Subjectivity and 3D Modelling in Archaeology

I was in Tübingen last week for the Computer Applications and Quantitative Methods in Archaeology conference, partly to present my own work but largely (and more importantly, in my opinion) to see what others are doing in digital archaeology. There were a number of very good papers that made me think quite a bit about various things, so I will try to organise all that in a series of posts over the next couple of weeks.

One talk produced a thought/statement that more or less summarises much of my thoughts during this PhD process: by treating subjectivity in visualisation as a negative to be avoided, we are avoiding much of the very nature of archaeology itself, and also the very nature of archaeological visualisation.

There is a tendency in digital archaeology (and also much of archaeology) to strive for the most objective representation possible, the most objective measurements possible. I am not opposed to objective measurements, but there tends to be the assumption that an object modelled with lasers is objective, that a photogrammetric 3D model is objective. But there is no such thing as a purely objective model.

No matter how objective we may strive to be, there is always human choice in science. Choice to measure certain variables and not others, choice in how we measure those variables, and choice in how to analyse and then represent the data we collect. There is then a large amount of human choice in determining whether patterns exist and what they mean, if anything.

The same is true with a 3D model. We choose what object to model, at what resolution, with which tools. We choose which representation we prefer, for a variety of reasons. We delete points that we deem incorrect, we disable images we feel are inaccurate, and we apply the textures we feel best represent what the object looks like.

It is true that certain techniques produce more accurate models of an object, in that the surface they create is more similar or more likely to be similar to the actual surface of the object. But accuracy is itself a relative term, defined by what it is you are trying to achieve.

There is nothing wrong with 3D models being subjective. They can never really not be, at least not with current techniques. The danger is in assuming that what is produced through laser scanning or white light scanning is entirely objective, free of any human bias. This assumption seems to permeate discussions of 3D models, particularly those using models to calculate measurements. As if human error only applies to measurements made with a tape on the ground.

We must always remember that our models are subjective. We make choices in making visual representations in archaeology. We choose what to represent and how, which will invariably affect what we see. To deny our models’ subjectivity is to deny our role in the process of their creation.

What is a Bead?

It’s occurred to me with all these posts about beads, I have yet to write a post that actually defines what a bead is. That’s a bit surprising, given how often people ask me this question, so here’s a post on what they actually are. It’s more complicated than you might think.

Definitions I use:

Generally speaking, I define a bead as an object that can be strung and that has either a single, central perforation or multiple perforations that are centred within the object.

A pendant is decidedly not a bead. Pendants generally are objects that can be strung, but they tend to have a perforation that is offset from the centre:

Problems with these definitions:

This seems relatively straightforward, but there are actually multiple problems with these definitions. First, just because an object CAN be strung, doesn’t mean it was. I always refer back to the ancestor statue I saw in the National Museum of Indonesia, but it’s useful for dispelling a lot of stereotypes about beads. Neither of the beads on this statue were strung, and yet they are still beads. But if stones had been placed in the same spot for the same purpose, they would be decidedly not beads. Yes, I said a bead was an object that could be strung, not one that absolutely was, but it still calls into question one of the most common function-based definitions of a bead.

Seed beads in the eye sockets of an ancestor statue on display at the National Museum in Jakarta, Indonesia.

Second, there are many objects with a central perforation or with multiple centred perforations that are not beads. Spindle whorls are the main ones I encounter in Scotland. These are generally stone or ceramic objects with a central perforation that are attached to a rod and used to spin yarn. Weights, particularly loom weights, are another difficult object when it comes to beads. Many weights have a central perforation, particularly those used for weighing down the warp (verticle) threads on a loom. Both spindle whorls and loom weights tend to be larger that a bead, as more weight is usually needed for both spinning and weaving. Yet, if the desired thread from spinning or the thread used in weaving is particularly fine, the spindle whorls or loom weights can become quite small – small enough to be a bead. I should also note that there is technically no size limit on a bead, so they can easily be as large as a typical spindle whorl.

Spindle whorl from Lair, Scotland. © PKHT / Northlight Heritage, http://www.glenshee-archaeology.co.uk/news/finds-report-on-the-lair-spindlewhorl-out-now

Buttons are also objects with centred perforations. In modern times, we tend to differentiate between beads and buttons by saying that buttons fasten something closed, while beads are generally decorative. Buttons are functional. But many buttons aren’t functional, even in modern times, and many beads aren’t purely decorative. Even if they were, we generally can’t distinguish between them in older archaeological contexts unless they are still clearly associated with other objects. Most beads I see are stray finds, making it largely impossible to differentiate between objects defined by their function.

