Practice and Method in Creating 3D Models in Archaeology

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WORKING DRAFT. DO NOT CITE WITHOUT AUTHORS PERMISSION. 2014.

Practice and Method in Creating 3D Models in Archaeology

for

Digital Archaeological Practice

A Workshop on the use of Technology in the Field

February 6 - 7, 2014

University of Massachusetts Amherst

William R. Caraher

University of North Dakota

Introduction

As anyone who has heard me talk over the last few years -- including many of the people in the

room here -- knows Im both an enthusiastic supporter of digital methods in archaeology, and

deeply curious about how they are transforming archaeological practice. Today I want to consider

how the use of 3D imaging from photographs (structure-from-motion imaging) transforms certainaspects of archaeological practice and, as a result, forms part of a larger trend in how the discipline,

as a community of practice, is changing.

Most of my observations here come from two perspectives. First, my background is in survey

archaeology, and I have only come lately and reluctantly to excavation. [SLIDE]One of the major

conversations in survey involves methodology, and, in particular, the ability of "inexperienced" field

walkers to make "simple" identifications of material in the field. Part of the efficiency required (and

touted!) by intensive survey projects comes from the ability to make use of relatively untrained


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WORKING DRAFT. DO NOT CITE WITHOUT AUTHORS PERMISSION. 2014. 2

[SLIDE]Yet, despite careful attention to processes and procedures, there has been little

reflection on the practice of collecting 3D data. Like methods associated with survey archaeology,

scholars have recognized recent improvements in 3D imaging as a boon to field efficiency and way

to produce archaeological illustrations that are more accurate, consistent, and efficient than

traditional field recording practices. By simply following Brandon's step-by-step procedure even the

most clueless project director (or undergraduate!) can produce highly accurate and detailed 3D

images of stratigraphic relationships, architecture, or landscapes. This interest in efficiency and

streamlining the archaeological data collection process, then, follows a pattern visible in botharchaeological survey practice as well as in recent uses of iPads to replace traditional excavation

notebooks.

Practices

While advocates of 3D methods are quick to point out that producing "structure-from-motion"

images of a trench or a building is just one step in collecting and interpreting archaeological data, itis nevertheless true that this change in field practices will contribute to how archaeological

knowledge is produced and consumed. The primary concern in my paper today is how the practices

associated with producing "structure-from-motion" image, recently facilitated by remarkably easy

software like Agisoft Photoscan, continue a trend toward simplifying and "de-skilling" in-field data

collection.

In this context, I should clarify what I mean by deskilling. I am not referring to specific

archaeological skills in the field (nor that individual excavators have become less skillful), but rather


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revising archaeological descriptions longhand. [SLIDE] I have wondered, for example, whether the

ease with which a user can edit, revise, and delete data in some of the most recent implementations

of trench-side data collecting might undermine traditional best-practices which require trench

supervisors to strike through and initial revisions in their notebooks rather than deleting them

completely. It will be interesting to understand how later revisionssay of an error in instrument

height or in interpretationwill appear in digital notebooks. It is easy to imagine a system that

preserves all changes to an entry, of course, but Ive yet to see a system where a wiki-like interface

exists.

My Luddite perspectives could easily extend from a genuine concern about data integrity to the

more elusive realm of changing archaeological experience. [SLIDE] Data collected through GPS

units, remote sensing, and increasingly automated and regularized methods in the field threaten to

erode less structured engagement with the environment and to isolate the essentially haptic

experience of walking through the landscape from the work of formal archaeological data collection.

As an example, my long-time collaborator David Pettegrew found it necessary to return to the

Isthmus of Corinth where he had conducted a three-year rigorously systematic intensive pedestriansurvey to attempt to understand the experience of moving and living in the landscape. During the

formal field seasons, David kept his head inclined toward his clipboard and forms while mapping

new units, collecting environmental data from each 3000 sq. m. unit, and recording artifact counts

on highly-specific paper forms. In his return trips to the same region, he maintained an unstructured

notebook to record many large-scale observations that he missed during the structured field seasons.

This is no fault of Davids, but a typical byproduct of intensive survey methods that privilege both

highly granular approaches to space as well as the methods used to document this space. In fact,

Richard Blanton has referred to this almost-atomic focus on intensive data collection as


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preserved in the exposed trench. [SLIDE] Plans are sometimes festooned with interpretative notes

and contribute to the first steps in archaeological interpretation.

[SLIDE]While the number, detail, and frequency of trench plans vary according to project,

typically each context receives a plan. Drawing the plan represents a pause in the hectic routine of

excavation and an opportunity to clarify features in the trench and the excavation process. Like

maintaining the trench notebook, the act of drawing is slow and methodical, encouraging the kind of

scrutiny that can inform later excavation decisions and produce features and relationships obscured

by visual noise or revealed through careful measurement. Depending on the size of the trench, thenumber of features, the scale, and the amount of detail, trench plans can take anywhere from 20

minutes to an hour to illustrate.

