Tuesday, May 19, 2009

GPR Technology and the Magruder House

We wanted to introduce some of the neat technology we are employing in our investigations. Last November we contracted Bryan Haley of the University of Mississippi to conduct a Ground Penetrating Radar (GPR) survey of the three properties. This survey helped us to look underground at the three properties, to help us plan where to dig. Here is a video of what resulted:

GPR works by sending electromagnetic pulses underground, which bounce off buried objects like artifact deposits or masonry features. In the video, buried objects, called anomalies, appear as brownish or yellowish blobs. It takes a trained eye to interpret these shapes into meaningful information. Bryan wrote us a report with recommendations for what we should concentrate on in our investigation. At the moment, we are examining the images from the Market Master's House to help plan our excavation. This gives us a chance to look underground before even picking up a shovel!

Here is Bryan's website: http://www.olemiss.edu/research/anthropology/haley/


  1. Did the GPR prove to be a reliable indicator of valid historical deposits? Do you feel comfortable that there are not items left uncovered on the Magruder House property?

  2. Ed,
    GPR is great for the exploratory stage of testing. It works well for strategizing our excavation methods, but does not stand in for an actual excavation.

    We had something of a limited scope during this excavation: about ten units and twenty shovel tests. The GPR really helped us to maximize the effectiveness of using those units. That being said, we didn't test everything that showed up on the GPR, only those that appeared most interesting.

    GPR is a great tool, but nothing beats a shovel!

  3. Jim Pomfret (GDOT)May 28, 2009 at 2:02 PM

    We do a lot of geophysical work at GDOT and I was also interested in the GPR results. How many GPR anomalies were ground truthed? What types of archaeological features were identifed as a result?

  4. The results were interesting. I think in the case of the Magruder House the major advantage of doing GPR was meeting the relatively non-invasive requirements of working in a registered historic area, while still thoroughly surveying the entire area. We tested about four large anomalies that appeared on the map as large swatches of varied deposits. The features we found when testing the anomalies, about sixteen or so in total, included post-holes, pits, utility piping, and renovation rubble. That being said, the GPR is not precise enough, at least in the context we found at Magruder, to have identified these small features. But it did lead us to the areas where we could find them. I think we can also rule out the possibility of major architectural features existing in the entire area tested. If you send me your email address (to bladenarch@gmail.com) I can send you some of the maps, figures and text that resulted from the survey that we used to make our decisions. Hope this answered your questions....