Archaeology in a Whole New Dimension

By Victoria Pagano

Hello again, it’s Victoria here to tell you that I’m excited. Excited about the work we’re doing out here in Eagle Cave and with the ASWT project as a whole. Now this is not to say that I wasn’t enthusiastic when I first found I would get a chance to intern in an amazing place, with knowledgeable people, learning and doing great new things; but, I’m writing now with a little training under my belt as to the way things work and and a better understanding of how absolutely fantastic it really is.

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Okay, this isn’t at Buenavista, but it is one of the sites that is worked on by the project. Mighty “El Castillo” at Xunantunich, just one example of the architecture and archaeology to be found in Belize.

Before ASWT

First, I would like to tell you a bit about my first and only field work in archaeology…just to offer a bit of perspective. I was unbelievably lucky to work in Belize. A beautiful country full of cultural and ecological diversity– not to mention the incredible historical and archaeological richness it holds as well. The project was based in the Mopan River Valley, studying the ancient Maya sites of San Lorenzo, Xunantunich, and Buenavista del Cayo. My work was focused at Buenavista, a mid-level city center with plazas and stone structures that had been reclaimed by the jungle.

Belize

That’s where I worked, Buenavista del Cayo. Just down the river from Xunantunich and many other archaeological sites.

It was in Belize that I learned basic excavation procedures:

Step 1: Find somewhere you want to excavate and establish an excavation unit. This includes (for most) establishing a permanent datum, laying out the unit, and taking starting measurements.

Step 2: Establish your excavation protocol. Are you going to follow natural breaks in the stratigraphy, or are you going to use an arbitrary measurement to create your strata, lots, layers, etc. You’ll probably want to sketch and photograph the starting and ending surfaces, too, as you work your way down.

Step 3: You find something really cool in the floor or wall of your unit… a hearth, post-hole, projectile point, a body, etc. — you decide you want to make sure this is in your notes (hopefully you are taking notes, good notes), so you need to take additional steps.

Step 4-6: You need to 4) Take photographs— with a scale and some indication of direction 5) Map it i.e. create a drawing by measuring to and from objects in your unit to an established point or points, like a sub-datum. This will yield a plan or profile map with detail as to where your find is and where everything else in your unit is in relation to your find. Detail, detail, detail!  Depending on how precise you want your map to be, if you have help, and your level of OCD, drawing a map can take anywhere from minutes to hours.  6) Take more notes of the object’s location, this may include a GPS point that you tie to your datum later, or measurements that you will use to associate the object’s location relative to the datum.

Step 7: You’re probably pretty tired from all those steps you took to draw your unit. You need a nap, but chin up, you established your unit today AND you found something! Hopefully your notes are good, you read that compass properly, and you’re mapping skills are adequate enough that your map doesn’t simply look like a box with a few misshapen circles, squiggly lines, and a triangle.

Now I have nothing against all those steps (the old fashioned paper and pen method works), but there is always room for improvement.  So why is it I am so ecstatic to work in a place where there isn’t monumental architecture, elaborate burials, mysterious mythology and codices? Structure from Motion.

What is Structure from Motion?

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Here I am focused on photographing my unit for SfM.

Structure from Motion (SfM) is a surprisingly simple technique that is easy to learn, quick to do in the field, and potentially available to archaeologists wherever they work, or at least those with access to modern technology. SfM uses still-motion photography to rebuild real-world, dimensional objects. Using a digital camera you take a series of overlapping, sequential photographs of your desired target and run them through a software program, such as Agisoft Photoscan.  The software is able to match up all the different photographs and build a virtual 3D model of the target (for more info on what Structure from Motion is, see our blog post from last spring:  Structure from Motion).

For the ASWT project, we are using SfM to document and record everything from entire sites to small excavation layers.  In other words, a digital camera and a computer take the place of the traditional pencil and sketch map technique that I became familiar with in Belize.  Creating sketch maps is somewhat fallible in terms of reliability due to human error; we can only record and note what we see or notice at the site. Often, having only a single chance to record something before we move on to the next layer. Even more often when we sketch we focus on the big things, the obvious things, not necessarily because we think the rest inconsequential, but because we cannot physically draw every detail. SfM captures all of the visual detail that we can’t see or maybe don’t even think to include at the time because we’re so focused on recording our super cool projectile point or rock alignment.

