Part 3 – Sources and Paradata

Before going into the bulk of how to model an archaeological site and why do it, I would like to spend a moment discussing the research that should be at the basis of the model itself. The fact that 3D Reconstruction is in its infancy brings many advantages and disadvantages to the table. On the one part, it is exciting to think there is so much we do not know as it means endless applications are there just waiting to be discovered. On the other hand however, there is a distinct lack of consistent methodology between projects and while some publication are clearly founded on extensive research (Dawson et al. 2011 amongst many others), others seem to be more loosely interpreted.

324t343t
Fig.1 – The first steps in modelling, based on a plan of the site to scale.

This is one of the reasons behind ‘paradata’, a term that has recently been applied to the field. To understand paradata we need to first discuss metadata. Especially in computer science, many authors have lamented the inability to replicate experiments involving code (Hafer and Kirkpatrick 2009; Boon 2009; Ducke 2012; Hayashi 2012). In the words of Marwick:

“This ability to reproduce the results of other researchers is a core tenet of scientific method, and when reproductions are successful, our field advances (Marwick 2016, pp.1).”

and

“A study is reproducible if there is a specific set of computational functions/analyses (usually specified in terms of code) that exactly reproduce all of the numbers and data visualizations in a published paper from raw data (Marwick 2016, pp.4).”

Essentially the debate is that publishing results is not enough, but that instead we should include additional information, such as settings used in a program or the raw code. This collection of information is referred to as ‘metadata’. Some authors on the other hand have taken it a step forward, arguing that we should include descriptions of the process, a discussion of the choices made and the probabilities (Denard 2009; Beacham 2011, D’Andrea and Fernie 2013). This ‘paradata’ is best described in the London Charter, which is the first attempt to creating a methodology in 3D Reconstruction:

“Documentation of the evaluative, analytical, deductive, interpretative and creative decisions made in the course of computer-based visualisation should be disseminated in such a way that the relationship between research sources, implicit knowledge, explicit reasoning, and visualisation-based outcomes can be understood (Denard 2009, pp.8-9).”

Given that a major critique in 3D Reconstruction is accuracy (Miller and Richards 1995; Richards 1998; Devlin et al. 2003; Johnson et al. 2009), paradata is our way to defend ourselves. While it is impossible to create the perfect model, by demonstrating the process behind the reconstruction allows a user to understand the interpretation given and draw their own conclusions.

Roman Villa 4
Fig.2 – A highly speculative Roman Villa. Without knowledge of the process it is impossible to know how accurate each element is.

One of the elements we have mentioned previously are sources. While the process itself has to be methodical in order to gain accurate results, the sources provide the wireframe upon which the interpretation can take place. It therefore essential that the sources are well researched and well documented. For this purpose I like the classification proposed by Dell’Unto et al. (2011), which sees different categories based on accuracy:

  • Reconstruction by Objectivity: sources based on in situ elements, like plans, 3D scans, archives.
  • Reconstruction by Testimony: illustrations, literary sources, notes.
  • Reconstruction by Deduction: elements that can be deduced from in situ remains, but that are not actually there.
  • Reconstruction by Comparison: based on other sites, this is actually quite an important one as a lot of features carry on between remains of the same regions.
  • Reconstruction by Analogy of Styles: especially for decoration, looking at other stylistic elements that have been preserved can help make the whole model look more realistic.
  • Reconstruction by Hypothesis: an essential part of reconstruction, but the most inaccurate.

Of course, the more we go down this ladder, the more inaccurate the sources are. Yet it is by combining all the different sources that we get the finished model. Paradata can help with determining which sources were used for each part of the model, and therefore provide information of the model as a whole.

house6
Fig 3 = Partly completed model of a Greek house, based on plan, excavation reports and site comparison.

In conclusion, there are many sources that can be used when constructing a model and although some are more precise than others, all of them contribute to the final result. If they are applied methodologically and the process is recorded, we can provide an accurate and reliable reconstruction.