Third, many objects used as pendants have a central perforation. Archaeologically, we might call it a large bead, a spindle whorl, or a loom weight, but it may have been used as a pendant. Pendants are generally larger objects that are strung to hang in a central or prominent way, and if it has a single, central perforation, it hangs so that you see the perforation. But this definition once again relies on function. Without associated objects or individuals, we can’t necessarily tell if a larger centrally perforated object was a spindle whorl, a loom weight, a pendant, or a bead.

Fourth, just because an object has a perforation doesn’t mean it could ever have been strung. I have seen objects with perforations that are far too small to string on anything thicker than a single strand of hair (such as the model below), rendering the object fairly useless as a bead. I have also seen glass pressed around a rod, pin, or other rounded object. When the object was in use, the glass would be considered a decoration, but not a bead. When the glass cracked, it retained the circular ‘perforation’ of the rod or pin, but the object never really served as a bead.

The net result is that defining a bead is relatively simple if you don’t need to technically differentiate it from a lot of other things. If you need to tell the difference between a bead, a spindle whorl, a loom weight, a pendant, or an interesting decoration, however, then defining a bead is rather difficult. So while I use the above definitions in my work, I am keenly aware of the possible issues with that definition.

Update: 10 June 2017

I realised today that I haven’t posted anything to this blog in over a year. OVER A YEAR. I look at beads and 3D modelling and glass all day, nearly every day, and I somehow haven’t posted here in over a year. Which isn’t good.

I will say that it’s a bit difficult knowing what to write about. I’ve already done most of the easy posts (easy to think of, that is, not necessarily easy to write!), and I’ve done some larger general posts. Since I’m in the middle of my PhD, you’d think that would be the obvious thing to write about. I do all this research after all, and it could easily go into a blog.

The problem is that all of that research either involves objects with significant licensing issues (so I can’t just put them up online) or is crucial to my PhD (so I can’t really publish it ahead of time). So I find myself struggling to write about anything on this blog, and as any normal person would, I have thus avoided writing. Apparently I’ve been avoiding it for just over a year.

A lot of people have said I could write about the process of the PhD. That’s certainly an option, but I feel that most PhD students end up doing that, I don’t really want to become yet another person who writes about the PhD experience.

All that being said, I’m being a bit ridiculous acting like there’s nothing to write about. There are articles I’ve read, stories about new bead finds, new glass finds, new information about the objects, the people, and the properties or characteristics of both that I really do have a wealth of possible blog posts. I just need to motivate myself to do it. So that’s what I’m going to do, hopefully for the rest of this PhD.

So what have I been doing for the last year?

A lot, though sometimes it feels like relatively little. I’ve been attending conferences and have had a bid accepted to host one here in Glasgow. I’ve been on four field projects since my last post – all in Scotland. Only one of which directly related to my PhD work, but all of them were good experiences and all of them involved digital imaging techniques in one way or another. And then I’ve been working on my PhD, which has changed a bit in the last year. Not astronomically, but significantly.

I’ve also applied for a lot of funding from various groups, and have received very little. That’s perhaps been the most frustrating element of all this, is the degree to which funding decisions have hurt my ability to complete this research. In truth, funding bodies deciding not to fund me is disappointing, but understandable. They get a lot of applications, and my research is such that it often doesn’t quite conform to exactly what these funding bodies are looking for. What’s more frustrating is the number of times I have been told I am ineligible for funding because I am American, or because I started my studies in January instead of September (and am therefore too ‘young’ for one round of applications and too ‘old’ for the next). But what’s most frustrating is having someone who is supposedly an expert in 3D modelling and digital imaging saying I don’t deserve funding because my research is too ‘peripheral and unimportant’ (actual words) or because it’s ‘no different than laser scanning a building’ (also actual words) and is therefore really easy to do.

So I’ve had some serious funding issues.

