If you live in Tallahassee, or have visited Florida’s Capital, you are likely familiar with a Tallahassee landmark – Mission San Luis, or San Luis de Talimali as it was named by the Spanish. It was a 17th Century Spanish Mission located on the present-day corner of Ocala Road and West Tennessee Street. From 1656-1704 it was the western capital of La Florida, and housed approximately 1400 Apalachee, including the chief, a resident Franciscan friar, a Spanish military garrison, the soldiers’ families, and other civilians (McEwan 1993).
Previous archaeological excavations focused on determining the site layout and uncovering the larger structures, especially the Apalachee Council House and the Mission Church. A Spanish-style domestic structure and associated features were also investigated. The ten field seasons (not contiguous) or archaeological investigations at San Luis have yielded important information about the Spanish presence in the capital. Likewise, the excavations of the Apalachee Council House have given us insight into this important structure that centered indigenous public and ceremonial life. With the information gained from archaeological excavations and documentary resources as our foundation, we propose to explore the community of Apalachees and Spaniards who lived, worked, and died at San Luis.
*Inside of reconstructed Apalachee Council House at Mission San Luis. Photo taken by author, January 2017.
– post by Tristan Harrenstein, Florida Public Archaeology Network
In the last few years, archaeologists have been getting excited by the potential for recent advances in something called photogrammetry. This technology takes a collection of photographs of an object, plugs them into a program (Agisoft PhotoScan in this case), and builds a digital 3D model.
This is exciting! Photogrammetry is already useful for research and education, but it is also changing the way we record archaeological sites. Dr. Kotaro Yamafune (Research Associate in Nautical Archaeology at Texas A&M University) has an impressive body of work using this technology to record underwater shipwrecks. After five days of photographing, he was able to generate highly accurate and easily manipulated maps that would normally take years and many divers. The use of photogrammetry saved money and people hours, without sacrificing accuracy or data.
Which brings us to the purpose for this blog post. Since there has been so much success modeling underwater archaeological sites, what potential does photogrammetry have for sites on land? Might this technology someday replace hand drawn maps? To test this, Barbara Clark and I visited Florida State University’s archaeological field school this summer and modeled one of their excavated units.
One limitation of photogrammetry software is that it needs identifiable features so that it can figure out where each picture was taken in relation to the others. I was concerned that the unit walls would look too much alike for the program to align the pictures properly. As a result, we made two models of the same unit. The first set of photos were of the plain unit walls while the second set included some photo board symbols pushed into the sides to provide points of reference for the program.
To be clear, this experiment was not supposed to be definitive. The goal was to get some idea of how much potential there currently is for photogrammetry as a tool for recording terrestrial archaeological excavations and to better understand what equipment we would need. That being said, these models turned out far better than I had expected, with very little difference in quality between the two tests.
See an example of the terrestrial photogrammetry we did on one excavation unit at the FSU Anthropology’s 2016 Archaeological Field School HERE!
*Please note, these examples are using just 500k faces each. A much higher resolution of 25 million faces is possible, but not many computers can currently handle this.
As far as the equipment goes, we need better photographing methods. Even with the monopod, taking pictures of a unit this deep was difficult and uncomfortable. I spent a lot of time with my head in the unit, or standing at awkward angles inside the unit, trying to hold still for the camera while yellow flies gleefully seized upon the opportunity to grab a bite.
On the upside, the solution to this is relatively simple. All we would need is a pvc pole, a camera mount for bicycle handlebars, and a remote for our camera. This would take a few test shots to make sure the angle was correct, then the rest would be faster and much more comfortable. Throw in a white tent to help diffuse the light evenly and we should be in good shape.
But is this worth pursuing further? We certainly do not have the same limitations on land that our underwater peers do, and photogrammetry cannot replace hand-drawn profiles of unit walls any more than pictures can (due to a tendency to distort colors). Does this mean that photogrammetry has no current value for terrestrial archaeology?
Absolutely not. There are a lot of ways this technology could be invaluable right now. Do you have an artifact that you cannot take back to the lab with you? A few minutes of photographing means you can examine it later at your leisure. This also has excellent applications for complex features that do not just rely upon soil changes, such as brick structures. Photogrammetry models provide a sense of depth that even the most diligent hand-drawn maps or pictures cannot capture very well.