When it comes down to it, many of the steps and methods are the same (we’re still completing forms and taking notes and we aren’t taking any shortcuts), but what really changes is the end product: our results. Our notes, drawings, photos, and forms are all we have left after an excavation. SfM offers us a permanent, virtual record that preserves and offers accessibility to our excavation data for years to come (and dozens more eyes). Nothing gets skipped over, nothing forgotten.

Our Work So Far

Eagle Cave South Trench Strip numbering system.

Eagle Cave South Trench Strip numbering system. Strip 4 is where I focused my work for the first session in Eagle Cave.

As I mentioned in my introductory blog post, I am interested in archaeological applications of GIS. I also mentioned that I was intrigued by the SfM technique that I myself first learned about from this blog [Eagle Nest Canyon at the Texas Archeological Society Annual Meeting]. Now I come to you one month in, with a bit more knowledge on the project and the technique to present another perspective.

I spent the January session re-exposing a profile face, PS005, that was initially exposed in 2014. This profile sits in what we now call Strip 4, almost smack dab in the center, top section of the South Trench wall of Eagle Cave.

Digital annotation of PS005 orthophoto from 2014 before profile sampling.

Digital annotation of PS005 orthophoto from 2014 before profile sampling.

PS005 with micromorph samples superimposed and georeferenced onto the profile.

PS005 with micromorph samples superimposed and georeferenced onto the profile.

At first it was a mess. After removing the backfill and geo-cloth, we discovered that the profile face had suffered damage from continued erosion and rodent burrowing since it was originally exposed. In 2014, the investigators assigned strat numbers based on their original profile exposure –i.e. each visible stratum received a unique number.  However, they then excavated a small sampling column and did their best to follow the layer seen in profile across the unit. The presence of numerous rodent burrows, especially through the ashy layers, made strat definition challenging.

I should add one more factor, at the end of the 2014 excavations the PS005 profile was sampled by the geoarchaeologists who removed micromorphology samples.  Although done carefully, the wall was no longer pristine.

PS005 profile we exposed in 2015.

PS005 profile we exposed in 2015.

This helps explain why when we re-exposed the PS005 profile we could not easily match what we were seeing in the field to the original profile illustration. So, we decided to excavate a sampling column through a portion of the jumbled profile, using the 2014 strat numbers for our layer designations . This was done with two goals in mind:

1) Cut back eroded face (profile) and re-expose the stratigraphy.

2) Collect high-resolution samples of the matrix and artifacts within the profile.

Excavating a sampling column involves collecting the matrix of each layer (along with things like Spot Samples, Geo-matrix Samples, and samples for radiocarbon dating) that can be further analyzed in a lab.  We are not only collecting samples of each strat, but using the TDS shots of each sample and the strat location, we will add them all to the SfM model. So whoever processes and analyzes the samples can have a virtually exact geospatial reference of its origin. This will help us build an assemblage of associated artifacts, radiocarbon dates, and deposition event, aiding in our understanding of the shelter and the canyon: how it was used, when it was used, what they were doing there.

Rather than draw a standard paper and pen illustration of each layer as we excavated, we instead used SfM to document the top surface of each strat. This not only gives us an idea of what we were looking at, but it allows us to use GIS to calculate volume of matrix removed.

Field annotation of the strats in PS0010: 2015, previously PS005: 2014, that Charles and I completed.

Field annotation of the strats in PS0010: 2015, previously PS005: 2014, that Charles and I completed.

Once I finished with the sampling column, attempting to follow the strats that were assigned the previous year, the profile face that was exposed was extraordinarily rich.  In other words, by cutting back the wall we found better preserved and more complex stratigraphy. The newly exposed profile exposure is called PS010.

Previously, only about 10-12 strats were identified in this area.  We have now defined 22 individual strata from the “same” exposure. I re-photographed the profile giving us three sets of 3D data: TDS shots, 3D models of all the excavation layers, and now the model of newly exposed PS010. We now have a new high resolution 3D model to overlay all of the excavation layers and samples onto – all of which can be manipulated to aid in analysis.

