-committee survey asked student members what technologies are necessary in archaeology and as professionals. In continuing support of the identification, discussion, and application of relevant technologies, student member, Tim Goddard, agreed to (re)introduce the concept behind the Technology Room – a great space for students and professionals to engage in one-on-one conversations about current technologies in historical archaeology.

Thank you for the opportunity to blog about the Technology room from/for a student’s perspective. I gladly serve on the SHA’s Technology committee. I am also a Graduate student finalizing my PhD. Several years ago, when I first joined the committee, one of my first conversations with fellow members explored the challenges of presenting the use of technology to SHA members who were not already a part of the “technology crowd”. For many previous years, the same group of colleagues presented the latest technologies they were playing with and composed the small number of technology sessions at annual meetings. Despite the fun of this, rarely did we see new faces – especially people wanting to learn about technology.

The Technology Committee was created to serve the SHA’s needs as they relate to technology. This can include almost anything, which has been the case thus far. Only the Website has remained outside the purview of the technology committee. We serve to advise the SHA board and any interested members on almost any technology-related application, either for the Society, or for use in the field of archaeology. As you can imagine, this is an extensive scope. The diverse technical needs of archaeologists require that the committee have a number of members from a wide variety of technological backgrounds. We cover topics including: social media, geophysics, remote sensing, data collection, data management, GIS, LIDAR, 3D, virtual worlds, network management, etc.

pXRF Technology Leicester 2013. PxRF technology allows us to identify the chemical composition of soils and/or artifacts. The committee regularly offers workshops at the SHA to learn how to use this technology. The following link is an example of one use by one of our committee members David Morgan (http://ncptt.nps.gov/blog/pxrf-presentation-at-lasmaa/).

With some of my own work in WebGIS, I was frustrated that it was not possible to demonstrate my research in a virtual poster session allowing people to view and interact with my presentation via a computer terminal. To do so would have meant me renting a table space, electricity and Wi-Fi, in the exhibition room. Something that is not really feasible for most students! I also know firsthand from teaching that there are a large number of archaeologists that have technology phobias. This fear can be found in young students as well as established emeritus colleagues around the world. So I wanted to know how we could better serve those members at the conferences. We developed the idea of the Technology Room.

Our first experiment with a dedicated technology demonstration space was at the 2011 meeting in Austin, Texas. We decided to focus on three to four key technologies that we felt every archaeologist should know about. We found a handful of our colleagues working with these technologies and invited them to bring the actual technology to our room and to sit down for a block of time to answer questions and provide demonstrations, and hands on experience were possible, for interested colleagues. We strove to recruit archaeologists using technologies in their research projects rather than sales representatives. The idea was great and we got positive feedback, but our execution that first year needed some help.

LIDAR technology Leicester 2013. LIDAR typically comes in aerial or terrestrial applications. This is a terrestrial style scanner being demonstrated in the Technology Room. A good link to see LIDAR uses in heritage is http://archive.cyark.org/?gclid=CPX7m8a13boCFQLl7AodR0oAXw.

In the following years we continued to showcase various technologies by having practicing archaeologists demonstrate the technology in the exhibition room, which was always problematic and also made communicating difficult with all the noise. Last year, in Leicester, was the first year that we had our own dedicated room, making communicating much easier. We saw a drop in traffic indicating that we still need to get the word out there about the Technology Room. An undergraduate student who I supported at Leicester found the Room worth noting in a blog he posted about his first conference experience. There is something for everyone in the Technology Room.

UAV Technology Leicester 2013. Unmanned Aerial Vehicles are popping up everywhere in archaeology. From a simpler Quadcopter to multiple thousand dollar units with multiple sensor platforms are finding many uses every year in archaeology.

What are the purposes of the Technology Room?

  1. Present the latest and greatest technologies being used in archaeology.
  2. Have a practicing archaeologist familiar with the technology to educate others about what did and didn’t work.
  3. Learn what pitfalls to avoid.
  4. The real costs involved.
  5. Share technology driven research that can’t always be demonstrated in a traditional symposium.
  6. Network with various technology minded colleagues

What is the benefit to Students? Students:

  1. learn about technologies that you might not know about through your own institution;
  2. are often our best presenters as they grew up in a technology age and can help others with technology phobias in a professional context;
  3. can learn and see technology in a low pressure environment;
  4. and can network to find projects using a technology they might be interested in working with.

So I challenge you:

What Technology are you interested in? What role do you feel technology should play in archaeology? What are the problems we face with technology? How can we (SHA) or your institution better train you for technology-related applications?

Comment below as well as stop by the Technology Room this January.

Tim Goddard

Examining Space of a Resting Place: GIS of a New York Cemetery

This post is part of Tech Week, which highlights a group of posts about specific applications of technology to archaeological investigations. This week, the focus is on Technology and Mortuary Archaeology. See the other posts in this series here.

“Will you be buried or will you be cremated? I think I’d like to be buried so I have a headstone like Elvis. Though I think that when you have a headstone and you’re in a place it puts great pressure on your family, your surviving family, to visit you.”

-Rob Brydon, The Trip

Place is important. As Brydon says in the movie “The Trip”, place allows you to create a mark and leave something tangible behind in your memory, but it also puts a responsibility upon the mourning community. Place gives us a sense of belonging, a heritage and ancestry, and a deeper connection to our surroundings. Burials are the final statement of place that humans get to make- for themselves through wills, for their loved ones, or even for their enemies in battle. Both the manner of the burial, memorial and the place are important.