Mapping a feature like this one on 2D graph paper is very challenging and time consuming. Photogrammetry is already an improvement for a situation like this.
In a nutshell, photogrammetry currently has some excellent, if situational, uses in terrestrial archaeology. Perhaps this will revolutionize the way we record sites, or perhaps it will just remain a very specific tool for a specific job. However, technology is advancing quickly and I would not be surprised if photogrammetry, scanning, or just tablets make hand-drawn profiles obsolete someday. We will need further testing to fully understand the potential of photogrammetry, but now is the time to begin.
Tristan Harrenstein is trained as an archaeologist and has a passion for outreach and education. This is fortunate as he is also an employee of the Florida Public Archaeology Network, an organization dedicated to promoting the preservation and appreciation of our archaeological resources. He shares a blog space with his boss (Barbara Clark) and you can read more blog posts on other archaeology related subjects that tickle our fancy here.
If you recall from a few weeks ago, FSU Office of University Communications spent a few hours in the field with us to document our work and uniqueness of the archaeological field school as a hands-on learning opportunity for FSU students. Staff of the FSU Communications office – Nora Bertolaet, Digital Content Producer, Ryan Ruditz, Videographer and Editor, and their skilled crew produced a fabulous piece that we are all proud of.
We also had a visit by a retired soil scientist that has worked all over but is especially knowledgable about the soils in our area. We need to figure out if some of the sands we are encountering in our excavations are naturally occurring or if the people that lived here 1200-1400 years ago brought them to this specific location. If it is the latter, we then get to puzzle over (and hopefully answer) – Why? Next week we will take sediment samples and cores of various parts of the site for further analysis.
We were very excited to host staff from the FSU University Communications office. They brought out a number of digital and video cameras to capture our work. It was wonderful to share our passion for archaeology and the excitement for what we are learning about the last people to live here is palpable. Nora Bertolaet, Ryan Ruditz, and their team were wonderful to work with and asked really great questions! We can’t wait to see the finished product (which we will post here of course)!
We were anxious as we returned to the site this morning, unsure of the extent of any damage to our excavations from Tropical Storm Colin. On Friday of last week we took extra precautions when we covered the excavation units in anticipation of three days of rain – but that was before the rain turned into TS Colin! We are so glad we bought plywood and made extra efforts – they paid off!
In several of our units near the swamp (and on a downslope) we were not so lucky. We had to create a bucket brigade to get the nearly 40 cm of water out of the deepest unit!
Fortunately for us, we are nearly finished excavating the units that were inundated. This means we can leave them to dry out over the next few days and finish our work in there later this week.
So, the crews that were in those units were sent to join the rest of the group and we opened three more excavation units to extend our view into the site. We still have lots of work to do as we uncover features and try to figure out the puzzle of the past, but we are having a great time! Thanks for reading!
If you have watched or listened to the news, you know that Tropical Storm Colin is crossing the state of Florida as we write this. The rains from TS Colin arrived in Tallahassee overnight and continued throughout the day. This meant no fieldwork for us. Instead we spent the morning in the lab at the FSU Department of Anthropology washing, sorting, and re-bagging dry artifacts. These are important first steps in artifact analysis.
After lunch we were able to take a tour of the State Archaeological Collections curated by the Bureau of Archaeological Research, Florida Division of Historical Resources (thanks to Haley Messer for arranging and the staff of BAR for taking time out of their busy day to show us around).
We are headed out to the site tomorrow, rain or shine, to check on the status of our excavation units and continue where we left off last week. Stay tuned!
Today we continued excavating our units (there are 13 total units being excavated). Each unit is along the same coordinate line so that we can eventually create one continuous trench.
Many of the excavation units thus far have contained pottery sherds and lithics while others have contained shells and bones.
The discovery of these artifacts allows us to map out the site and see how far the plaza, the place where people once used for daily activities, extends and where the shell midden ring, where they discarded their waste, begins. In addition to the artifacts we are discovering in each unit, the color changes in the soils can also tell us important information about the site. For instance, a few of the units have contained a light yellowish colored soil that is distinct from the usual light brown colored soil.
The units with the light yellow soil have been marked as a part of the plaza area. These particular features are also starting to appear in adjacent units as well. The more units we open up the more we can tell about where the plaza ends and where the outer shell midden begins. This information will help us map and better visualize the perimeters of the site.