Research Assistance Centres

Geophysics with Georadar 3D

The georadar prospecting technique allows to determine, indirectly, the structure of the subsoil from the transmission of electromagnetic impulses and the subsequent reception of the reflections generated by discontinuities present in the subsoil. In physical terms, the technique is sensitive to all those variations of conductivity, electrical permittivity and magnetic permeability that can occur in a medium, whether due to lithological changes or due to the presence of buried structures.
A georadar device consists of a data control, storage and display unit connected to an antenna that emits and receives the electromagnetic signal as it travels along a pre-established direction. The technique consists of the transmission in the subsoil of electromagnetic pulses of brief duration (1-4 ns) and high frequency that propagate in depth with a certain speed. Depending on the frequency used, results of greater or lesser depth and of higher or lower resolution can be obtained.
The CAI Archeometry team consists of two DML antennas of 200 and 600 MHz. The first consists of 16 V dipoles 12 cm apart, which gives it a sweep width of 1, 8 meters. It is carried on a stabilizing crane that allows it to work in rough terrain and can be dragged by a conventional vehicle or by a Quad, to reach areas with low accessibility. The antenna of 600 MHz, has 12 dipoles in V at a spacing of 8 cm which gives it a sweep width of 0.88 meters and reaches a higher resolution at a lower depth.
Regarding conventional georadards that obtain information in 2D, the difference of a 3D device is very large, since having a multi-channel antenna with 16 dipoles, parallel sections can be made with very little spacing and a higher acquisition speed. With this you get a great resolution of measurement in a real 3D, investing less time.
Instrumentation
Staff
Javier Vallés Iriso
CAI Ciencias de la Tierra y Arqueometría
Archeometry and Archeological Analysis Unit