Where it All Comes Together

Our field lab is where all the sets of photographs are processed. Using Photoscan we align and georeference all the images for each individual layer. The photographs, GCPs, TDS, and notes are all combined to digitally rebuild the excavation. A 3-dimensional, manipulable dataset that works hand-in-hand with all of the physical data—matrix, artifacts, etc.—and the recorded data i.e. notes, photos, etc. In order to have these georeferenced for GIS or used in photogrammetry, no less than six GCPs, ground control points, are included in each excavation exposure. Ground control points are geospatial reference points that you place on your object or in your unit, shoot in with a TDS or GPS, so that photographs and models can not only be more accurately aligned with each other, but linked to a geographic grid. This becomes incredibly handy when you are working in say, a canyon with multiple sites carrying on extensive excavations that you would like to map and relate to one another. Then, not only can you reference all of your units and sites among the canyon, but you can reference and cross-analyze your work with other sites across the region or the world. Once we have our models we can then export all or parts of the model into many different formats; GeoTIFF, TIFF, JPEG, KMZ, etc. Our models are ready to imported into GIS software where we can further manipulate and analyze them.

This shows the samples that were taken in the PS005 sampling column. They are superimposed onto the 2015: PS010 orthophoto.

This shows the samples that were taken in the PS005 sampling column. They are superimposed onto the 2015: PS010 orthophoto.

Orthophoto of complete PS010 profile face.

Orthophoto of complete PS010 profile face. An orthophoto is created once the SfM modeling is completed, GCPs added into the model, and then exported into ArcGIS for more analysis.

Our Answer

A goal of the ASWT project is to not only excavate and collect, but to gather the best data we can – or best representation of that data –backing it all up with SfM and GIS.  Structure from Motion gives us the opportunity to not only georeference our units, finds, and strata, but we can literally rebuild them, at least digitally speaking. No longer are we relying upon the traditional mapping, measuring, and sketching techniques of years past that result in rather dimensionless visualizations of excavations.

SfM also easily provides a new solution to an old problem: excavation vs. preservation. The basis of archaeology is essentially destroying material history in the name of research and discovery, so that we can preserve and record it as best we can. Granted we have gotten much, much better at recording and excavating than back in the early days of the field, there is still room for improvement and innovation. In 2014, Bryan Heisinger (2014 ASWT Intern; 2015 ASWT Staff Archaeologist) presented at the Texas Archeological Society annual meeting, on the uses of SfM and GIS for not only modeling, but extrapolating volumes of material removed and creating digital elevation models (DEMs). These can be used to study stratigraphy and depositional events of floods, people, and even animals– as Emily and Larsen can attest to. Our documentation of profiles, like PS005 and PS010 helps us build a database of all the excavations and the shelters to aid in the analysis of what is to some a rather abstract concept of time. Our work becomes more dimensional, more visible. You aren’t just looking at the profile of a wall or structure or shelter. You can virtually walk around that wall, walk into that structure, and around that shelter, without ever being there. The outreach potential is exponential.

The ASWT project personnel and many of our colleagues believe that SfM is that next step in improving archaeological documentation. Incorporating SfM and GIS technology we can model excavations with millimeter level precision recording finer detail in stratigraphy and location than ever before. Physical 3-D models that can be pieced together or pulled a part. High resolution, detailed, and accurate data that can be manipulated, viewed, and analyzed virtually any way we desire. Even better we can share our results in a brand new ways: 3D printing, virtual tours, etc., we could and can literally print pieces of art, artifacts, even a scale model of the canyon if we wanted to! This project, this technique isn’t just for the archaeologists and researchers understand the shelters better, our goal is to be able to help everyone understand the shelters better because the shelters are a part of all our histories.

To elaborate on what Charles has said numerous times and will likely say many more, “50 years ago they were using completely different techniques..50 years from now they’ll be using completely different techniques…but right now we have the technology and the opportunity to set those standards for the next 50 years. We are doing something amazing here with SfM, and sure, we’re not the only people using this method, but there could be a dang lot more of us using it.”

If you haven’t already, you should click on over to our older posts on the subject, and I highly encourage you to visit the Mark Willis Blog http://palentier.blogspot.com/, where you can see some of the other extraordinary uses of SfM 3-D modeling.

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Eagle Nest Canyon at the Texas Archeological Society Annual Meeting

By Charles Koenig

This past weekend the Texas Archeological Society held its 85th annual meeting in San Marcos, Texas, and the Eagle Nest Canyon project was well represented.  Steve Black and I began the symposium with a 40-minute introduction highlighted by a series of animations created from the 3D models we have generated from our work thus far.  The six animations, such as that of Eagle Cave shown below, were narrated and aided by additional images.

