The paper deals with the evaluation of transmitted electric field in the ground due to the GPR dipole antenna. The frequency domain formulation is based on the integro-differential equation of the Pocklington type. The influence of the earth– air interface is taken into account via the simplified reflection/transmission coefficient arising from the Modified Image Theory (MIT). The space-frequency Pocklington equation is solved via the Galerkin–Bubnov variant of the Indirect Boundary Element Method (GB-IBEM) and the corresponding transmitted field is obtained by numerically computing field integrals. Some preliminary results for the electric field transmitted into material media are presented.