BUT, that is also where my biggest breaks have come from. The organisations that have funded me for smaller amounts have been incredibly supportive. More commonly, though, a number of people in Scotland have seen or heard of my digital imaging abilities, particularly in relation to difficult objects, and have hired me for various freelance jobs. Freelance work is currently the largest funder of my PhD aside from student loans, and I am eternally grateful for all those who contributed to that work.

Despite the funding chaos, my PhD has been an incredibly positive experience so far – a stressful one, but still very positive. My supervisors are incredibly supportive, as are the departments in which I am housed. The research continues to move forward in ways I would never have predicted, as is the nature of a PhD. And so I find myself just over a month shy of the halfway mark feeling a bit of disbelief that I’m nearly halfway done, but largely contentment and even excitement at what I’ve done and where the project appears to be going at the moment.

I know I said I didn’t want this to turn into a blog about the process of the PhD, but it seems to be doing just that. And maybe I’ll let it, at least to some degree. So I’m going to keep plugging away at it and keep applying for funding and keep doing what I do, but hopefully I’ll remember to post a lot more frequently from now on!

3D Modelling Techniques

When we hear 3D modelling, we tend to think either that the model was created by hand in something like AutoCAD or by scanning an object with lasers to get its exact dimensions. But there are actually a number of different ways to make a 3D model, each of which are suited to different needs.

Laser Scanning

Laser scanning is probably the most well-known technique because they are usually used when modelling landscapes, monuments and buildings. There are a few ways to laser scan an object, but larger scanners tend to operate using time of flight while smaller handheld scanners use triangulation. Time of flight works a lot like echolocation—a laser is fired at a surface and the time it takes the laser to travel back to the sensor indicates the distance of that surface point from the sensor. Do this enough times on enough points around the object and you end up with enough points for a model.

Excavating My Own Research

This morning I was writing an idea I’d had down in my notebook. It’s a bead research notebook that I’ve had for about six years, but I’ve had phases of being really bad about writing stuff in it. As a result, I have just over 100 pages of notes in here spanning 6 years of work (like I said, some periods were REALLY bad).

But what’s cool about it is that I have notes from when I first started looking at beads. Not all the way back to the fall of 2009, which was my very first foray into beads, but it goes back to 30 April 2010. It’s now 14 May 2016.

The Early Medieval Archaeology Student Symposium 2016

Presenting in the Chapter House

This past week, I found myself in Bristol, attending and presenting at the 10^th Annual Early Medieval Archaeology Student Symposium. It was held in the chapter house of Bristol Cathedral, which I believe was the first time an academic conference had chosen the cathedral as a venue. I found that surprising, as the cathedral was a wonderful venue with marvelous staff.

The conference was relatively small – no more than about 40 people – but I would argue the papers delivered were strong and the research solid. And the smallish nature of the conference let everyone get to know each other much more than you would at larger symposiums, making the whole thing a touch less formal, more familiar.

John Tighe made some really interesting points about mortuary practices in Ireland during the transition from Paganism to Christianity, stating that for at least 2 centuries, many cemeteries would have both Pagans and Christians buried within them. Cemeteries were organised by family, not religion, and so this blend was entirely possible.

A number of people commented on complexity – Scott Chausee remarked that texts say the Anglo-Saxons just showed up and started killing people, but it’s probably more complicated than that. People interact in more complex ways, and while there was warfare in certain areas, that wasn’t the case everywhere. Justine Biddle urged us to look at the full story and possibilities of meaning behind an object, the changing biography it has rather than choosing an arbitrary point in time as the ‘truth’ and all other changes being some aberration of that. Finally, Catrine Jarman looked at mortuary practices and assemblages in mass graves across Viking Age England and discovered differences in how remains were treated, even within mass graves.

Bristol Cathedral from the outside – it was rather rainy both days.

Robert Smisson had one of the best quotable lines, in my opinion, stating that when your crop fails, you don’t immediately care so much about why it happened, you care about not dying. The point was that the questions we often ask of the past are not the questions individuals at the time were asking, and the issues we concentrate on differ from those seen as important in the past.

Rose Hedley made a similar remark, this time focusing on soldiers. Soldiers, she argued, would hardly be completely unaware of the political contexts or the conflicts in which they fought. While they may have differed in their perception of that context or the degree to which they understood the complete context, no soldier walked into war entirely blind, just because. This is a seemingly obvious statement, but sometimes scholars need reminding of seemingly obvious things.

