Total Station, Totally Cool
Courtesy of Provo Police Department
If you've ever passed a construction site, been stuck in a "workers ahead" traffic jam, or picnicked in a public park, you've probably seen a Total Station. They're usually accompanied by one or two people wearing brightly colored vests and taking scrupulous notes. What you may not know is that these tall yellow tripodic devices are also used by archaeologists in the field. And to archaeologists, these machines are totally cool.
"When I was at Colorado State, when we first got it, I was like, 'Oooh we got a Total Station? Can I take it out and use it?'" remembers Dr. Jonathan Burns, who visited our field school in Maryland. There's a steep learning curve, he explains, but the more you learn about the Total Station the more useful you are on site, making you more likely to become crew chief. It didn't take him long to buy one of his own so that he could use it whenever he wanted and nowadays he, "...would never start an excavation or survey without it."
Time Team America field school director Dr. Alex Jones doesn't hide her enthusiasm for the Total Station either. "I tell my friends that if I ever get married, forget the diamond, just get me a Total Station!" she laughs. "Seriously! People see them all the time on the side of the road or in a field, but I don't think they realize just how valuable they are."
What makes the Total Station so special? In a word: accuracy. The measurements made are so precise that they're accurate down to a millimeter. This machine is so accurate in fact, that in over 20 years the technology has gone relatively unchanged. You can get newer models with GPS or photographic measuring functions, Burns explains, but all of those technological "improvements" actually end up making the measurements themselves less accurate. So many archaeologists prefer the older models—tried and true.
At the most basic level, the Total Station, or EDM (Electronic Distances Measurement), is a tool that is used to measure the distance between two points. By positioning the station in the middle of a site and establishing two reference points, or datums, the device uses trigonometry and triangulation to calculate the distance between any two objects. After collecting datum points all over the site, the data is processed by computer software and used to generate a map of the site.
Generally, a survey is done at the beginning of an archaeological dig in order to give the excavators a basic outline of the area. But additional surveying occurs throughout the dig, expanding the site map to give archaeologists more and more context. The more datums, or reference points, that are collected during the survey, the more detailed the map will be.
Map of Justice William Smith House in Mercersburg, PA, Courtesy of AXIS Research, Inc.
Part of the reason that the Total Station is so precise is because it measures very straight. The electronic signal it emits across a site is relatively unaffected by slopes or other features (rocks, shrubs, etc.) in the landscape. Surveyors who use measuring tapes, on the other hand, face the inevitable introduction of "slop" into their data. As they pull their tapes up or down even a gentle slopes in the ground, that fluctuation leaves a lot of room for error in their measurements. The more room for error, the more room for interpretation and compensation.
"Back in the day, if you had 10 different archaeologists map this yard with just tapes and line levels, you're gonna get 10 different maps," Burns says.
Burns demonstrates how to use the Total Station for Time Team America's field school students in Bethesda, Maryland. He helps them establish a baseline, and shows them how the electronic signal sent out by the main instrument is reflected back by a prism in the top of the red and white pole at the other end.
Burns also explains to the students that mapping is essential to archaeology, or to any survey site, because it provides the scientist with critical context for the study. And context gives the features meaning. The space in between artifacts, or their position on a site, can be just as important to understanding their significance as knowing what the artifacts are themselves.
"If you don't have the grid and the context established with [the Total Station], then they're just artifacts," Burns says.
Ultimately, the Total Station is all about being able to communicate. The maps that it helps to generate are an extremely important form of communication, allowing scientists to record and share their findings with other people. When the data from a site is recorded accurately, the study can live on even without the site. Records make it accessible to other scientists from all over the world. Or, the study can be revisited in the future.
"100 years later someone could come excavate my site if my datums survived," Burns says enthusiastically, "So that's one of the beauties of [the Total Station] too..."
So the next time you pass by one of these big bright instruments in the road, stop and think about what's being surveyed. Imagine it's an archaeological dig site, and think about how the map that's being created will help inform decisions that are made about that area. Appreciate the fact that as fast as technology changes these days, the Total Station has remained relatively unchanged for over two decades. Accuracy, context, communication—that is why the Total Station is so totally cool.