This is my paper for this afternoon’s Digital Lightning event. If you’re in Grand Forks, the event showcases the recent efforts of the Working Group in Digital and New Media. It will be at 4 pm in the Gorecki Alumni Center on the University of North Dakota’s campus. If you can’t make it to UND, that’s ok, you can enjoy the live stream of the even here.
My talk will look at what’s next in 3D imaging. It’s pretty speculative, but that’s ok, because it’s only 6 minutes long.
This image, by UND MFA Ryan Stander, captures the traditional view of archaeological fieldwork. The use of a dental tool to meticulously extract a bowl of the 4th century BC resting on the floor of a collapsed house. This vessel tells us something about the economic conditions among mercenaries at a fortified settlement on the south coast of the island of Cyprus. It’s pretty analogue.
Anyone with even a little more archaeological experience knows that publication remains a crucial step in the archaeological process. Mediterranean archaeology remains committed to old school paper publications. (This article actually details how our project used a custom web application to collect data in the field. So I’m fudging a bit.
Traditionally, the publication process begins on the side of the trench with paper paper plans and textual descriptions. For over 100 years, these rather primitive tools have allowed archaeologists to describe the horizontal and vertical relationships between layers of soil, objects, and architecture that they excavate.
In the last 3 decades, new tools have allowed archaeologists to document more precisely these spatial relationships. Here UND alumnus Brandon Olson uses a laser theodolite “total station” that uses precision optics to measure distance and plot features in tranches. Brandon is a Ph.D. student at Boston University and our field director on Cyprus.
The precision of the total station allowed us to create a precise plan of the architecture that we find in our trench. This plan here derives from traditional excavation methods and the data collected from the total station. This plan is suitable for publication with only a few modifications and depicts the line of a massive 2 m wide wall that fortified the mercenaries stationed at our site on the south coast of Cyprus. The dashed line shows the location of a deep pit on the south side of the wall. This stone lined pit on the interior of the wall was probably for storage and was filled with over 100 kg of pottery probably representing a clean up at the site after an episode of destruction.
Photography has also played a key role how we document the results of excavation. A photograph of our trench from above makes more clear the line of the wall and the stone lined storage pit on its south side. You can also see where we stepped the trench back to prevent stones collapse from falling into the stone lined put area while we excavated it. This image, obviously, provides additional, useful information on the arrangement of the trench, the storage pit, and the fortification wall. There’s a secret to this image, though.
The overhead photograph is actually a mosaic made from over 200 individual digital photographs. The blue rectangles on this image are the individual photographs. We then processed these images using 3D photogrammetry software called Agisoft Photoscan. This software uses overlapping photographs to not only create a mosaic image, but also to measure the relative vertical and horizontal position of the objects in the image.
This allows us to create a point cloud with each point having an X, Y, and Z coordinate – I’ll talk more about this later – and then to create a 3D surface from these points. This is what the 3D surface looks like. This surface took about 10 hours to process using a laptop computer with an 12 gigs of ram, 1 gb graphics card, and an 2.8 gb Intel i7 processor. With 200 photographs, we know that this surface is accurate within a couple of centimeters. The software adds some shading to make the 3D image standout more.
We can then drape this surface with the photomosaic to create a photorealistic 3D image of our trench. We can rotate the image so that we can present new perspectives on the trench in traditional 2D publications. We can also georeference the image so that we can measure vertical and horizontal distances and place the trench and its features in relation to other things on the site. From this image you can now get a clear idea what the stone lined pit looks like as well as see the neatly stacked south face of the fortification wall.
3D models like this are getting to be old hat in archaeology. In the past 2 decades, however, they were built using ground mounted LiDAR which use lasers to measure three dimension objects. In fact, this summer we’ll compare Agisoft Photoscan to results produced by a $80,0000 Leica Scanstation at my new project at the site of Polis-Chrysochous on the western side of the island.
These technologies, however, still do little more than amount to a different way to display the three dimensional space of the archaeological intervention in a static two dimensional medium. The three dimensional image remains a measured representation of the trench.
What’s next is making this image dynamic. We already can rotate the image and zoom in and out. This is not the next step. The next step is bringing the archaeological data the we produce during excavation and allowing a the viewer to access this data through this image. Each point, for example, could link to more than just locational data, but also to interpretative data. Points could tell us about the features that they constitute, their stratigraphic context, and any objects related to the these strata. The 3D image will go from being a static surface to a dynamic interface allowing the viewer to “dig down” into archaeological data to explore the myriad interpretations that make up our understanding of the past.