Eleven additional speakers and ENC research team members rounded out the ENC symposium (abstracts below).  We also created a poster (Skiles et al. Eagle Cave_TAS2014 Poster) to highlight the excavation methodology we are using at Eagle Cave.  All of the presenters gave excellent presentations, and we are looking forward to learning from the ongoing analyses.  Stay tuned for new blog posts, and we will have another symposium at the Society for American Archaeology Meeting in San Francisco next April!

2014 Expedition to Eagle Nest Canyon

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Eagle Nest Canyon from the air. UAV Imagery courtesy Mark Willis.

Stephen L. Black, Charles W. Koenig, Mark D. Willis, and Charles D. Frederick

This presentation introduces the symposium and the 2014 Expedition by the Ancient Southwest Texas Project of Texas State University, as well as sites within Eagle Nest Canyon with an animated overview of the canyon. The ENC Expedition has three overarching research goals: 1) understand the human and natural history of the canyon; 2) share what we learn; and 3), conserve the archaeological record for future generations. From January through June a small core research team worked side-by-side with landowners Jack and Wilmuth Skiles and dedicated volunteers, collaborators, and partners to further these goals.  Our strategy is to apply state-of-the-art, multi-disciplinary research methods to documenting and sampling the complexly and deeply stratified deposits at two dry rockshelters with extremely well preserved organic remains and two shelters with shallow overhangs.  Our guiding motto “Low Impact, High Resolution” characterizes our approach.

Sites, Features, and Artifacts of the Canyon Edge, Eagle Nest Canyon

Matt describing a small upland burned rock feature on the Canyon Edge.

Matt Basham describing a small upland burned rock feature on the Canyon Edge.

Matt Basham, Texas State University

The canyon edge is a common geographic zone throughout the Lower Pecos Canyonlands of southwest Texas.  The edge around Eagle Nest Canyon, in particular, was used by prehistoric people for thousands of years.  Archaeological surveys of the area, most recently by the Ancient Southwest Texas Project of Texas State University, have documented a variety of sites, features, and artifacts that have helped reveal the length and scope of human activity in this unique geographic setting.  This paper will present an overview of the canyon edge around Eagle Nest Canyon.  A brief description will be given of each site in this zone.  In addition, the radiocarbon dates of several burned rock features and diagnostic projectile points will be discussed that are relevant to determining the length and scope of human activity on the edge of Eagle Nest Canyon.

In Search of the Basketmakers: The Story of the Early Witte Museum Expeditions to Eagle Nest Canyon

Stephanie Mueller excavating PS05 in Eagle Cave.

Stephanie Mueller excavating PS05 in Eagle Cave.

Stephanie Mueller, Witte Museum

In a race to be among one of the first institutions to acquire artifacts from the earliest known culture in Texas at the time, the Witte Memorial Museum sent out fifteen known expeditions to archeological sites throughout western Texas within the first two decades of its institutional history.  At least five of those expeditions ended up in Eagle Nest Canyon.  The first of those was a scouting expedition in 1922 to Eagle Cave (41V167).  Four other expeditions followed in the 1930s where the museum conducted excavations in Eagle Cave, Jacal Shelter (41VV674), and other sites in the vicinity of Langtry, Texas.  This paper provides an overview of the known Witte expeditions to Eagle Nest Canyon and reports recent findings of one of the museum’s campsites utilized during the later expeditions.

A Microstratigraphic Approach to Evaluating Site Formation Processes at Eagle Cave

Tina running the TDS in Eagle Cave.

Tina running the TDS in Eagle Cave.

Christina Nielsen, Texas State University

Eagle Cave (41VV167) is a large dry rockshelter with deep stratified deposits spanning the Early Archaic through the Late Prehistoric periods. My thesis research focuses on the deposits in the northern sector of the shelter sampled during the 1963 excavations by UT-Austin and again a half century later by Texas State University in 2014.  My goal is to use multiple lines of evidence to evaluate the natural and cultural formation processes that resulted in the complexly stratified, culturally rich deposits present in Eagle Cave.  By using data derived from stratigraphic documentation, geoarchaeological sampling, artifact analysis, macrobotanical and faunal identification, constituent size distribution, and radiocarbon dating, I hope to develop a viable protocol for understanding the site formation processes evident at Eagle Cave and many other Lower Pecos rockshelters.  This presentation summarizes the microstratigraphic approach taken during the 2014 field investigations and highlights methodological and analytic challenges.

