The Digital Humanities GeoInformatics Laboratory conducts systematic geophysical surveys in archaeological sites belonging to different environmental contexts (both urban and rural). Geophysical prospection methods contribute towards the mapping of the subsurface architectural relics, contributing to a better understanding of the buried features, the urban planning, and the organization of settlements. Geophysical investigations constitute a vital tool for planning the archaeological excavations and landscape archaeological investigation targeting towards reconstructions of the ancient landscapes. Similarly, geophysical methods can contribute to the planning of large construction and development works.
Researchers of the Lab are also involved in training activities providing hands-on experience to students and professionals. The Laboratory is using cutting-edge technologies to meet the professional standards of archaeological research. Geophysical investigations performed by the laboratory include the use of magnetometry, earth resistance (ER), electrical resistivity tomography (ERT), and ground-penetrating radar (GPR). All the measurements are assisted by high-resolution differential GPS units for accurate positioning.

Magnetometry

In the context of non-invasive archaeological research, magnetometry is the most widely used method. Magnetometry measures changes of the local magnetic field either due to the existence of underground architectural relics or due to anthropogenic activities that have altered the local magnetic susceptibility. The magnetic susceptibility of materials is directly proportional to the iron content, typically in the form of hematite (Fe2O3) or magnetite (Fe3O4) minerals.
Fluxgate gradiometers and total field intensity sensors are usually employed in the magnetic archaeological investigations. The fluxgate sensors measure the magnetic gradient, while the total field sensors measure the absolute intensity of the Earth’s magnetic field. The outcome of the measurements is a magnetic map showing anomalous magnetic areas of a site. The archaeological features are generating changes in the magnetic field which are recognized as anomalies. Magnetometry can detect pits, postholes, huts, kilns, walls, buildings, or any other structural remains retaining a magnetic footprint. It is a very sensitive method, which works only in areas with no modern infrastructure.

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Ground Penetrating Radar (GPR)
 
Ground Penetrating Radar (GPR) measurements help us to establish a three-dimensional view of the below-ground features over almost any type of surface and even within buildings. Therefore, this geophysical method is effective where other techniques such as magnetic and earth resistance survey fail, or when we want to have a detailed mapping of the stratigraphy. A GPR unit, composed of a transmitter and a receiver antenna, operates by transferring the electromagnetic pulse into the ground at unvarying intervals. The electromagnetic pulse reflects off features in the ground and it is detected by the receiver antenna. The depth and characteristics of the archaeological features, such as shape and size, are estimated by decoding the strength and time delay of the reflected signal.
Archaeologists rely on GPR measurements as a very useful tool for non-invasive surveys, landscape-scale site mapping, excavation planning, and locating cultural heritage targets.

 

Electrical methods 
 
Earth resistance (ER) and Electrical resistivity tomography (ERT) are the most used resistivity methods for archaeological and cultural heritage mapping. Resistivity methods rely on the transmission of electrical current through the ground. The presence of archaeological remains affects the flow of electrical current in the soil. Hence, a wall or a compact building will generate a higher resistance, while a pit or a ditch saturated in water will allow the electrical current to flow easier and engender a small resistance.
Earth resistance instruments are composed of a resistivity meter and two or four metal electrodes usually mounted on a frame. The electrodes are installed with a specific distance apart, being inserted into the soil at regular distance intervals.
Electrical Resistivity Tomography (ERT) is basically an advanced earth resistance system that uses a computer to control multiple electrode arrays for data acquisition, numerical modeling methods, and tomographic inversion algorithms. ERT allows creating 3D resistivity models of buried features and as it can provide deep stratigraphic images (5-30m in depth), it can also be used for archaeo-environmental reconstructions of the landscape (e.g. mapping of ancient port depressions).
   
 
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