A number focused on spatial relations between sites. Matt Austin reminded us that centrality is relative – a central place now was not necessarily central a millennium ago, and a place is only central within the context of its surrounding area. Adam McBride mapped distributions of wealth (as far as can be determined) in 6^th – 7^th century graves along the Upper Thames and found that centres of wealth, at least in terms of burials, changed through the period and differed based on the sex of the individual. Andrew Welton then took an interesting stance in looking at recycled iron in spearheads, concluding that the recycling was actually decorative, and the connection of the material to land claims in post-Roman Britain.

The Wills Memorial Building – not technically related to the conference, but cool building near the department

The next day began with digital technologies, specifically a paper by yours truly, but I will post on that later. Megan Kasten followed it up with a paper about 3-dimensional reconstructions of the grooves in carved stones, specifically those at Govan Old in Glasgow, to uncover differences in carving styles and techniques.

Then we took a quick jaunt to the Mediterranean, where Simona Uccella spoke about the San Donato Church in Capodrise, Italy. The church was badly damaged in WWII and was never restored, but its unusual architecture reveals a complexity in religious practice during the early medieval period.

The final two papers talked about landscape, one by Alex Thomas in relation to the boundary of the Danelaw in England, and the other by Beatrice Widell in attempting to identify possible location for lost Columban monasteries.

All in all, it was a strong conference, with interesting remarks by those involved. The weather was a bit miserable, but the subsequent lighting made the chapter house of Bristol Cathedral an even more interesting place to hold a conference than it already was. The relatively small size let us cram ourselves into pubs and restaurants with relative ease and float between tables to chat about our research. It also led to everyone learning there would be a bid for Trinity College Dublin to host the conference next year, and rather than putting up any counter offers, we decided to unanimously support the decision.

So thank you to those who organised EMASS 2016 in Bristol, thank you to those who presented and attended and made the week as much fun as it was, and thank you to Trinity College Dublin for taking up the task of hosting next year!

Delegates relaxing on the grass outside Odda’s Chapel in Deerhurst before heading our various ways home.

What is the Purpose of Heritage Visualisation?

Generally speaking, when you hear of heritage visualisation, you’re first reaction may be something along the lines of, ‘What’s that?’ A perfectly valid reaction, since we tend to talk about visualisation in terms of specific techniques (e.g. photography, 3D modelling, etc.) rather than as the more general term. Heritage visualisation is simply representing heritage materials (e.g. objects, sites, monuments, texts, etc.) in a visual way. Drawings, photographs, and 3D models all fall under this larger term, as well as any other way of visually representing these materials.

Photography and Its Effects on Museums

I was doing a fair amount of reading this week and came across a chapter that discussed the overwhelming influence photography has had on art, history, and museums. You can see how it would have a large influence pretty easily, but it brought up a lot of good points I’d not really thought of before, so I thought I would post about it.

The work of Louis-Jacques-Mandé Daguerre was presented to the Institut de France on August 19, 1839. Daguerre had created what we know as a daguerreotype (hence the name), which was a silver-plated piece of copper that was treated with fumes to make it light-sensitive. It was then exposed through a camera and the first photographs were created.

At the same general time, Henry Fox Talbot had invented the photographic calotype or talbotype, which was a piece of paper coated with silver iodide and then exposed for as long as necessary to create an image.

Interestingly, Samuel Morse (known best for his invention of the telegraph and Morse Code), was one of the first people to introduce the daguerreotype to the US, where it quickly caught on. The calotype/talbotype was less popular, because it required much longer exposure times than the daguerreotype.

All this happened within a few years, and the result had an enormous influence on Western culture. Many first photographs were produced in that time, such as the Boulevard du Temple (1838, pictured right), which is believed to be the first photograph (or at least the earliest surviving one with a human being in it. It’s really more of a cityscape, but there are two individuals towards the bottom, one having his boot polished by the other.

Photographs earned a fair amount of prestige for two main reasons: 1) they were incredibly detailed, often so much so that the image remained clear under a hand lens; and 2) they were perceived to capture the truth, nothing more, nothing less. Paintings could embellish or omit certain features, whereas photographs captured the truth of a person or scene.

