A non-destructive and minimally invasive characterization of non-directly accessible spatial regions is of huge interest in several applicative fields. Examples are:

- detection and monitoring of utilities;

- mapping of asphalt layers extent and status;

- remote investigation of planets’ soil in order to detect the presence of water;

- archeological prospection, to localize archeological sites and map their plant in order to properly address stratigraphic essays as well as acquire information on buried structures located in areas where direct inspection is not possible;

- forensic framework in order to localize corpses as well as weapons;

- mitigation of anthropic risk.

In all these applicative frameworks, the capability of microwaves to penetrate opaque media is exploited to acquire information on hidden targets from remote or in situ radar measurements. This is possible owing to active microwave imaging technologies, such as the ground penetrating radar or georadar.

Ground penetrating radar is one of the most flexible and effective tools for electromagnetic non-invasive diagnostics, which is based on the capability of radiating a microwaves fields and measuring the back-scattered field due to changes of the electromagnetic features of the probed medium. Therefore, a knowledge of the inner structure of the surveyed region is achieved by means of approaches, that are specifically tailored to process radar data. Among these approaches microwave tomography techniques are worth to be considered. As a matter of fact,  being based on the use of mathematical models capable of accurately describing the interaction among waves and materials, microwave tomography techniques are able to generate images which are easily interpretable by non-expert users and provide qualitative information (i.e., location, shape and size) as well as quantitative knowledge (i.e., maps of the electromagnetic features) of the investigated domain.