GIS for Archaeology, Module 9

For this week's lab, focusing on remote sensing, we worked with an aerial photograph of the area around Cahokia. Cahokia is a large Mississippian site in what is now southern Illinois. Constructed and occupied from about the 800s to about 1300, the city originally covered about 6 square miles and contained some 120 earthen mounds. Part of this area, including about 80 mounds, are now preserved as a National Historic Landmark and state historic site. It is the largest pre-Columbian archaeological site north of Mexico.

For the lab assignment, we obtained an aerial photo from the USGS database and performed two different land cover classifications in ArcMap, one unsupervised (classified entirely by the program's algorithms) and one supervised (classified with the guidance of a set of points with user-assigned values). The resulting maps are below. The unsupervised classification resulted in only three easily defined land cover classes, while I was able to create five using the supervised method and produce a more detailed image, but both contain many errors resulting from the algorithm being unable to tell the difference between similar pixels representing different land cover types (e.g. water and dark-colored trees, or pavement vs. a barren agricultural field). However, it might be possible to refine the supervised classification by adding additional control points. 

GIS for Archaeology, Module 8

This week the topic was 3D modeling, which I was excited about as there are numerous ways to use 3D modeling in archaeology. For this assignment, we used data from a shovel test survey to predict and model the stratigraphy across the entire study area, using ArcMap for analysis and ArcScene for visualization. I did my best to describe the size and orientation of these views, since ArcMap can't create an accurate scale bar or north arrow for a 3D scene. I forgot to note, however, that the shovel tests were dug to a depth of one meter, and these surfaces represent the top of each stratum.

We also used ArcScene to create a 3D visualization of the stratigraphy within the shovel tests themselves, and ArcScene's Fly tool to explore it. My video is a little awkward because I'm still getting the hang of using the Fly tool, but here it is:

Finally, we used the interpolated stratigraphic surfaces to predict the stratigraphy of a cross section of the site, using points along a line through the study area. Below you can see these points, with predicted stratum depths, fitted into the interpolations from before.

GIS for Archaeology, Module 7

This week was all about interpolations, and I ran many of them, comparing the results of different interpolation methods and different parameters for some of them. We used two different datasets for this lab, one for shovel test results from a site in Panama and one for population estimates for a regional survey in Ecuador. For the latter, we then used the interpolations to consider settlement patterning for a particular time period, having read an interesting article that described several case studies using a similar methodology. There are more complete descriptions on the map posters below.