We Dig GIS! Studying Lower Pecos Stratigraphy with ArcGIS

Bryan standing in front of PS3 in Eagle Cave.

Bryan standing in front of PS3 in Eagle Cave.

 Bryan Heisinger, U.S. Forest Service (2014 ASWT Intern)

Throughout the ENC 2014 project we used Structure from Motion to document and photograph each excavation unit-layer.  Using the photogrammetry software, we are able to create digital surface terrain representations and digital elevation models (DEMs) of excavation unit-layers with sub-millimeter accuracy.  In turn, each DEM can then be manipulated with ArcGIS in such a way to not only show and measure the precise opening and closing dimensions of an excavated unit, but also calculate total volume of material excavated—no matter the shape or size.  Additionally, these digitally recreated excavation layers can be overlaid onto a unit’s stratigraphic profile in ArcGIS to compare the pre-defined strata of a profile to what was actually excavated and seen in profile view.  Together by using ArcGIS and Structure from Motion photogrammetry software, the ASWT Project has begun extracting excavation unit data in a new and potentially more efficient way.

Preliminary Analysis of Archaeobotanical Materials from Kelley Cave

Kevin (far right) points out scars that suggest the deep mortar hole that goes all the way through this small boulder was quite intentional.  He has seen similar "artifacts" in Tamaulipas.  Incidentally, we think J. Charles Kelley described this very rock in May 1932 when he and E. B. Sayles dug small tests in Eagle Cave.

The Macrobotanical team examining a large grinding slab in Eagle Cave.

Kevin Hanselka, Leslie L. Bush, J. Philip Dering, and Stephen L. Black

Abundant well-preserved plant remains recovered from sheltered sites in Eagle Nest Canyon illuminate ecological interrelations between the prehistoric site occupants and the surrounding natural landscape. These materials have implications regarding: preferences and selection of local plants for food and fuelwood; behavioral patterns of food plant harvesting and processing; modification of plant parts into material culture such as tools, cordage, and textiles; seasonality of site use; and the nature of past environments surrounding the shelters at time of site occupation. In this paper we present the preliminary results of ongoing archaeobotanical analysis of plant materials recovered from Kelley Cave (41VV164). In particular we focus on evidence from Feature 4, a large pit thought to represent an earth oven facility with a complex history of use and abandonment.

Floods, Muds, and Plant Baking: ASWT Excavations at Skiles Shelter

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Charles discussing excavations in Eagle Cave with Matt Larsen and Lindsay Vermillion.

 Charles W. Koenig, Texas State University

Of the Eagle Nest Canyon sites, Skiles Shelter is located closest to the Rio Grande and is the most at-risk for damage from flooding.  Dan Rodriguez tested Skiles during the 2013 Texas State field school. The Ancient  Southwest Texas Project greatly expanded on this initial work in 2014.  Excavations this past spring at Skiles Shelter focused on three main research objectives: 1) understanding the site’s depositional history; 2) quantifying how much earth oven baking occurred there; and 3) relating the prehistoric record at Skiles to the other sites within Eagle Nest Canyon.  Excavations were conducted using similar methodologies employed by ASWT at other Lower Pecos BRM sites, with a focus on collecting samples for radiocarbon dating, geoarchaeology, archaeobotany, and zooarchaelogy.  This presentation will highlight preliminary results of the excavations and ongoing analysis.

 

Morphological Variation of Bedrock Features in Eagle Nest Canyon

Amanda recording the bedrock features at Skiles Shelter.

Amanda recording the bedrock features at Skiles Shelter.

Amanda M. Castañeda, Texas State University

Bedrock features are a common archaeological occurrence in the Lower Pecos Canyonlands. These occur in a wide range of forms, from polished “slicks”, cupules, and small grinding facets to large, deep, well-developed mortar holes. Even though relatively common, bedrock features, and ground stone in general, have received very little directed research in the region. This paper focuses on *** bedrock features from five sites within Eagle Nest Canyon, and highlights ongoing research examining bedrock feature morphology. On-site morphological and macroscopic use wear attributes were recorded for each individual work station, and Structure from Motion photogrammetry was employed to further assess this feature type. Additionally, experimental residue samples were collected from several features in Skiles Shelter. This project will contribute to creating a typology of bedrock features for the region and a base line data set for future studies to expand upon.