Over the next posts I will start looking at SketchUp for modelling, although the ideas will carry over to other software such as 3Ds Max.

REFERENCES:

Beacham, R. C. (2011). Concerning the Paradox of Paradata. Or, “I don’t want realism; I want magic!”. Virtual Archaeology Review Vol.2 No.4 pp.49-52.

Boon, P., Van Der Maaten, L., Paijmans, H., Postma, E. and Lange, G. (2009). Digital Support for Archaeology. Interdisciplinary Science Reviews 34:2-3 pp.189-205.

D’Andrea, A. and Fernie, K. (2013). CARARE 2.0: a metadata schema for 3D Cultural Objects. Digital Heritage International Congress Vol.2 pp.137-143.

Dawson, P., Levy, R. and Lyons, N. (2011). “Breaking the fourth wall”: 3D virtual worlds as tools for knowledge repatriation in archaeology. Journal of Social Archaeology 11(3) pp.387-402.

Dell’Unto, N., Leander, A. M., Ferdani, D., Dellepiane, M., Callieri, M., Lindgren, S. (2013). Digital reconstruction and visualisation in archaeology: case-study drawn from the work of the Swedish Pompeii Project. Digital Heritage International Congress pp.621-628.

Denard, H. (2009). The London Charter: for the computer-based visualisation of cultural heritage.

Devlin, K., Chalmers, A. and Brown, D. (2003). Predictive lighting and perception in archaeological representation. UNESCO World Heritage in the Digital Age.

Ducke, B. (2012). Natives of a connected world: free and open source software in archaeology. World Archaeology 44:4 pp.571-579.

Hafer, L. and Kirkpatrick, A. E. (2009). Assessing Open Source Software as a Scholarly Contribution. Communication of the ACM Vol.52 No.12 pp.126-129.

Hayashi, T. (2012). Source Code Publishing on World Wide Web. International Conference on Advanced Information Networking and Applications Workshops pp.35-40.

Johnson, D. S. (2009). Testing Geometric Authenticity: Standards, Methods, and Criteria for Evaluating the Accuracy and Completeness of Archaeometric Computer Reconstructions. Visual Resources 25:4 pp.333-344.

Marwick, B. (2016). Computational Reproducibility in Archaeological Research: Basic Principles and a Case Study of Their Implementation. Journal of Archaeological Method and Theory pp.1-27.

Miller, P. and Richards, J. (1995). The Good, the Bad, and the Downright Misleading: Archaeological Adoption of Computer Visualisation. In: Huggett, J. and Ryan, N. Computer Applications and Quantitative Methods in Archaeology. Oxford: Tempus Reparatum pp.19-22.

Richards, J. D. (1998). Recent Trends in Computer Applications in Archaeology. Journal of Archaeological Research Vol.6 No.4 pp.331-382.

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Part 2 – 3D Reconstruction Literature

In this section I would like to go through some projects I have been reading about that I think are very useful for understanding 3D Reconstruction in Archaeology. Before delving into the practicalities of the technology it is important to assess where the field is at right now.

champion
An image from Champion et al. (2012) showing the reconstructed city of Palenque.

If you look through the literature, 3D Reconstruction is often scarcely documented and results are limited. The three major critique points I have encountered are to do with accuracy, lack of human element and on use. Here is a brief overview:

  • Accuracy: studies lack background information on how the model was achieved, and create the false idea that the reconstruction is absolutely certain, while often it is simply one of many interpretations.
  • Lack of human element: based on Thomas (2004a; 2004b) and Tilley (2004), 3D Reconstruction is seen as a purely visual subject, alienated from human experience.
  • Use: 3D modelling is used simply to present sites, and are seen as add-ons. In reality, they provide great scope for interpretation.