[SLIDE] In comparison, it took a trench supervisor 10-15 minutes to take a sufficient number

of photographs for a 5 x 5 m. trench to produce an accurate Agisoft Photoscan 3D image at Tel

Akko. The computer time to process these images, of course, was much longer, but this occurred

either simultaneous with field work or at times when field work was not possible. This reflects asubstantial improvement in efficiency when compared with experiments conducted just a few years

earlier at Chersonesos, where a combination of georeferenced photographs and elevation control

points on the features and the surface of the trench took the same amount of time as a trench plan

executed by a skilled illustrator. The improvements in software have eliminated the need to collect

numerous control points as well as photographs, while maintaining a level of spatial control that is

superior to even the most skilled illustrator. At the same time, the issues noted by Adam Rabinowitz

at Chersonesos persist: photographs cannot replace the interpretative aspect of trench side

illustrating. Preparing an illustration from a structure-from-motion model or a georeferenced


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performance to materials. This ecology defines a wide range of social, political, disciplinary,

economic, and personal relationships.

When we reflect on material corollaries for past practices, we would not hesitate to understand

variations in both the practices and materials as keys to understanding how ancient societies

structured certain kinds of social relations. In fact, the act of writing or drawing is often vital to

understanding past communities of practice that embody the relationship between individual

agency and structured social expectations. [SLIDE] Latour is willing to extend the status of agency

even further to include individual objects and pieces of technology that he sees as actors embeddedwithin dense networks (ANT). Ingold, and others, are skeptical, but nevertheless emphasize the role

that technology, practices, and individuals play in constructing the conditions for agency and its

(reciprocating) products. From the perspective of archaeological tools and practices, we can argue

that using a digital camera, iPad, or laptop in the field creates fundamentally different relationships

than using an architects table, clipboard, or field notebook. If we see disciplines as communities of

practice then the changing roles of technology and practices in the field impact the situation of

disciplinary knowledge.

[SLIDE] Maguire and Shanks 1996 article on archaeology as craft provides another context for

understanding archaeology as disciplinary practice. They argue that archaeological knowledge is

produced through a socially engaged practice which is not alienating, which edifies and provides

diverse experience. The character of archaeology as craft grounds it both in experience and resists

the alienating division of labor. This is a romantic notion, that corresponds awkwardly to the realities

of large and complex archaeological projects which rely on increasingly atomized and deskilled

practices that remove the interpretative function from both the space of the field and the purview of


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[SLIDE]Technological changes coincided with the shift from authorizing practices resting in

the individual artisanal archaeologist to our disciplinary discourse. The collection of numerous

photographs to produce a structure-from-motion model of a site, trench, context, or object,

depends less upon the unique abilities of the photographer and more upon a set of established

practices and software algorithms. Even access to photographic equipment is no longer a source of

distinction on the project as relatively high-quality digital cameras are inexpensive, available, and

satisfactory for the production of 3D images.

[SLIDE] Photographic 3D models do not replace illustration entirely, of course, but they move

the act of illustrating from the trench side to the computer lab. The displacement of this part of the

archaeological process from the field to the lab represents a transformation of the haptic aspects of

archaeological inquiry. The computer monitor becomes the trench and the impulse to maximize the

quantity (and resolution) of the data collected in the field moves more time consuming practices of

analysis to the margins of the archaeological field day and, sometimes, the field season. As a result,

(in my somewhat alarmist and apocalyptic perspective) the object of archaeological investigationshifts from the trench to its digital surrogate (using Adam Rabinowitzs term), and the posture of the

archaeologist shifts from stooping at trench side to hunched over a laptop.

[SLIDE] Imagining the future, we can see significant trends in how the locus of authority has

changed as the process of deskilling archaeological practice continues. The use of technology like

Agisoft to document the daily work and stratigraphic context present in each trench frees the trench

supervisors from the responsibilities of trench illustration and corresponding role in the time

consuming interpretative process (as the increasingly form-driven data collection forms replace the


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methodology present a challenge of sorts. It challenges us to become more aware of the relationship

between the practice and the structure of archaeological knowledge.


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Practice and Method in Creating 3D Models in Archaeology

Digital Archaeological Practice

A Workshop on the use of Technology in the Field

William Caraher, University of North Dakota


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Corinth Notebook: 988Field ValueTitle Zygouries Field Notebook

Author Blegen, C.W.Contents Field Notes

Area Agios BasiliosCorinthiaZygouries

Site ZygouriesCity CorinthCountry Greecehttp://...//id/corinth/notebook/988/html


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Practice and Method in Creating 3D Models in Archaeology