The most recent issue of the Journal of Field Archaeology has a little gaggle of interesting contributions to digital methods in our discipline. The two that stood out most to me involved the use of 3D modeling to map complex and challenging site types resistant to traditional forms of archaeological documentation. These articles both demonstrated how digital techniques are doing more than producing flashy presentations and moving field documentation forward in terms of efficiency, accuracy, and precision.
The first article looked at the use of photogrammetry and structure-from-motion imaging to document the 4th c. B.C. Mazotos shipwreck near Cape Kiti, Cyprus. The complexities of documenting shipwreck sites and particularly those in relatively deep water, are well-known. Using digital cameras and straightforward structure-from-motion software like Agisoft Photoscan, S. Demesticha and her team were able to document the substantial pile of amphora left behind after the ship sank of the south coast of Cyprus. Using Agisoft Photoscan required that a diver take a series of photos from both directly above the wreck, but also at oblique angles. This software, however, eliminated the need for myriad control points or grids to ensure that the photographs overlapped enough to be accurate. As a result it was possible to take the photographs necessary to produce a highly accurate plan of the shipwreck on a daily basis during excavation. One of the upshots of this easy and accurate technique of recording their excavation was that they were able to identify the 6th century A.D. seabed level on the basis of a stray amphora sherd, and document more accurately the undersea formation processes that shaped the site.
The second interesting article discussed the potential for using a laser scanner to document the Skoteino Cave on Crete. The cave saw occupation from the Bronze Age through the modern period and has long been the object of archaeological investigation. Caves, however, are particularly difficult to document accurately as steep grades, difficult sight lines, and their unsuitability for GIS has tended to produce plans rife with errors and inconsistencies. 3D laser scanning is an expensive alternative to these other techniques with gear costing into 6 figures, but one that offers the possibility of creating highly accurate 3D models (and plans) of the cave. Interestingly, the use of laser scanning at Skoteino cave did not produce a more accurate plan of the site prior to the publication of the article. This is largely because of the massive size of the data set produced by the laser scanner was too difficult to manipulate in a way that retained accuracy. This, however, is a limitation that will soon be ameliorated through the use of cloud computing, higher-powered processors, and ever increasing amounts of RAM and hard disk speeds.
Both articles showcased the next generation of archaeological documentation in a journal that most would regard as traditional, but not unsophisticated in character. Predictable, both articles demonstrated the limitation of print journals in an era of 3D field documentation. The flat images in Demesticha et al.’s article on the Mazotos shipwreck simply did not do justice to the dynamic methods used to document their work. The existence of sites that make 3D manipulation possible on the web makes the absence of a link to even one 3D model a shortcoming rather than an oversight.
I wonder if we’re close to the point where it might be excepted that the team from Skoteino cave should make their dataset – however massive – available for someone with substantial processing power to convert into either a 3D or even old fashioned 2D plan. Since the article did not present the fruit of their labor and the limitation was largely technological, I can see no reason not to share the raw data to at least demonstrate the validity of their approach.
Despite these shortcomings, these two articles and the others in this volume show that 3D imaging technologies are no longer the domain of a fringe group of tech savvy (tech obsessed?) archaeologists, but increasingly available to solve real archaeological problems of field documentation.