The memorials of the deceased reflect the historical present in which they were buried. Grave markers, location of burial and epitaphs all follow trends that help us better interpret what was of social importance during these periods. Due to the high emotion of death, the trends associated with burial are usually slow to change and have high social significance. Examining the patterns of grave markers and epitaphs aids in creating more nuanced interpretations of how individuals wanted to memorialize and remember their relatives, and also how these patterns changed through time.  As Cannon (2002:191) argues: “the growth and transformation of these expressions over time can therefore be read as a historical narrative of individual choices made in response to spatial representations of the immediate past and perceptions of current and anticipated social and political circumstances”.

A geographic information system (GIS) is a computer based program that allows us create spatial maps in order to visualize, analyze, and interpret data to reveal patterns. Spatial data (data with longitude and latitude, or other geographic coordinates) is given attribute data (any information about the spatial points such as type of grave marker, date of death, name of individual buried within), and is input into GIS. The program has a number of statistical and spatial tools that allow us to analyze the spatial patterns of the associated attributes. An example would be examining whether individuals near to one another were died in similar years. By using GIS, we can better analyze historic cemeteries to understand the importance of place in both the deceased and mourning communities.

The Mount Pleasant Cemetery is approximately an acre in size, and located off Interstate 390 and Route 20A in Livingston County, New York (Figure 1). It is one of ten cemeteries registered to the town of Geneseo, a small farming community established in 1790. The Mount Pleasant Cemetery was established in the early 1800’s by the Kelly Family, and was the first cemetery for Presbyterians in the area. The original date of origin is unknown, though newspaper clippings from the 1850’s note that it was already well established by then. From an outsider perspective, the cemetery appears to have a random organization, lacking distinct rows and coordinated orientations to cardinal directions. In order to better interpret one of the early cemeteries of this small New York community, GIS was employed.

Each grave marker was spatially located using GPS, and attribute data was taken. Stones were first given a ranking of primary through quaternary. It was immediately apparent upon collecting the data that stones fell into a number of categories based on ancestry. Most of the plots within the cemetery were small and consisted of one large grave marker with the family name, and then a number of secondary, tertiary and quaternary stones in increasing distance from the primary marker. The primary stone included the main family stone only, usually found at the center of the plot with the patriarch’s name and death date highlighted, and other family members listed below. Secondary markers were smaller and usually lacked personal names, instead noting only familial relationship to the patriarch. Tertiary and quaternary markers were often different in style, material, and contained more information such as name and death date. Style of grave marker was also noted, and included obelisk, column, mausoleum, pulpit, tablet and flush. Family name, epitaph and death date were also recorded. In total, 34 family plots and 265 grave markers were mapped and assigned attribute data on ranking, style, and dates (Figure 2).

The presence of these large family memorials and lack of personal names reveals the high importance of family. Due to this, the analysis using GIS was employed to determine whether distance to the family marker correlated to dates or relationship, and whether space within each plot had specific organization. Both nearest neighbor and Moran’s I was employed. Neither revealed any strong correlation between the rank of the stone, relationship of the person and distance to the primary family marker. Instead, the stone appear to have more random distribution within the family plot. This, however, does seem to be a common characteristic of this era and style of cemetery. As Mytum (2004:126) writes, “such memorials usually have no individual epitaphs or descriptors of any kind, and it would seem that after death all that mattered was familial association”. Other GIS studies such as Hoogendoorn 2007 found similar results, with stone organization being due to family relationship.

However, an analysis purely of style revealed that there were areas in the cemetery where specific styles of family markers were more popular than others. Further examination revealed this was related to date and shows the growth of the cemetery and change in the fashion trend. However, this correlation works for only the earliest date. The cemetery continues to be used, and families have maintained their connections with their 19th century ancestors. These newer stones, usually quaternary, have the names of the individual and their death date written on them rather than simply being noted on the family marker like the secondary or tertiary markers.

Place is important throughout our lives, and our final burial location is indicative of this importance. GIS is a powerful tool to allow us to find patterns and from these make interpretations of why communities chose to bury their loved ones in specific arrangements. It is interesting to watch this landscape change as we become more mobile, and people are less tied to their ancestral lands. It seems now that the place we find important, and one that may be our lasting memorial is more digital, such as Facebook pages for the deceased… but this is a conversation for another post.

Read the Second Post in Tech Week: “Application of Advanced Technologies in Excavation, Analysis, Consultation, and Reburial: The Alameda-Stone Cemetery in Tucson Arizona” by Michael Heilen

Works Cited

Cannon, Aubrey
2002 “Spatial Narratives of Death, Memory and Transcendence” in Archeological Papers of the American Anthropological Association 11(1) Jan. 2002: 191-199.

Hoogendoorn, Arie, Jeffrey C. Brunskill, PhD and Sandra Kehoe-Forutan
2007 “A Study of Spatial and Temporal Anomolies Associated with the Placement of Gravestones at McHenry Cemetery in Orangeville, Pennsylvania”. Poster presented at Middle States Division of the Association of American Geographers, Pennsylvania, November 2007.

Mytum, Harold
2004 Mortuary Monuments and Burial Grounds of the Historic Period. Kluwer Academic/Plenum Publishers, New York.