Photography quickly destroyed two art forms that had recently gained prominence: miniature portraiture and reproductive engravings. Miniature portraits claimed to be truthful, detailed, and provide the owner with fairly high social status. Daguerreotypes could do the same thing, but to an even larger degree. It wasn’t so much that they were cheaper (because they weren’t, at least in the beginning), it’s that they did the job so much better. Reproductive engravings fell out of favour because they took longer and daguerreotypes could capture the detail much better. The market value for both art forms was destroyed very quickly and they never really recovered.

This doesn’t necessarily mean photography held a high status or that it gained favour overnight. One particularly good quote I’ve come across is that from Rosen and Zerner: “Many artists and critics affected to despise the new invention until… they decided they wanted photographs of their mothers,”

But photography also completely changed museums. Museums before photography had been invented or even before it gained traction were generally founded to house existing collections of original pieces that had been acquired one way or another. They weren’t meant to represent a discipline or a culture or a medium as a whole, they were more collections and cabinets of curiosities. They also often served as showcases for imperial power and national prestige, which is one reason why the non-western sections of art museums tend to be more ethnographic as a whole.

Once photography came out, anyone could make a print of any painting, sculpture, object, or piece of art, so long as they were willing and able to travel to the original to capture the photograph. Because of this, newer museums (i.e. post-photographic museums) were generally founded to create collections rather than house existing ones, and they placed a heavy emphasis on education.

© Victoria and Albert Museum

A good example was the South Kensington Museum, now called the Victoria and Albert Museum often seen as one of the first of these post-photographic museums. Their photographer, Charles Thurston Thompson, photographed nearly everything that was loaned to the museum. He also travelled to take photographs of other collections or objects being cast for installation. Thompson even photographed objects or architecture that were not usually on display. The late 12^th century portico of the Santiago Cathedral in Spain, for example, was concealed behind later architecture and was therefore virtually unknown before Thompson photographed it (left).

 

A number of museums modelled themselves after the South Kensington Museum, including the Museum of Fine Art in Boston.

It also changed how art was displayed to the public. Museums rarely showed damaged or incomplete works prior to photography, but the appeal of truthfulness presented by photography drove museums to present pieces as they were, rather than as they felt the pieces should be. This led to a change in art conservation, where conservators needed to be skilled in photography as well as other art forms. This included complex forms of photography as well, such as infrared, x-ray, and ultraviolet.

I find the appeal of the truthfulness of photography interesting, since it is now so often suspect given the rise of Photoshop and other similar programs. Nowadays, we often feel that seeing the original is more truthful than seeing the photography, or seeing the landscape or subject photographed is more truthful than the photograph itself.

I have a fair amount of thoughts on all this, and a fair amount more that was in the chapter that I want to talk about, but I’m going to need another day or so to wrestle with them before I can post about it. In the meantime, if anyone else has thoughts or questions or comments, feel free to leave them below – I’d love to hear them!

 

All information in this post taken from:

Walsh, P. 2012. Rise and Fall of the Post-Photographic Museum: Technology and the Transformation of Art. In: Cameron, F. and Kenderdine, S. eds. Theorizing Digital Cultural Heritage: A Critical Discourse. London: The MIT Press, pp. 19-34.

Images from:

Boulevard du Temple: https://en.wikipedia.org/wiki/File:Boulevard_du_Temple_by_Daguerre.jpg

Bead Design: Take 2

You may remember that back in October, I started to write a series of posts about documenting the designs of polychrome beads. I started to describe my system, and then promptly fell into one of the busiest three months of my life, so I stopped posting.

A lot happened in those three months, one of which was that I changed my system for documenting bead designs. The old system worked, but only to a degree, and when we got into things like the lines on a bead and the designs or orientations they could have, there were easily over a hundred different options. It got too confusing keeping track of all of them, and then there were issues with colour and all sorts of things.

Yes, I’ve changed my methods. Research is an ever-evolving process, and what may seem to work for one dataset actually doesn’t work for another. What may seem to work initially might be alright, but it’s actually cumbersome and clunky when you try to use it on a larger scale. Refining techniques is simply a part of the research process.

So I’m going to start back from the beginning with bead design, describing the new set of methods. You’ll notice they aren’t so different from the old set of methods – everything is still there, just shifted to make it easier to talk about.

Stereoscopes and Archaeology

I’ve just started my PhD, which means this blog is about to get a LOT more active! If you’re curious about what my PhD is in, you can check out the longer description here. For now, I’m looking at finding a practical, portable, and affordable way to create 3D models of small, reflective, and translucent objects (using beads as a case study, because they fit perfectly). You can check out the reasoning in the longer description, too.

