Archaeogeophysical research is a long-standing part of applied research activities at the Institute of Archaeology and Museology. The geophysical survey focused on archaeology contributes to the sustainable development of the landscape with an emphasis on protecting its historical component. The aim may be to document an archaeological site or to determine its extent. Various human activities (e.g., construction, mining, etc.) may also threaten an archaeological site. Therefore, our work includes not only documentation and presentation of historical heritage but also efforts to rescue information threatened with irreversible destruction. Geophysical surveys help determine an area's potential and contribute to more sensitive and anticipatory building planning.

Geophysical survey falls into the category of methods of non-destructive archaeology, which aims to achieve non-invasive localization, identification, and interpretation of the remains of human activity. Through geophysical surveys, we can understand the extent of individual sites, observe anomalies' shape and physical characteristics, and, if necessary, determine their damage state. The principle of geophysical prospecting methods is based on monitoring changes in specific physical quantities in a given area. Based on the physical principle, the nature of the physical field being monitored, and the measurement methods, they can be divided into several groups. Our geophysical department has instruments for magnetometry, GPR, Electro-Resistive Tomography and Electromagnetic induction.

 

Magnetometry

Magnetometry is the most suitable geophysical method for exploring and detecting shallow subsurface structures outside the city area. The magnetic survey measures the intensity of the Earth's magnetic field, within which local anomalies are identified. The occurrence of these anomalies is associated with the presence of subsurface structures of various, but mainly geological, pedological or anthropogenic origin. Anthropogenic structures include archaeological features.

This method is suitable for detection:

• sunken features,
• features with traces of firing or burning,
• burial pits, burial chambers and mounds,
• defining the extent, number, dimensions and orientation of production features,
• metal objects, recent deposits and landscaping at the location of former quarries,
• buried ditches and enclosures, including entrances,
• survey of sacral buildings, rectangular structures and other architectural elements (monasteries, castles, chateaux).

Georadar survey (GPR)

In the georadar survey in archaeology, the most used method is the area survey. It allows interpreting the measured data with the help of individual 2D-time slices (radargrams) and three-dimensional when a 3D spatial model of the surveyed area is created from the radargrams. This 3D model can then be analysed horizontally and vertically in time/depth slices (X, Y, Z axes).

This method is suitable for detection:

• masonry features and features with stone construction,
• hollow spaces, unfilled or partially filled features,
• residential features or features in more complicated stratigraphic situations,
• fortification elements with preserved aboveground parts, locating and identifying their construction elements or destruction horizons,
• destruction horizons (stone destruction, etc.).

Electro-Resistive Tomography

Direct current (DC) methods refer to a geoelectric method that examines the distribution of the electric potential or gradient of the direct current potential. The most widely used method is the electro-resistive method.

This method is suitable for detection:

• masonry features and features with stone construction,
• fortification elements with preserved aboveground parts, locating and identifying their structural elements or destruction horizons,
• hollow spaces, unfilled or partially filled features,
• buried features of larger dimensions.

 

Electromagnetic induction (EMI) methods

Electromagnetic induction methods record subsurface structures of geological, pedological or anthropogenic origin. They are also beginning to be used more frequently in archaeological research. Their advantage is the ability to make measurements non-contact and continuously. The instruments measure the conductivity of the environment in millisiemens per meter (mS/m) and can also be used to measure inphase, which is related to magnetic susceptibility.

This method is suitable for detection:

• masonry and stone-built features,
• locating and identifying structural elements at different depth horizons,
• localization and identification of fortification elements and buried trenches of even larger dimensions,
• settlement features, or features in more complicated stratigraphic situations,
• identification of unfilled or partially filled features,
• modern deposits and landscaping.