The geophysical surveys are increasingly being used for research and geometric reconstruction of underground networks, reservoirs, and underground artifacts, archaeological remains and structures in general, in order to limit the risks of damage or interference to them. In particular, the methodology GPR GPR (Ground Penetration Radar) is a technique non-destructive diagnostics based on entering into the subsoil, or in a manufactured product of electromagnetic waves to radio frequency (100-1500 MHz), which allows to detect, with good precision and detail, any type of abnormality present in the first meters of the subsoil of the site in question, ensuring at the same time, low cost and speed of action.

This makes it possible to investigate areas of considerable size, and identify areas in which to focus any future investigations directed (excavations, surveys and the like).

The GPR surveys or GPR (Ground Penetrating Radar) are based on the response of an electromagnetic signal of impulsive high frequency that is sent from a transmitting antenna.

The principle of operation of the GPR differs from that of the conventional radar as the transmission medium is no longer the air but a rock or soil.

In particular, the electromagnetic signal generated from the transmitting propagates down: the presence of gaps of electromagnetic properties of the material causes the phenomena of refraction, reflection and diffraction of the electromagnetic energy incident on this discontinuity. In general, we analyze the response of the electromagnetic wave that is reflected in correspondence with the discontinuity of the medium and that returns to the surface, where it is picked up by a receiving antenna. The resolution is typically decimeter or centimeter, and the measurement range is limited to a few meters deep.

The choice of the frequency to be used for the survey is a function of depth and size of the target object:

• high frequencies (with a wavelength very small and very high resolution) have a depth of inspection limited to a few decimeters. And 'the case of 1.5-2 GHz antennas (used mainly for measurements of concrete structures) that allow to obtain very detailed but have a maximum depth of investigation of 50 cm;

• low frequencies, or antennas of 100-200 MHz, have a longer wavelength and lower resolution capabilities. They can reach depths of 6-7 m, but can only resolve structures of size at least decimetre. Generally for the search of underground antennas are used with intermediate frequencies (250-500 MHz) as they ensure a better compromise between resolution capabilities and depth of investigation.

The GEOSIS srl with the instrumentation of high precision in its possession is capable of detecting the presence of underground and underground objects in order to avoid problems during excavation.