I. Introduction
Migration is the most common algorithm exploited in GPR data processing and in seismic data processing in order to focus the echoes coming from the buried targets. The applicative cases where it has been applied are endless and any list would be insufficient. So, we will limit to say that it has been historically imported in the GPR data processing from the seismics but can be also derived form the Maxwell’s equations, under several assumptions and approximations. In particular, it is a kind of linear inversion [ 1 – 2 ] where the inverse of linearised scattering operator is replaced by the adjoint operator [3] , which allows to avoid the instability problems intrinsically related to the ill-posedness of the inverse scattering operator [4] .