Ongoing Geoarchaeological Investigations in Eagle Nest Canyon

Charles Frederick and Ken Lawrence removing a micromorphology sample from Skiles Shelter.

Charles Frederick and Ken Lawrence removing a micromorphology sample from Skiles Shelter.

Ken Lawrence, Charles D. Frederick, Jacob I. Sullivan, and Christina Nielsen

This presentation summarizes the 2014 geoarchaeological investigations conducted at Kelley Cave (41VV164), Skiles Shelter (41VV165), and Eagle Cave (41VV167) and highlights elements of the ongoing analyses. Research begun in 2013 at Kelley Cave and Skiles Shelter was expanded and new work was begun in Eagle Cave. The geoarchaeological investigations have encountered new problems, opportunities, and several surprises. The data obtained from each site includes micromorphological samples, high-resolution cube samples, and bulk matrix samples. This presentation discusses the preliminary results of these investigations, their interpretations, and how they correlate to the cultural deposits from the excavations.

The ENC Micromorphing Power Rangers: Challenges, Trials, and Tribulations of Micromorphology in Dry Shelter Deposits

Jake preparing a micromorphology sample from Skiles Shelter for extraction from the wall.

Jake preparing a micromorphology sample from Skiles Shelter for extraction from the wall.

 Jacob I. Sullivan, Charles D. Frederick, and Ken Lawrence

Documenting stratigraphic exposures can be exceptionally difficult within the dry rockshelter deposits from sites within Eagle Nest Canyon—especially when dealing with the micro-stratigraphy often visible.  Fine dust, carried by wind or cascading down a profile face, threatens to obscure these sometimes delicate and subtle lamina we seek to record.  In order to gain a clearer understanding of the site use and depositional history, we have undertaken an ambitious micromorphology collection strategy for all the sites within ENC.  Micromorphology blocks are carefully removed from exposed profiles, and imbedded within a polyester resin which allows for detailed analysis back in the lab. These  block sampling columns provide high resolution vignettes into the natural and anthropogenic depositional processes at work within each of the rockshelters. This paper is an overview of the methodology and analysis of micromorphology samples taken from Profile Section 5 in Eagle Cave.

Flooding Past and Present: Extreme Geomorphic in the Lower Pecos Canyonlands

Noon, view upstream from above Eagle Cave.

Eagle Nest Canyon flooding during the June 20th flood.

Charles D. Frederick, Mark Willis, Ken Lawrence, Jacob I. Sullivan, Rudy Herrmann, Charles Koenig and Steve Black

Although presently a desert environment, extreme flood events are part of life in the Lower Pecos Canyonlands. This paper examines two such flood events, one preserved in the deposits of Skiles Shelter and Kelly Cave, and another that occurred on June 20th 2014. These events provide examples of catastrophic floods that punctuate the sedimentary records in the shelters and contrast with the more incrementally formed deposits that occur in association with human activity in these settings.  The presentation also examines the issue of which process is more formative in the local landscape: rare extreme magnitude flood events or low magnitude but higher frequency floods.

Preliminary Results from Zooarchaeological Analysis of Eagle Nest Canyon Sites

Dr. Chris Jergens studying faunal remains under a microscope.

Dr. Chris Jurgens studying faunal remains under a microscope.

Christopher J. Jurgens

Distance and a decade of life separate the subjects of doctoral zooarchaeological research and current Eagle Nest Canyon research efforts.  The author returns to Lower Pecos research as an extension to his earlier doctoral research.  Zooarchaeology and bone technology was the focus of the earlier research at Arenosa Shelter (41VV99), the deeply stratified site located in the Pecos River canyon 25 km (15 miles) southeast of Eagle Nest Canyon. Analysis results from Eagle Nest Canyon sites are comparable with those from the upper strata at Arenosa Shelter. Preliminary analyses of faunal materials from the Eagle Nest Canyon sites reveal patterns that compare favorably with those at Arenosa Shelter.  The patterns are similar for skinning, butchering, and bone fracturing; bone tool and ornament manufacture; and subsequent use wear.  Formal and informally manufactured tools are present in both locales.  Tool forms are very similar. Informally manufactured tools are present at both locales.

