Geophysical Training at the Sebittu Project
During the 2024 field season, we concentrated our efforts on conducting a form of shallow subsurface geophysical survey called magnetic field gradiometry. In this technique, archaeologists use a hand-held instrument to measure the strength and direction of the Earth’s magnetic field immediately below the surface. By taking measurements across a field in a grid pattern, we can create maps of archaeological (and modern) features up to a depth of about 1.0m below the current ground surface.
The photo to the left shows one of our team, Rafeeq Bradosti, using a GeoScan FM-256 fluxgate gradiometer in the field. On the right, the image is the raw data from the gradiometer presented as a plan from one of the Sebittu sites. The darker and lighter features are a mix of modern and ancient pits, plow scars, piece of ferrous metal, and so forth. Archaeologists routinely use these maps to determine both the overall structure of a settlement and where to place their excavations. The map on the right represents an area of 40 m by 140 m, far too large an area to excavate. Using the maps we can make smaller excavations (time and effort saved) and with a higher likelihood of good results.
The Sebittu Project is committed to training Kurdish archaeologists in the technique of magnetic field gradiometry. The materials in this section of my website are some basic instructional materials, as well as some more detailed information on the GeoScan FM-256 gradiometer. The Sebittu Project has made its equipment and software available for training and use by our Kurdish colleagues in the field. My first two “students” have informally started the training with me, and I look forward to working with other colleagues in future seasons.
Training materials
I have been teaching applied geophysical survey techniques in archaeology since 2001 and have provided basic instruction in field techniques to scores of students, the majority of whom had some training in archaeology but not in the fields of geophysics, geology, soil science, physics. This is true of my own training. My approach is practical with the goal of training field practitioners. In 2018, I had the opportunity to work with the Iraq Heritage Management Training Scheme run by the British Museum at sites in Darband-i Rania pass. Some of the materials below were created for that course, and have been subsequently modified below.
In my current training project, I will be teaching colleagues how to set up and operate the FM-256 gradiometer, how to collect data in a survey grid, download the data from the instrument, and process the collected data into a useable map. This requires students to learn some basic principles that will guide them in assessing when magnetic field gradiometry is (and is not!) appropriate for any given site. This knowledge is transferable to any geophysical survey technique or system. The students will also be instructed on the use of the specific equipment we have available for this training.
We are using the GeoScan FM-256 gradiometer. This gradiometer is no longer manufactured by GeoScan Research, although their website maintains links to the manuals for the equipment and their proprietary processing software, GeoPlot 4.0.
Download a copy of the GeoScan FM-256 user manual (version 1.7) here: http://www.geoscan-research.co.uk/FM256Manual1_7.pdf
Download a copy of the GeoPlot 4 user manual here: http://www.geoscan-research.co.uk/Geoplot_4_Instruction_Manual_Summary.pdf
The GeoScan Research website has other useful links, including information on how to purchase or upgrade the software dongle (key) that is required to run GeoPlot 4.0.