But as a result of having just started, I am in the middle of a LOT of reading, which means I have a lot to talk about, at least theoretically speaking. So I’m going to start doing more of these posts, talking about what I’ve read, what I’ve learned, and why it’s important for not just my research, but bead studies and archaeology in general. Hopefully you guys can benefit from some of this, and at the very least, it’ll help me internalise what it is I’m reading.

So this week, I didn’t do crazy amount of reading because most of the week was running around taking care of logistics – picking up residence permits, filling out loan paperwork, etc., etc., etc.

But I did read something really cool, and it had to do with using stereoscopic images as a way of viewing enhanced macro photographs and even semi-3D images (Campana, 1977). Stereoscopes are those contraptions you’ve probably seen from the 1800s that look like a View-Master we all know and love from childhood, just bigger (because that’s exactly what it is). You place a card with two slightly offset images in the holder and look through the lenses. Because the images are slightly offset, when you look through the lenses, the image appears to be 3-dimensional.

19th century stereoscope

In the 1970s, this was one really effective way of making 3D images in archaeology (1977, 435). Taking photos from a microscope or using a macro lens was really difficult to preserve in publication. The depth of field is generally quite small, and while our human eyes can account for it and adjust accordingly (at least to some degree), cameras really couldn’t (and still aren’t great at it). So, at least in the 1970s, creating stereophotograph pairs was one fairly simple way of preserving photomacrographs or photomicrographs for others to view (Ibid). It also helped in cases where a researcher was looking at various collections in different locations, because you could preserve the images from your first collection and bring them to the second for comparison (Ibid).

Stereo-photomacrographs, as these images are called (or stereo-photomicrographs when created from microscopes) are created by taking two separate photographs where the lenses are offset by 6.5cm (Ibid, 436). This is the average distance between human eyes, so it needs to be the distance offset for these photographs. With photomacrographs, it gets a little dicier, because you’re so close to the object. For these photos, you offset the image by 15° instead (Ibid).

You can use two cameras simultaneously to take the photos, but with macro photos (or microphotos), you can’t really place two cameras close enough together to get the right image. So instead, you use the same camera and just move it (Ibid).

Photomacrographs have a better depth of field than micrographs, because you can control more of the functionalities of the lens. So up to a certain magnification, photomacrographs are actually better than photomicrographs.

To view the images, you can build a lens system similar to the stereoscopes used in the 19^th century, or you could just find one and use it. According to the main article I was reading (Ibid, 439), you can also train yourself to see the images without a stereoscope, but I don’t know if I’ll ever be able to do that.

Not only was this all really fascinating to read anyway, it was particularly fascinating having just come from working in a museum specialising in the 19^th century and particularly working with a stereoscope and a set of three images. I never really would have guessed that they could be used as a precursor to computerised models, but now that I’ve seen it and read it, it makes complete sense. And now I just really want to try it, despite having zero access to stereoscopes.

There are probably a certain number of you saying something along the lines of “this is really cool, but what’s the point? Why use these images?”

Good question. The main point in the 1970s was to view objects in different ways, with different depths and lighting than the human eye naturally did. Doing so allows us to see things like wear patterns, designs, or cut marks on objects that we may not be able to see with the naked eye. Our eyes are really good at adjusting to different circumstances, so they can often block out things that we actually DO want to see. Creating stereoscopic images provide a depth of field to the objects that often allowed for more clarity and a stronger ability to see those thing we might not otherwise see.

When it comes to macro photography, these lenses allow us to zoom into objects that are quite small, or zoom into areas our eyes can’t see simply due to the size of what we’re trying to look at. I’ve used this with beads quite a lot, and have posted a number of the results on this blog (like the image above). But I’ve never tried stereo-photomacrographs before, and I’m quite keen to try, if only could find a viewer.

 

Everything I talk about in this post comes from the following source as well as personal experience in museums:

Campana, Douglas. 1977. Making Stereo-Photomacrographs for Archaeological Studies. Journal of Field Archaeology. 4, 435-440.

Stereoscope image from https://upload.wikimedia.org/wikipedia/commons/f/f6/Holmes_stereoscope.jpg