Skiles Shelter 3D Animation

By Charles Koenig

Welcome to the dog days of summer!  I realize it has been over a month since our last post, so I wanted to share a little bit of what we have been working on.

The crew standing on top of the UT north unit in Eagle Cave after it was backfilled.

The crew standing on top of the UT north unit in Eagle Cave after it was backfilled.

Since the flooding at the end of June, we were able to wrap up our excavations and finish backfilling all of our excavation units.  Once we got back to San Marcos, Steve and I were faced with the realization of how much data we had collected: nearly 900 GB of data (including over 50,000 photographs), several hundred 3D models (we still have not counted exactly how many we have), and thousands of TDS points.  So, what we’ve started doing is focusing on bringing together all the spatial data (specifically 3D models and TDS data) from each of the sites.  As we’re doing this, we’re beginning to experiment with creating fly-through animations of the 3D models.

The first animation we have created is of Skiles Shelter prior to any excavations.  This is the first-draft of this animation, but I wanted to give people an idea of the direction we’re going with the 3D data.  In the animation, there are actually 2 different 3D models: one of the shelter and one of the talus.  The shelter was photographed in 2013 prior to the field school, and about 2500 photographs were used to produce the model.  When we started working at Skiles this past spring, we mapped the talus in order to estimate the volume of FCR on the slope in front of the shelter.  Because the vegetation was so thick, we decided to clear narrow “senderos” down the talus (the narrow “strips” extending downslope in the 3D model) rather than clear the entire talus.  The talus was photographed using 2 canon point-and-shoot cameras attached to the end of a pole (see SfM blog post from January), and the model was created from about 300 photographs.  The difference in lighting between the shelter and the talus is due to the each location being photographed at different times and with different lighting conditions.

As we continue to bring all of our spatial data in order, we will create more 3D animations.  Eventually, the goal is to have all the 3D data put into a digital environment where people can navigate between the sites, as well as explore the sites in their own way (rather than being limited to watching an animation).

The Structure from Motion Revolution: Digitally Documenting the Archaeology of Eagle Nest Canyon

By Charles Koenig

In several previous posts we have mentioned the use of Structure from Motion (SfM) photogrammetry during the ENC project.  Before I begin explaining what SfM is, I want to explain how we (ASWT) came to be using SfM on the ENC project.  I was first introduced to SfM at the 2009 TAS Annual Meeting in Del Rio.  I had just received my BA from the University of Colorado in May 2009, and had only 5 months of field experience as an intern working with SHUMLA—in other words, I was young and impressionable.  I attended a presentation by Mark Willis where he explained how he used Microsoft Photosynth to create a 3D model from photographs he took using a hand held camera (for more info see Mark’s Blog: http://palentier.blogspot.com/).  To me, Mark was describing something straight out of video games and movies, and I remember thinking how cool it was that archaeologists were creating 3D images using just a camera!

Dr. Black’s (Steve’s) 2010 Texas State Archaeological Field School was the first time I was able to see Mark in action.  That summer I was finishing my internship at SHUMLA and gearing up to enter graduate school under Black at Texas State.  The field school was headquartered at the Shumla Campus on Jack and Missy Harrington’s Shumla Ranch and I was taking the field school unofficially as a SHUMLA representative.  Back to Mark in action.  He suspended a simple point-and-shoot camera about 100 feet up in the air from a kite and mapped the upland stone alignment site of Javelina Heights, which the field school was excavating.  The basic principle by which a 3D surface is created using SfM is to take dozens—or sometimes 1000’s—of overlapping photographs of the object/area being mapped.  These photographs are then put into specialized software that matches each photograph up to other photographs of the same area, and it builds a 3D surface from the 2D photographs.  This 3D surface, which is essentially a topographic map, can then have geo-referenced real-world coordinates (e.g., meters or UTM coordinates) assigned to the model so measurements can be taken from the surface.  Mark spent only a few hours on site, but he was able to produce a higher-resolution site map than the one we produced after 5 weeks and 1000’s of topographic shots with a Total Data Station.