The first paper I would like to mention is “Digital reconstruction and visualisation in archaeology” by Dell’Unto et al. (2012). On the subject of accuracy in 3D Reconstruction, Dell’Unto et al. propose the use of a series of levels of reconstruction: by identifying and recording the sources for each portion of the model, it is possible to assess the relative accuracy of each part. The first level of reconstruction is based on in situ elements, which are nearly certain, while the last level is dedicated to purely hypothetical reconstructions. This is a great approach as it means the modeller is accountable for the model, but at the same time they have the freedom to experiment as it is clear from the recording what they have done.

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Levels of reconstruction by Dell’Unto et al. (2012).

On the topic of human experience, I can mention a few papers that implicitly refute the ideas proposed by Tilley and Thomas. While 3D modelling is indeed an exceptionally visual subject, it is not simply about looking at images. An entire current of thought deals with ‘presence’, the feeling of belonging a person gets when exploring a 3D environment. It seems that people get involved with the models to the point they ‘experience’ them, as if they were present on site. So while Tilley and Thomas refuse Visualisation as they prefer to explore the site in first person, I would argue that you can do that with 3D Reconstruction. An author I have come across which deals with ‘presence’ is Ch’ng (2009; Ch’ng and Stone 2006; Ch’ng et al. 2011), although I think the forerunner of this field is Chalmers (2002; Chalmers and DeBattista 2009; Devlin and Chalmers 2001; Devlin et al. 2003; Gutierrez et al. 2006). He has made exceptional steps in recreating archaeological sites with near perfect realism, in order to increase the sense of ‘presence’ people experience. His work on illumination is unmatched, and his articles are well worth a read.

chalmers and debattista
Different lighting effects as studied by Chalmers and DeBattista (2009).

Additionally the work of Dawson and Levy (2006; Dawson et al. 2007, 2011, 2013) are an exceptional testimony of how people respond to 3D environments. They recreated a Thule hut and then invited some members to explore them, recording their reactions and showing their emotional attachment.

Dawson and Levy are also prime examples of 3D Reconstruction being used for interpretation, as their analysis of hut building showed that there was significant reuse of bone structures. Many others have explored the utility of this type of technology, so it is hard to pinpoint individual papers of significance. Champion et al. (2012) use gaming software to educate users on the archaeology of the Palenque city. This is by far one of the best studies I have encountered, and I believe they are the forerunners of ‘serious games’ for archaeology.

champion 2
Another view of the ‘serious game’ by Champion et al. (2012).

Similarly the work of Forte et al. (2012) shows much promise in the same area. Finally, the work of Murgatroyd et al.(2011) is not strictly related to reconstruction, but the simulations they have run on Byzantine army movement is very important for understanding the reach of scripting, which can be combined to 3D reconstruction.

I hope this has provided you with an overlook of all the potential applications of 3D software. Over the next couple of weeks I aim to outline the reconstruction process, in order to open up the path to scripting.

 

REFERENCES:

Ch’ng, E. and Stone, R. J. (2006). 3D Archaeological Reconstruction and Visualisation: An Artificial Life Model for Determining Vegetation Dispersal Patterns in Ancient Landscapes. Proceedings of the International Conference on Computer Graphics, Imaging and Visualisation.

Ch’ng, E. (2009). Experimental archaeology: is virtual time travel possible? Journal of Cultural Heritage 10 pp.458-470.

Ch’ng, E., Chapman, H., Gaffney, V., Murgatrayd, P.. Gaffney, C. and Neubauer, W. (2011). From sites to landscapes: how computer technology is shaping archaeological practice. IEEE Computer Society 11 pp.40-46.

Chalmers, A. (2002). Very realistic graphics for visualising archaeological site reconstruction. Proceedings of the 18th Spring Conference on Computer Graphics pp. 7-12.

Chalmers, A. and DeBattista, K. (2009). Level of realism for serious games. 2009 Conference in Games and Virtual Worlds for Serious Applications pp.225-232.

Champion, E., Bishop, I. and Dave, B. (2012). The Palenque project: evaluating interaction in an online virtual archaeology site. Virtual Reality 16 pp.121-139.

