Field School Week 2: Mapping and Context
Students learn mapping as their first major field research skill. We begin with mapping because this is the first skill from which all other archaeological tools derive: the ability to know where something is in relation to other things. An archaeologist must be able to control their data collection, locating things in space and time on the landscape. You can think of this in one way as the X, Y, and Z coordinates where a thing was found. We call that information an artifacts provenience, and because we know how things relate to each other in space (and thus time), we can say things like “These two artifacts were buried at the same time, roughly 1855” or “That button was manufactured in 1863 and it was in a layer of sediment deposited when this foundation was laid, so this building was built sometime in or after that year.” If someone brings me a button or bottle that they have removed from a site, they have lost most of this information and that greatly reduces the information we can learn about daily life at the site through that object.
So knowing where things are is key. Building from that, an archaeologist needs to be able to put things they see on or in the ground into the absolute space of maps, using systems like UTM, Township and Range, or Latitude and Longitude. These skills matter because it takes a great deal of work to be able to look at a foundation on the ground today and definitively say, this is the foundation of this structure indicated on this 1849 map. Figuring that out can be very hard. Just ask Sean and the other research team members.
The students eventually learn to work with an EDM/Total Station, GPS, and sometimes other technologies like LiDAR. When we teach mapping, however, we really start with basics because we want the students to understand the processes behind the button pushing for digital data. The students start learning basics: the significance of triangles and trigonometry; triangulation by measurements, triangulation by bearing, and bearing-and-distance mapping; determining scales; and drawing by hand.
We spent time during the first and second weeks making maps of campus buildings. One team stretched tape measures to build a triangle of three base points, then measured distances from those points to all the key building corners. The second team used magnetic compasses to take bearing readings off magnetic north from a single point, then measure the distance. Then both teams plotted their buildings onto hand-drawn maps at the same scale. This was the result:
Not bad for a first try!
Later, when we went into the field to the South Cliff Stamp Mill, we pulled tape measures to lay in base points and started making our map of the building remains. We also started learning how to use an optical transit. This is pretty easy to learn until you depress or incline the angle of your telescope, so I’ll spare you all the math. Using the optical equipment certainly prepared the students to appreciate the EDM and GPS units!
As the work progressed, the students generated a scaled drawing of the mill’s main features in the field. Working from this drawing, they were able to then select areas for shovel test pits. We wanted to assess the potential of the South Cliff Stamp Mill for archaeological excavation.
The third week, Tim Goddard was able to spend some time with us in the field, teaching about the EDM/Total Station as a tool for collecting geospatial data. The students learned quickly and they reshot many of the South Cliff points again, so we will be able to compare the digital with our “analog” data. The EDM data will allow us to easily add the new information about the South Cliff Stamp Mill into the CliffMAP GIS.
We were generally pleased with the results and look forward to showing our open house visitors the stamp mill site and explaining what we have learned about it during the week we spent studying it. We’ve only had a quick and preliminary view, but it looks very promising for more research. This mill also has an interesting story as a place of technological experimentation and it gave us tantalizing clues!