A small sample of imagery captured from Javelina Heights (left); Mark Willis and Steve Black discussing rigging a camera to the kite (top right); Mark Willis flying a kite in the Lower Pecos (bottom right)

After Mark’s mapping of Javelina Heights on I was convinced—Steve slightly less so—that SfM was the way to go.  Again in 2011 Mark came out to Dr. Black’s field school and used a kite to map Little Sotol (a terrace/rockshelter burned rock midden along a tributary to the Devils River where the field school was held).  That year my fellow Coloradoan and graduate student Ashleigh Knapp and I were the field school teaching assistants and developing our Master’s thesis research projects (Little Sotol for her, the survey of Dead Man’s Creek drainage for me).  I began to experiment taking my own SfM shots of different rockshelters I recorded as part of my survey, and even with just my basic understanding of the technique I was able to produce 3D point clouds of rockshelters.  My early efforts were mere baby steps compared to what Mark was doing at Panther Cave as part of SHUMLA’s 2011 Field School (http://www.youtube.com/watch?v=vbmgpKKLMyY).  But, Mark’s work at Panther Cave coupled with my own experimentation was enough to convince Steve that SfM could be used effectively to map sites.  So, in 2012, during continued research along Dead Man’s Creek we began to use only SfM to map and document our excavations at three burned rock midden sites.

SfM models of Hibiscus Shelter (left) and Tractor Terrace (right). The model for Hibiscus was created using 950 photographs, and the Tractor Terrace model produced using 750. The photographs for both models were taken after excavations were completed.

After our work in the summer of 2012 along the Devils River, my TxState coursework was completed and I returned to SHUMLA to work part time as I completed my thesis; but, SfM was not forgotten.  At SHUMLA we began to produce 3D models of all the sites where SHUMLA was recording pictographs.  In part because we were constantly face to face with 3D models of archaeological sites, we began to realize what we were creating: a digital, interactive record of Lower Pecos archaeology. We were creating something that could be shared with the world.

As for me, I finished my MA in December, 2012 and worked full-time at SHUMLA through August.  I was one of the rock art instructors during the TxState Archaeological Field School at Eagle Nest Canyon that Steve co-directed with Carolyn Boyd.  I am now back at TxState working for ASWT as the project archaeologist and Steve’s second-in-command.

Fast forward to 2014 and the Eagle Nest Canyon project. We are using SfM to document and model sites, excavation units, excavation layers, profiles—essentially we are using SfM to photo-document anything and everything.  Depending on the size of the area being mapped, we can produce 3D surfaces with sub-millimeter accuracy.  In fact, SfM produces results rivaling LiDAR, but for a fraction of the cost.

With the help of Mark Willis, we have taken photographs from a UAV and remote controlled helicopter to create maps of the Eagle Nest Canyon area with centimeter resolution.

UAV imagery from Eagle Nest Canyon, courtesy Mark Willis.

Using cameras suspended from a pole (PAP, pole aerial photography), we have mapped the talus of Skiles Shelter and the floor of Eagle Cave to sub-centimeter resolution.

Image

Charles using PAP to map the surface of Eagle Cave (top left); Jacob and Charles running PAP in Skiles Shelter (top right); a 3D surface of Eagle Cave generated from 1800 photographs.

Using just a hand-held camera we have modeled all of our excavation layers and profiles so we can better understand the deposits of the sites we are excavating.

The crew works together to photograph a 1.5m deep profile in Skiles (top). The 3D model (bottom) was created from 85 photographs.

Archaeological excavation and testing is inherently destructive—we are excavating intact deposits that once we are finished will never be intact again.  Using SfM, we are able to create a 3D record of not only the archaeological sites, but also the archaeological process.  By creating 3D records of each layer, level, and excavation unit we can digitally preserve things that are destroyed through the course of excavation.

This is a goal shared by SHUMLA and Texas State’s ASWT Project, and we are both striving to create a 3D digital record of Lower Pecos Archaeology.  From burned rock middens to rockshelters and from pictographs to painted pebbles, we are collaborating to document as many sites and artifacts as we can using SfM.  Imagine a video game-like environment where you navigate into an unexcavated rockshelter, and walk over to an area where we are currently conducting excavations.  With one click of a button you can begin excavating the site just like we did – one layer at a time.  Inside every layer you can appreciate the artifacts, look at the rodent burrows, and ponder the microstratigraphy.  Once you finish looking at the dirt, you can turn your attention to the pictographs along the rear wall and begin exploring the data recorded by SHUMLA.

We have an obligation as scientists and stewards to both study the archaeology and preserve it for future generations—SfM provides us with a means to begin creating a digital archaeological record to be accessed and studied for generations to come.