Dawson, P., Levy, R., Gardner, D. and Walls M. (2007). Simulating the Behaviour of Light inside Arctic Dwellings: Implications for Assessing the Role of Vision in Task Performance. World Archaeology Vol.39 No.1 pp.17-35.

Dawson, P., Levy, R. and Lyons, N. (2011). “Breaking the fourth wall”: 3D virtual worlds as tools for knowledge repatriation in archaeology. Journal of Social Archaeology 11(3) pp.387-402.

Dawson, T., Vermehren, A., Miller, A., Oliver, I. and Kennedy, S. (2013). Digitally enhanced community rescue archaeology. Proceedings of First International Congress on Digital Heritage pp.29-36.

Devlin, K. and Chalmers, A. (2001). Realistic visualisation of the Pompeii frescoes. Proceedings of the 1st International Conference on Computer Graphics, Virtual Reality and Visualisation pp.43-48.

Devlin, K., Chalmers, A. and Brown, D. (2003). Predictive lighting and perception in archaeological representation. UNESCO World Heritage in the Digital Age.

Dell’Unto, N., Leander, A. M., Ferdani, D., Dellepiane, M., Callieri, M., Lindgren, S. (2013). Digital reconstruction and visualisation in archaeology: case-study drawn from the work of the Swedish Pompeii Project. Digital Heritage International Congress pp.621-628.

Forte, M., Lercari, N., Onsurez, L., Issavi, J. and Prather, E. (2012). The Fort Ross Virtual Warehouse Project: A Serious Game for Research and Education. 18th International Conference on Virtual Systems and Multimedia pp.315-322.

Gutierrez, D., Sundstedt, V., Gomez, F. and Chalmers, A. (2006). Dust and light: predictive virtual archaeology. Journal of Cultural Heritage 8 pp.209-214.

Levy, R. and Dawson, P. (2006). Reconstructing a Thule whalebone house using 3D imaging. IEEE MultiMedia. Vol.13 No.2 pp.78-83.

Murgatroyd, P., Crenen, B., Theodoropoulos, G., Gaffney, V. and Haldon, J. (2011). Modelling medieval military logistics: an agent-based simulation of a Byzantine army on the march. Computational and Mathematical Organization Theory Vol.18 No.4 pp.488-506.

Thomas, J. (2004). Archaeology and Modernity. London: Routledge.

Thomas, J. (2004). The Great Dark Book: Archaeology, Experience, and Interpretation. In: Earle, T. and Pebbles, C. S. A Companion to Archaeology. Oxford: Blackwell Publishing pp.21-36.

Tilley, C. (2004). The materiality of stone: exploration in landscape phenomenology. Oxford: Berg.

PART 1 – Visualisation

ggantija

“Visualisation” is a term that is used quite consistently in recent archaeological publications. It refers to the reconstruction of archaeological evidence through the use of computer software, although it originates in the practise of recording the site using 2D drawings which has been around for a few centuries. Although the meaning of the word and what it entails fluctuates somewhat, I’ve come to identify three types of technologies that fall within this category:

  • Photogrammetry
  • Laser Scanning
  • 3D Reconstruction

Photogrammetry is also referred to as Structure From Motion, and differs from the other methods as the 3D models are based on photographs (Pedersini et al. 2000). Similarly to laser scanning, the result is a high density point cloud, with photorealistic textures.

Laser scanning is a powerful tool widely used in large scale recording. It uses laser measurements to calculate the position of points in a site, and like Photogrammetry it produces a textured mesh, although generally laser scanning models are much more dense and therefore more accurate.

3D reconstruction is the method we will be primarily dealing with. It is less accurate than Photogrammetry and laser scanning, and the results are less realistic. It does however possess some distinct advantages. Reconstructed models are easily manipulated, and often represent elements of a site that have been lost (Fig.1). They can also be combined with gaming software to create interactive environments (I could cite many authors here, but just as a taster I would recommend reading Champion et al. 2012).

image 1
Fig.1 = 3D Reconstruction of the site of Ggantija, Gozo.

The three methods have very different aims, and as such it is important to know what you want to achieve before applying them:

  • For small and medium scale recording Photogrammetry is excellent (Scopigno 2012). It is very cheap and fast, and possesses the accuracy and visual effects that are necessary for recording and presenting. It is ideal for cataloguing finds or small scale excavations, although it can be used for larger features if necessary (see the current Must Farm excavation models by Donald Horne for more details: https://sketchfab.com/mustfarm). The fact it possesses lower points than laser scanning makes it easy to manage, and it requires little training.
  • For detailed models and large sites Laser Scanning is the tool of choice. More expensive and computationally challenging than Photogrammetry, laser scanning creates precise models that are perfect for recording, presenting and some interpreting. A great example is the work of John Meneele (https://www.facebook.com/1manscan/) who has been analysing stone decay be comparing models taken in different years. I personally have little experience with laser scanning, but the results I have seen have shown a lot of promise.
  • 3D Reconstruction is mainly for presentation and interpretation. Although some arguments have been put forward on using 3D reconstructions for metadata recording, this is not where the technology shines (Reilly 1990; Barreau et al. 2013). 3D reconstructions can show a site “as it was” rather than “as it is”, leading to a more vivid understanding of archaeological contexts (Miller and Richards 1995; Lewin and Gross 1996). For the general public it is perfect, and it can be made highly interactive in order to further increase user comprehension of the archaeology. As for interpretation, the use of scripting allows a number of tools to be created in order to answer archaeological questions. One of the projects I have been working on was looking at analysing solar alignment at a Maltese site, and through a custom-written script I concluded the site is illuminated on the winter solstice (Fig.2). While Photogrammetry and Laser scanning shine with precision and photorealism, 3D Reconstruction truly dominates in presentation and interpretation.

 

overall image
Fig.2 – Overview of the script interface.

It is important however to mention how these methodologies are not mutually exclusive. Little work has been done in combining different techniques, but the results show much promise. A previous article on this blog discussed virtual museums, and the combination of a 3D reconstructed environment, with Photogrammetric models within.

In conclusion, there is a lot of technology put there, and although research is slowly unveiling the advantages of each there is much to be discovered still. With 3D Reconstruction we are barely scratching the surface, and only in the last 10 years we have had custom written scripts for archaeology. It may take a while, but once we uncover what is possible, archaeology will really reap the results.

 

In the next post I will be looking at previous work in 3D reconstruction, with a few examples of significant projects that have helped shape the methodology.

 

REFERENCES:

Barreau, J., Gaugne, R., Bernard, Y., Le Cloiree, G. and Gouranton, V. (2013). The West Digital Conservatory of Archaeological Heritage Project. Digital Heritage International Congress. Vol.1 pp.547-554.

Champion, E., Bishop, I. and Dave, B. (2012). The Palenque project: evaluating interaction in an online virtual archaeology site. Virtual Reality 16 pp.121-139.

Lewin, J. S. and Gross, M. D. (1996). Resolving Archaeological Site Data With 3D Computer Modeling: The Case of Ceren. Acadia pp. 255-266.

Miller, P. and Richards, J. (1995). The Good, the Bad, and the Downright Misleading: Archaeological Adoption of Computer Visualisation. In: Huggett, J. and Ryan, N. Computer Applications and Quantitative Methods in Archaeology. Oxford: Tempus Reparatum pp.19-22.

Pedersini, F., Sarti, A. and Tubaro, S. (2000). Automatic monitoring and 3d reconstruction applied to cultural heritage. Journal of Cultural Heritage 1 pp.301-313.

Reilly, P. (1990). Towards a virtual archaeology. In: Lockyear, K. and Rahtz, S. Computer Applications in Archaeology pp.133-139.

Scopigno, R. (2012). Sampled 3D models for Cultural Heritage: which uses beyond visualisation? Virtual Archaeology Review Vol.3 No.5 pp.109-115.